Measurement of lateral loads exerted on the maxillofacial region by habitual postures.

Lateral loads exerted on the maxillofacial region by habitual postures and habits may cause lateral shift or deformity of the mandible. These loads were measured with a desktop dynamic-strain gauge (DPM-600, Kyowa Co.) connected to a small, highly sensitive pressure sensor (PSL-A type, Kyowa Co.), and recorded with an oscillographic recorder (RDM-100A, Kyowa Co.). Measurements were taken with a pressure sensor embedded in silicone impression material placed in a vinyl chloride resin bag, on which pressures were applied. A preliminary study was conducted to obtain a proportional constant and a conversion formula for load calculation. The subsequent main study included 20 healthy male volunteers for load measurement in 12 positions. The mean load exerted on the mandible was 43.7 N when the subjects lay face down and approximately 20 N when they sat resting the lateral part of the chin on the hand, indicating that these loads are greater than regular orthodontic forces.