MANDIBULAR REFERENCE POSITION - CHIN-POINT GUIDED CLOSURE VS FINAL DEGLUTITION

The study investigated two mandibular positions based upon computerize d axiography recordings of hinge axis movements of 262 subjects. Next to the well-known guided closure position RP (reference position by ch in-point guidance), the position of final deglutition (FD) was quantif ied, FD represented the hinge axis position at the end of the swallowi ng movement. The results elicited average linear distances of 0.32 +/- 0.43 mm on the right and 0.33 +/- 0.40 mm on the left side between bo th positions in the sagittal plane. The average distance in the fronta l plane was 0.02 mm (right) and 0.04 mm (left). Approximately 46 per c ent of FD recordings were found anterior and inferior to RP, and showe d significant difference to posterior and anterior-superior FD recordi ngs. The replicability of both positions was tested on 53 subjects and averaged 0.04 mm (FD) and 0.09 mm (RP). Average deviations of repeate d recordings within the subject ranged from 0.07 to 0.47 mm (FD) and 0 .07 to 0.57 mm (RP) for each spatial direction. The results of this st udy showed a relative coincidence of an average FD and RP. Variation o f FD in anterior inferior direction questioned the clinical reliabilit y of FD to reassure the guided closure position.