Reaction of facial soft tissues to treatment with a Herbst appliance

Abstract

The objective of this prospective longitudinal study was to investigate the reaction of facial soft tissues to treatment with a Herbst appliance. We aimed to quantify three-dimensionally (3D) the isolated effect of the Herbst appliance and volume changes in the lip profile. The 3D data of the facial soft tissues of 34 patients with skeletal Class II (17 female and 17 male, mean age 13.5 ± 1.8 years) were prepared in a standardized manner immediately before (T1) and after (T2) treatment with a Herbst appliance. Anthropometric evaluation was carried out in sagittal and vertical dimensions. To quantify volume changes, pretherapeutic and posttherapeutic images were superimposed three-dimensionally and the difference volumes calculated. Following testing for normal distribution, a statistical analysis was carried out using the paired t test. We observed ventral development of the soft tissues of the lower jaw with flattening of the profile curvature and anterior displacement of the sublabial region in a total of 27 patients. Anterior facial height was lengthened and the facial depth at the lower jaw increased. The largest percentage changes were noted in the lip profile, with a reduction in the red margin of the upper lip and an increase in lower lip height. We also observed a reduction of the sublabial fold in conjunction with a simultaneous increase in volume. The influence of the Herbst appliance on the facial soft tissues is expected to result in a positive treatment outcome, particularly in patients with a convex profile, a retrusive lower lip, and a marked sublabial fold. We observed a broad clinical spectrum of individual reactions in the facial soft tissues. It is, thus, not possible to detect a linear relationship between the Herbst treatment and soft tissue changes, making soft tissue changes difficult to predict.