Mandibular lateral translation during symmetric mandibular movement
PURPOSE: The purposes of this research were to investigate the mandibular lateral translation (ΔYMLT) during asymmetric mandibular movement and to clarify the relationship between the occurrence of ΔYMLT and temporomandibular joint (TMJ) status. MATERIALS AND METHODS: Lateral deviation of the condyle during the mandibular functional movement of 1658 orthodontic patients was screened using computerized condylography. Maximum lateral deviation during opening/closing, mastication, and grinding movements were calculated. RESULTS: Occurrence of ΔYMLT in orthodontic patients was 26% and consisted of three types: ΔYMLT, over rotation MLT, and closed lock MLT. Occurring point of ΔYMLT in the condylar movement was in between 1 and 3.5 mm from reference position (RP). Maximum ΔYMLT tends to increase with age and ΔYMLT started at an early stage of growth and development. Subjects in the ΔYMLT group showed significantly more lateral deviation during mastication and bruxism than those in the non-ΔYMLT control group. CONCLUSION: It is suggested that the ΔYMLT of the condyle occurs in the lower joint after disk displacement, and that the analysis of condylar tracking can be useful for early detection of dysfunction.