Appliance for temporomandibular joint dysfunction

An intraoral appliance to be worn for the diagnosis and treatment of temporomandibular joint dysfunction. The appliance has upper and lower members which fit respectively on the person's maxillary and mandibular arch. The lower member has an upward projection which makes low friction gliding contact against a smooth surface located anteriorly on the upper member. This maintains vertical clearance between the maxillary arch and the mandibular arch and ensures free horizontal movement of the mandible to allow it to assume a position wherein the masticatory muscles are allowed to relax. Wearing the appliance for a period of time relieves the symptoms of acute and/or chronic headaches which result from temporomandibular joint dysfunction.

BACKGROUND OF THE INVENTION 
This invention relates generally to dental appliances and more particularly 
to an appliance for the diagnosis and treatment of temporomandibular joint 
dysfunction. 
The temporomandibular joints are located on opposite sides of the cranium. 
On each side, the mandible has a smoothly curved condyle which is received 
in a matching fossa in the cranium. A meniscus or articular disc is 
located between the condyle and fossa to provide a cushion between them. 
Numerous masticatory muscles connect to the mandible to provide for any 
combination of horizontal and vertical movements relative to the maxilla. 
It is well known that temporomandibular joint dysfunction is normally 
caused by malocclusion due to misalignment of the mandible with the 
maxilla and/or some of the upper and lower teeth. Proprioceptive nerve 
endings in the periodontal ligaments surrounding the roots of the teeth 
send messages that control the manner in which the masticatory muscles 
close the mandible. The primary function of this myo-neural mechanism is 
to protect the teeth, supporting bone, and soft tissue from the adverse 
affects of malocclusion. The muscles, while functioning in disharmony, 
react and bruxism or grinding is initiated in an effort to correct the 
malocclusion. The result is mild to severe muscle fatigue and in some 
cases a complete derangement of the temporomandibular joint whereby the 
articular discs are pulled forward leaving the condyles to function on the 
retro-discal fibres and the cranial fossae. While temporomandibular joint 
dysfunction has various symptoms such as neck and ear pain, it usually 
causes acute and/or chronic headaches which are frequently mistakenly 
attributed to other causes such as stress or migraine. 
Previous attempts to overcome this problem fall into two categories. The 
first category is appliances which are worn by a person to relieve pain or 
to reposition the mandible. The second category is devices which are 
temporarily placed in the mouth of a patient during a dental procedure. An 
example of the first category is shown in Canadian patent number 1,136,450 
to Lerman which issued Nov. 30, 1982 wherein a fluid containing portion of 
the appliance extends between the upper and lower teeth. Other examples of 
this category are seen in Canadian patent numbers 1,147,583 to Dufour 
which issued Jun. 7, 1983, 1,221,254 to Ahlin which issued May 5, 1987 and 
U.S. Pat. No. 4,671,766 to Norton which issued Jun. 9, 1987 all of which 
show various appliances to be worn to relocate the mandible to its proper 
position. Examples of devices in the second category which are used during 
balancing of dentures or teeth are shown in U.S. Pat. No. 3,068,570 to 
Thompson et al which issued Dec. 18, 1962 and U.S. Pat. No. 4,964,769 to 
Hass which issued Oct. 23, 1990. The devices in the second category have 
the disadvantage that they are not suitable for wear over any extended 
period of time, while the appliances in the first category have the 
disadvantages that they are not comfortable to wear and do not 
satisfactorily relieve the symptoms of temporomandibular joint 
dysfunction. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to overcome at least 
some of the disadvantages of the prior art by providing an intraoral 
appliance which is worn to maintain clearance between the maxillary arch 
and the mandibular arch and ensure relatively free horizontal movement of 
the mandible to relieve the symptoms of temporomandibular joint 
dysfunction. 
To this end, in one of its aspects, the invention provides an intraoral 
appliance to be worn by a person having a maxilla with a maxillary arch, a 
mandible with a mandibular arch, and temporomandibular joints which 
provide for motion of the mandible relative to the maxilla, the appliance 
comprising an upper member and a separate lower member, the upper member 
being removably mountable on the maxillary arch, the lower member being 
removably mountable on the mandibular arch, one of the upper and lower 
members having an anteriorly located smooth surface facing towards the 
other of the upper and lower members, the other member having an 
anteriorly located projection to extend towards the smooth surface of said 
one member, whereby gliding contact of the projection from said other 
member against the smooth surface of said one member maintains vertical 
clearance between the maxillary arch and the mandibular arch and ensures 
relatively free horizontal movement of the mandible throughout horizontal 
border movement of the mandible. 
Further objects and advantages of the invention will appear from the 
following description, taken together with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
Reference is first made to FIG. 1 which shows the structure of a normal 
temporomandibular joint in the closed and open (shown dotted) positions. 
The mandible 10 has a smoothly curved condyle 12 which is received in a 
matching fossa 14 in the temporal bone 16 of the cranium. A meniscus or 
articular disc 18 extends between the condyle 12 and the fossa 14 to 
provide a cushion between them. Numerous masticatory muscles 20 connect to 
the mandible 10 and to the meniscus 18 to articulate the mandible 10 and 
to guide the meniscus 18 posteriorly to retain it in position between the 
condyle 12 and the fossa 14 as the mandible 10 articulates. Of course, 
there are temporomandibular joints on both sides of the cranium to provide 
the mandible 10 with the required full range of horizontal as well as 
vertical movement. 
As seen in FIG. 2-4, the intraoral appliance according to a first 
embodiment of the invention has an upper member 22 and a lower member 24. 
These members 22, 24 are injection molded of a suitable plastic material 
and coated with dental acrylic. As seen in FIG. 3, these members 22, 24 
are fitted to be removably mounted comfortably on the maxillary and 
mandibular arches 26, 28 respectively. While the appliance according to 
the invention can be used with artificial dentures as well as natural 
teeth, in the embodiment both the upper and lower members 22, 24 have 
posteriorly extending portions 30, 32 which are fitted along the inner 
sides of the natural teeth 34. In this case, these portions 30, 32 have 
retaining wires 36 which are anchored in the plastic and bent to extend 
across the teeth 34 to keep them in place in the absence of contact 
between the upper and lower teeth. Of course, other tooth retaining means 
can be used as well. 
The upper member 22 has a smooth glide surface 38 which faces downwardly 
towards the lower member 24. In this embodiment, the smooth glide surface 
38 is provided by a stainless steel plate 40 which is securely embedded in 
the plastic, but other suitable strong materials or arrangements can be 
used as well. The smooth glide surface 38 can be flat or slightly curved, 
and in this embodiment is somewhat concave. However, the surface 38 must 
be smooth and very resistant to wear. When the upper member 22 is mounted 
in position, the smooth glide surface 38 is centrally located anteriorly 
in the maxillary arch 26 to leave sufficient space for the tongue for 
comfortable wear over an extended period of time. 
The lower member 24 has a projection 42 which extends upwards to contact 
the smooth glide surface 38 of the upper member 22 when the mandible is 
elevated towards the closed position. The vertical position of the smooth 
glide surface 38 on the upper member 22 and the height of the projection 
42 from the lower member 24 are calculated to ensure vertical clearance 
between the maxillary arch 26 and the mandibular arch 2 throughout the 
entire horizontal border movement of the mandible 10. This clearance 
should not be greater than the freeway space between the closed and 
relaxed positions of the mandible. In this embodiment, the projection 42 
has a ball bearing 44 to provide rolling contact against the smooth glide 
surface 38 of the upper member 22. However, in other embodiments the 
projection can have a point made of stainless steel or other suitable 
configurations and materials to provide low friction gliding contact 
against the smooth glide surface 38 of the upper member 22. The projection 
42 is located to extend centrally near the mid sagittal line in the 
relaxed position of the mandible 10. The projection 42 is also anteriorly 
located to contact the smooth glide surface 38 of the upper member 22 when 
the mandible 10 is elevated towards the closed position which similarly 
provides a comfortable space for the persons' tongue. The smooth glide 
surface 38 of the upper member 22 must be of sufficient size and shape to 
provide for gliding contact of the projection 42 against it throughout the 
entire horizontal border movement of the mandible. This gliding contact of 
the projection 42 of the lower member 24 against the smooth glide surface 
38 of the upper member 22 must have sufficiently low friction to ensure 
relatively free horizontal movement of the mandible at all times. In other 
embodiments, the smooth glide surface 38 can be on the lower member 24 and 
the projection 42 on the upper member. However, they must be positioned to 
contact throughout the range of horizontal motion of the mandible to 
ensure there is clearance between the maxillary arch 26 and the mandibular 
arch 28. 
In use, the appliance is made to fit securely and is mounted (as seen in 
FIG. 3), in the mouth of a person having the symptoms of temporomandibular 
joint dysfunction. When the mandible is elevated towards the closed 
position, the projection 42 on the lower member 24 makes gliding contact 
against the smooth glide surface 38 on the upper member 22 to maintain 
clearance between the maxillary arch 26 and the mandibular arch 28 
throughout the entire range of movement of the mandible 10. The low 
friction of the gliding contact between the projection 42 and the smooth 
glide surface 38 ensures relatively free horizontal movement of the 
mandible. This allows the mandible to readily assume a normal position 
wherein the masticatory muscles which control the horizontal movement are 
relaxed. As the clearance between the teeth is not greater than the 
freeway space, the mandible elevator muscles are also relaxed in this 
position. While the appliance is removed during eating, otherwise constant 
wearing of the appliance for a period of several days will normally 
considerably alleviate pain and/or headache which are, in fact, the result 
of temporomandibular joint dysfunction. Thus the appliance can be used to 
both diagnose temporomandibular joint dysfunction and to treat its 
symptoms. After the pain has initially been relieved, more intermittent 
wearing of the appliance such as only when sleeping may be sufficient to 
satisfactorily relieve the symptoms. The extent of use required varies 
from person to person depending upon the severity of the condition. 
Reference is now made to FIG. 5 which shows a second embodiment of the 
invention. As can be seen, in this embodiment the appliance is smaller 
than described above in that the upper and lower members 22, 24 do not 
have the portions extending posteriorly along the teeth to retain them in 
place. This embodiment of the appliance is even more comfortable to wear 
and is used with artificial dentures or for short periods of wear (such as 
less than two days) with natural teeth where tooth migration is not a 
concern. Otherwise the structure and use of the upper and lower members 
22, 24 with the smooth glide surface 38 and projection 42 is the same as 
that described above and need not be repeated. 
While the description of the appliance has been given with respect to 
preferred embodiments, it will be evident that various modifications are 
possible without departing from the scope of the invention as understood 
by those skilled in the art and as defined in the following claims.