LABIAL INCOMPETENCE - A MARKER FOR PROGRESSIVE BONE-RESORPTION IN SILASTIC CHIN AUGMENTATION

Bone erosion below silicone rubber implants is a well-known sequela, o ccurring in a majority of patients undergoing augmentation genioplasty . It is generally considered to be self-limiting and with minimal adve rse consequences. However, if bone erosion progresses to the extent to which teeth are jeopardized or alterations in sensibility of the ment al nerve occur, removal of the implant is indicated. Osteoplastic geni oplasty may be required to restore aesthetic contour to the chin and t o avoid functional anomalies that may occur from explantation. A numbe r of factors have been identified that contribute to this phenomenon; however, speculation regarding its etiology has not acknowledged the f unctional aberration of a tensed mentalis muscle. A study of six patie nts with aesthetically positioned and appropriately sized Silastic imp lants revealed a correlation between preoperative baseline labial inco mpetence and mentalis muscle hyperactivity and progressive bony erosio n. One patient had grade II erosion and four patients had grade III er osion, one with the exposure of dental roots. The sixth patient with m entalis muscle strain, subsequent to attempts to contain her lower den ture, also had severe resorption. Such findings suggest that attention should be paid to an alternative approach in microgenic patients pres enting with lip strain, since labial incompetence appears to be a reli able marker for ongoing mandibular resorption following Silastic augme ntation. Furthermore, since most patients are asymptomatic until signi ficant erosion occurs or are satisfied and do not return, in those ind ividuals with labial incompetence who have already had Silastic chin i mplants, consideration should be given to routine follow-up examinatio n and radiographs.