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ABSTRACT
The influence of reduced anterior disc displacement on condylar motion has not been fully examined in young adults. Reduced anterior disc displacement was hypothesized to inhibit condylar motion. Using a six-degrees-of-freedom jawtracking system, we recorded bilateral condylar motion during maximum open-close jaw movement and gum-chewing on both sides in ten young adults with unilateral reduced anterior disc displacement and in ten control subjects without temporomandibular disorders. The bilateral condylar motion during both maximum open-close jaw movement and chewing on the discdisplacement side was inhibited in the test group. The condylar motion on the disc-displacement side during chewing on the non-disc-displacement side was also inhibited in the test group. These results suggest that the limitation of condylar motion on the disc-displacement side may influence condylar motion on the non-discdisplacement side during maximum open-close jaw movement, and mastication on the discdisplacement side in young adults.
KEY WORDS: anterior disc displacement, condyle, mastication, temporomandibular disorders (TMD), with reduction.
INTRODUCTION
It is well-known that patients suffering from internal derangements of the temporomandibular joint, such as anterior disc displacement, occupy a large proportion of patients with temporomandibular disorders (SanchezWoodworth et al., 1988; Paesani et al., 1992). Generally, the amount of mandibular condylar motion has been suggested to be a good index for assessment of the state of the temporomandibular joint (Harper, 1990; Harper and Schneiderman, 1996). However, our knowledge is limited concerning condylar motion during mastication in such patients.
Several research groups have examined the condylar motion in patients with anterior disc displacement with reduction, which may progress to disc displacement without reduction, i.e., closed lock, during open-close jaw movement. However, a consensus on the characteristics of condylar motion in such patients has not been achieved, there being some reports with contradicting results. For example, it has been reported that the typical pattern of condylar paths in patients suffering from anterior disc displacement with reduction is figure-eight-shaped (Farrar, 1978; Farrar and McCarty, 1979; Mauderli et al., 1988). However, another report states that such a pattern is not typical (Parlett et al., 1993). One research group (Takeuchi et al., 1995) demonstrated a long condylar translation, but other groups (Fuma et al., 1998; Gsellmann et al., 1998) were in disagreement. Such differences among previous reports may be...