A. Matarasso et al., LABIAL INCOMPETENCE - A MARKER FOR PROGRESSIVE BONE-RESORPTION IN SILASTIC CHIN AUGMENTATION, Plastic and reconstructive surgery, 98(6), 1996, pp. 1007-1014
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.