Measurement of three-dimensional changes in lip vermilion in adult female patients after orthodontic extraction: a preliminary study

Abstract

Background The objective of this study was to evaluate three-dimensional (3D) morphological changes in the lip vermilion in adult females after orthodontic treatment for four-premolar extraction in patients with dentoalveolar protrusion using a structured light-based scanner. Methods Forty-two female subjects with protruding lips were recruited as the treatment group; these patients underwent extraction of the four first premolars (PM1) without mini-implants for anchorage control. A total of twenty female subjects were enrolled in the non-treatment group; these patients did not require orthodontic treatment. Six facial landmarks (Ls, Ll, R.Cu, L.Cu, R.Ch, L.Ch), three linear measurements (vermilion height, cupid’s bow width, mouth width), and three area measurements (upper, lower, and total vermilion area along the 3D surface of the lip vermilion) were measured using 3D facial scans. Superimposed color maps and spectra were constructed for visual analysis of morphological changes in the lip vermilion for qualitative evaluation. The spacial deviations of the three volumetric measurements (upper, lower, and total vermilion) were constructed for quantitative analysis. Results Vermilion height and cupid’s bow width decreased significantly and no significant change in mouth width was observed after extraction. The lower vermilion and total vermilion surface areas decreased significantly after orthodontic treatment in the extraction group, but the upper vermilion remained unchanged. Significant retractions were observed in vermilion volumetric measurements in the extraction group. Conclusions This study established a method to objectively and quantitatively compare the lip vermilion. Extraction of the four first premolars in adult females produced significant retraction in the lip vermilion. Morphological variation in the vermilion was different between the upper vermilion and the lower vermilion.