Date of Award

Spring 1989

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)



First Advisor

Ferguson, Donald

Second Advisor

Meyer, Ralph A.

Third Advisor

John Cheek


Maxillary impaction surgery with resultant mandibular autorotation has been documented as a viable treatment option when treating patients with the "longface syndrome". The purpose of this retrospective study was to carefully evaluate mandibular movement in eighteen surgical cases of this description in an attempt to locate a more representative "instantaneous" center of rotation of the mandible. Current surgical prediction tracing techniques locate the center of rotation at the condylar center. The evidence presented suggests rotation to occur posterior and inferior to the condylar center in the area of the mastoid process. Prediction tracings performed from both condylar center and mastoid center produced clinically significant discrepancies in the horizontal component of mandibular movement associated with vertical change. The alteration of lower incisor angulation postsurgically suggests an attempt by the orthodontist to compensate for the horizontal discrepancy experienced clinically. Modification of prediction tracing techniques, commercial articulator systems, or cephalometric procedures could be indicated.



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