Changes in horizontal jaw position and intraoral pressure

OBJECTIVE: To determine the effect of an imbalance in buccolingual pressure that may be involved in molar dental compensation in the mandible and asymmetry of the dental arch in subjects with facial asymmetry. MATERIALS AND METHODS: We performed simultaneous measurement of the buccolingual pressure on the mandibular right first molar when subjects without facial asymmetry experimentally shifted the mandible laterally. Buccolingual pressures in the rest position (RP), right-shifted position (RS), and left-shifted position (LS) were compared. Moreover, T1-weighted magnetic resonance images were obtained in RP, RS, and LS. RESULTS: Tongue pressure tended to decrease in the order LS > RP > RS, while cheek pressure tended to increase in the order LS < RP < RS. The tongue/cheek pressure ratio tended to decrease in the order LS > RP > RS. There were significant positive (in RS) and negative (in LS) correlations between displacement of the tongue and tongue pressure. CONCLUSIONS: This imbalance in buccolingual pressures in the laterally-shifted mandibular position may partly explain molar dental compensation in the mandible and asymmetry of the dental arch in subjects with facial asymmetry.