The Temporomandibular joint (TMJ) repositioning by use of interocclusal splints has become a popular treatment for head, neck and facial pain. There is a growing feeling that the proper use of occlusal appliances with the resultant correct positioning and stability of the mandible, affects total head posture to bring about proper alignment of the cervical vertebrae.¹⁻² Improper TMJ biomechanics will have a negative effect on the skeletal frame in general, and the relatively large neural and vascular component in the TMJ region in particular.³ For those with a TMJ imbalance, proponents of repositioning appliances maintain that the proper occlusal splint will reduce tension, alleviate negative neural and vascular input from the oro-facial area to the brain, improve muscle balance and performance, and augment blood flow in major areas of the body.⁴⁻⁹
Occlusal splints are removable interocclusal appliances that are usually fabricated out of hard acrylic. The objectives of splint use in the treatment of temporomandibular disorders (TMD) and myofascial pain dysfunction (MPD) include: eliminating occlusal interferences, stabilizing tooth and joint relationships, passive stretching of the musculature to reduce abnormal muscle activity, decreasing parafunctional habits, protecting against tooth abrasion and decreasing joint loading. Splints also function diagnostically as an indirect method of altering occlusion.
Major theories covering the mechanism of action of splints include: occlusal disengagement theory, vertical dimension theory, maxillo-mandibular realignment theory, TM joint repositioning theory and the cognitive awareness theory. Each has multiple proponents with many variations.
The occlusal disengagement theory proposes that the placement of an appliance, with proper occlusal relationships, replaces previously faulty occlusal relationships. This eliminates the stimulus causing muscular hypertrophy and in turn allows for proper joint and mandibular function.¹⁰
The vertical dimension theory suggests that the cranio-mandibular system is adaptive and can function in the presence of vertical change. When the change becomes excessive, and adaptive capacity is overcome, pathology and dysfunction may result. Therefore, placing an appliance to restore a more normal vertical dimension of occlusion may cause a decrease in dysfunction.¹¹
The maxillo-mandibular realignment theory proposes that the mandible is malpositioned relative to the maxilla at the position of maximum tooth intercuspation. It is believed that if the mandible is repositioned, a more optimum maxillo-mandibular relationship can be evolved, and the symptoms eliminated. Splints are an intermediary step in the process, interposing a new interarch relationship that achieves a balanced mandibular position.¹²
The temporomandibular joint repositioning theory proposes that a change in the condylar position within an involved TM joint will improve joint function and relieve symptoms.¹³
The cognitive awareness theory states that the presence of any splint in the patient's mouth is a constant reminder to alter previous behavior patterns.¹⁴
It is important to understand that splint therapy is a concept, not merely the introduction of a piece of plastic (acrylic). It is not a treatment that functions alone, but within the context of other treatment measures including physical therapy and/or chiropractic care, medication, psychological counseling and other branches of medical and dental care.
Splint therapy should be performed with specific objectives in mind. The ideal splint should be comfortable, non-invasive, reversible, aesthetic and functional. It should stabilize jaw relationships, provide desired occlusal patterns, and decrease abnormal muscle activity, parafunctional oral habits and joint loading.
Proper selection of splint type depends on an individual patient's needs. Above all, splint selection depends on an accurate diagnosis. Muscular disorders without joint involvement have different requirements from internal derangements. Internal derangements differ in the extent of meniscus displacement, chronicity and degree of pathologic tissue change.
MPD is one of the most common ailments of humankind and the condition will linger without specific treatment. MPD patients are seen by the entire gamut of pain practitioners including neurologists, orthopedists, physical therapists, chiropractors, myotherapists, dentists and acupuncturists.
An appliance (interocclusal splint) that acts as an initial treatment and diagnostic appliance, is a preformed, fluid-filled, inter-occlusal device designed to balance and cushion the dental bite. An interocclusal splint is a disposable oral splint with fluid filled pads that sit between the patient's posterior teeth, bilaterally. From a physiologic standpoint, the interocclusal splint acts by allowing muscle-dominated mandibular repositioning and perfectly distributing the occlusal forces. Because the surface of this appliance is slick and extremely flexible, the teeth can easily slide across it. By interposing the flexible fluid layer between the upper and lower occlusal surfaces of the teeth, and not allowing occlusal contact, the interocclusal splint eliminates the occlusion as a factor in mandibular placement. The muscles are now free to slide into a position of maximal muscle comfort. The muscles of mandibular closure respond by instantly moving the mandible into the most comfortable, least accommodated position. Generally, within the first minute, this occlusal/muscle harmony eliminates the muscle spasm. Over the next days and weeks, elimination of muscle spasm contributes to the muscles healing themselves.
Splint therapy should be performed with specific objectives in mind. The ideal splint should be comfortable, non-invasive, reversible, aesthetic and functional.
The interocclusal splint incorporates a fluid-filled system that responds dynamically as the mandible is shifting to a position of maximal muscle comfort. The sterile water continuously re-adjusts to the changing relationships of the teeth. This appliance takes full advantage of Pascal's Law of Hydrodynamics that states that a property of an enclosed fluid system is the perfect distribution of forces in every dimension. Ideally, occlusal forces are perfectly axial and equal. The pain practitioner accomplishes this by simply inserting the self-adjusting interocclusal splint.
Clinical studies have confirmed that the sequence of muscle dysfunction spreads beyond the masticatory muscles, producing an entire constellation of secondary symptoms that are referred to other, more distant areas of the head and neck. These secondary symptoms include some of the most widespread and problematic conditions presenting to the healing professions for diagnosis and treatment. These conditions include tension type (muscle contraction) headaches, atypical facial pain, tinnitus, neck pain and ear pain among others. These secondary symptoms are functional disturbances which exhibit no organic changes in the affected tissues, making diagnosis difficult.¹⁵
The masticatory muscle origin of these symptoms is not readily apparent. The usual result is that treatment is mistakenly directed to the secondary symptoms locale, rather than the underlying dysfunction of the muscles of the stomatognathic system
The hydrostatic appliance has been shown to be highly effective for temporary and emergency pain relief at the first visit. Within five to 20 minutes of insertion of the hydrostatic appliance, the muscles of the stomatognathic system relax profoundly. By accomplishing this quick muscle relaxation, with concomitant pain relief, patients are encouraged to follow treatment recommendations.