Abstract:
An intraoral device makes a new treatment of dental problems possible. The device includes electronic circuitry to sense unwanted or undesirable relative positions of body parts within the oral cavity. The undersirable position may be teeth clenched, jaw open with teeth unclenched, tongue pressed against teeth or a retruded position of the lower jaw. When these positions have been assumed for too long, a signal reminds the patient. This automatic signal makes it possible for the patient to unlearn bad habits or learn new habits. The dentist may then treat the dental problems caused by the bad habit in a conventional way, knowing that because the habit is broken, recurrence of the dental problem is unlikely. The circuitry includes a proximity detector, a variable time delay and signal generator along with a power supply. When tongue thrusting is to be treated a cage is mounted in the mouth almost against the inside of the front teeth. Tongue contact moves the cage forward actuating the proximity detector.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to dentistry and specifically to a method and apparatus for the treatment of various problems related to improper use of jaw musculature. 
     BACKGROUND OF THE INVENTION 
     There are numerous dental problems that arise from improper use of jaw musculature. One of these is clenching, a condition in which a patient constantly or excessively presses his or her teeth against each other. Clenching can cause excessive wear of the teeth, headaches, and fatigue and soreness of the jaw muscles. 
     There are at least three schools of thought on the treatment of clenching. One traditional treatment involves placing a protective layer of acrylic material (called a splint) over the involved teeth. This acrylic layer serves to protect the teeth from direct contact, thus reducing wear, and to spread the load caused by clenching so that it is shared more equally among the neighboring teeth. This reduces wear of the teeth, but the acrylic protective layer does not address the problem of clenching, which frequently continues indefinitely. This forces the patient to wear the splint indefinitely. In some cases the urge to clench is worsened. 
     A second traditional treatment for clenching is occlusal adjustment. This treatment involves selective grinding of teeth so that the load on the teeth caused by clenching is carried evenly by several teeth rather than being concentrated on one or two. This technique is successful with some but not all types of clenching. However, if not carefully practiced, it can lead to subsequent legal liability which is enhanced because of the permanent nature of the procedure. 
     A third school of thought is that there is nothing that can be done about clenching. This approach may have heretofore had the advantage of candor, but it left patients with unnecessary discomfort. Muscle relaxants are often prescribed in these instances. This group of drugs may adversely effect performance, and therefore can only be used when the patient is at home. 
     A second class of dental problems relates to what are termed problems in the vertical frame of reference. Examples of these problems are: (1) Dental open bite which is characterized by contact between the posterior teeth without contact between the front teeth when the jaw is closed; (2) skeletal open bite which is characterized by a sloping mandibular plane and a long face; and (3) skeletal deep bite which is characterized by short faces and mandibular planes that are nearly horizontal or parallel with the floor. Skeletal deep bite patients also have dental deep bite which is characterized by excessive overlap of the front teeth. Treatments for problems of this type are discussed below. 
     One method of treating a dental open bite is to mount ceramic magnets on the rearmost molars with like poles facing each other so that the molars are slowly forced more deeply into the bone which supports them. A disadvantage to this method is that the magnets and their acrylic housing force the jaw open 5-6 millimeters in the rear and perhaps twice that at the front. This imposes the responsibility upon the patient to walk around with his or her mouth open, which is embarrassing and uncomfortable. Patients also have difficulty keeping their jaws in such a position that the repelling magnets are directly opposing one another. Thus, there is a tendency for the lower jaw to slide from side to side and not to stay centered. As a result, these patients are frequently asked to wear a chin strap headgear apparatus to center the lower jaw. This method of treating open bites is prone to the problem of lack of patient cooperation. 
     Another method for treating dental open bites is to place a cage directly behind the upper or lower front teeth. This appliance restrains the tongue from coming forward where it has forced the front teeth apart. The patient is instructed to keep the tongue behind the cage without touching it, and whenever he or she feels their tongue touching the cage to move the tongue backward, away from the cage. The problem with this appliance is that patients forget to remind themselves to move their tongues backward and rest their tongues against the cage. When the appliance comes off, the tongue frequently comes forward to rest against the front teeth. Relapses will inevitably occur. 
     When dental open bites are present in patients in their teens, or later as an adult, the treatments for dental open bite are orthondontic treatment in combination with extractions of permanent teeth, or orthodontic treatment in combination with surgery, which usually includes extraction of permanent teeth. 
     Skeletal open bites are traditionally treated by orthodontics that includes extracting teeth and using orthopedic force in the form of headgear which imposes an intrusive force to the maxilla and maxillary teeth. Extractions help to solve the problem in a minor way and require the removal of four perfectly good teeth. The successful use of headgear is dependent upon the cooperation of the patient. The headgear includes a brace that circumscribes the head and neck, and it is cumbersome and uncomfortable. Experience has shown that cooperation in wearing the headgear is often less than complete. The use of extractions and headgear treat only the symptoms of skeletal open bites. The underlying cause of the problem which is the lack of sustained contact between the teeth is not addressed by this treatment. 
     Dental and skeletal deep bite are treated with orthondontic treatment which often includes propping the front teeth open with an acrylic bite plane. This leaves the posterior teeth apart and allows them to erupt into contact with each other. In the short run this treatment appears to be stable, but after about a year the deep bite may begin to return because the underlying cause of the problem (chronic clenching of teeth) was never addressed. 
     Another class of dental problems relates to what is termed problems in the horizontal frame of reference. Mandibular retrognathia is one such problem. It is characterized by the lower jaw being positioned too far behind the upper jaw in the horizontal frame of reference. This condition is conventionally treated with bulky acrylic appliances which hold the lower jaw forward and restrain the lower jaw from moving backward. These appliances have been shown to create undesirable side effects related to this restraint such as proclination of the lower anterior teeth. Other treatments have been: Orthodontics that usually includes extraction of teeth, or orthodontics that utilize orthopedic forces to push the upper jaw backward to meet the lower jaw. If the problem of mandibular retrognathia has not been treated by 12 to 14 years of age, it is often necessary to treat the problem with orthodontics in combination with surgery that is designed to bring the lower jaw forward. 
     SUMMARY OF THE INVENTION 
     The present invention provides a new approach to treating the dental problems discussed above. The present invention can remind the patient of unconscious, undesirable behavior every time it occurs and can teach the patient new habits. This is accomplished by the use of electronic circuitry attached to, e.g., the upper teeth which senses the proximity of the lower teeth and signals the patient when the jaw is in an undesirable position. For patients who clench, the circuitry senses a closed jaw, and when the jaw has been held closed too long, say 3 or 5 seconds, a signal sounds alerting the patient to relax his or her jaw muscles by opening the jaw. Similarly, with open bite patients the circuitry is arranged to signal the patient when the jaw has been open too long. Another feature of the present invention signals the patient when his or her tongue is being pressed against the back sides of the front teeth. By providing a signal to the patient at the appropriate time, the patient can modify his or her behavior so that the cause of the patient&#39;s problem can be treated: Clenchers learn to relax their jaw muscles; open bite patients strengthen their jaw muscles; and tongue thrusters learn not to press against their teeth. 
     This invention may also be adapted to create habits that are lacking by reminding the patient when the desired habit or function is not being practiced. Examples of this application are in the treatment of skeletal open bite or mandibular retrognathia. In skeletal open bite patients there is thought to exist a lack of sustained contact between upper and lower jaws. This results in the tendency for the face to grow downward instead of forward. The result is these patients have extremely long faces. By using this invention to sense the lack of contact between teeth, the patients can be trained to keep their teeth in contact during certain periods during the day. This stops or reverses the downward growth and at the same time trains the muscles to keep the lower jaw in more frequent contact with the upper jaw. Mandibuar retrognathia patients may use the present invention to train themselves to hold their jaws forward in the correct lower jaw position. 
     The present invention includes an electronic circuit comprising a reed switch, time delay, oscillator, signal generator and power supply all encapsulated in an acrylic resin and mounted to a molar, usually a maxillary molar. To treat clenching or open bite problems the opposing molar carries a small magnet to actuate the reed switch. The device is removably mounted to a band surrounding the tooth so that it may readily be removed for repair or when it is not desirable to have it operating. 
     To treat tongue thrusting, a cage is mounted just behind the upper front teeth. The cage is movable and spring biased rearwardly to a position slightly spaced from the upper front teeth. When the tongue is pressed against the cage, the cage moves forward. A magnet is mounted to the cage, and when the cage moves, the magnet actuates the circuitry to alert the patient. The tongue thrusting treating device is mounted by means of a pair of acrylic splints which surround the three or four rearmost maxillary teeth on each side and in one of which the circuitry is embedded. The splints are connected by thick wires or bars which are contoured to follow the roof of the mouth. Because tongue thrusting is often accompanied by an open bite, circuitry arranged to detect an open bite also may be embedded in one of the acrylic splints. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the annexed drawings: 
     FIG. 1 is a side skeletal view showing one embodiment of an intraoral appliance constructed in accordance with the present invention; 
     FIG. 2 is a view looking generally in the direction of arrows 2--2 of FIG. 1 but further showing the soft tissues including cheek, tongue, gums and roof of the mouth; 
     FIG. 3 is a schematic illustration of a circuit utilized in the present invention; 
     FIG. 4 is a plan view showing a tooth with a band around the tooth for securing an apparatus which forms a part of the present invention; 
     FIG. 5 is an elevation view of the tooth of FIG. 4 with band attached and further showing another component of the present invention prior to installation; 
     FIG. 6 is a view looking in the direction of arrows 6--6 of FIG. 5; 
     FIG. 7 is a partly cut away perspective illustration of a second embodiment of the present invention especially adapted to treat tongue thrusting; 
     FIG. 8 is a side elevation view of the apparatus shown in situ in FIG. 7; and 
     FIG. 9 is a view generally looking in the direction of arrows 9--9 of FIG. 8. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The intraoral appliance 10 illustrated in FIGS. 1 and 2 includes an electronic signaling circuit 12 embedded in an acrylic housing 14. The circuit 12, which will be described in greater detail below, includes a detector for sensing the relative position of body parts within the oral cavity. In the embodiment illustrated in FIGS. 1 and 2, proximity of the first mandibular molar 22 to the first maxillary molar 24 is sensed by means of a reed switch 16 mounted within the acrylic housing 14 and a magnet 18 embedded in another acrylic housing 20 mounted to the mandibular molar 22. The acrylic housings 14 and 20 are molded to conform to the particular patient&#39;s morphology, and the circuitry is extremely compact so that the resulting apparatus may be worn without discomfort and discreetly. 
     Where the intraoral appliance 10 is used for the treatment of clenching, the circuitry 12 is arranged so that when the mandibular and maxillary molars 22, 24 are in contact, the reed switch 16 is closed. When the teeth 22 and 24 remain in contact for more than a predetermined length of time, perhaps three or five seconds, a signal is generated which is audible to the patient in whose mouth the appliance is installed. By being reminded that his or her jaw is clenched, the patient can break this bad habit and thus alleviate the symptoms it causes. 
     The circuit 12 includes a detector for detecting the proximity of body parts. In the embodiment of the invention illustrated in FIGS. 1 and 2 the detector comprises the reed switch 16 and magnet 18 (FIG. 3). When the reed switch 16 is closed, power from a battery 26 flows through a time delay circuit 28, and after a predetermined length of time, power is then passed to an oscillator 30 and from the oscillator 30 to a piezoelectric transducer 32 to alert the patient that he or she is clenching and has been clenching for too long. All of these circuit elements are conventional. It is contemplated that in practice the circuit elements 28 and 30 will be formed in a single integrated circuit. 
     The strength of the magnetic field surrounding the magnet 18 and its position relative to the reed switch 16 determines when the reed switch will close for treating clenching. The magnet 18 should be positioned so that when the teeth 22 and 24 come into contact the magnetic field at the reed switch 16 is just sufficient to close the switch. This is accomplished either by proper selection of the magent&#39;s size or field strength or by moving the magnet 18 relative to the reed switch 16. For treatments which involve teaching the patient to hold his or her jaw closed, the magnet 18 might be such as to actuate the reed switch when teeth 22 and 24 are close to each other but not yet touching. 
     The time delay circuit 28 provides a time delay of between approximately three and five seconds. This delay allows the patient to talk, eat, and swallow, all of which require contact between mandibular and maxillary teeth. The length of the time delay may be made variable. This can be done in a number of ways. Either a potentiometer can be used so that the resistance in an R-C circuit may be varied, or electronic components (either resistors or capacitors) could be removed or added to the circuit to achieve the same result. The same result could be obtained digitally with a clock and counter. The length of time would be varied by varying the length of the count. Again, such a circuit is conventional. 
     As discussed above, proximity of the mandibular and maxillary teeth is sensed by means of the detector including the reed switch 16 and magnet 18. The detector could also be responsive to inductance or capacitance in which case a magnet would not be required but merely a piece of metal, stainless steel, for example. The important thing is not what type of proximity detector is used, but that it be capable of generating a signal when the body parts whose positions are to be detected come into a preselected spatial relation and of stopping the signal once the body parts move to a different position. Further, an advantage to the use of a reed switch/magnet and/or capacitance/inductance detector is that full freedom of movement of the mandible is maintained because there is no mechanical interconnection between the body parts whose position is being detected. 
     The circuit 12 is embedded in an acrylic housing 14 (FIG. 2). Similarly, the magnet 18 is embedded in a second acrylic housing 20. Both of these housings are secured to their respective teeth by means of orthodontic bands 40, 42. The band 40 is illustrated in FIG. 4. It is formed of a conventional steel alloy which circumscribes the mandibular molar 22. A U-shaped band 42 extends from the buccal surface of the band 40 and is connected to it by, for example, welding. The loop 42 and band 40 together define an opening 44 which receives a pin 46 (FIG. 5) which extends from the acrylic housing 20. 
     The pin 46 is L-shaped and projects laterally from the acrylic housing 20 and then downward, the downward leg being proportioned to fit in the opening 44. A U-shaped wire spring 50 is mounted to the horizontal leg of the pin 46. The wire spring 50 is mounted horizontally so that its lowermost leg 52 (FIGS. 5 and 6) is slightly above the bottom of the downward leg of pin 46. As the downward leg of pin 46 is inserted into the opening 44, the leg 52 of spring 50 encounters a dimple 54 which projects laterally from the outside surface of the loop 42. The spring 50 yields as the acrylic housing 20 is pushed downward, and ultimately the lowermost leg 52 of the spring snaps under the bottom side of the dimple 54 to hold the acrylic housing 20 firmly in place. There are times when a patient may choose not to have his intraoral appliance operative. In this case, the spring 50 may be easily manipulated to permit the downward leg of pin 46 to be withdrawn from the opening 44. A similar band and pin arrangement is used to secure the circuit 12 and the acrylic housing 14 to the maxillary molar 24. 
     The intraoral appliance 10 as illustrated in FIGS. 1-6 is suited for the treatment of clenching. Specifically, the circuitry is arranged to generate a signal when mandibular and maxillary molars have been in contact with each other for a period of time which exceeds that required for eating, talking or swallowing. By being reminded of the improper or undesirable action every time it occurs, the patient is able to break bad habits, in this case excessive clenching. 
     The circuitry 12 may also be arranged to generate a signal when the opposite condition obtains. For a variety of reasons, including the treatment of an open bite, a patient might need to learn to keep the jaw muscles tense. In this case, rather than using a normally open reed switch 16, a normally closed reed switch is included in the circuit. The effect is that whenever the maxillary and mandibular teeth are out of contact for a length of time which exceeds a predetermined length of time, an audible signal is generated to alert the patient to close his mouth. To treat mandibular retrognathia, the circuitry 12 is arranged as for open bite treatment, but the magnet and reed switch are positioned so that the alarm is quiet only when the jaw is thrust forward. 
     For treatment of mandibular retrognathia, open bite, or other condition where closing the jaw would help in treatment, circuitry arrangements are possible other than that discussed in the preceding paragraph. For example, a normally open reed switch could be used together with a circuit which will actuate the oscillator 30 when the reed switch has been open more than a predetermined length of time. Regardless of which arrangement is used, the patient receives an audible signal whenever his or her jaw has been too long in an undesirable position. 
     For treatment of open bite problems, the circuit 12 illustrated in FIG. 3 includes an additional timer circuit 56 in series with the other circuit elements. The timer circuit 56 is conventional and includes a twenty-four hour clock which is programmed to limit the number of hours that the circuit 12 operates in the course of a day. This permits the jaw muscles to relax and rest and prevents the creation of a clenching problem. For example, the timer circuit 56 may actuate the circuit 12 only between 7 p.m. and 11 p.m. and may be programmed so that during this four hour period it is on only for alternative 20 minute intervals. Later in treatment, the dentist may want to change the times to 9 p.m. to 11 p.m. with the circuit on for alternate 15 minute intervals. 
     In a commercial device, it is contemplated that the timer circuit 56 is integrated into a single chip together with the other circuit elements. The timer circuit 56, as indicated, is adjustable to control when the circuit 12 is operative. Therefore, the timer circuit 56 may be helpful in the treatment of problems in addition to open bites. 
     A further embodiment of the present invention is illustrated in FIGS. 7-9. Here the purpose is to treat tongue thrusting. Persistent tongue thrusting can result in moving teeth out of their desired alignment. In this case the relative position between the tongue and the incisors is what is being sensed. To achieve this a U-shaped cage 60 is fashioned out of a suitable metal or plastic. The cage 60 includes an upper and lower U-shaped horizontal band 62 and 64, respectively, interconnected by three vertical braces 66. The U-shaped members 62 and 64 merge into rods 68 and 70 which extend rearwardly from about the first or second premolar. 
     The rods 68 and 70 slide in bushings 72 (FIG. 8) which are embedded in acrylic housings 74 and 76. A magnet 18 is mounted to the rearmost end of the rod 68 and a reed switch 16 is embedded in the housing. A spring 80 biases the cage 60 rearwardly and the magnet 18 away from the reed switch 16. The spring 80 extends between one of the bushings 72 and the magnet 18. The housing 74 is formed with an appropriate internal cavity 82 which accommodates the movement of the rod 68, spring 80 and magnet 18. 
     When the tongue presses toward the inside of the front teeth, the cage 60 is moved forward, taking with it the magnet 18. This in turn brings the magnet into alignment with the reed switch 16 which is part of the circuit 12. This circuitry is essentially similar to that for treating clenching in that a signal is produced when the tongue has been pressed forward too long. 
     The acrylic housing 74 forms a splint covering the rearmost three or four upper teeth. The bushings 72, spring 80, magnet 18, and reed switch 16 are mounted in its lingual side. The circuitry 12, except for the reed switch 16, is carried in the buccal side of the splint 74. The splints 74 and 76 may be interconnected by a plastic arch which conforms to the shape of the palate, or as shown in the drawings, by a pair of wires 84, 86 and interconnecting ring 88. 
     The splint arrangement shown in FIG. 7 may be also used with the type of circuitry intended to treat clenching or in the alternative an open bite. In this case the upper band 42 (FIG. 2) would be eliminated while the lower band 40 would be retained to mount the magnet 18. Whether the splints 74 and 76 (FIG. 7) are used to secure the circuitry or an orthodontic band (e.g., 42, FIG. 2) depends on individual morphology and/or conditions present in the particular patient. 
     In some circumstances it might be useful to have a signal generated both when the tongue is thrust forward and when the jaw is slackened. In this case the acrylic splint 76 could contain circuitry like that discussed in connection with FIGS. 1-3 and an additional magnet would be attached to a mandibular tooth to actuate the circuitry. Such an arrangement could provide one signal when the tongue was thrust forward and a different and independent signal when the jaw has been excessively open. Once the patient has learned to keep his or her jaw tight and tongue relaxed, conventional orthodontia may be used to pull the teeth into proper alignment with the confidence that bad muscle habits will not undo what the orthodontia can achieve. 
     As a further and optional feature, the circuit 12 (FIGS. 3 and 7) may include a memory and readout device 90. This device would record the patient&#39;s progress by measuring the number of times the tone generator 32 was actuated and for how long. The device also includes means for permitting the dentist to read the stored information and display it, for example, on a computer screen or a computer controlled printer. The connection between the memory and readout device 90 and the dentist&#39;s computer could be a direct electrical connection through a jack in the device 90 or it could be an inductive or capacitive connection. Such memories and readout devices are well known in the medical electronics field and are used extensively in cardiac pacemakers. If the circuit 12 is made with the memory and readout device 90, it is contemplated that it be integrated with the other circuit elements into a single integrated circuit. 
     Thus, it is clear that the present invention provides a new approach to treating both clenching, open bite/tongue thrusting and retrognathia problems. The electronic circuitry 12 may be attached to the upper teeth as in FIGS. 2 and 7 to sense the proximity of the lower teeth and to signal the patient when the jaw or tongue are in an undesirable position. For patients who clench, the circuitry 12 senses a closed jaw, and when the jaw has been held closed too long, a signal sounds alerting the patient to relax his or her jaw muscles. With open bite patients the circuitry 12 is arranged to signal the patient when the jaw has been open too long, and in the embodiment of FIGS. 7-9 the patient is signaled when his or her tongue is being pressed against the back sides of the front teeth. By providing a signal to the patient at the appropriate time, the patient can modify his or her behavior so that the cause of the patient&#39;s problem can be treated rather than merely the dental symptoms.