Patent Publication Number: US-2016220013-A1

Title: Short wavelength visible light-emitting toothbrush with an electronic signal interlock control

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to increasing the safety of a dental hygiene implement such as a light-emitting manual or an electrically operated motorized toothbrush which emits radiation, in the violet and/or blue region of the visible spectrum, between 400 nm and 500 nm, in order to:
         oxidize and destroy potentially harmful bacteria and/or other contaminants or compounds contained within the mouth without harming or destroying human cells;   exert a phototoxic effect on pathogenic periodontal and oral bacteria such as;  P. Gingivalis  and  F. Nucleatum,  and  S. Mutans;      activate a photo catalyst that may be deposited on the teeth and the gums of the person utilizing the toothbrush during normal brushing; and/or   accelerate the whitening effects of a tooth bleaching agent added to toothpaste or toothgel such as carbamide peroxide or hydrogen peroxide.       

     The electronic interlock control mechanism in this toothbrush will reduce the possibility of accidental direct eye exposure to high flux visible light radiation emitted from this toothbrush when it is removed from the mouth. 
     Light-emitting toothbrushes have been developed over the past several years for teeth whitening applications in addition to the known oral hygiene benefits of regular brushing. When combined with a teeth whitening agent such as carbamide peroxide or hydrogen peroxide, studies have shown that light in the 400-500 nm range accelerates the whitening effect of these agents. Wolfgang Buchallaa, Thomas Attina:  External bleaching therapy with activation by heat, light or laser—A systematic review;  Karen Luk, D. D. S.; Laura Tam, D. D. S., M. Sc.; Manfred Hubert, Ph.D.:  Effect of light energy on peroxide tooth bleaching.    
     In addition, violet light in the 400 nm-420 nm range has been shown to have a phototoxic effect on pathogenic oral bacteria such as  P. Gingivalis, S. Mutans  and others. Michelle Maclean, Scott J. MacGregor, John G. Anderson, and Gerry Woolsey:  Inactivation of Bacterial Pathogens following Exposure to Light from a  405- Nanometer Light - Emitting Diode Array.  Doron Steinberg, Daniel Moreinos, John Featherstone, Moshe Shemesh, and Osnat Feuerstein:  Genetic and Physiological Effects of Noncoherent Visible Light Combined with Hydrogen Peroxide on Streptococcus mutants in Biofilm.  The inventors have previously shown the use of a light-emitting diode (LED) within a toothbrush provides anti-microbial properties of benefit to the oral hygiene of the end-user. 
     Current light-emitting toothbrushes have a manual on/off switch which activates the light-emitting device. This manual activation mechanism may lead to a safety risk because the user may activate the light and expose his or her eyes to high levels of light that may be harmful to the retina or optic nerve. The potentially harmful properties of visible light and maximum exposure levels are documented in ANSI standards. François C. Delori, Robert H. Webb, David H. Sliney:  Maximum permissible exposures for ocular safety  ( ANSI  2000),  with emphasis on ophthalmic devices.  David H. Sliney, M. S.:  Biohazards of Ultraviolet, Visible and Infrared Radiation.  For example, the maximum permissible radiant power (thermal and photo-acoustic) entering a dilated pupil is 1.5×10 −4  Watts. This limit would be exceeded if a user were to stare at a 420 nm LED of 250 mW radiant flux at a distance of 10 cm for a period of 0.5 seconds. To prevent accidental eye exposure, a special electronic interlock control mechanism has been implemented to keep the optical source turned off if the toothbrush is not inserted in the user&#39;s mouth. The control mechanism will turn the optical source off immediately if the toothbrush is removed from the mouth prior to completing the brushing cycle. 
     A toothbrush is typically used in close proximity to the eyes of the user, and if ocular exposure to the light lasts several seconds, eye damage may occur. Furthermore, the ocular safety risk of manually activated light precludes the use of more powerful light-emitting devices such as high-powered LEDs, laser diodes, or vertical cavity surface emitting lasers, which would increase the teeth-whitening and antimicrobial benefits in proportion to the energy delivered. For example, studies show that effective whitening treatments require a minimum energy density of 30-50 J cm −2  to produce noticeable shade whitening. However, such energy levels would not be readily achievable with a typical two minute brushing interval using a low-powered LED that would also be safe when directly placed in front of the eyes, even when used over a period of several weeks. Similar limitations exist for the anti-microbial properties of violet light as well. 
     It is therefore desirable to control the “on” state of the light-emitting device to a time period when it is in use in the oral cavity but to shut “off” this high power light source immediately, when it is removed from the mouth to prevent direct eye exposure. This feature would also extend battery life of a battery operated brush since power is only used to illuminate the light source when in direct contact with the oral cavity. 
     SUMMARY OF THE INVENTION 
     This invention relates to increasing the safety of a dental hygiene implement that emits radiation in the violet and/or blue region of the visible spectrum, between 400 nm and 500 nm, by determining whether the implement is within the user&#39;s mouth or outside of the user&#39;s mouth. Direct eye exposure to such light can be avoided using a sensor or combination of sensors that deactivate the light source whenever it is outside the environment of the mouth and permits activation only when inside the mouth of the user. 
     In one embodiment, the dental hygiene implement may be a light emitting toothbrush. The light emitting toothbrush, according to the present invention, will typically further include a control circuitry which will typically be located in the handle and normally include functions such as a timer circuitry (which times the duration(s) of use of the toothbrush while brushing), an on/off duty cycle of the violet light source or sources, a battery replacement indicator, and so on. 
     Preferably the driver, for driving the violet light source, is equipped with constant electrical current control electronics and a suitable driver is supplied by Linear Technology, of San Jose Calif., as part no. LTC3454 which is an integrated circuit high current LED driver. The control circuitry may also include violet light source control circuitry, which may be connected with one or more sensors located in the brush head, for detecting when the brush head is actually located within a user&#39;s mouth, thereby reducing the possibility of the violet light being inadvertently emitted except when the toothbrush is actually located within the mouth of the user. In another embodiment, the control circuitry may alternatively include one more sensors located on the handle to determine whether the brush head is actually located within a user&#39;s mouth. 
     In one embodiment, an AC or DC signal loop sensor establishes a signal loop through the user&#39;s mouth to the user&#39;s hand grasping the handle of the toothbrush to verify if the toothbrush head is within the user&#39;s mouth. If the sensor establishes a signal loop, the light source remains on until the toothbrush head is removed from the user&#39;s mouth breaking the signal loop. Once the signal loop is broken, the light source may be extinguished as soon as the brush head is removed from the mouth. 
     In another embodiment, the dental hygiene implement uses a capacitive sensor to determine whether the implement is within the user&#39;s mouth or outside of the user&#39;s mouth. The capacitive sensor may use a current loop which detects current flowing through the body of the end user when the brush head or bristles are in contact with the mouth and the handle is in contact with the hand. 
     In another embodiment, the dental hygiene implement uses a capacitive displacement sensor to determine whether the implement is within the user&#39;s mouth or outside of the user&#39;s mouth. The capacitive displacement sensor can detect change of position of any conductive target such as the human body. 
     In another embodiment, the dental hygiene implement uses an inductive sensor to determine whether the implement is within the user&#39;s mouth or outside of the user&#39;s mouth. The inductive sensor uses an inductance loop to measure the proximity of conductors such as the human body. 
     In another embodiment, the dental hygiene implement uses a passive thermal infrared sensor to determine whether the implement is within the user&#39;s mouth or outside of the user&#39;s mouth. The passive thermal infrared sensor detects the warmth of the human mouth to determine whether the implement is within the user&#39;s mouth. 
     In another embodiment, the dental hygiene implement uses an active thermal infrared sensor to determine whether the implement is within the user&#39;s mouth or outside of the user&#39;s mouth. The active thermal infrared sensor uses a photoelectric sensor that detects reflected IR light emitted and absorbed by the sensor itself. This could be used to detect proximity inside the mouth. 
     In another embodiment, the dental hygiene implement uses a passive optical sensor to determine whether the implement is within the user&#39;s mouth or outside of the user&#39;s mouth. The passive optical sensor is a light sensor that triggers the LED when it detects darkness when present inside the user&#39;s mouth. For increased sensitivity to changes in light intensity, the light sensor may be sensitive to a wavelength at least 50 nm different from the LED. 
     In yet another embodiment, the dental hygiene implement uses a photocell to determine whether the implement is within the user&#39;s mouth or outside of the user&#39;s mouth. A photocell is a light sensor that detects the reflection of light from a second light source on the implement when the implement is turned on. In one embodiment, the photocell may turn on the LED when it detects the reflection of light from a second light source while in the user&#39;s mouth. 
     In another embodiment, the dental hygiene implement uses an ultrasonic sensor to determine whether the implement is within the user&#39;s mouth or outside of the user&#39;s mouth. The ultrasonic sensor may use echo location to detect the confines of the mouth. 
     In another embodiment, the dental hygiene implement uses a passive optical sensor to determine whether the implement is within the user&#39;s mouth or outside of the user&#39;s mouth. 
     In yet another embodiment, the dental hygiene implement uses a magnetic sensor to determine whether the implement is within the user&#39;s mouth or outside of the user&#39;s mouth. In one embodiment of the present invention, the magnetic sensor may turn on the LED when it detects the proximity of metals such as the hemoglobin present in blood. 
     In yet another embodiment, the dental hygiene implement uses a pressure sensor to determine whether the implement is within the user&#39;s mouth or outside of the user&#39;s mouth. In one embodiment, the pressure sensor may be located under the brush head to detect movement and pressure of the brush head being pressed against the teeth. The type of pressure sensor such may be piezoelectric, capacitive, potentiometric, optical or electromagnetic. In another embodiment, the pressure sensor may be located on the handle—detects torque and tension in the handle of the brush due to brushing action. The pressure sensor could be Piezoelectric, Capacitive, Potentiometric, Optical or Electromagnetic. 
     In yet another embodiment, the dental hygiene implement uses a moisture sensor to detect a highly moist environment such as the mouth. This can be accomplished through various types of moisture sensors for example; capacitive or chilled mirror dew point sensors. 
     Other embodiments of the present invention may include combinations of two or more of these sensor types as disclosed above. Furthermore, the sensor examples listed above is not intended to be a complete list of the sensors available for use with the present invention. Therefore, the present invention is not to be limited to the use of the specific sensors or oral care instruments described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood by a reading of the Detailed Description of the Examples of the Invention along with a review of the drawings, in which: 
         FIG. 1  shows the completion of a signal loop by a user inserting a toothbrush into his mouth; 
         FIG. 2  depicts a representative oral care instrument, a toothbrush, illustrating various aspects; 
         FIG. 3  depicts an alternate embodiment in which the wet bristles of the brush head are conductive to form a contact for completion of the signal loop; 
         FIG. 4  shows a toothbrush with conductive metal pads; 
         FIG. 5  shows a toothbrush with conductive plastic pads; 
         FIG. 6  is a schematic of an exemplary control circuit; 
         FIG. 7  is a schematic of an exemplary oral care instrument that has a replaceable head and neck; 
         FIG. 8  is a schematic of an exemplary oral care instrument that has a replaceable brush head; 
         FIG. 9  is an exploded view of a toothbrush with a capacitive sensor; 
         FIG. 10  is a circuit view of the embodiment shown in  FIG. 9 ; 
         FIG. 11  is a partial cross-sectional view of an embodiment of the invention where the sensor is a capacitive displacement sensor placed on the handle; 
         FIG. 12  is a circuit view of an embodiment of the invention where the sensor is a capacitive displacement sensor; 
         FIG. 13  is depicts an alternate embodiment where the sensor is an inductive proximity sensor; 
         FIG. 14  shows an embodiment where the sensor is a passive thermal sensor placed near the upper portion of the handle of a toothbrush; 
         FIG. 15  shows an embodiment where two passive thermal sensors are placed near the upper portion of the handle of a toothbrush; 
         FIG. 16  shows an embodiment where the sensor is a passive thermal sensor placed on the back of the bristle plate of a toothbrush; 
         FIG. 17  shows an embodiment where the sensor is an active thermal infrared sensor placed on the back of the bristle plate of a toothbrush; 
         FIG. 18  shows an embodiment where the sensor is a passive optical sensor placed on the back of the bristle plate of a toothbrush; 
         FIG. 19  shows an embodiment where the sensor is a photocell placed on the brush head of a toothbrush; 
         FIG. 20  shows an embodiment where the sensor is an ultrasonic sensor placed on the brush head of a toothbrush; 
         FIG. 21  is a partially exploded view of another embodiment of the present invention, where the sensor is a pressure sensing system; 
         FIG. 22  is a side view of a portion of the pressure sensing system of  FIG. 21 ; 
         FIG. 23  is a perspective view of the pressure sensing system of  FIG. 21 ; 
         FIG. 24  is an exploded view of the pressure sensing system of  FIG. 21 ; 
         FIG. 25  is a side elevational view of a portion of the pressure sensing system of  FIG. 21 ; 
         FIG. 26  is a side elevational view of another portion of the pressure sensing system of  FIG. 21 ; 
         FIG. 27  is a cross-sectional view of a portion of the pressure sensing system of  FIG. 21 ; 
         FIG. 28  is a schematic drawing showing a circuit according to another embodiment of the invention where the sensor is a pressure sensing system; 
         FIG. 29  is a schematic perspective view, in partial cross-section, of a toothbrush having a pressure sensing system according to another embodiment of the invention; 
         FIG. 30  is an enlarged detail view of a portion of the toothbrush shown in  FIG. 29 ; 
         FIG. 31  is an enlarged detail view, in partial cross-section, of a toothbrush head according to another embodiment of the invention where the sensor is a pressure sensing system; 
         FIG. 32  is an enlarged detail view, in partial cross-section, of a toothbrush head according to another embodiment of the invention where the sensor is a pressure sensing system; 
         FIG. 33  is an enlarged detail view, in partial cross-section, of a toothbrush head according to another embodiment of the invention where the sensor is a pressure sensing system; 
         FIG. 34  is a detail view of the toothbrush head of  FIG. 33  taken along  507 - 507 ; 
         FIG. 35  is a simplified descriptive view of another embodiment of the invention where the sensor is a pressure sensing system; 
         FIG. 36  is a partial fragmentary view of a switch used in the toothbrush shown in  FIG. 35 , the switch being shown in a first position; 
         FIG. 37  is a partial fragmentary view of the switch shown in  FIG. 36 , the switch being shown in a second position; 
         FIG. 38  is a simplified wiring schematic for the toothbrush shown in  FIG. 35 ; 
         FIG. 39  is a perspective view of another embodiment of the invention where the sensor is a pressure sensing system including a one-piece compressible portion; 
         FIG. 40  is a perspective view of another embodiment of the invention where the sensor is a pressure sensing system including a two-piece compressible portion; 
         FIG. 41  is a partial fragmentary perspective view of another embodiment of the invention; 
         FIG. 42  is a detail view of a switch shown in  FIG. 41 ; 
         FIG. 43  is a detail view of the switch shown in  FIG. 42 , the switch being shown in a closed position; 
         FIG. 44  is a partial fragmentary perspective view of another embodiment of the invention where the oral care instrument is a toothbrush having a Hall effect sensor; 
         FIG. 45  is a partial fragmentary perspective view of a toothbrush in accordance with another embodiment of the present invention; 
         FIG. 46  is a partial fragmentary perspective view of another embodiment of the invention; 
         FIG. 47  is a simplified wiring schematic illustrating an electrical circuit that can be used with the toothbrush shown in  FIG. 46 ; 
         FIG. 48  is a partial fragmentary perspective view of another embodiment of the invention; 
         FIG. 49  is a simplified wiring schematic illustrating a circuit that can be used with the toothbrush shown in  FIG. 48 ; 
         FIG. 50  shows a simplified descriptive view of a toothbrush in accordance with another embodiment of the present invention where the sensor is a pressure sensor; 
         FIG. 51  shows a simple wiring schematic for the toothbrush shown in  FIG. 50 ; 
         FIG. 52  shows a simple wiring schematic for a toothbrush that includes a three position switch; 
         FIG. 53  shows a simple wiring schematic for a toothbrush with only one switch; 
         FIG. 54  shows an exploded view of the toothbrush shown in  FIG. 50 ; 
         FIG. 55  shows an alternative configuration for the contact plates shown in  FIG. 54 ; 
         FIG. 56  shows the contact plates of  FIG. 55  when a force is applied to the bristle head of the toothbrush; 
         FIG. 57  shows the contact plates of  FIG. 55  when the force applied to the bristle head exceeds a predetermined level; 
         FIG. 58  shows a perspective view of a portion of a toothbrush in accordance with another embodiment of the invention where the sensor is a pressure sensor; 
         FIG. 59  shows a partially exploded perspective view of a portion of the toothbrush shown in  FIG. 58 ; 
         FIG. 60  shows a sectional view of a portion of the toothbrush shown in  FIG. 58 ; 
         FIG. 61  shows another sectional view of the toothbrush shown in  FIG. 58 ; 
         FIG. 62  shows a partially exploded perspective view of a portion of a toothbrush in accordance with another embodiment of the invention where the sensor is a pressure sensor; 
         FIG. 63  shows a sectional view of a portion of the toothbrush shown in  FIG. 62 ; 
         FIG. 64  shows a perspective view of a toothbrush having a one-piece compressible portion in the handle in accordance with another embodiment of the present invention; 
         FIG. 65  shows a perspective view of a toothbrush having a two-piece compressible portion in the handle in accordance with another embodiment of the present invention; 
         FIG. 66  shows a simplified descriptive view of a toothbrush in accordance with another embodiment where the sensor is a pressure sensor; 
         FIG. 67  shows an enlarged detail of a switch shown in  FIG. 66 , the switch being shown in a first position; 
         FIG. 68  shows the switch from  FIG. 67  in a second position; 
         FIG. 69  shows a simplified descriptive view of a toothbrush in accordance with another embodiment of the present invention; 
         FIG. 70  depicts a toothbrush illustrating various aspects of another embodiment of the present invention wherein the sensor is a moisture sensor; 
         FIG. 71  depicts another embodiment of a toothbrush wherein the sensor is a moisture sensor; 
         FIG. 72  shows an embodiment of the present invention wherein the sensor is an accelerometer; 
         FIG. 73  shows an embodiment of a toothbrush including a fingerprint sensing module; 
         FIG. 74  is a flowchart illustrating an embodiment of steps for use of a toothbrush having a fingerprint sensing module and a plurality of LED status indicators; and 
         FIG. 75  is a simplified schematic of an embodiment of a toothbrush including a fingerprint sensing module and a plurality of LED status indicators. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLES OF THE INVENTION 
     Exposing the mouth to light in the violet and/or blue region of the visible spectrum, between 400 nm and 500 nm, can be useful for a variety of purposes, including destroying bacteria and accelerating the whitening effects of a tooth bleaching agent. However, direct eye exposure should be limited in order to prevent eye damage. Thus, an aim of the present invention is to determine whether an oral care instrument is within the user&#39;s mouth or outside of the user&#39;s mouth. If the instrument is within the user&#39;s mouth, then a light emitting source such as an LED is turned on to emit light. However, if the instrument is outside the user&#39;s mouth, the LED shuts off to prevent light exposure to the eyes. 
     Aspects of the invention are illustrated in the remainder of this disclosure with reference to a manual or electric motorized toothbrush, although it is understood that the operation of any number of light-emitting oral care instruments, together with the associated advantageous features and/or beneficial effects described herein, could likewise be achieved. Other oral care instruments may include those used in dental curing lamps, oral flossing implements, and oral surgical instruments, etc. 
     In one embodiment, as shown in  FIG. 1 , a light-emitting oral care instrument  100  activates upon the completion of an electrical circuit between the brush handle in contact with the user&#39;s hand and contact of the brush head with the user&#39;s mouth. 
     In the embodiment of the light-emitting toothbrush  100  shown in  FIG. 2 , the brush head  118  and the handle  114  are injection molded of an electrically-conductive plastic with a non-conductive hydrophobic plastic spacer  112  located between the brush head  118  and the handle  114 . The nonconductive plastic spacer  112  electrically insulates the brush head  118  and the handle  114  from each other. The brush head  118  and handle  114  are electrically connected, via a lead  116 , to a control circuit  110  that can produce a low level electrical signal. While DC current is likely easiest with a battery source, the signal could be AC. The control circuit  110  can include a high sensitivity current sensor, such as Linear Technology LTC1440 Ultralow Power Single/Dual Comparator with Reference located on the control circuit  110 . That comparator is available from Linear Technology Corporation, 1630 McCarthy Blvd., Milpitas, Calif. 95035-74171(408) 432-1900, linear-tech.com. 
     Alternatively, the signal loop sensor circuit can be the one seen in  FIG. 6 , implemented with off the shelf components. An integrated circuit (IC 1 ) shown in  FIG. 6  can be a TPS2812 Dual High-Speed Mosfet Driver available from Texas Instruments, Inc. of Dallas, Tex. One of the sensor electrodes  116  is connected through a battery supplying from three to twelve volts, to pins  1 - 3  and  6  of IC 1 . The other sensor electrode  115  is connected across and adjustment bridge variable resistor R 2  and to pin  4  of IC 1  across resistor R 1  to pins  1 - 3 . Pin  4  is tied through Zener diode CR 1  to pins  1 - 3 . Pin  5  of IC 1  is tied as the output to the LED driver. When the signal loop through electrodes  115  and  116  is completed, the current is sensed in IC 1 , outputting a signal on pin  5  to activate the driver for the LED. 
     Prior art toothbrush sensors were implemented with older bipolar transistor technology and required high currents in the signal loop and higher voltages, producing undesirable tingling sensations for the user. The preferred signal loop sensor uses ultra-low-power CMOS technology to reduce the detection current threshold to a sub-microampere level at around one volt of potential difference, preventing any tingling sensation. Another advantage is an ultra-low battery consumption current. 
     A signal loop is formed through the body of the user by holding the brush handle  114  and placing the brush head  118  or wet bristles of the brush  113  in contact with the mouth. A voltage across the handle and the brush head results in a small signal current that flows through the loop and is detected by the current sensor. The current sensor outputs a signal through the control circuit  110  to the LED driver  111 , which delivers current to the LED  117  within the user&#39;s mouth, causing the LED  117  to illuminate the mouth of the user. The LED preferably emits short wave length light in the band between 400-500 nm, more preferably 400-450 nm, and more preferably yet of 400-420 nm. 
     In an alternate embodiment  130  shown in  FIG. 3 , conductive plastic is used in the part  133  of the brush connecting the bristles  132  to a sheet of conductive plastic  133 , instead of the entire brush head. Alternatively, but also possibly in combination, as shown in  FIG. 3 , the bristles  132  of the brush may also be conductive. When wet bristles  132  come in contact with the mouth of the user during normal brushing operations a circuit is formed via a sense electrode  135  connected to the control circuit  110 , which can be used to detect the completion of the electrical signal loop and signals the driver  111  to supply electricity to the LED  131 . The remainder of the brushhead  134 , is composed of non-conductive plastic. 
     Typically when brushing teeth, a user will grasp the handle  114  of toothbrush  100 , apply toothpaste to the bristles  113  and place the brush head  118  in the mouth and proceed to brush their teeth. While the toothbrush handle  114  is in contact with the user&#39;s hand and the brush head  118  is located in the mouth of the user, contact between the electrically conductive plastic of the brush head  118  and mouth of the user completes the signal loop, enabling a small DC or AC current (sensor current) to be initiated and detected by the control circuit  110 . The receipt of the sensor current is signaled to the LED driver which, in turn, controls illumination of the LED  117 , in this case, turns on the LED  117 . When contact between the brush head  118  and the mouth is broken, i.e., when the brush head  118  is withdrawn from the mouth, the signal loop is broken, the flow of sensor current stops, and the LED  117  is turned off. It is to be appreciated that the sensor current required to control the LED  117  will preferably be in the 10 and 100 nanoampere range and would only be detectable with a high sensitivity current meter associated with the control circuitry  110 . Due to the use of such a low electrical current, the user will be safe from harm and will not be exposed to danger. The galvanic current generated when a person touches a wet metal object is far greater than the current used in our application, so the current passing through the user&#39;s body is harmless and imperceptible. 
     The electronics, i.e. the LED driver and control circuitry  110  are configured to regulate or adjust the sensor current so that the brush head  118  must be in contact with the user&#39;s mouth to turn on the LED  117 . Merely contacting the dry skin from hand to hand will not turn the LED  117  on since the dry hand is not as conductive as the wet mouth. This reduces the possibility of turning the LED  117  on merely by handling the toothbrush  100  with bare hands and inadvertently activating the LED  117  while the brush head  118  is not in the user&#39;s mouth. 
     In a further embodiment of the toothbrush  150  as illustrated in  FIG. 4  which is similar to the prior embodiment, the brush head and handle  153  could be formed from a hydrophobic, nonconductive plastic instead of the electrically conductive plastic. In this embodiment, electrically conductive metal pads  151 ,  152  are located on the exterior surface of the toothbrush  150 . One or more metal pads  151  are located on the handle  112 ′ and one or more metal pads  152  are located on the brush head. The metal pads  151  are positioned on the toothbrush  150  for optimal contact with the skin of the hand and pad  152  is mounted for contact with the mouth or bristles of the toothbrush. When the wet tips of the brush bristles are in contact with incisor teeth or mouth and the pad  151  is in contact with the user&#39;s hand, an electrical circuit is formed through the body of the user. It is to be understood that the metal pads  152  of the brush head should be spaced apart from the metal pads  151  of the handle. 
     In use, while the metal pads  151  of the toothbrush handle are in contact with the user&#39;s hand and when the brush head  152  is located in the mouth of the user or wet bristles are in contact with any wet portion of the mouth or teeth, contact between the metal pads  152  of the brush head and mouth of the user completes a signal loop, enabling a small DC current (sensor current) to be initiated and detected by the control circuit  110 . The sensed current causes the control circuit to activate the LED driver to turn on the LED  126 . When contact between the brush head and the mouth is broken, i.e., when the brush head is withdrawn from the mouth, the signal loop is broken, the flow of sensor current stops, and the control circuit turns off 
     A further embodiment  160  is shown in  FIG. 5 . The handle has a portion  161  of conductive plastic, and the head has a portion  162  of conductive plastic. Portion  163  is non-conductive. The conductive plastic areas are connected internally to circuits as described in connection with  FIG. 2  and so the toothbrush of  FIG. 5  can be used in like manner to the toothbrush of  FIG. 2 . 
     Many electric toothbrushes employ a timer to alert the user of the end of a preset brushing time, for example, two minutes, as recommended by the American Dental Association. These timer circuits are commonly combined with vibration or noise to alert the end user to the completion of a recommended brushing period. The signal loop sensor disclosed herein can be combined with such a timing circuit in a manner that causes elapsed time to be recorded only when the sensor is activated (i.e. light is on). This would facilitate the assurance that the brush timer was actually measuring elapsed time in the mouth of the user and not simply elapsed time of the manual activation of the brush. The control circuit can also include a timer to turn off the LED at a preset time, such as two minutes, signaling to the user that tooth brushing has lasted two minutes. Other ways to signal the user of the completion of two minutes can be substituted. 
     A conventional make/break switch can be included in one of the conductors  115  or  116  or elsewhere in the electrical circuit, if desired. Thus, the signal loop is completed only if the user closes that switch AND inserts the toothbrush head into the mouth. This can provide a further safety and convenience feature. Alternatively, a make/break switch could be located elsewhere in the circuit from the battery, to the control circuit through the LED driver to LED. 
     Since the LED will be on only when the light from the LED is safely and effectively used, the life of a charge on the battery should be longer. 
     The battery can be rechargeable or replaceable, as will be apparent to those of ordinary skill in the art. 
     The brush head and/or neck can be replaceable, as long as the replacement part has the correct electrical contact and a conductor that can reliably connect to a mating conductor in the brush handle. The design can allow the sensor current to flow across the junction of the permanent part and the replaceable part through either two sheets of conducting plastic or a metal connector such as a pin connector. Examples are seen in  FIGS. 7 and 8 . 
     As seen in  FIGS. 7 and 8 , a brush handle  146  is provided having the necessary battery, charging electronics and LED, all self-contained and water-tightly encapsulated within the handle. The handle includes a stem  148  in which the LED  126  is mounted.  FIGS. 7 and 8  show two different embodiments, with the stem  148  in  FIG. 7  being longer than the stem  148  of  FIG. 8 . The replaceable brush head  157  has a hollow shaft  154  of an internal diameter slightly larger than the diameter of the stem  148 , so the stem  148  can be inserted into the hollow shaft  154 . The brush head has an array of bristles  156  and an opening  158  to allow the light from the LED  126  to pass toward the teeth as they are brushed by the bristles. Preferably the stem and hollow shaft have complementary, non-circular shapes so that the bristles do not rotate around the stem, but stay in a fixed orientation. When the bristles are spent, the brush head  157  can be removed from the stem  148  and replaced with a new brush head. Other appliances appropriate for a tooth whitening brush pattern, light curing of gum infections, tongue scraper, flosser, etc can be configured with similarly shaped hollow shafts so they can also be mounted onto the stem  148 . 
     In the embodiment shown in  FIG. 7  the plastic of the stem  148  and the head  157  are made electrically conductive, so that the signal loop can be completed as the user puts the head  157  (as installed on the stem  148 ) into his or her mouth and grasps the handle  146 . 
     In the embodiment shown in  FIG. 8  a conductor in the plastic of the stem  148  has an electrical contact  170 ; the head  157  has an electrical contact  172  within the shaft  154  positioned to mate with contact  170  when the head is mounted on the stem. The signal loop can be completed as the user puts the head  157  (as installed on the stem  148 ) into his or her mouth and grasps the handle  146 . 
     A further enhancement of the interlock control feature of this toothbrush can be realized using an AC control signal in place of the DC loop sensor current. A low-frequency 200 Hz to 10 kHz square or sinusoidal waveform AC signal with a peak to peak voltage of no greater than 1 V will be applied to the toothbrush handle. This AC signal will be conducted through the user&#39;s body in much the same way as a DC current, as described above. One way to implement this is through selective tone filtering in which a Controlled Oscillator in the handle puts off a square wave form in the low audio band of 1 to 2 kHz. A narrow band tone filter only allows one tone to come through in the brush head. This Selective Tone Filter in the brush head is looking for one certain tone. When it receives that tone, it turns on the LED. 
     In another embodiment of the present invention, as shown in  FIGS. 9 and 10 , the sensor used to detect whether the oral care instrument  180  is within the user&#39;s mouth is a capacitive sensor. The oral care instrument may be a toothbrush  180  with a battery  186 , a LED driver  200 , and an on/off switch  202 . An electronics ground  204  is located on the handle  182  of the brush. A conductive electrode sensing element  206  is installed preferably on the brush head  184 . A sensor system  210  measures the capacitance  216  between the sensing element  206  and the electronics ground  204 . A microprocessor/controller  212  determines whether the measured capacitance  216  is above a threshold value, which indicates that the toothbrush  180  is inside the user&#39;s mouth. If the measured capacitance exceeds the threshold value, then the LED driver  200  receives a signal and turns on the LED  214 . If the measured capacitance drops below the threshold value, then the LED driver turns off the LED  214 . 
     In yet another embodiment, the sensor of the present invention may be a capacitive displacement sensor. One or more tactile sensors are preferably placed on the handle portion of the oral care instrument, and measure capacitance of a conductive target such as the human body. As shown in  FIG. 11 , the oral care instrument is a toothbrush  220  with a battery  222  and tactile sensors  224 ,  224 ′ placed on opposing sides of the handle  226 . A switch  230  is off when in its first position. When a user grips the handle  226  at both tactile sensors  224  and  224 ′, preferably when the brush head  232  is inserted inside the user&#39;s mouth, the capacitive sensor  240  senses an increase in capacitance. As shown in  FIG. 12 , the capacitive sensor  240  causes switch  230  to move to its second position, signaling the LED drive  234  to turn on the LED  236 . An additional on/off switch  242  operated by the user may be installed onto the oral care instrument. 
     In another embodiment of the invention, the sensor is an inductance proximity sensor which uses a radio frequency loop to sense the proximity of conductors such as the human body. In one embodiment, as shown in  FIG. 13 , the dental hygiene implement is a toothbrush  245  having a brush head  246  and handle  247 . In this embodiment, the proximity sensor  248  is on the back of brush head  246 . The inductance proximity sensor  248  is comprised of an LC oscillating circuit with a signal evaluator. The LC oscillating circuit is comprised of a coil and a capacitor that emits a high-frequency electromagnetic alternating field at the sensing face of the sensor. When the brush head is inserted into the user&#39;s mouth, Eddy currents are generated that reduces the oscillations within the LC oscillating circuit. The signal evaluator detects this change in oscillation frequency, and the resulting reduction in oscillations sends a signal to the LED driver to turn on LED  249 . When the brush head is removed from the user&#39;s mouth, the oscillations from the LC oscillating circuit return to normal and the LED driver turns LED  249  off. Different types of inductor circuits may be used in other embodiments of the present invention. 
     In another embodiment of the invention, the sensor is a passive thermal infrared sensor. The passive thermal infrared sensor may be placed anywhere on an oral care instrument. In the embodiment shown in  FIGS. 14 and 15 , the oral care instrument is a toothbrush  250  with a handle  252  and brush head  254 . At least one passive thermal infrared sensor  256  is placed near the upper portion of the handle  252  toward the brush head  254 . As the user inserts the brush head into the mouth, the microprocessor  260  detects a change in infrared light as detected by the passive IR sensor  256 . The resulting increase in IR light causes the microprocessor  260  to turn on LED  262 . As the user removes the brush head out of the mouth, the resulting decrease in IR light sensed by the passive IR sensor  256  causes the microprocessor  260  to turn off LED  262 . 
     In another embodiment, the passive thermal infrared sensor is placed on the brush head as opposed to the handle. In the embodiment shown in  FIG. 16 , the passive IR sensor  256  is placed on the back of the bristle plate  264 . Like the embodiment in  FIGS. 14 and 15 , if the user places the brush head in his mouth, then the microprocessor  260  will turn on LED  262  due to the increase in IR light as sensed by passive IR sensor  256 . As the user removes the brush head out of the mouth, the resulting decrease in IR light sensed by the passive IR sensor  256  causes the microprocessor  260  to turn off LED  262 . The change in infrared light as the brush head enters the mouth is understood to be a result of the change in temperature. Thus, it is understood that the passive IR sensor disclosed herein may be substituted with other means for detecting changes in temperature. 
     In another embodiment of the invention, the sensor is an active thermal infrared. This sensor uses a photoelectric sensor that detects reflected IR light emitted and absorbed by the sensor itself. This could be used to detect proximity inside the mouth. The active thermal IR sensor  280  is typically comprised of a light source  282  that emits IR light and a photo diode  284  that detects changes in the sensing environment as the IR emitted from the light source is redirected. In one embodiment, an active thermal infrared sensor is placed on the brush head  272  of a toothbrush  270 . The active thermal infrared sensor may be placed either on the front face of the plate with the bristles  276  and LED  286 . Alternatively, as shown in the embodiment in  FIG. 17 , the active thermal infrared sensor  280  may be placed on the back of the bristle plate  274 . If the user places the brush head in his mouth, then the microprocessor  290  will turn on LED  286  due to the change in IR light as sensed by photo diode  284 . As the user removes the brush head out of the mouth, the IR light returns to a default value as detected by photo diode  284  which causes the microprocessor  290  to turn off LED  286 . 
     In another embodiment of the invention, the sensor is a passive optical sensor where the darkness caused by inserting the oral care instrument into the mouth triggers the short wavelength LED to turn on.  FIG. 18  shows an embodiment wherein the passive optical sensor is installed on a toothbrush  300 . In this embodiment, the passive optical sensor  306  is preferably on the brush head  302  of the toothbrush. In the embodiment shown in  FIG. 18 , the passive optical sensor  306  is placed on the back of the bristle plate  304 . If the user places the brush head in his mouth, then the microprocessor  310  will turn on LED  312  due to the decrease in light as sensed by passive optical sensor  306 . As the user removes the brush head out of the mouth, the resulting increase in light sensed by the passive optical sensor  306  causes the microprocessor  310  to turn off LED  312 . 
     In another embodiment of the invention, the sensor is a photocell  314  that detects the reflection of light from a second light source  316  on the oral care instrument. In one embodiment, a photocell is placed on the brush head  322  of a toothbrush  320 . The photocell  314  and accompanying light source  316  may be placed either on the front face of the plate with the bristles  324  and LED  330 . Alternatively, as shown in the embodiment in  FIG. 19 , the photocell  314  and secondary light source  316  may be placed on the back of the bristle plate  326 . If the user places the brush head in his mouth, then the light emitted by light source  316  will reflect and be detected by the photocell  314 . As the reflected light is detected by photocell  314 , the microprocessor  332  will turn on LED  330 . As the user removes the brush head out of the mouth, the photocell  314  will no longer detect the reflected light which causes the microprocessor  332  to turn off LED  330 . 
     In another embodiment of the invention, the sensor is an ultrasonic sensor that emits sound waves and uses echo location to detect whether the oral care instrument is within the confines of the mouth. In one embodiment, an ultrasonic sensor  334  is placed on the brush head  342  of a toothbrush  340 . The ultrasonic sensor  334  may be placed either on the front face of the plate with the bristles  344  and LED  336 . Alternatively, as shown in the embodiment in  FIG. 20 , the ultrasonic sensor  334  may be placed on the back of the bristle plate  346 . If the user places the brush head  342  in his mouth, then the duration that it takes for the sound emitted by ultrasonic sensor  334  to be received back will decrease. The decrease in durational response will cause the microprocessor  348  will turn on LED  336 . As the user removes the brush head out of the mouth, the duration that it takes for the sound emitted by ultrasonic sensor  334  to be received back will increase causing the microprocessor  348  to turn off LED  336 . 
     In another embodiment of the invention, the sensor is a pressure sensor under the brush head that detects movement and pressure of the brush head being pressed against the teeth.  FIG. 21  shows the pressure sensing system  410  of the present invention  410  and a toothbrush body referred to generally at  411 . Generally, toothbrush body  411  will be a manual toothbrush. The toothbrush body  411  includes a handle portion  412 , which is configured to be grasped by the hand of the user. In the embodiment shown, handle  412  is approximately 3.75 inches long, while the entire toothbrush body  411  is approximately 7.5 inches long. In the embodiment shown, toothbrush body  411  is made of a filled nylon, but could be other materials as well, including polypropylene and other plastics. Handle portion  412  is in the embodiment shown approximately 0.5 inches wide and approximately ⅜-inch high. The handle portion  412  is closed about all four sides and its two ends. 
     At the distal end of handle  412  is a portion  414  which in the embodiment shown is adapted to receive a hinged member portion  416  of the pressure sensing assembly  410 . The remaining portion of the toothbrush body is referred to at  418 , and is generally U-shaped in cross-section, open at the top. The remaining portion  418  comprises a base  420 , two upstanding sides  421 ,  423  and a forward end wall  426 . This arrangement provides rigidity for the toothbrush body. From the receiving portion  414 , toothbrush body  411  begins to taper inwardly at both sides over a short distance until the width of the toothbrush body is approximately 0.25 inches. Over this distance, the top edges of the sides  421 ,  423  toothbrush body are flat for a small distance and then angle downwardly until point  425  on the toothbrush body. Over this distance, base  420  angles slightly downwardly. The drawings show this structural arrangement, in particular  FIG. 22 . 
     From point  425  to forward end wall  426 , the toothbrush body is flat and is adapted to receive a conventional toothbrush brushhead  432 . The distance from the lower surface  429  of the flat section  431  to the upper surface  433  of handle portion  412  is approximately 0.75 inches, while the height of the toothbrush body in the flat section  431  is approximately 0.28 inches. 
     The sides  421  and  423  and the base  420  over the length of the toothbrush body from receiving portion  414  to the forward end wall  426  have a plurality of openings  427 - 427  therethrough. In the embodiment shown, these openings are circular, approximately 0.125 inches in diameter, spaced approximately 0.25-0.35 inches apart. In base  420  of flat section  431  is an elongated slot  437 , which is discussed in more detail below. The openings could have other shapes and spacing, however. The use of openings, with an entirely open top, has several advantages. It allows fluid to easily escape the brush, without trapping oral tissue in the openings. This arrangement further permits the use of the hinged arm pressure sensing assembly  411  without the use of seals between the arm and the body. The openings further are large enough to not only allow rinsing water to move freely in and through the toothbrush body during cleaning, but also allows the unit to dry out thoroughly between uses. 
     The pressure sensor assembly  410  is shown in relation to the toothbrush body  411  in  FIG. 21 , and in an exploded view by itself in  FIG. 24 . Two of the component parts thereof are furthermore shown in more detail in  FIGS. 25 and 26 . The pressure sensor assembly/system includes a hinged member  416 , an elongated aim  430 , a brushhead  432  which includes a striking element  434  extending away from a rear surface  433  of the brushhead, and a deformable dome element  436 , conventionally referred to as a “snappy” member, since it makes a snap-like sound when deformed past a threshold point. Most round snap domes cannot be moved beyond a “flat” position without turning inside out. The rectangular snap dome shown and described herein can be moved to a “beyond flat” position, thereby providing a longer collapsing distance and greater tactile feel. 
     Hinged member  416  is attached to toothbrush body  411  at receiving portion  414 , by means of a screw  435  or the like. It could also be a quick disconnect arrangement to allow convenient replacement of the brushhead. Hinged member  416  in the embodiment shown is made from polypropylene or acetal resin (Delrin) or similar plastic. The hinged member  416  ( FIG. 25 ) includes a rear portion  438  which is approximately square in the embodiment shown and approximately ⅛-inch thick. Forward of base portion  438  is a narrow hinge portion  442  which in the embodiment shown is approximately 0.015 inches thick, which is sufficiently thin to permit a hinge-like action, and approximately one-half inch wide. 
     Forward of hinge portion  442  is a receiving portion  444 , which is approximately 0.25 inches thick. The receiving portion  444  is approximately 0.3-0.5 inches wide at hinge portion  442  and tapers to approximately 0.3 inches at a forward end  45  thereof. The longitudinal edges of the receiving portion  444  are in the embodiment shown rounded. The receiving portion  444  is configured to fit within the toothbrush body, near a rear end of the remaining open portion  418  thereof. An octagonal (in cross-section) central opening  448  extends longitudinally inward of receiving portion  444  from forward end  445  and receives one end of an arm  430 . 
     Elongated arm  330  in the embodiment shown ( FIG. 24 ) includes proximal and distal portions  450  and  452 , connected by an intermediate rod-like portion  454 . In the embodiment shown, arm  430  is made from stainless steel, but other materials could be used as well, such as various plastic materials. Proximal portion  450  is approximately 0.4 inches long and is configured to snugly fit into opening  448  in receiving portion  444  of the hinged member, while distal portion  452  upon which brushhead  432  is mounted is approximately 0.5 inches long. The intermediate portion  454  is approximately 1.328 inches long in the embodiment shown. 
     The arm  430  has a total length of 2.245 inches, because the intermediate portion is arranged such that it angles downwardly between the proximal and distal portions. The distance between the centerlines of the proximal and distal portions is approximately 0.35 inches. The angle of the intermediate portion of the embodiment shown is approximately within the range of 5°-20°, preferably 15°. The intermediate portion  454  is configured to closely follow the portions of the toothbrush body in which it fits. 
     Although the hinged member  416  and arm  430  are shown as two pieces in the present embodiment, they could be made, i.e. molded, as a single unit. 
     Mounted on distal end portion  452  of arm  430  is a brushhead  432 . Brushhead  432  includes a base portion  458  and a bristle portion  460  which is mounted in base  458  and extends upwardly therefrom in conventional fashion. The bristle portion can take various configurations, including conventional arrangements or special configurations to accomplish particular brushing effects. In the arrangement shown, the tops of the bristles are in approximately the same plane as the hinge portion  442  of the hinged member to prevent in/out brushing forces at the bristle tips from causing turning moments around the hinge member and distorting the accuracy of the force sensing system. The combination of the hinged member  416 , arm  430  and brushhead  432  can be replaceable as a unit if desired. 
     Mounted in the base of the brushhead, approximately central thereof in the embodiment shown, is a set-screw which is the striking element  434 . The set-screw extends through the base portion  458  and below the lower surface  433  of the brushhead, approximately 0.08 inches in the embodiment shown. The setscrew in the embodiment shown is approximately 3/32 inches in diameter and ⅛ inch long and is made from stainless steel. Alternatively a bump could be molded into the toothbrush base portion  458 . Further, the hinged element, the arm and the brushhead could be a single piece. The brushhead  432  could also be made removable from the arm portion. 
     When hinged member  416  is secured to the receiving portion  414  of the toothbrush body, application of force against the brushhead  432  toward the toothbrush body will result in the brushhead moving about hinged portion  442  of hinged member  416 . 
     A thin dome element  436  is secured to interior surface of flat section  431  of the toothbrush body, directly beneath base portion  458  of the brushhead. Dome element  436  in the embodiment shown is a conventional snap dome member having an obround configuration, similar generally to a child&#39;s “cricket” toy. The obround snap dome element  436  is capable of moving “beyond flat” when it suddenly collapses due to pressure against it exceeding a particular value by action of the striking element  434 . This is shown by the dotted lines in  FIG. 27 . The “beyond flat” capability, as discussed above, is important to provide a sufficient collapsing distance that the user can recognize the collapse of the element. The snap dome is mounted on a ridge within the brushhead receiving portion to permit the center portion of the snap dome element to go beyond flat. 
     In the embodiment shown, the dome element collapses approximately 1/16 inch, and beyond flat by approximately 0.045 inches. The force necessary to collapse the dome is preferably under 200 grams, since selected force values above this range are generally considered as a threshold for excessive pressure. Snap dome elements are available with various collapse forces. 
     By default, a switch  490  is in an “off” state. In one embodiment, when the snap dome  436  collapses it mechanically triggers the switch  490  to an “on” state. Turning the switch onto its “on” state closes the circuit containing battery  496  and causes the LED driver  492  to turn on the LED  494 . While the snap dome  436  remains collapsed due to the pressure applied when a user brushes his teeth, the LED  494  remains on. Other types of switches may be used, including a magnetic sensor where the striking element  434  causes a first magnetic plate to come into contact with a second magnetic plate. 
     The snap dome is secured to the toothbrush body beneath the brushhead by means of an adhesive or tape or a trapping element. Slot  437  ( FIG. 23 ) in the base portion of the toothbrush body extends beneath the snap dome, and prevents the possible damping of the snap dome action due to fluid being trapped beneath the dome when it collapses. The slot allows the ready escape of the fluid from the toothbrush body and allows for complete rinsing and drying of the toothbrush between uses. 
     In the embodiment shown, the snap dome element is secured to the toothbrush body beneath the brushhead and the striking element extends from the brushhead. In another embodiment, the snap dome element could be positioned on a lower surface of the brushhead and the striking element could be positioned on the toothbrush body beneath the brushhead. 
     Other pressure sensors may be used with the present invention. Toothbrush  510  for sensing pressure applied during brushing and for indicating when the pressure exceeds a predetermined value is shown in partial cross-section in  FIG. 29 . Toothbrush  510  includes a piezoelectric film  524  disposed within brush head  512  and an indicator circuit  530 , including LED  534 , disposed within handle  508 . 
     Referring to  FIG. 30 , an enlarged cross-sectional view of brush head  512  is shown. Tufts  518  of bristles  506  extend through openings  516  in member  514  of head  512 . Each tuft has a crest end  520  extending outward from opening  516  and a root end  522  disposed beneath opening  516  in member  514 . The length of bristles extending between crest end  520  and root end  522  of tuft  518  has a cross-sectional dimension that is less than the cross-sectional dimension of opening  516  so that tuft  518  can move axially through opening  516  and retract downwardly toward piezoelectric film  524 . The cross-sectional dimension of root end  522  is greater than the cross-sectional dimension of opening  516 , which inhibits root end  522  from passing through opening  516  and retains tuft  518  within head  512 . 
     Piezoelectric film  524  is disposed within head  512  beneath root ends  522  of tufts  518  so that film  524  will experience strain when pressure is applied to tufts  518 . When pressure is applied to tufts  518 , root ends  522  are forced into contact with piezoelectric film  524 . The pressure exerted by root ends  522  on film  524  causes a change in the strain of film  524 , which causes film  524  to generate voltage. As is well known in the piezoelectric art, piezoelectric films carry a permanent dipole moment that, when the film is at rest, is cancelled out by charges in the atmosphere. Deforming the film, i.e., applying a force to the film that generates a strain, changes the orientation of the polymer backbone of the film, which causes the strength of the dipole to change and generates an electrical voltage. If the piezoelectric film comes to rest in its deformed position, i.e., the pressure applied is constant and no new strain is generated, the new dipole will again be cancelled out by atmospheric charges and the voltage will cease. As long as the orientation of the polymer is being changed by application of a varying degree of pressure to the film, voltage will be generated. 
     Referring to  FIGS. 28 and 29 , indicator circuit  530 , located within the handle  508  of toothbrush  510 , senses the voltage generated in piezoelectric film  524  and determines whether the voltage generated is greater than a predetermined value, e.g., a value that represents a level of brushing pressure. If the voltage is greater than the predetermined value, then indicator circuit  540  turns LED  534  on. If the voltage drops below the predetermined value, then the indicator circuit  540  turns LED  534  off Any circuit capable of receiving a signal from the piezoelectric film, determining if the signal is greater than a predetermined value, and subsequently turning on the LED  534  can be used as the indicator circuit. Such circuits can be readily constructed by those skilled in the art. 
     One example of a suitable indicator circuit is shown in  FIG. 28 . The voltage generated in piezoelectric film is transferred via lead  536  to an indicator circuit  530  that includes comparator  540  and a single LED  534 . LED  534  turns on when the output voltage from the piezoelectric film (applied to variable input  541  of comparator  540 ) exceeds the voltage drop across resistor  538  as applied to reference input  537  of comparator  540 . 
     The LED of the indicator circuit is preferably located on the toothbrush in such a way that it is not seen by the user when brushing. Thus, the LED is preferably located at the brush head  512 . 
     Referring to  FIG. 31 , an alternate embodiment of toothbrush head  542  is shown in which a resiliently deformable membrane material  556  capable of resilient spot deformation, i.e, a membrane that has highly localized zones which can be resiliently displaced relative to the rest of the membrane without affecting the zones immediately adjacent to the displaced zone, is disposed beneath piezoelectric film  554 . Such a membrane material is described, e.g., in U.S. Pat. No. 4,633,542 (Taravel), the disclosure of which is hereby incorporated herein by reference. 
     When the toothbrush is at rest, i.e., when no pressure is applied to tuft  548  urging it against piezoelectric film  554 , membrane  556  is taut and resiliently biases root end  552  of tuft  548  against member  544 . When pressure is applied to tuft  548 , tuft  548  retracts into contact with piezoelectric film  554  by sliding through opening  546  and causing resilient spot deformation of membrane  556  at the point where tuft  548  is urged against piezoelectric film  554 , without displacing the contact zones between the root ends of the respective immediately adjacent tufts and the membrane. Once the strain is released from the membrane, the membrane material regains its original structure. When the toothbrush is removed from the oral surface, i.e., the pressure is removed, tufts  548  return to their initial position with their respective root ends  552  abutting against member  544  by virtue of resilient membrane  556  returning to its initial position. Membrane  556  is preferably under tension since tension facilitates this spot deformation. 
     Membrane  556  is preferably formed from an isotropic elastomeric material selected for its ability to behave anisotropically in that it gives the membrane the property of being able to exhibit resilient deformation in localized spots. The choice of material for the membrane and the appropriate thickness are readily determined by the person skilled in the art as a function of the mechanical characteristics and, in particular, the elasticity required for the membrane. Suitable membrane materials include, e.g, natural or synthetic latex type elastomers (e.g., polychloroprenes), natural rubber, and silicones. 
     The thickness of the membrane in the relaxed state will generally vary in the range of 0.10 mm to less than 1 mm. Such a thickness will enable localized or spot resilient deformation with an amplitude of 0.5 mm to 5 mm for a force of about 1 Newton (N) to 7.5 N (i.e., about 150 grams-force to about 750 gf) applied in a distributed manner over the set of tufts of bristles. 
     Alternatively, membrane  576  may be disposed above piezoelectric film  584  between root ends  582  of tufts  578  and piezoelectric film  584 , as shown in  FIG. 32 . 
     Referring to  FIG. 33 , in another embodiment, membrane  666  extends across a cavity  638  defined by member  644  in head  612  so as to seal cavity  638 . The toothbrush also includes piezoelectric film  664 . During assembly of the toothbrush membrane  666  is fixed, while taut, to head  612  at the periphery of cavity  638 . Cavity  638  and membrane  666  enclose a cushion of air, the presence of which facilitates vertical spot deformation of membrane  666  in response to axial retraction of a tuft of bristles. Member  614 , which is made of rigid material, e.g., a plastic material, like the remainder of the brush head, is fixed to the brush head and together therewith clamps the membrane in continuous manner all around the periphery of cavity  638 . Member  614  may be a separate piece forming a rigid extension of the head or may be integrally molded with the head. 
     A continuous rim  606  projects substantially perpendicularly from an area near the perimeter of member  614 . A continuous peripheral zone  608  of membrane  666  is clamped between the side of head  612  and rim  606  thereby fixing membrane  666  to the head and ensuring that membrane  666 , member  614  and head  612  are fixed relative to one another. In addition or alternatively, membrane  666  may be affixed to rim  620  around the edge of cavity  638 , e.g., by glue or a heat weld, as shown in  FIG. 34 . 
     Any method may be used to fix the periphery of the membrane to member  614  or rim  620 , provided the portion of the membrane that contacts the root ends  622  of tufts  618  remains resiliently deformable. Tufts  622  retract into and are biased by membrane  666  in the same manner as discussed above with reference to  FIGS. 31 and 32 . 
     Other embodiments are within the claims and include, for example, an embodiment in which the piezoelectric film extends across a cavity, e.g., the cavity shown in  FIG. 33 , in the absence of a membrane. In another embodiment, the indicator circuit is located external to the toothbrush. 
     In another embodiment of the invention, the sensor is a pressure sensor in the neck that detects torque and tension in the neck of the brush due to brushing action. The pressure sensor could be Piezoelectric, Capacitive, Potentiometric, Optical or Electromagnetic. Such a pressure sensor is disclosed in US 20030205492 to Ferber et al, and is hereby incorporated by reference. 
       FIG. 35  shows a simplified descriptive view of a light emitting toothbrush  710  in accordance with the present invention. The toothbrush  710  includes a toothbrush body  712  that has a handle portion  713  and a brush head portion  714 . Within the brush head portion  714  is light source  716 . The light sources  716  are powered by a battery  718 , and controlled by electrical circuitry, or a control circuit  720 . Although only one battery  718  is illustrated in  FIG. 35 , it is contemplated that more than one battery may also be used. The toothbrush body  712  includes a flexible portion  722  that facilitates some movement of the brush head portion  714  when a force is applied to the brush head portion  714 , for example, when bristles  724  are applied to an operator&#39;s teeth. A switch  726 , which is configured to activate the light source  716 , is actuated when a first predetermined force is applied to the brush head portion  714 . 
     The interaction of the switch  726  and the movement of the brush head portion  714  exemplifies one of the benefits of the present invention. It has been shown that effective brushing occurs when a force of 2N-3N is applied in a direction normal to the teeth. When the brushing force is significantly less than 2N, cleaning of the teeth may not be adequate. When a brushing force of significantly more than 3N is applied to the teeth, unacceptably high levels of enamel abrading may occur. 
     For example, referring to the toothbrush  10  illustrated in  FIG. 35 , the brush head portion  714  moves slightly as the bristles  724  contact an operator&#39;s teeth. As more force is applied, the movement of the brush head portion  714  will increase. It is contemplated that as the force reaches the level of a predetermined force, for example, a force of approximately 2N, the movement of the brush head portion  714  will actuate the switch  726  and the light source  716  will be activated. To ensure that the brushing force meets the minimal level desired, the switch  726  may be configured with a spring actuator having a known stiffness. Thus, the switch  726  could be configured such that it is actuated only when a force of at least 2N is applied to the brush head portion  714 . Of course, the predetermined force, or minimum required brushing force, can be changed by configuring the switch  726  with a spring actuator having a different stiffness. 
     As an alternative to configuring the switch  726  with a spring actuator to control activation of the light source  716 , a load cell, or force sensor  728  (illustrated in  FIG. 38  and discussed in more detail below), can be included in the toothbrush  710  to ensure that the light source  716  is activated upon application of the predetermined force. 
       FIGS. 36-37  illustrate one possible configuration for the switch  726 . As seen in  FIG. 36 , the switch  726  comprises first and second contact plates  729 ,  731 , and a magnet  733  having a limiting device  735 . In  FIG. 36 , the switch  726  is in a first position, configured to prevent activation of the light sources  716 . With no force being applied to the brush head portion  714 , the magnet  733  is at a distance (d) from a magnetic contact  737  disposed on the first contact plate  729 . The magnetic contact  37  is separated from the second contact plate  731 , such that the two contact plates  729 ,  731  are not electrically connected. 
     As a force is applied to the brush head portion  714 , the magnet  733  begins to move toward the two contact plates  729 ,  731 , until the attraction from the magnet  733  causes the magnetic contact  737  to move toward the magnet  733 . The magnetic contact  737  then makes contact with the second contact plate  731 , thereby placing the switch  726  in a second position and activating the light sources  716  (see  FIG. 37 ). The switch  26  can be configured so that the magnetic contact  737  is impelled toward the second contact plate  731 , only after the first predetermined force has been applied to the brush head portion  714 . 
     By adjusting various parameters such as the distance between the contact plates  729 ,  731 , the strength of the magnet, and size of the limiting device  735 , the predetermined force can be adjusted. Thus, the switch  726  can be configured to require different amounts of force to activate or stop the light sources  716 . 
     The toothbrush body  712  has a generally cylindrical shape, though it could be made in almost any shape desired. For example, the translucent portion  742  could be beveled or faceted to create a prismatic affect as the emitted light passes through it. The minimal space required by the light source  716  and the control circuit  720 , allows for design flexibility. Indeed, the present invention contemplates the use of more traditional toothbrush bodies, for example, ones having rectangular cross sections. In addition, the light source need not be an LED, but rather, may be a light bulb. As explained below in conjunction with other embodiments of the invention, the light source is not limited to only one particular kind—e.g., LED. 
     In addition to varying the arrangement of the light sources, the pattern of light generated by any set of light sources may be varied, depending on the configuration of the control circuit. For example, the toothbrush  710  may be configured with a control circuit that allows the LED to varying in intensity of the light emitted. 
       FIG. 38  shows a simple wiring schematic of a circuit  750  that can be used in the embodiment illustrated in  FIG. 35 . The circuit  750  includes the battery  718 , the switch  726 , the LED  730  and the control circuit  720 . The control circuit  720 , includes resistors  752  and an electronic control module (ECM)  758 . Any suitable ECM may be used with a control circuit such as the control circuit  720 , though a Philips 51 LPC is one type of ECM known to work in this application. As discussed above, activation of the light sources in a light emitting toothbrush, such as the toothbrush  710 , may be controlled by a switch that includes a spring having a known stiffness. Alternatively, a load cell, such as the force sensor  728  may be used to sense the force being exerted on the brush head portion  714 , and provide a brush force input signal to the ECM  758 . This allows the ECM  758  to appropriately control the LED  730  based on the brush force input signal. It is readily understood by those skilled in the art that the circuit  50  shown in  FIG. 8 , represents but one of many circuits that can be used with the present invention. For example, a separate power supply, along with capacitive and additional resistive elements, can be added to the circuit to provide greater control of the power being delivered to the LED. 
     The embodiments described thus far have each included a switch that is actuated by a force applied to a brush head portion of a toothbrush body, such as the brush head portion  714  shown in  FIG. 35 . This configuration may be particularly useful when an object of the toothbrush is to train an operator to apply a proper amount of force during brushing. There are however, other ways in which a switch, such as the switch  726 , may be actuated. For example,  FIG. 39  shows a toothbrush  764  comprising a toothbrush body  766  that includes a handle portion  768  and a brush head portion  770  including bristles  772 . The handle portion  768  includes a compressible portion  774  that is configured to be compressed when an operator uses the toothbrush  764 . The compressible portion  774  comprises a non-rigid material, such as an elastomer. Alternatively,  FIG. 40  shows a toothbrush  776  comprising a toothbrush body  778  including a handle portion  780  and a brush head portion  782 , including bristles  784 . The handle portion  780  includes a compressible portion  786  that comprises a rigid portion  788  surrounded by a non-rigid portion  790 . This configuration may provide a compressible portion having greater stiffness than the compressible portion  774  shown in  FIG. 39 . 
     The embodiments shown in  FIGS. 39 and 40  have compressible portions  774 ,  786  disposed on the same side of the toothbrush body as the bristles  772 ,  784 . Of course, a compressible portion of a toothbrush handle portion may be located virtually anywhere on a toothbrush body, for example, on a side of the toothbrush body opposite the bristles.  FIG. 41  shows a toothbrush  792  comprising a toothbrush body  794  including a handle portion  796  and a brush head portion  798 , having bristles  800 . The handle portion  796  includes a compressible portion  802  that is disposed on a side of the toothbrush  792  opposite the bristles  800 . A switch  804  is disposed in relation to the compressible portion  802  such that compressing the compressible portion  802  actuates the switch  804 . Actuating the switch  804  activates light source  806  which may be an LED as described above, or may be a light bulb. The switch  804  is shown in detail in  FIGS. 42 and 43 . The switch  804  includes a magnet  808 , a magnetic plate  810 , and a nonmagnetic plate  812 . When a force (F) is exerted on the compressible portion  102 , the force causes the magnet  808  to move in close proximity to the magnetic and nonmagnetic plates  810 ,  812 . When the distance between the magnet  808  and the magnetic plate  810  drops below a fixed distance  814 , the two plates  810 ,  812  contact each other (see  FIG. 43 ), thereby activating the light sources  806 . 
     Other types of switches may be used with a toothbrush having a compressible portion, two of which are shown in  FIGS. 44 and 45 .  FIG. 44  shows a toothbrush  816  comprising a toothbrush body  818  including a handle portion  820  and a brush head portion  822 , including bristles  824 . The handle portion  818  includes a compressible portion  826 . A switch  828  is disposed in relation to the compressible portion  826  such that compressing the compressible portion  826  actuates the switch  828 , which activates light sources  830 . The switch  828  comprises a magnet  832  and a Hall effect sensor  834 . The magnet  832  is located beneath the compressible portion  826  such that application of a force (F) to the compressible portion  826  causes the distance between the magnet  832  and the Hall effect sensor  834  to decrease. When this distance is small enough, current flows through the Hall effect sensor  834  and the light sources  830  are activated. 
     Another type of switch that can be used in conjunction with a compressible portion on a toothbrush handle is shown in  FIG. 45 . A toothbrush  836  comprises a toothbrush body  838  including a handle portion  840  and a brush head portion  842 , including bristles  844 . A switch  846  comprises first and second contact plates  848 ,  850  disposed in relation to a compressible portion  852  of the handle portion  838  such that compressing the compressible portion  852  causes the two contact plates  848 ,  850  to move closer to each other until they contact, thereby actuating the switch  846  and activating light sources  854 . 
       FIG. 46  illustrates another way by which the light source in a toothbrush may be activated. A toothbrush  854  comprises a toothbrush body  856  including a handle portion  858  and a brush head portion  860 , including bristles  862 . The toothbrush  854  includes a sensing device  864  which comprises a capacitive sensor  866  attached to a pair of tactile sensors  868 ,  870  partially disposed on an external portion  871  of the toothbrush body  856 . The presence of an operator&#39;s hand on the tactile sensors  868 ,  870  closes a switch  874  (see  FIG. 47 ) that allows current to flow from a battery  876  to a control circuit  878  for controlling light source  880 . The control circuit  878  may be configured similarly to the control circuit  750  shown in  FIG. 38 , or may have any configuration suitable to its use in the circuit  872 . Thus, the mere presence of an operator&#39;s hand on the tactile sensors  868 ,  870  causes the light source  880  to emit light according to the programming and configuration of the control circuit  878 . 
     The embodiments thus far described include only manual—i.e., not motorized—toothbrushes. It is important to note that the present invention can be easily utilized with motorized electric toothbrushes as well.  FIG. 48  shows a simplified descriptive view of a motorized electric toothbrush  882  in accordance with the present invention. The toothbrush  882  comprises a toothbrush body  884  including a handle portion  186  and a brush head portion  888 . The brush head portion  888  includes a bristle head  890 . A flexible portion  892  is provided that facilitates some movement of the brush head portion  888  when a force is applied to it. A first switch  894  is disposed on the handle portion  886 , and is configured to connect a motor  896  and light source  898  to an electric source, such as battery  680 . When engaged, the motor  896  drives the bristle head  890 . The first switch  892  has a first position for preventing activation of the light source  898  and the motor  896 , and a second position for facilitating automatic activation of the light source  898  and the motor  896 . 
     A second switch  682  is disposed within the toothbrush body  884 . The second switch  682  has a first position for preventing activation of the light sources  898  and the motor  896 , and a second position for activating the light sources  898  and the motor  896  when the first switch is in the second position. The second switch  682  is placed in the second position when a predetermined force is applied to the brush head portion  888 . The force may be applied during use, when the bristle head  890  is brought into contact with a user&#39;s teeth. 
     As in the previous embodiments, the predetermined force may be set by using a spring having a known stiffness. Specifically, such a spring may be used to resist a force applied to the brush head portion  888 . In this way, the spring force will need to be at least partially overcome—i.e., a force equal to the predetermined force will need to be applied to the brush head portion  888 —in order to place the second switch  682  in the second position. 
     As an alternative to using a spring to control the predetermined force, a separate load cell, or force sensor  684  may be utilized (see  FIG. 49 ).  FIG. 49  shows a simple wiring schematic of a circuit  686  that can be used with a motorized toothbrush  882 . As shown in  FIG. 19 , the light source  898  comprises LED  688  and is controlled by electrical circuitry, or a control circuit  694 . The control circuit  694  includes resistor  698  and an electronic control module (ECM)  699 . 
     Another useable pressure sensor is disclosed in US2003/0135940 to Lev et al.  FIG. 50  shows a simplified descriptive side view of a motorized electric toothbrush  1010  in accordance with another embodiment of the present invention. A first switch  1012 , located in a handle portion  1013 , has a first or “off” position, and a second or “automatic” position, which places the toothbrush  1010  in an automatic mode. While the toothbrush  1010  is in the automatic mode, a LED  1015  is engaged only when a force (F) is exerted on a removable head portion  1016 . This occurs when a bristle head  1018  sufficiently contacts an operator&#39;s teeth. As used here and throughout, the term “sufficiently contacts” implies a contact that is sufficient to cause a slight movement of at least a part of the removable head portion  1016  in the direction of the force. The force exerted by an operator (a user of the toothbrush) during normal brushing typically constitutes a sufficient contact. Thus, as the user begins brushing, a second switch  1020  automatically moves from a first position to a second position, an electric circuit is completed, and current flows from a battery  1022  to the LED driver  1024  that regulates and transmits power to LED  1015 . 
       FIG. 51  shows a simple wiring schematic  1026  of a circuit for the toothbrush  1010  shown in  FIG. 50 . The LED driver  1024  is electrically connected between an electric source (the battery  1022 ) and the first switch  1012 . When the first switch  1012  is in the first, or “off” position, the circuit  1028  is open and there is no voltage across LED driver  1024 . When the first switch  1012  is in the second, or “automatic” position, control of the current flow to LED driver  1024  is transferred to the second switch  1020 . While the toothbrush  1010  is in the automatic mode, the LED driver  1024  is only engaged when a force (such as (F) shown in  FIG. 1 ) is applied to the bristle head  1018 . An exception to this occurs when the toothbrush is programmed with a “delayed off” feature, discussed in more detail below. With the delayed off feature, the LED  1015  continues to operate for a short time after the force is removed from the bristle head  1018 . 
     A number of alternative electrical circuits can be used with the present invention, two of which are shown in  FIGS. 52 and 53 . In  FIG. 52 , a wiring schematic  1026 ′ shows a LED driver  1024 ′ wired between a battery  1022 ′ and a first switch  1012 ′. The first switch  1012 ′ is a three position switch, having a first position in which circuits  1028 ′,  1030  are both open. While the first switch  1012 ′ is in the first position, no current can flow to the LED driver  1024 ′, and the LED  1015  remains off. The first switch  1012 ′ has a second position in which control of the current flow to LED driver  1024 ′ is transferred to a second switch  1020 ′. When the second switch  1020 ′ is in a first position, the circuit  1028 ′ is open, and LED  1015  remains off. When a force is applied to a bristle head of the toothbrush, the second switch  1020 ′ automatically moves to a second position such that the circuit  1028 ′ is closed and the LED driver  1024 ′ is engaged. The first switch  1012 ′ also has a third position, in which the circuit  1030  is closed, and the toothbrush operates continuously. 
     Yet another wiring configuration is illustrated in the wiring schematic  1026 ” shown in  FIG. 53 . In this configuration, there is only one switch  1020 ″ to control the flow of current from a battery  1022 ″ to a LED driver  1024 ″. When the switch  1020 ″ is in a first position, circuit  1028 ″ is open, thereby preventing the LED  1015  from turning on. When the switch  1020 ″ is in a second position, the circuit  1028 ″ is closed and current flows to LED driver  1024 ″. As in the previous wiring configurations, the switch  1020 ″ automatically moves from the first position to the second position when a force is applied to a bristle head of the toothbrush. As described above, each of the switches  1020 ,  1020 ′, and  1020 ″ “automatically” moves from a first position to a second position when the toothbrush is used by an operator. This implies that the user need not manually place the switch in the second position. Rather, the contact between the user&#39;s teeth and the bristle head automatically places the switch  1020 ,  1020 ′, or  1020 ″ in the second position. 
     Toothbrushes in accordance with these embodiments can be configured such that applying a force to the handle portion, rather than the bristle head, effects operation of the LED  1015  when it is in the automatic mode. For example, any of the switches  1020 ,  1020 ′,  1020 ″ can be positioned within the handle portion  1013  of the toothbrush  1010 , shown in  FIG. 1 . In such a case, the switch may be automatically moved from the first position to the second position not by a force applied to the bristle head  1018 , but rather, by a force applied to some part of the handle portion  1013 . Embodiments of the invention utilizing this feature are described in more detail below. 
     Each of the wiring configurations shown in  FIGS. 51-53  allow a toothbrush to be used in an automatic mode. That is, the toothbrush motor is engaged whenever a force is applied to that portion of the toothbrush that contains the switch  1020 ,  1020 ′, or  1020 ″. This facilitates ease of use, eliminating the need to operate a typical button switch after the bristle head is placed in the user&#39;s mouth. Another advantage of such a configuration is that a consumer can engage the toothbrush motor while the toothbrush is still packaged—i.e., prior to sale. In this way, the consumer can evaluate the operation of the toothbrush before purchase. Some prior art toothbrushes have a multi-function switch configured such that the consumer operates the toothbrush in the package using one activation mode, then operates the toothbrush during normal use in another activation mode. Such is not the case with the present invention, which affords the consumer the opportunity to activate the toothbrush in the package substantially as it will be activated during normal use. In today&#39;s consumer savvy environment, this feature provides another advantage over prior art toothbrushes. 
       FIG. 52  shows an exploded view of the electric toothbrush  1010  in accordance with another embodiment. The toothbrush  1010  includes the handle portion  1013  and the removable head portion  1016 , which is shown having first and second housing elements  1032 ,  1034 . The handle portion  1013  will usually be made from a polymeric material, and may be opaque, clear, or translucent. When the handle portion  1013  is clear or translucent, the toothbrush operator may see the movement of some of the toothbrush components when the motor  1014  is engaged. In addition, aesthetically pleasing features such as flashing lights (not shown) can be added to the components within the handle portion  1013  to augment the visual appearance. The removable head portion  1016  also includes a shaft  1036  that on one end has a pinion carrier  1038  and on the other a yoke  1040  configured to attach to a drive shaft  1042 . A pinion  1044  is attached to the bristle head  1018  with a threaded fastener  1046  and a washer  1048 . The pinion  1044  interfaces with a rack  1050 , only a portion of which is visible through an opening  1052  in the first housing element  1032 . Also included in the removable head portion  1016  is a snap ring  1054  that is manufactured in different colors such that removable brush heads belonging to different users can have different colored snap rings for easy identification. 
     This embodiment includes a rocker element  1056 , which serves a number of functions. First, it contains clips  1058  (only one of which is visible in this view) that help secure the removable head portion  1016  to the handle portion  1013 . In addition, trunnions  1060  (only one of which is visible), rotate in apertures  1062  thereby allowing the rocker element  1056  to pivot as force is applied to the removable head portion  1016 . As the rocker element  1056  pivots about the trunnions  1060 , a pin  1064  moves within a slot  1066 . The slot  1066  is located in a first casing portion  1068  which also contains one of the apertures  1062  in which one of the trunnions  1060  rotates. Also located in the first casing portion  1068  is the first switch  1020 , which comprises first and second contact plates  1070 ,  1072 . As noted above, the first switch  1020  is optional (see  FIG. 53 ), in which case, the toothbrush  1010  will always be in the automatic mode. 
     The contact plates  1070 ,  1072  are attached to the first casing portion  1068  in such a way that movement of the pin  1064  within the slot  1066  selectively causes the contact plates  1070 ,  1072  to contact each other and electrically connect. Electrically connecting the contact plates  1070 ,  1072  places the second switch  1020  is in the second position. This means that when the toothbrush  1010  is in the automatic mode of operation—i.e., when the first switch  1012  is in the second position—electrical connection of the contact plates  1070 ,  1072  engages the LED driver  1024  and causes LED  1015  to turn on. Thus, when the toothbrush  1010  is in the automatic mode of operation, sufficient contact of the bristle head  1018  with the user&#39;s teeth will cause a slight deflection of the removable head portion  1016 . This in turn causes the rocker element  1056  to pivot on its trunnions  1060 , thereby moving the pin  1064  within the slot  1066 . When the pin  1064  causes electrical connection of the contact plates  1070 ,  1072 , the LED driver  1024  is engaged without the user having to manually actuate any switches. Hence, turning on of LED  1015  is “automatic”. The contact plate  1070  also acts like a spring, so that when the bristle head  1018  is not in contact with the user&#39;s teeth, the contact plate  1070  pushes against the pin  1064  and biases away from the contact plate  1072 . Thus, the second switch  1020  returns to the first position when the bristle head  1018  is no longer in contact with the user&#39;s teeth. 
     Although the second switch  1020  returns to the first position when the bristle head  1018  is no longer in contact with the user&#39;s teeth, the LED driver  1024  may not immediately disengage. The action of the LED driver  1024  in this situation is dependent upon the configuration of a printed circuit (PC) board  1074 . The PC board  1074  is an electronic controller that controls the electrical components of the toothbrush  1010 . The PC board  1074  can be configured such that the LED driver  1024  continues to operate for a finite time after the second switch  1020  is moved from the second position to the first position. The finite time can be a very short interval, perhaps as little as a fraction of a second. This feature may be useful when the bristle head  1018  momentarily disengages contact with the user&#39;s teeth during normal brushing. During the short interval, until the time the bristle head  1018  is again in contact with the user&#39;s teeth, the LED driver  1024  will continue to run. 
     Although the wires are removed from this figure for clarity, the simple wiring involved in the present invention is easily understood by one skilled in the art. The PC board  1074  is wired to the motor  1014  at terminals  1076 ,  1078 . Similarly, battery terminals  1080 ,  1082  are wired to the PC board  1074  through spring terminals  1084 ,  1086 . The PC board  1074  can also be configured to control other functions in addition to the “delayed off” feature. For example, the PC board  1074  may not only control the delay of turning on/off LED  1015 , but also the intensity of LED  1015  output. In addition, if indicator lights are used in conjunction with a transparent or translucent cover, as described above, the PC board  1074  can be configured to control the colors, duration, and sequence of such lights. In addition, the PC board  1074  can be configured to control sound elements, either alone, or in combination with the LED or indicator lights. 
     The first switch  1012  includes a switch cover  1088  and a switch button  1090 . When an operator presses the switch cover  1088  the switch button  1090  contacts an electrical component  1092  of the PC board  1074 , thereby placing the switch  1012  in the second position. Further pressing of the switch cover  1088  toggles the switch  1012  between the first and second positions. The handle portion  1013  also includes a drive shaft seal  1094  and a seal support  1096 . The drive shaft seal  1094  helps to ensure that fluid does not reach the electrical components of the toothbrush  1010 . The PC board  1074  includes an indicator LED  1098  that is visible to a user through a translucent cover  1100 . The indicator LED  1098  may be used to indicate when the first switch  1012  is in the second position—i.e., when the toothbrush  1010  is in the automatic mode—or may be used to indicate when the battery  1022  is being charged. The battery  1022  is held in place by an end cap  1102  that is provided with an  0 -ring seal  1104  to further ensure that fluids do not reach the electrical components of the toothbrush  1010 . Also included in the handle portion  1013  is a seat element  1106  that allows the toothbrush  1010  to be laid on a flat surface such that the bristle head  1018  remains pointing upward. This helps to keep the toothbrush  1010  stationary on a surface that is not level, and keeps the bristle head  1018  from contacting the surface. Aesthetic features  1108  are added to enhance the visual appeal of the toothbrush  1010 . 
     The sensors described in these embodiments may be used in any type of dental hygiene implement. In the embodiments shown in  FIGS. 54, 58-60 , the dental hygiene implement is a motorized toothbrush. The reciprocating movement of the drive shaft  1042  is guided by a bushing  1108 . The actual movement of the drive shaft  1042  resembles a typical slider crank mechanism. The motor  1014  has a rotating motor shaft  1110  that has a spur gear  1112  attached to it. The spur gear  1112  intermeshes with and rotates a ring gear  1114  that has integrally attached to it a cam  1116 . The ring gear  1114  and the cam  1116  are held in a second casing portion  1118  with a pin  1120 . The cam  1116  rotates within a cam follower  1122  that is attached to the drive shaft  1042 . Thus, the rotational motion of the motor shaft  1110  is translated into reciprocating motion of the drive shaft  1042 . When the removable head portion  1016  is attached to the handle portion  1013 , the yoke  1040  connects to a head  1124  on the drive shaft  1042  such that the shaft  1036  reciprocates along with the drive shaft  1042 . This in turn moves the pinion  1044  along the rack  1050  which causes the bristle head  1018  to translate and rotate simultaneously. 
     An alternative configuration for the second switch  1020  is shown in  FIGS. 55-57 . This configuration provides for automatically stopping operation of LED  1015  on the toothbrush when the force on the bristle head in response to contact with the operator&#39;s teeth exceeds a predetermined level.  FIG. 55  shows a portion of a rocker element  1101  that pivots about trunnions  1103  (only one of which is visible). A first contact plate  1105  is attached to the rocker element  1101  with a fastener  1107 . A second contact plate  1109  is attached to a casing with another fastener  1107 , a portion of the casing being shown as  1111 . The casing has a stop block  1113  integrally formed therewith. The rocker element  1101  includes an electrically conductive contact pad  1115 , which is an option that can be used when the first switch is a three-position switch (see  FIG. 51 ). As illustrated in  FIG. 55 , the contact pad  1115  is electrically connected to the contact plate  1105 , and when a three-position first switch is used, the contact pad  1115  will be wired to the first switch. Thus, when the first switch is in the third position, the toothbrush motor (such as  1014  shown in  FIG. 51 ) will operate continuously. A spring  1117  is disposed between the rocker element  1101  and another portion of the casing (not shown), and biases the first contact plate  1105  away from the second contact plate  1109 . 
       FIG. 56  is illustrative of automatic operation of the toothbrush. As the bristle head contacts the operator&#39;s teeth, the rocker element  1101  pivots about the trunnions  1103 , thereby electrically connecting the contact plates  1105 ,  1109 . As illustrated in  FIGS. 55-57 , the first contact plate  1105  is wired to the LED driver, and the second contact plate  1109  is wired to the battery. Thus, when the first switch is in the second position, or when there is only one switch (see  FIG. 52 ), the electrical connection of the contact plates  1105 ,  1109  causes operation of LED  1015  on the toothbrush. If the operator continues to apply force to the bristle head beyond a predetermined level, the first contact plate  1105  will impinge on stop block  1113 , but the rocker element  1101  will continue to pivot (see  FIG. 57 ). A protrusion  1119  on the rocker element  1101  then contacts the second contact plate  1109  and pushes it away from the first contact plate  1105 . This opens an electric circuit and turns off the LED  1015 . Even if the toothbrush has a “continuous on” feature, the LED  1015  will still turn off when the first contact plate  1105  impinges on the stop block  1113 . This is because the contact pad  1115  will no longer be in contact with the first contact plate  1105 . The predetermined level at which the LED  1015  turns off can be easily adjusted by changing the spring  1117 , the size of the stop block  1113 , or the size of the protrusion  1119 . 
       FIGS. 58-62  show portions of a toothbrush  1126  in accordance with another embodiment of the present invention. The toothbrush  1126  comprises a handle portion  1128  that includes a first housing  1130 , and a removable head portion  1132  that includes a bristle head  1134  and a second housing  1136 . This includes a shaft and a pinion which interfaces with a rack to drive the bristle head  1134 . A yoke  1138 , seen in  FIGS. 60 and 61 , connects to a head  1140  of a drive shaft  1142  which reciprocates when a motor (not shown) is engaged. A seal  1144  is disposed around the drive shaft  1142  to protect the electrical components of the toothbrush  1126  from contamination by fluids. 
     As in the previous embodiment, the toothbrush  1126  includes an automatic mode of operation. To facilitate the automatic mode of operation, the toothbrush  1126  has a first switch (not shown) that is configured as in the previous embodiment. A second switch  1146 , seen in  FIGS. 59 and 61 , includes a contact plate  1148  having legs  1150  and a contact rod  1152 . The contact plate  1148  and the contact rod  1152  are disposed within the handle portion  1128  and are covered by a seal  1154 . Similar to the contact plates  1070 ,  1072  used in the first embodiment, the contact plate  1148  and the contact rod  1152  are wired to a PC board (not shown). 
     The method by which the removable head portion  1132  attaches to the handle portion  1128  is also different from the first embodiment. An adaptor  1156 , seen in  FIGS. 60 and 61 , is located inside the housing  1136  of the removable head portion  1132 , and snaps into recesses  1157  in the handle portion  1128 , (see  FIG. 60 ). This attachment allows the removable head portion  1132  to be securely attached to the handle portion  1128 , and at the same time allows the head portion  1132  to pivot in relation to the handle portion  1128  when the bristle head  1134  sufficiently contacts the user&#39;s teeth. As consistently used throughout the various embodiments, “sufficiently contacts” merely implies a contact that is sufficient to cause a slight movement of at least a part of the removable head portion  1132 . 
     As the removable head portion  1132  undergoes the slight pivoting motion caused by contact with the user&#39;s teeth, a projection  1158  pushes into a notch  1159  in the seal  1154 . As the projection  1158  moves into the notch  1159 , it pushes the seal  1154  against the contact plate  1148 . With the legs  1150  held stationary, the contact plate  1148  deflects in a spring-like fashion until it contacts the contact rod  1152 . This places the second switch  1146  in the second position, and enables LED  1015  to turn on when it is in the automatic mode. The spring-like deflection of the contact plate  1148  also acts to bias it away from the contact rod  1152 , to turn off LED  1015  when the bristle head is not in contact with the user&#39;s teeth. As in the previous embodiment, the PC board can be configured such that the LED  1015  does not disengage immediately, but rather, remains engaged for a short time after the bristle head is removed from the user&#39;s teeth. 
     Although both of the embodiments described above have a two-position first switch, as illustrated schematically in  FIG. 51 , a three-position switch (as shown in  FIG. 52 ) can be used. Alternatively, the first switch can be eliminated, as in  FIG. 53 , so that the toothbrush is always in the automatic mode. The two toothbrushes described above include removable brush head portions; however, either can be made with a non-removable brush head portion. In fact, any of the embodiments described herein can be made with a non-removable brush head portion, which may be particularly well suited to disposable toothbrush designs. 
     Portions of a third embodiment of the present invention are shown in  FIGS. 62 and 63 . In this embodiment, a toothbrush  1160  includes a handle portion  1162  that has a first housing  1163 , and a removable head portion  1164  that has a second housing  1165  and a bristle head (not shown). As in the previous embodiments, the toothbrush  1160  includes a first switch (not shown) having a first, or “off” position that prevents the LED  1015  from turning on, and a second, or “automatic” position that allows the LED  1015  to function in an automatic mode. A second switch  1166  comprises first and second stationary contact plates  1168 ,  1170 , and a third contact plate  1172 . The removable head portion  1164  includes a projection  1174  that fits into a notch  1176  in the first housing  1163  of the handle portion  1162 . 
     The removable head portion  1164  attaches to the handle portion  1162  at snaps  1178 . This connection allows the removable head portion  1164  be securely attached to the handle portion  1162 , and at the same time allows the head portion  1164  to pivot in relation to the handle portion  1162  when a bristle head (not shown) sufficiently contacts the user&#39;s teeth. As the removable head portion  1164  pivots, the third contact plate  1172  contacts, and thereby electrically connects, the stationary contact plates  1168 ,  1170 . This places the second switch  1166  in the second position, and causes LED  1015  to turn on when it is in the automatic mode. The projection  1174  also acts as a spring as the removable head portion  1164  pivots, thereby keeping the third plate  1172  biased away from the stationary plates  1168 ,  1170  when the bristle head is not in contact with the user&#39;s teeth. 
     In each of the embodiments described above, the second switch was automatically moved from the first position to the second position when a force was applied to the bristle head. Specifically, a force on the bristle head in response to its contact with the operator&#39;s teeth caused the second switch to move to the second position and the motor was engaged. As previously noted however, the second switch need not be activated by a force on the bristle head. Rather, the second, switch may be located such that it is automatically placed in the second position when the user grips the handle portion. One way to accomplish this is to provide the handle portion with a compressible portion, and dispose the second switch in relation to the compressible portion such that compressing the compressible portion moves the second switch from the first position to the second position, thereby turning on LED  1015 . 
       FIGS. 64 and 65  illustrate two embodiments of toothbrushes having differently configured handle portions.  FIG. 64  illustrates a toothbrush  1180  having a compressible portion  1182 . The compressible portion  1182  can be molded integrally with toothbrush handle housing  1184 , or may be attached in a separate operation. The compressible portion  1182  is typically made from a polymeric material that deflects when the toothbrush is used in a normal brushing operation. The handle housing  1184  may be configured with a relatively small, or a relatively large compressible portion. In this embodiment, the compressible portion  1182  occupies a large area of the handle housing  1184 , thereby helping to ensure that users having different gripping preferences will be accommodated. 
       FIG. 65  illustrates a toothbrush  1186  having a compressible portion  1188  located in a housing  1190  of a handle portion  1192 . In this embodiment, the compressible portion  1188  includes a rigid portion  1194  and a non-rigid portion  1196 . When a user compresses the compressible portion  1188 , the non-rigid portion deflects, thereby moving a switch (not shown) from a first position to a second position to turn on LED  1015 . Having a two-piece compressible portion such as  1188  not only changes the look, but also the feel of the toothbrush when compared to a toothbrush having a single piece compressible portion. Thus, the designer is allowed flexibility with regard to both form and function. 
       FIG. 66  shows a toothbrush  1198  that includes a removable head portion  1200  and a handle portion  1202 . The handle portion  1202  includes a first switch  1204  which has first and second positions for respectively turning off and on LED  1015 . The handle portion  1202  includes a handle housing  1206  that has a compressible portion  1208 . Disposed within the handle portion  1202  in close proximity to the compressible portion  1208 , is a second switch  1210 , shown in detail in  FIG. 67 . 
     The switch  1210  shown in  FIG. 67  includes a magnet  1212 , a magnetic plate  1214 , and a non-magnetic plate  1216 . When the first switch  1204  is in the second position, motorized operation of the toothbrush  1198  occurs only when a force (F) is exerted on the compressible portion  1208 . This force causes the magnet  1212  to move in close proximity to the magnetic and non-magnetic plates  1214 ,  1216 . When the distance between the magnet  1212  and the magnetic plate  1214  drops below a fixed distance  1218 , the two plates  1214 ,  1216  contact each other (see  FIG. 68 ). When the first switch  1204  is in the second position, and the two plates  1214 ,  1216  contact each other, the LED driver is engaged (not shown), thereby causing LED  1215  to turn on. 
       FIG. 69  shows another embodiment of a toothbrush  1222 . The toothbrush  1222  has a handle portion  1224  and a removable head portion  1226 . The handle portion  1224  includes a compressible portion  1228 . In this embodiment, toothbrush  1222  only has one switch  1229  which comprises a magnet  1230  and a Hall effect sensor  1232 . The magnet  1230  is located beneath the compressible portion  1228 , and application of force (F) to the compressible portion  1228  causes the distance between the magnet  1230  and the Hall effect sensor  1232  to decrease. When this distance is small enough, current flows through the Hall effect sensor  1232 , and LED  1215  turns on. 
     In another embodiment of the invention, the sensor is a moisture detection—uses a moisture sensor to detect a highly moist environment such as the mouth. This can be accomplished through various types of moisture sensors for example; capacitive or chilled mirror dew point sensors. Such a sensor is disclosed in US 2009/0087813 to Cai et al, and hereby incorporated by reference. 
     These motion sensor embodiments of the present invention relate to a bio-active oral care instrument, having the ability to active an LED automatically, when the instrument or a portion thereof is exposed to one or more conditions, such as the ambient electrical conductivity, existing in the oral environment. Other conditions and combinations of conditions, such as pH, temperature, solute concentrations, etc. could likewise be detected and used as the basis for automatic operation. Furthermore, aspects of these embodiments are illustrated in the remainder of this disclosure with reference to an electric motorized toothbrush, although it is understood that the operation of any number of oral care instruments, together with the associated advantageous features and/or beneficial effects described herein, could likewise be achieved. Other oral care instruments, for example, include those used in dental drilling, polishing, and grinding; oral suction instruments, oral surgical instruments; and other instruments used in the oral cavity which are powered by motorized devices and especially electrical devices. 
     The representative toothbrush illustrated in  FIG. 70  has a handle  901  and a head  905  carrying one or more cleaning elements, which are depicted in  FIG. 70  as a plurality of bristles  906 . Also illustrated is a neck  904  located between, and connecting, handle  901  and head  905 . The bristles  906 , as shown, form clusters that are anchored to the head  905  and provide a profiled brushing surface with their free ends. Other bristle configurations are of course possible, as well as removable/exchangeable bristle clusters. Different types of cleaning elements (e.g., elastomeric wipers, nodules, pointed structures, etc.) may also be carried on head  905  instead of, or in addition to, bristles. 
     The neck  904  is provided with electrical conducting elements  907  (e.g., an anode and a cathode) that are exposed to the exterior surface of the toothbrush. In other embodiments, the electrical conducting elements  907  can be located on the head  905 , for example on the surface opposite that which carries bristles  906 . The use of electrical conducting elements  907  on different parts of the toothbrush is also possible. A plurality of electrical conducting elements  907  can also be incorporated in various positions to activate the instrument in the event that sufficient electrical conductivity is established between any given pair(s) of electrical conducting elements  907  located at any desired position. Integrated in the region of the neck  904  which is adjacent to the head  905  is a LED driver  911  that is operably connected to LED  960 . The motorized device  911  is operably connected, via electrical connections  934  in the neck  904  to a power source (e.g., a battery, not shown), which may be accommodated in the handle  901 . Operably connected and operably connectable refer to the ability of the electrical connections, or other elements, to readily foam an electrical circuit (e.g., when a switch is depressed or when a power source is connected or installed). Operably connected and operably connectable may also refer to the ability of mechanical components to be connected to one another in such a manner as to allow or provide for physical movement of one or more elements. The LED driver may be alternatively incorporated in the head  905  or handle  901  of the toothbrush. In representative embodiments, electrical connections  934  may be metal wire or electrically conductive plastic tracks. 
     In particular embodiments where the toothbrush uses a vibratory device, it will have a vibratory element which can be in the form of an eccentric, which produces mechanical vibrations and can be rotated about an axis located in the longitudinal direction of the toothbrush. Alternatively, instead of an eccentric which can be driven in rotation, it would also be possible to have a vibratory element which can be driven in a translational manner Otherwise, the bristle-carrying head  905  can be arranged such that it can be moved in relation to the neck  904  in order for the latter, in the case of vibrations produced by motorized device  911 , to move in relation to the rest of the toothbrush. 
     As shown, also accommodated in the handle  901  is a sheath or sleeve  920  which extends in the longitudinal direction of the handle  901  and is made of electrically conductive material. In the representative embodiment shown, both the handle  901  and the sleeve  920  are open to the rear, thus forming a cavity  921  which can be closed from the rear by a closure part  922  and into which it is possible to insert a battery, such as a commercially available, non-rechargeable cylindrical battery, with a defined voltage (e.g. 1.5 V), as the power or voltage source for LED driver  911 . It would also be possible, however, for a button cell or for a rechargeable storage batter to be used as the power source. An external power source such as a conventional electrical outlet or a combination of voltage sources may be employed as the power source. 
     Also shown in the particular illustrative embodiment of  FIG. 70  is a spring contact  929  for a positive pole of a battery (not shown), which is fitted in the sleeve  920 , on a transverse wall  92 S, and is electrically connected to the LED driver  911  through the electrical connections  934  and switch  932 , which is installed in the sleeve  920  and can be actuated from the outside of the handle  901 . Switch  932  may also be, for example, a magnetic switch pulse switch or a pulse switch arranged on a printed circuit board with further electronic components that store the switching state. In other embodiments, closure part  922  can itself act as a switch, such that electrical contact between the power source and LED driver  911  is established or interrupted by turning closure part  922  to alter the position of contact surface  922   b  relative to the negative pole of a battery. 
     It is to be appreciated, as discussed in greater detail below, that switch  932  is not necessary due to the ability of the toothbrush to turn on automatically when in the user&#39;s mouth. In some embodiments, therefore, the toothbrush can be “switchless” or “buttonless.” 
     Switch  932  may be depressed or adjusted by the user to effect a number of operating modes. For example, in “on” and “off” positions or settings, electrical communication or an electrical circuit between the power source and LED driver  911  may be continually established or continually interrupted, respectively. In the former case, for example, the electrical conducting elements  907  may be bypassed to allow continuous operation of motorized device  911 , regardless of the presence of a conductive medium between electrical conducting elements  907 . Switch  932  may also have a position corresponding to conditional completion of the electrical circuit. 
     Also as shown in  FIG. 70 , the closure part  922  is provided with a threaded stub  922   a  made of an electrically conductive material, which may be the same material (e.g., a metal such as copper or a conductive plastic) used for the electrical conducting elements  907 , electrical connections  934 , spring contact  929 , and/or sleeve  920 . Closure part  922  can be screwed into the handle  901  and/or into the sleeve  920  by way of said threaded stub  922   a.  The threaded stub  922   a  is provided with a contact surface  922   b  which, with the closure part  922  screwed in, comes into abutment against the negative pole of a battery (not shown) when inserted into the sleeve  920 . During operation of the motorized toothbrush, this negative pole is electrically connected to LED driver  911  via the threaded stub  922   a,  the sleeve  920  itself, and electrical connections  934  connecting sleeve  920  to LED driver  911 . It would also be possible, instead of through the use of sleeve  920 , for the power from the negative pole to be transmitted in some other way, for example using wires or electrically conductive plastic tracks. Instead of the rear closure part  922  being screwed to the handle  901 , it would, of course, also be possible to have some other type of releasable connection (e.g. plug-in connection, bayonet connection, etc.) and a corresponding configuration of the contact part interacting with the negative pole of the battery. 
     One representative characteristic of the oral environment which differs significantly from the surrounding or ambient “non-use” environment is electrical conductivity, which increases directionally with the concentration of electrolytes in the surrounding medium (e.g., saliva). In some embodiments, this “non-use” environment may even include rinsing or submersing the portion of the instrument that is normally placed in the mouth (e.g., the head  905  of the toothbrush) in water (e.g., for pre-wetting or rinsing purposes), since the electrical conductivity of saliva is higher than that of water. This difference can thus be utilized to allow the instrument to “detect” when it is being used and thereby operate in an automatic mode. 
     Additionally, the combination of water, saliva, and dentifrice (e.g., toothpaste or other ingredient that is generated in the mouth during use of the instrument) often affords even a significantly higher electrical conductivity than saliva alone. This is due to the generation of ions, often in large concentrations, from typical oral care products, including tooth fluoridating, whitening, and/or remineralization products which contain or form aqueous cations, such as sodium (Na + ), potassium (K + ), calcium (Ca +2 ), magnesium (Mg +2 ), iron (Fe +3 ), etc. and anions, such as phosphate (PO 4   −3 ), diphosphate (P 2 O 7   −4 ), carbonate (CO 3   −2 ), fluoride (F − ), chloride (Cl − ), etc. 
     In view of the above, the increase in electrical conductivity surrounding a portion of the toothbrush, e.g., head  905  or head  905  and neck  904 , when placed in the mouth, can be used to complete an electrical circuit, together with an electrical power or voltage source such as an external electrical outlet or an internal battery to activate LED driver  911 , causing LED  960  to turn on. 
     In an “auto” position or setting, LED driver  911  is powered by the power source only in the event that sufficient electrical conductivity (e.g., a threshold level of conductivity, or sufficiently low resistance) exists between electrical conducting elements  907  in the neck  904 . The required electrical conductivity, as needed for the “conditional completion” of the electrical circuit to power motorized device it, may be provided, for example, by an electrolyte solution containing ions (e.g., calcium, phosphate, fluoride, or peroxide ions) such as that generated from a combination of saliva, water, and toothpaste existing in the oral environment during use. When the electrical conductivity between conducting elements  907  is no longer present, the electrical circuit is incomplete, thereby deactivating LED driver  911  and LED  960 . Thus, in an “auto” or automatic operating mode, LED driver  911  and LED  960  will not be activated when the toothbrush is stored since air is the medium between electrical conducting elements  907 . According to some embodiments, when the brush is being rinsed outside the mouth, the water between electrical conducting elements  907  will not have sufficient electrical conductivity to activate LED driver  911  and LED  960 . 
     According to some embodiments, it may be desired to require that the electrolyte solution (e.g., saliva or a water/saliva/toothpaste mixture), to which the toothbrush is exposed during use, have a threshold (or minimum) level of conductivity before LED driver  911  is activated. This threshold level of conductivity, for example, may be based on a threshold (or minimum) current needed to activate LED driver  911 . This threshold conductivity, required to automatically turn on the toothbrush, may be associated with the electrical conductivity of saliva alone or an electrolyte solution having a relatively higher conductivity (e.g., an aqueous solution of toothpaste) or lower (e.g., a mixture of saliva and water) conductivity. For example, the threshold conductivity may be associated with a standard or model electrolyte solution designed to mimic the electrical conductivity of saliva having one or more specified, additional concentrations of dissolved ions such as calcium phosphate, fluoride, peroxide, and other ions or mixtures of ions. 
     In this manner, the automatic functioning of the oral care instrument can be made more or less sensitive to the particular conditions or conditions associated with the environment in which the instrument is used (i.e., the “use” condition(s) required to activate the instrument). It is also possible that the sensitivity of the instrument can be adjusted by, set by, or tailored to, the user (e.g., to avoid either activation of the instrument during “non-use” conditions or non-activation during “use” conditions) and thereby ensure effective functioning of the instrument in automatic mode. 
     In certain embodiments, the change in conductivity of the medium between electrical conducting elements  907  is measured by a sensing device  938 , such as a circuit board  938  or other suitable sensing device, connected to electrical conducting elements  907  by electrical connections  940 . In certain embodiments, sensing device  938  may measure the drop in resistance between conducting elements  907 . When the conductivity change reaches a preset value as detected by sensing device  938 , switch  932  may be activated so as to complete the electrical circuit to power LED driver  911 . In such an embodiment, the electrical circuit need not include the electrolyte solution between conducting elements  907 . That is, the electrolyte solution is used as a trigger to activate switch  932  by way of sensing device  938 , but does not actually form part of the electrical circuit that powers LED driver  911 . 
     In other embodiments, switch  932  could be activated based on the differential change in conductivity between conducting elements  907 . It is to be appreciated that the level of electrolyte in the medium will vary from person to person, and/or may vary based on the formula of the oral care solution used. In such embodiments, these variations will not affect the current level delivered to the motor. Thus, for example, when using a sensitivity type toothpaste product having 5% KNO 3 , the toothbrush would not operate differently than when used with a standard toothpaste product having a lower ionic strength. 
     According to other embodiments, when exposed to a solution with a threshold level of electrical conductivity, LED driver  911  and, therefore, the LED  960  itself may be set or adjusted (e.g., using a timer) to activate for a minimum duration. This ensures that the toothbrush or other instrument will function for at least enough time to effectively accomplish a given task (e.g., tooth cleaning and/or whitening). This also promotes continuous operation, even if contact between the instrument and the electrolyte solution is temporarily lost, for example, when a toothbrush is temporarily removed from the mouth during brushing. The minimum duration for activation of the LED (e.g., two minutes) may be fixed or may otherwise be set or adjusted according to a user&#39;s preferences. 
     As discussed above, the ability of a dental instrument to “activate” (e.g., to turn on a motor) when exposed to the environment in which it is used (e.g., an electrolyte solution in the mouth) can obviate the need for an “on/off” switch or button, creating a simplified operation. 
     Another embodiment of a motorized device activated when conducting elements  907  are exposed to an electrolyte solution is shown in  FIG. 71 . A reservoir  944  is provided in handle  901  for storing an active agent. Conducting elements  907  are used to activate a pump  946 , which causes a predetermined quantity of the active agent to be delivered from reservoir  944  through a channel  948  leading to a plurality of outlets  950  located in head  905 . An exemplary delivery system for an active agent is described in U.S. application Ser. No. 11/457,086, the entire disclosure of which is incorporated herein. Other examples of oral care instruments that can activate an LED upon exposure of conducting elements  907  to an electrolyte solution will become readily apparent to those skilled in the art, given the benefit of this disclosure. 
     In yet another embodiment, the sensor may be one or more accelerometers within a dental hygiene implement that detect the user&#39;s brushing movement and compare it to previously stored brushing profiles to determine if the brush is in use or not. In the embodiment shown in  FIG. 72 , the dental hygiene implement is a toothbrush  100  with an accelerometer  119  connected to a control circuit  110 . If the accelerometer  119  detects that the brush is in use, the control circuit  110  will signal to the LED driver  111  to maintain the light source  117  until the brushing time has expired. The brushing time is adjustable, and may be set by either the manufacturer or the user. If the brushing time has expired, then the light source  117  will turn off and an indicator (not shown) will signal to the user that brushing has been completed. In one embodiment, the indicator is an additional LED light located on the handle of the toothbrush. In another embodiment, the indicator is an audio signal relayed to the user. 
     One or more accelerometers may be installed in the toothbrush to measure the x-, y- and z-axis of the toothbrush at any given moment while the user is brushing his teeth. The control circuit may signal to the LED driver to turn on the light source when the accelerometers indicate that the toothbrush is in an orientation within a predetermined range. In another embodiment of the invention, there is a time delay between the moment the accelerometers indicate that the toothbrush is in a brushing orientation and the moment where the control circuit signals to the LED driver to turn on the light source. 
     In yet another embodiment, the user may pre-program his brushing pattern to the control circuit such that the LED driver will only activate the light source only when the control circuit recognizes the user&#39;s brushing pattern. In one embodiment, the control circuit signals to the LED driver to activate the light source for a predetermined amount of time set by either the manufacturer or user. Alternatively, in another embodiment, the control circuit may continuously signal to the LED driver to keep the light source on until the accelerometer indicates that the user is no longer brushing. 
     In other embodiments of the invention, the sensor is a combination of two or more of these sensor types. 
     Embodiments may further include a mechanism for alerting a user that LED  117  is about to be powered on. In some embodiments, toothbrush  100  may include a light emitter to signal the status of LED  117 . The light emitter may be controlled in such a matter as to alert the user that the light is about to come on to full power, through a gradual increase in power from 5% of full power, up to 100% of full power, for a period of between 0.5 seconds to 2 seconds before a complete and full power is achieved on the light emitting toothbrush. In one embodiment, the light emitter may be an additional LED on toothbrush  100 . In various embodiments, the light emitter may operate by providing a short burst of low frequency light pulses or flashes, using a rectangular, saw-tooth, pulsed, sinusoidal or other types of common periodic waveforms, in the range of 2-10 Hertz at partial or full power, for a period of between about 0.5 seconds to about 5 seconds before full power is achieved on the LED in the toothbrush  100 . In combination or in the alternative, light emitter may also emit color-coded signals dependent on the amount of power supplied to LED  117 . The color of the light emitter may gradually change from a first color to at least a second color as power to the LED  117  gradually increases. Alternatively, the color of the light emitter may change in discrete increments from a first color to at least a second color as LED  117  gradually increases in power. 
     Other mechanisms may be used to alert a user of the power status of LED  117 . In one embodiment, a vibrator such as a motor may be incorporated into toothbrush  100 . The vibrator may operate by providing a series of pulsed vibration for a short duration of time, such as between about 0.5 seconds to about 2 seconds, before LED  117  is fully powered. In another embodiment, the vibrator may provide a constant vibration with increasing intensity as the power of LED  117  gradually increases. The vibrator may be a motor used to drive the brush head of a motorized toothbrush. In yet another embodiment, toothbrush  100  may further include an auditory device for emitting a sound to alert a user of the power status of LED  117 . For example, the speaker may provide a pulsating beep for a short duration to indicate that LED  117  is about to emit at full power. 
     One or more mechanisms may be included with toothbrush  100  to indicate the upcoming power status of LED  117 . These and other identifiers may be useful as a safety feature to prevent a user from inadvertently looking directly at LED  117  while it is fully powered. 
     It may be possible to inadvertently and momentarily break the interlock safety circuit during normal brushing while the brush head is still in the mouth. For example, when using the current loop embodiment of  FIGS. 1-8 , such a momentary break may happen when the brush head is moved from one side of the mouth to the other, breaking the biological circuit between the brush head and the brush handle. This break could cause the light to momentarily shut-off while still in use, creating an unintentional flicker. To prevent this situation, the micro-controller circuit can be programmed to introduce a shut-off delay such that the circuit does not shut-off until the interlock circuit has been broken for more than a predefined period of time. In one embodiment, the predefined period of time is between about 0.1 to about 0.5 seconds. In another embodiment, the break could cause the light to dim for a short period, such as between about 0.1 to about 0.5 seconds before actually shutting off. If the interlock circuit is reengaged during this dimmed time, the light goes back to full power without the need to alert the user. 
     These embodiments and others may further include a fingerprint module mounted on the handle to verify if the user is authorized. In particular, to keep children from playing with the device and defeating the safety measures that prevent the LED from coming on unless it is in a user&#39;s mouth, the fingerprint module may be included to only allow the LED to come on if a finger of a hand of an authorized adult is detected. The fingerprint reader may be a button or simply a surface. Various fingerprint sensors are known and can be used in combination with the embodiments disclosed. The fingerprint reader preferably includes a memory for storage of fingerprint data of authorized users and sufficient processing capability to compare stored fingerprint data with new data read as a user attempts to use the toothbrush. Alternatively, the toothbrush could include a data link as in the “internet of things” to compare the fingerprint data remotely and return a “match” or “no match” decision. In the embodiment shown in  FIG. 73 , the dental hygiene implement is a toothbrush  100  having a LED  117  at the brush head connected to a LED driver  111  located in the handle of the toothbrush. The control circuit  110  is connected to the LED driver  111  as well as a battery  109  and a fingerprint module  2126 . The fingerprint module  2126  may be initialized to recognize a user, with such information stored in the control circuit  110 . Subsequent uses of the toothbrush will require the user to verify his identity by placing his fingerprint on the fingerprint module  2126 . 
     In one embodiment, if the user&#39;s identity is correct, then the user may proceed to insert the brush head into his mouth and the LED will turn on in response to the installed sensor (not shown). If the user&#39;s identity is incorrect, then the LED will not turn on even if the installed sensor detects pressure, moisture, capacitance, etc. In another embodiment, the toothbrush  100  may further include an on/off switch where the fingerprint module and LED remain completely inactive in the “off” setting. In yet another embodiment, the toothbrush  100  further includes an additional indicator to indicate whether the user is authorized. This indicator may be a visual light source that turns green when a user is authorized to use the brush. A red light source may be activated to indicate that the user is not authorized to use the toothbrush. Other types of indicators may be used, such as an audio indicator. 
       FIG. 74  illustrates one example of a toothbrush having a fingerprint module for authorization. The fingerprint module may be presented as a start button for the user to depress and hold for a short duration  2200 . The duration may be between about 1 to about 3 seconds. An indicator may be provided to alert the user that the fingerprint has been read. In the example provided, a green light flashes once the fingerprint is read  2202 . If an error occurs, the light may flash red and emit a sound  2204 . Once the fingerprint is authorized, the light emitter may flash red and provide a pulsing vibration and sound to alert the user that the LED is about to become fully powered  2206 . Simultaneously, the current loop detector determines whether the toothbrush is being inserted into the mouth (or a detector using any of the mechanisms as described in the embodiments above)  2210 . If no current is detected after a preset time interval, then the toothbrush shuts off  2212 . If a current is detected, then the LED and brush motor are activated  2216 . A timer indicates when a sufficient duration of brushing has been reached by beeping an auditory signal to the user  2220 . Once the user removes the brush from the mouth, the current loop is broken  2214 . If the toothbrush remains out of mouth for 30 seconds, the system turns off and the fingerprint reader will need to be used to reactivate system  2212 . 
       FIG. 75  illustrates one embodiment of how the fingerprint module and status indicators are connected with other components of the toothbrush using a circuit block diagram. The microcontroller  2300  is wired to the following components: the fingerprint module  2302 , a red LED  2304 , a green LED  2306 , a beeper  2310 , a current loop detector  2312 , a LED/motor driver  2314 , and a power supply  2322 / 2324 . The LED/motor driver  2314  is responsible for activating the UV LED  2316  and the brush head motor  2320 . LED/motor driver  2314  is also connected to the power supply  2322 / 2324 . 
     Of course, the fingerprint module and warning feature may be used with non-motorized toothbrushes. 
     In another embodiment, the fingerprint module  2126  acts as the sensor for toothbrush  100 . The LED will turn on once an authorized user places his fingerprint over the module. In this embodiment, it is intended for the user to place the fingerprint over the module only after the brush head is inserted within the mouth. 
     Certain modifications and improvements will occur to those skilled in the art upon reading the foregoing description. It should be understood that all such modifications and improvements have been omitted for the sake of conciseness and readability, but are properly within the scope of the following claims.