Change of lower facial contour with unilateral botulinum toxin injection in different facial asymmetry types using posteroanterior cephalogram

Abstract

Recently, interest of facial asymmetry has been considered increasingly, so people who want to correct that cosmetically visit hospital gradually. The awareness of them have been increased, even patients with mild facial asymmetry have been increased. With medical development, treatments of these facial asymmetry have been more various and simple gradually. Especially, botulinum toxin type A therapy is relatively simple and aesthetically effective for bilateral hypertrophy of masseters or unilateral hypertrophy of masseter muscle inducing facial asymmetry. It was known that the efficacy of botulinum toxin type A was evaluated using three dimensional (3D) laser scan, and it was effective for the facial asymmetry. We assumed that if the effect is different according to the facial asymmetry type after analysis, we can predict the proper effect of treatment. The purpose of this study is to suggest a simple guideline for unilateral injection of botulinum toxin type A in facial asymmetry patients using posteroanterior cephalogram as a method for analysis.The volume and bulkiest height of lower face of 16 facial asymmetry patients were measured with 3D laser scan before 25 units of botulinum toxin type A injected unilaterally. In same way, the volume and bulkiest height of lower face were measured 4, 8, 12 weeks after injection and superposed 3D laser scan of before injection, and then changed volume and bulkiest height were determined. We classified them into two types according the deviation of menton from midsagittal reference line in posteroanterior cephalogram. When the deviation was less than 3 mm, those subjects were classified into “Type I”. When the deviation was more than 3 mm, those subjects were classified into “Type II”.The volume and bulkiest height of lower face of the injected sides were statistically decreased with time in both types. And there were

statistically differences between the injected and noninjected sides at each time point. In type I, the volume and bulkiest height of lower face were more decreased significantly than type II. Considering the results of our study, it is thought that when the menton deviation is less than 3 mm, botulinum toxin type A as the treatment of facial asymmetry is more effective.