156 Further passive jaw opening beyond active opening
Passive jaw opening is usually executed with both hands. The index or middle fingers are placed on the upper premolars and the thumbs on the lower incisal edges. The patient opens the mouth as far as possible and at the end of the active movement the clinician assists further opening. The amount of passive movement is evaluated. If the one-handed technique is used the distance can be measured with the other hand.
Left: Chart entry.
157 Section of examination form dealing with passive jaw opening
If there is pain upon passive jaw opening, the amount of movement is written in red. Then the amount of force needed to elicit pain is indicated by means of red plus signs (+, ++, +++) written in the box for the painful side. The endfeel is recorded only when jaw opening is painless, otherwise the patient will reflexively tense the muscles.
158 Limited jaw opening resulting from skin changes in scleroderma
Left: In a patient with scleroderma, taut cords form In the skin during passive jaw opening and the end-feel is “too hard.” Right: Sclerosing of the skin causes typical limitation of jaw opening to 30-35 mm. This must not be confused with a nonreducing disk displacement.
159 A “too soft endfeel” with passive jaw opening
Left An endfeel that is “too soft” accompanied by condylar hypermobility. The length of the jaw-closing muscles limits opening movements when there is lengthening or overstretching of the capsule and ligaments. Rigbt: A “too soft” endfeel accompanied by reduction of jaw opening. Tensed or shortened elevator muscles are limiting the extent of jaw opening.
160 An endfeel that is “too hard” and “rebounding”
Left: A “too hard” endfeel with restricted jaw opening. The shortened capsule and ligaments are limiting jaw opening.
Center: MRI image of the nonreducing disk displacement at maximal jaw opening.
Right: Rebounding endfeel at the end of a restricted jaw-opening movement. The nonreducing anterior disk displacement limits jaw opening.
Differential Diagnosis of Restricted Movement
Nonpainful limitations of movement can be differentiated only by evaluating the endfeel after passive movement. The ability to make an exact determination of the endfeel requires practice and a little experience. This is the only method by which structural causes of restricted movement can be discovered. The elicited endfeel is merely verified secondarily through other methods such as the joint play technique, radiographs, or MRI. These, however, are not indicated for use as primary differential diagnostic procedures. During the passive jaw-opening procedure 92.5% of patients report a drawing sensation in the preauricular region (Hesse 1996). This false perception can be accounted for by the stretching of the joint capsule and the lateral ligament.
If passive jaw opening causes the patient pain, the endfeel cannot be used to aid in making a differential diagnosis of limited movement. Therefore, when the signs and symptoms include the combination “pain and restricted movement,” the pain must be treated first before an adequate differential diagnosis of the restricted movement can be made.
161 Examination sequence when there is a nonpainful limitation of jaw opening
The diagram shows the sequence in which the examination techniques are to be carried out. In a patient with scleroderma tight cords appear in the skin during passive jaw opening (Fig. 158). In these cases the dentist can prescribe mobilization exercises (“jawsercises,” Korn 1994) and refer the patient to a dermatologist if the disease is not already being treated. In patients with restricted jaw opening the endfeel may assume one of four characteristics: too soft, too hard, rebounding, or bony.
• Reduced jaw opening produced by shortening of the muscles gives a “too soft” endfeel during passive jaw opening (Groot Landeweer and Bumann 1991. Stengenge et al 1993).
• A “too hard” endfeel indicates a shortened capsule (Bumann et al. 1993). This finding can be corroborated by testing the endfeels from anterior translation and in ferior traction (Fig. 201ff).
• A “rebounding” endfeel is evidence of a nonreducing disk displacement (Fig. 160). This can be verified through MRI. However, a nonreducing disk displacement seen on a MRI is not necessarily the cause of restricted movement. Therefore the MRI cannot be relied upon as the primary diagnostic tool.
• A “bony” endfeel indicates osseous changes. Disrupted innervation can be ruled out through isometric contraction of the jaw-opening muscles.
Examination of the Joint Surfaces
The functional articulating surfaces of the temporomandibular joint are the fibrocartilaginous articular portions of the temporal bone and the condylar process of the mandible as well as the articular disk. Because the resultant force of the muscles of mastication is directed anterosuperiorly (Chen and Xu 1994), this is where the functional joint surfaces are found.
The proteoglycans in the fibrous cartilage are responsible for the disk’s resistance to compression (Kopp 1978, Axels-son et al. 1992). Although a reduced content of proteoglycan significantly alters the compressive characteristics of cartilage, it has no negative effect on its frictional properties (Pickard et al. 1998). The ability of the joint surfaces to deform serves to cushion and distribute peaks of stress. It also helps lubricate the contacting joint surfaces to minimize friction and wear (Mow et al. 1993, Murakami et al. 1998). The conformity of the joint surfaces plays a decisive role in the lubrication process (Nickel and McLachlan 1994b). The coefficient of friction of a healthy joint is 0.007. Lavage can cause this to increase three-fold, and following introduction of hyaluronic acid friction is reduced again by half(Mabuchi et al. 1994).
162 Form for recording signs and symptoms
Excerpt from the manual functional analysis examination form for recording the results of the dynamic compression and dynamic translation tests for the current degree of adaptation of the joint surfaces. The upper row is for the results of the dynamic compression test and the lower row is for the dynamic translation test. With these findings one can differentiate between osteoarthrosis, osteoarthritis, and capsulitis of the bilaminar zone with nonreducing disk displacement.
The joint surfaces in the temporomandibular joint become deformed when loaded (Moffet 1984). Destructive changes in the joint surfaces occur six to eight times more frequently in women than in men (Toller 1973, Rasmussen 1981, Tegelberg and Kopp 1987), which indicates that either the adaptability of women’s joints is less or the harmful influences are stronger. The effect of a force depends on its amplitude, frequency, and duration (Gradishar and Porterfield 1989, Bell 1990).
Motion reduces the deforming effects. Conversely, restrictions of movement intensify the deforming effects. As long as the adaptability of the tissue is not exceeded, the articulating surfaces of the temporal bone and condyle can become remodeled (adapted), but otherwise degenerative changes will occur in the joint surfaces (Moffet et al. 1964, Solberg 1986, Copray et al. 1988). The capacity for progressive and regressive adaptation of the osseous portions of the joints is present throughout life