Abstract:
The present invention discloses a negative-pressure oral apparatus capable of relieving discomfort of soft tissues in the oral cavity and improving fixation of the oral apparatus to prevent the oral apparatus from falling off due to mouth opening. The oral apparatus is compact and elastic so that it fits various shapes and sizes of the oral cavity and is easy to be put on and taken off to provide convenience and safety to the user. In another embodiment, a method for maintaining a negative oral pressure and collecting liquid by coupling the oral apparatus to a liquid collecting apparatus capable of effectively providing the oral cavity with a negative pressure to expel liquid in the oral apparatus and deliver the liquid to an absorbing element in the liquid collecting apparatus so as to prevent liquid leakage or contamination.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to an apparatus capable of preventing obstructive sleep apnea (OSA) and a method for maintaining a negative oral pressure and collecting liquid. More particularly, the present invention relates to a negative-pressure oral apparatus disposed in the oral cavity and capable of providing the oral cavity with a negative pressure to prevent obstructive sleep apnea (OSA) and snoring and expelling a liquid in the oral cavity to prevent liquid leakage or contamination and a method for maintaining a negative oral pressure and collecting liquid. 
         [0003]    2. Description of the Prior Art 
         [0004]    Obstructive sleep apnea (OSA) happens when the muscles in the oral cavity and the back of the gullet of a person are relaxed so that the person stops breathing intermittently for hundreds of times through the night. Each time may last as long as one minute.  FIG. 1A  shows the normal breathing condition of a sleeping person. In  FIG. 1A , the upper respiratory airway  10  is kept unobstructed.  FIG. 1B  shows the muscles in the oral cavity and the back of the gullet of a person are relaxed when he is sleeping so that the upper respiratory airway  10  is narrowed to cause upper airway resistance syndrome (UARS) and snoring. In  FIG. 1C , the muscles in the oral cavity and the back of the gullet of a person are relaxed when he is sleeping so that the upper respiratory airway  10  is blocked up to cause obstructive sleep apnea (OSA). 
         [0005]    It is estimated that ten percent of the people in the world suffer from OSA. However, only a few of them are treated. Those with OSA are faced with life-threatening situations such as higher death rate, higher hypertensive risk and higher myocardial infarction (MI) risk. The survival rate of the untreated patients with apnea-hypopnea index (AHI) larger than 20 is lowered by 36 percent than the survival rate of the untreated patients with AHI smaller than 20 in eight years. The ratio of hypertension rate of the patients with respiration disorder index (RDI) of 5 to that of those people without OSA is 2:1. The ratio of hypertension rate of the patients with respiration disorder index (RDI) of 25 to that of those people without OSA is 5:1. The possibility of a recurrence of hypertension of the patients with OSA is 23 times the possibility of a recurrence of hypertension of the people without OSA. The vehicle accident rate of the untreated patient with OSA is 7 times the vehicle accident rate of the people without OSA and it is 12 times for the vehicle accident rate per mile. 
         [0006]    Please refer to  FIG. 2 , which is a schematic diagram showing a constant positive airway pressure (CPAP) machine  11  used for treating OSA. The CPAP machine  11  is widely used for treating OSA by providing the patient with a constant positive airway pressure through a mask so that the upper respiratory airway is kept unobstructed. Even though the respiratory airway is kept unobstructed, it makes the patient uncomfortable because the high-pressure air flows into the upper respiratory airway. Therefore, the patient compliance rate is as low as 40 to 50%. Alternatively, OSA can also be treated by using soft tissues removal surgery, bone surgery or oral appliances. 
         [0007]    In U.S. Pat. No. 6,494,209, an oral device for treatment of obstructive sleep disorders is disclosed. It is characterized in that the tongue is protected and separated from the teeth when the device is in use. The oral device further comprises a tongue shaped cavity for receiving the tongue. Moreover, a negative pressure is applied directly on the soft tissues of the tongue to hold the tongue within the cavity. However, such negative pressure may cause damage to the soft tissues of the tongue. 
         [0008]    Moreover, in U.S. Pat. No. 5,957,133, an oral appliance with a negative air supply for reducing sleep apnea and snoring is provided, in which a negative air pressure source expels the air from the oral cavity to pull the tongue and the palate forward so that the upper airway is unobstructed. However, the oral appliance occupied a lot of the oral cavity and is vomitive. Meanwhile, the aforesaid patents do not teach how to effectively remove and store excess saliva. 
       SUMMARY OF THE INVENTION 
       [0009]    It is one object of the present invention to provide a negative-pressure oral apparatus, capable of alleviating or curing snore and obstructive sleep apnea (OSA). The apparatus can be installed between the lips and the teeth of the user to separate the soft tissues on the lips and the tongue from the teeth and prevent the negative pressure from being applied directly on the soft tissues of the tongue. 
         [0010]    It is another object of the present invention to provide a negative-pressure oral apparatus, capable of adjusting the position of soft tissues of the soft palate and the position of the tongue using the negative pressure so that the upper respiratory airway is kept unobstructed and the discomfort of soft tissues in the oral cavity due to the negative pressure interface is relieved. 
         [0011]    It is still another object of the present invention to provide a negative-pressure oral apparatus and a method for maintaining a negative oral pressure and collecting liquid, the oral apparatus comprising a detachable negative-pressure element and a detachable liquid-collecting element so that the part contaminated by the saliva can be detached to be cleaned, replaced or discarded. Since the oral apparatus is tubeless, the inconvenience due to lengthy tubes can be avoided and contamination and malfunction due to saliva can be prevented, and the loading of the pump is relieved. 
         [0012]    In one embodiment, the present invention provides a negative-pressure oral apparatus, comprising: a first gripping portion, comprising a first component and a second component having one end connected to the first component so that a first compartment is formed between the first component and the second component; and a third component, being connected to the first gripping portion so that a second compartment is formed between the third component and the second component and at least a channel is disposed between the third component and the first gripping portion. 
         [0013]    In another embodiment, the present invention provides a negative-pressure oral apparatus, comprising: a first gripping portion, comprising a first component and a second component having one end connected to the first component so that a first compartment is formed between the first component and the second component; a third component, being connected to the first gripping portion so that a second compartment is formed between the third component and the second component and at least a channel is disposed between the third component and the first gripping portion; and a liquid collecting apparatus, being connected to the channel and capable of storing a liquid collected in the second compartment. 
         [0014]    In another embodiment, the present invention provides a negative-pressure oral apparatus, comprising: a first gripping portion, comprising a first component and a second component having one end connected to the first component so that a first compartment is formed between the first component and the second component; a third component, being connected to the first gripping portion so that a second compartment is formed between the third component and the second component and at least a channel is disposed between the third component and the first gripping portion; and a negative-pressure element, being connected to the first gripping portion and capable of providing a negative pressure to expel gas and/or liquid in the second compartment through the channel. 
         [0015]    In another embodiment, the present invention provides a method for maintaining a negative oral pressure and collecting liquid, comprising steps of: attaching an oral apparatus comprising a liquid collecting apparatus to a mouth of a patient; applying a negative-pressure element on an outlet of the liquid collecting apparatus so that the negative-pressure element generates a negative pressure through a channel between the liquid collecting apparatus and the oral apparatus to expel gas and/or liquid from the oral cavity and maintain the negative oral pressure; and collecting liquid by an absorbing element in the liquid collecting apparatus, while the gas is expelled through the outlet from the liquid collecting apparatus. 
         [0016]    In another embodiment, the present invention provides a method for maintaining a negative oral pressure and collecting liquid, comprising steps of: attaching an oral apparatus comprising a negative-pressure element to a mouth of a patient; generating a negative pressure through an inlet of the negative-pressure element channeled with the oral apparatus to expel gas and/or liquid from the oral cavity and maintain the negative oral pressure; and collecting liquid by an absorbing element near the inlet of the negative-pressure element, while the gas is expelled from the absorbing element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The objects, spirits and advantages of the preferred embodiments of the present invention will be readily understood by the accompanying drawings and detailed descriptions, wherein: 
           [0018]      FIG. 1A  to  FIG. 1C  show the breathing conditions of a sleeping person having a normal respiratory airway or an abnormal respiratory airway; 
           [0019]      FIG. 2  is a schematic diagram showing a constant positive airway pressure (CPAP) machine  11  used for treating obstructive sleep apnea (OSA); 
           [0020]      FIG. 3A  is a 3-D view of a negative-pressure oral apparatus according to a first embodiment of the present invention; 
           [0021]      FIG. 3B  is a cross-sectional view of a negative-pressure oral apparatus in  FIG. 3A ; 
           [0022]      FIG. 4A  and  FIG. 4B  are schematic diagrams of a negative-pressure oral apparatus with strengthened fixation; 
           [0023]      FIG. 5A  and  FIG. 5B  show a 3-D view and a cross-sectional view of a negative-pressure oral apparatus according to a second embodiment of the present invention; 
           [0024]      FIG. 5C  is a cross-sectional view of a negative-pressure oral apparatus without a sixth component according to a second embodiment of the present invention; 
           [0025]      FIG. 6A  is a 3-D view of a negative-pressure oral apparatus according to a third embodiment of the present invention; 
           [0026]      FIG. 6B  is an exploded view of a negative-pressure oral apparatus in  FIG. 6A ; 
           [0027]      FIG. 6C  is a 3-D view of a negative-pressure oral apparatus according to a fourth embodiment of the present invention; 
           [0028]      FIG. 7  is a schematic diagram of an absorbing element of the present invention; 
           [0029]      FIG. 8A  is a 3-D view of a negative-pressure oral apparatus according to a fifth embodiment of the present invention; and 
           [0030]      FIG. 8B  is a cross-sectional view of a liquid collecting apparatus of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0031]    The present invention can be exemplified by several embodiments as described hereinafter. 
         [0032]    Please refer to  FIG. 3A  and  FIG. 3B .  FIG. 3A  is a 3-D view of a negative-pressure oral apparatus according to a first embodiment of the present invention.  FIG. 3B  is a cross-sectional view of a negative-pressure oral apparatus in  FIG. 3A . The negative-pressure oral apparatus  2  comprises a first gripping portion  20  and a third component  21 . The first gripping portion  20  comprises a first component  201  and a second component  202 . The second component  202  has one end connected to the first component  201  so that a first compartment  203  is formed between the first component  201  and the second component  202 . In the present embodiment, the first component  201  is attached to the outer surface of the upper lip of the user, while the second component  202  is disposed in the oral cavity and the inner surface of the upper lip is close to the outer surface of the upper teeth. 
         [0033]    The third component  21  is coupled to the first gripping portion  20  so that a second compartment  22  is formed between the third component  21  and the second component  202 . At least a channel  23  is further disposed between the third component  21  and the first gripping portion  20 . The third component  21  is disposed against the inner surface of the upper teeth and the upper gum in the oral cavity. Since the first gripping portion  20  and the third component  21  are engaged to the upper lip and the upper teeth, the negative-pressure oral apparatus  2  can be prevented from falling off due to mouth opening. In order to enhance the attachment to the oral cavity, gripping elements are embedded in the first gripping portion  20  and the third component  21 , respectively, to grip the upper lip and the upper teeth. The gripping element is formed of one of an elastic material, a thermoplastic material, a magnetic material, a spring and a memory-type metal material. Please refer to  FIG. 4A  and  FIG. 4B , which are schematic diagrams of a negative-pressure oral apparatus with strengthened fixation in another embodiment. In  FIG. 4A , a gripping element  204  or  211  formed of a magnetic material is embedded in the first gripping portion  20  and the third component  21  for strengthened fixation. In  FIG. 4B , a gripping element  205  or  212  formed of an elastic material, a memory-type metal material or a spring is embedded in the first gripping portion  20  and the third component  21  for strengthened fixation. 
         [0034]    As shown in  FIG. 3B  in the present embodiment, the channel  23  is further coupled to a negative-pressure source  24  to provide a negative pressure. The negative-pressure source  24  can be a pump, a vacuum device or the like, which is well known to those with ordinary skills in the art. Moreover, at least a groove  213  is formed on the surface of the third component  21  corresponding to the first gripping portion  20 . The groove  213  connects the external negative pressure to the oral cavity so that the soft palate and the surrounding soft tissues of the user are pulled towards the front portion of the oral cavity and the tongue is pulled towards the upper palate to keep the upper respiratory airway unobstructed. 
         [0035]    Please refer to  FIG. 5A , which shows a 3-D view of a negative-pressure oral apparatus according to a second embodiment of the present invention. In the present embodiment, the negative-pressure oral apparatus  2  is similar to that in the first embodiment except that the oral apparatus  2  further comprises a second gripping portion  25 , which is similar to the first gripping portion  20  in structure. The second gripping portion  25  comprises a fifth component  251  and a sixth component  252  to form a third compartment  250  therein so that the second gripping portion  25  is attached to the bottom lip of the user to further facilitate the fixation between the oral apparatus  2  and the oral cavity of the user. As shown in  FIG. 5B , a fourth component  26  is further provided to be coupled to the second gripping portion  25 . More particularly, a fourth compartment  260 , channeled with the channel  23 , is formed between the fourth component  26  and the fifth component  251 . The fourth component  26  is disposed against the inner surface of the bottom teeth and the bottom gum in the oral cavity. Moreover, the fourth component  26  further comprises at least a groove  261 , which is functionally similar to the groove  213 , and thus description thereof is not presented. As shown in  FIG. 5C , the second embodiment can do without the sixth component  252  of the second gripping portion  25 , but further comprise a compartment  260  formed between the fourth component  26  and the fifth component  251 . The compartment  260  can be channeled with the channel  23 . The second gripping portion  25  and the fourth component  26  can be formed of an elastic material or a thermoplastic material. Alternatively, as shown in  FIG. 4A  or  FIG. 4B , a gripping element formed of an elastic material, a memory-type material, a spring or a magnetic material can be embedded to strengthen fixation. 
         [0036]    Please refer to  FIG. 6A , which is a 3-D view of a negative-pressure oral apparatus according to a third embodiment of the present invention. The negative-pressure oral apparatus  3  comprises a first gripping portion  30 , a third component  31  and a liquid collecting apparatus  32 . The first gripping portion  30  and the third component  31  are structured as described in the first embodiment, and thus the descriptions thereof are not presented. The liquid collecting apparatus  32  is connected with the compartment between the third component  31  and the first gripping portion  30  via at least a channel  33 . The liquid collecting apparatus  32  is capable of sucking liquid from the compartment between the third component  31  and the first gripping portion  30 . The liquid collecting apparatus  32  comprises a container  321  and a negative-pressure element  320 . The liquid collecting apparatus  32  comprises an opening  34  and a sealing cap  35  at the bottom portion for internal cleaning. As shown in  FIG. 6B , which is an exploded view of a negative-pressure oral apparatus in  FIG. 6A . The container  321  comprises at least an inlet  3210  and an outlet  3211 . The inlet  3210  is connected with the channel  33  on the first gripping portion  20  to collect saliva in the oral cavity. In order to attach the container  321  firmly to the first gripping portion  30 , the container  321  further comprises at least a connecting member  3212  to be combined with a complementary connecting member  300  on the first gripping portion  30  so that the first gripping portion  30  and the container  321  can be securely attached to prevent leakage of gas/liquid. Moreover, the connecting member  3212  is designed so that the container  321  and the first gripping portion  30  can be easily disassembled to provide portability and convenience for the user to carry, clean and maintain. 
         [0037]    Please refer to  FIG. 6C , which is a 3-D view of a negative-pressure oral apparatus according to a fourth embodiment of the present invention. In the present embodiment, the negative-pressure oral apparatus  5  comprises a body  50 , a negative-pressure pump  51 , a liquid collector  52  and a control unit  53 . The body  50  comprises a first gripping portion  500  and the third component  501 , as described in the first embodiment. The negative-pressure pump  51  is connected with a channel (not shown but exemplified by label  23  in  FIG. 3B ) in the body  50  to provide negative pressure to suck fluid from the oral cavity through the channel into the liquid collector  52 , which is also channeled with the negative-pressure pump  51 . The control unit  53  is electrically connected to the negative-pressure pump  51  via an electrical wire  54  to control the negative-pressure pump. The embodiment in  FIG. 6C  is similar to the embodiment in  FIG. 6A  except that the liquid collector  52  in  FIG. 6C  is integrated with the negative-pressure pump  51  and is connected to the body  50  through the negative-pressure pump  51 . 
         [0038]    Please refer to  FIG. 7 , which is a schematic diagram of an absorbing element of the present invention. The container  321  comprises an absorbing element  322  to absorb liquid from the inlet. Referring to  FIG. 6A  and  FIG. 7 , the absorbing element  322  can be inserted into the liquid collecting apparatus  32  via the opening  34 , which is then sealed by the sealing cap  35 . Generally, the absorbing element  322  is formed of a absorbent material or a porous material, such as sponge, paper, cloth, foam, absorptive resin or the like. However, the present invention is not limited thereto. The absorbing element  322   a  is capable of absorbing liquid. On the other hand, the absorbing element  322   a  is porous to provide a negative-pressure gas flow. Moreover, the absorbing element  322  is removable, re-usable or disposable, and thus can be replaced or discarded according to practical usage to keep the oral apparatus  3  clean. In the present embodiment, the absorbing element  322  further comprises a winded channel  3220  to increase the probability that the liquid expelled (such as saliva) is absorbed by the absorbing element  322  and to allow the gas to flow through quickly. Returning to  FIG. 6A , the negative-pressure element  320  is a removable micro-pump attached to the oral apparatus  3 . The negative-pressure element  320  is coupled to the outlet  3211  through the tube  323  or is tubelessly coupled to the outlet  3211 . The negative-pressure element  320  is capable of providing a negative pressure so that the gas and/or liquid between the third component  31  and the first gripping portion  30  is pumped into the container  321 . Using such design of the absorbing element and the negative-pressure element, problems due to contamination caused by saliva can be prevented. 
         [0039]    As shown in  FIG. 6A ,  FIG. 6B  and  FIG. 7 , the present invention further provides a method for maintaining a negative oral pressure and collecting liquid, comprising steps of: attaching an oral apparatus  3  comprising a liquid collecting apparatus  32  to a mouth of a patient; applying a negative-pressure element  320  on an outlet  3211  of the liquid collecting apparatus  32   a  so that the negative-pressure element  320  generates a negative pressure through a channel  33  between the liquid collecting apparatus  32  and the oral apparatus  3  to expel gas and/or liquid from the oral cavity and maintain the negative oral pressure; and collecting liquid by an absorbing element  322  in the liquid collecting apparatus  32 , while the gas is expelled through the outlet  3211  from the liquid collecting apparatus  32 . Moreover, the method further comprises steps of: using a pressure sensor unit  36  to sense the pressure in the oral cavity after the negative-pressure element  320  is started; and turning off the negative-pressure element  320  automatically if the negative-pressure element  320  has been running for a period of time while the oral pressure does not reach its target value, which indicates that the oral apparatus  3  is not installed properly and may have leakage. Moreover, the pressure sensor unit  36  is capable of sensing the pressure in the oral cavity when the negative-pressure element  320  is not running; when the patient sucks voluntarily and man-made negative pressure in the oral cavity can be used as a triggering signal to start the negative-pressure element  320  automatically. Moreover, the method further comprises steps of: using a flow sensor unit  37  to sense the breathing air flow of the patient when the negative-pressure element  320  is started; and turning off the negative-pressure element  320  automatically if the breath is not sensed for a period of time. 
         [0040]    Please refer to  FIG. 8A  and  FIG. 8B . More particularly,  FIG. 8A  is a 3-D view of a negative-pressure oral apparatus according to a fifth embodiment of the present invention; and  FIG. 8B  is a cross-sectional view of a liquid collecting apparatus of the present invention. In the present embodiment, the oral apparatus  4  comprises a first gripping portion  40 , a third component  41 , a second gripping portion  42  and a liquid collecting apparatus  43 . The first gripping portion  40 , the third component  41  and the second gripping portion  42  are structured as previously described and thus descriptions thereof are not repeated. In the present embodiment, the liquid collecting apparatus  43  comprises a pumping element  44 , an absorbing element  431  and a control unit  432 . The pumping element  44  comprises an inlet  446  and an outlet  447 . The inlet  446  is connected with at least a channel (not shown but exemplified by label  23  in  FIG. 3B ) to suck gas and/or liquid and drain gas and/or liquid through the outlet  447 . The absorbing element  431  is coupled to the outlet  447  to absorb the liquid from the outlet  447 . The absorbing element  431  further comprises a hollow recessed part  4310  to embed the pumping element  44  and a protruding part  45  on the first gripping portion  40  so that the absorbing element  431  and the oral apparatus  4  are detachably connected to enable the user to replace the absorbing element  431  or to separate the absorbing element  431  and the pumping element  44  for cleaning according to usage conditions. The control unit  432  is electrically connected to the pumping element  44 . In the present embodiment, the control unit  432  controls the power module to provide the pumping element  44  with AC signals. The absorbing element  431  is structured as previously described and thus description thereof is not repeated. 
         [0041]    Moreover, the inlet  446  further comprises a pressure sensor unit  46  electrically connected to the control unit  432 . The pressure sensor unit  46  is capable of sensing the pressure in the oral cavity after the pumping element  44  is activated. The control unit  432  turns off the pumping element  44  automatically or an alarm unit  4320  issues an alarm signal if the pumping element  44  has been operated for a period of time while the sensed oral pressure does not reach its target value, which indicates that the oral apparatus  3  is not installed properly and may have leakage. Moreover, the pressure sensor unit  46  is capable of sensing the pressure in the oral cavity when the pumping element  44  is not started. The control unit  432  turns on the pumping element  44  automatically when the pressure is lowered by the man-made oral suction of the patient. When the pumping element  44  is activated, the negative pressure caused by the pumping element  44  pulls the soft palate and the surrounding soft tissues of the user towards the front portion of the oral cavity and the tongue towards the upper palate to keep the upper respiratory airway of the user unobstructed. Moreover, the oral apparatus  4  further comprises a flow sensor unit  47  electrically connected to the control unit  432 . The flow sensor unit  47  is capable of sensing the breathing flow of the user when the pumping element  44  is running so that the control unit  432  turns off the pumping element  44  automatically and the alarm unit  4320  issues an alarm signal if the breathing flow is not sensed for a period of time. 
         [0042]    The pumping element  44  comprises a casing  440 , a piston  441 , a thrust generator  442  and a winding portion  443 . The casing  40  further comprises a cylinder  444  therein to install the piston  441 . The piston  441  comprises a permanent magnetic field that is capable of performing movement in the cylinder  444 . In the present embodiment, the piston  441  further comprises a pair of magnetically permeable caps  4410  and  4411  and a magnetic body  4412 . The magnetic body  4412  is disposed between the pair of magnetically permeable caps  4410  and  4411  to provide the permanent magnetic field. In the present embodiment, the magnetic body  442  is a permanent magnet. The end of the magnetic body  442  corresponding to the casing  440  is the northern pole, while the other end of the magnetic body  442  is the southern pole. 
         [0043]    The thrust generator  442  is disposed on an inner wall of the casing  440  and is facing the piston  441 . In the present embodiment, the thrust generator  442  is a magnetic element, which is capable of providing a magnetic field having a direction opposite to magnetic field direction of the magnetic body  4412  so that a first action force is generated on the piston  441 . The winding portion  443  is disposed on one side of the cylinder  444 , to provide a second action force on the piston  441  to move the piston  441 . Therefore, the piston  441  can move up and down in the cylinder  444  due to the resultant of the second action force and the first action force. In the present embodiment, the winding portion  443  further comprises a top magnetic ring  4430 , a bottom magnetic ring  4431  and a coil  4432 . The coil  4432  is disposed in the compartment between the top magnetic ring  4430  and the bottom magnetic ring  4431 . The coil  4432  generates the second action force after it is fed with electrical signals. The cylinder  444  is further connected with a compression chamber  445 . The compression chamber  445  is coupled to the inlet and the outlet. Furthermore, a check valve  448  is disposed between the inlet  446  and the compression chamber  445 , and a check valve  449  is disposed between the outlet  447  and the compression chamber  445 . 
         [0044]    When the coil  4431  is not fed with electrical signals, a rejection force is generated between the piston  441  and the thrust generator  442  if the thrust generator  442  and the piston  441  faces with the same magnetic pole (for, example, the northern pole in the present embodiment) so that the piston  441  is departed from the center of the coil  4431 . When the coil  4431  is fed with an AC electrical signal, a reversed magnetic force is generated from the winding portion  443  to push the piston  441  out if the phase of the AC electrical signal is negative. On the contrary, a forward magnetic force is generated from the winding portion  443  to overcome the rejection force between the piston  441  and the thrust generator  442  to pull the piston  441  in if the phase of the AC electrical signal is positive. In this manner, with the repeatedly alternative positive and negative potentials, the resultant of the magnetic force generated from the winding portion  443  and the rejection force generated from the thrust generator  442  enables the piston  441  to move up and down in the cylinder  444 . As the piston  441  moves upwards in the cylinder  444 , a negative pressure is generated so that saliva is expelled via the channel between the third component  41  and the first gripping portion  40  to pass through the inlet  446  to enter the compression chamber  445 . As the piston  441  moves downwards in the cylinder  444 , a positive pressure is generated to push saliva through the outlet  447  to enter the absorbing element  431 . 
         [0045]    Using the apparatus as shown in  FIG. 8A  and  FIG. 8B , the present invention provides a tubeless method for maintaining a negative oral pressure and collecting liquid, comprising steps of: attaching an oral apparatus  4  comprising a negative-pressure element to a mouth of a patient; generating a negative pressure through an inlet of the negative-pressure element connected with the oral apparatus  4  to expel gas and/or liquid from the oral cavity and maintain the negative oral pressure; and collecting liquid by an absorbing element  431  near the inlet of the negative-pressure element, while the gas is expelled from the absorbing element  431 . In the present embodiment, the negative-pressure element is a micro pumping element  44  capable of generating a negative pressure. Moreover, the method further comprises steps of: using a pressure sensor unit  46  to sense the pressure in the oral cavity after the pumping element  44  is started; and turning off the pumping element  44  automatically if the pumping element  44  has been operated for a period of time while the sensed oral pressure does not reach its target value, which indicates that the oral apparatus  3  is not installed properly and may have leakage. Moreover, the pressure sensor unit  46  is capable of sensing the pressure in the oral cavity when the pumping element  44  is not started so that the pumping element  44  can be turned on automatically when the oral cavity pressure of the patient is lowered by man-made suction. Moreover, the method further comprises steps of: using a flow sensor unit  47  to sense the breathing flow of the patient when the pumping element  44  is started; and turning off the pumping element  44  automatically if the breathing flow is not sensed for a period of time. 
         [0046]    In the present invention, the liquid collecting apparatus and the gripping portion can be modified and combined. However, any person with ordinary skill in the art is able to make modifications within the scope of the present invention. Moreover, the negative-pressure source  24  in  FIG. 3B  and the negative-pressure element  320  in  FIG. 6A  can be replaced by the pumping element  44  in  FIG. 8B . 
         [0047]    Accordingly, the present invention discloses a negative-pressure oral apparatus disposed in the oral cavity and capable of providing the oral cavity with a negative pressure to prevent obstructive sleep apnea (OSA) and snoring and expelling a liquid in the oral cavity while preventing saliva leakage or contamination and a method for maintaining a negative oral pressure and collecting liquid. Therefore, the present invention is novel, useful and non-obvious. 
         [0048]    Although this invention has been disclosed and illustrated with reference to particular embodiments, the principles involved are susceptible for use in numerous other embodiments that will be apparent to persons skilled in the art. This invention is, therefore, to be limited only as indicated by the scope of the appended claims.