Three-Dimensional Analysis of Perioral Soft and Hard Tissue Changes After Non-Surgical Orthodontic Treatment in Class...

This study aimed to examine three-dimensional (3D) changes in perioral soft tissue after nonsurgical orthodontic treatment of Class III patients using a 3D structured light scanner.

The study included 32 Korean patients with skeletal Class III malocclusion who underwent nonsurgical orthodontic treatment with temporary skeletal anchorage devices (TSADs). Two-dimensional lateral cephalograms and 3D facial scans were taken before treatment and immediately after debonding. Seven hard-tissue landmarks were identified in the cephalometric images, and 29 perioral soft-tissue landmarks were identified in the 3D facial images. Changes in the 3D coordinates of these landmarks (x, y, z) were assessed by superimposing post-treatment images onto pre-treatment images.

After treatment, the maxillary central incisor tips moved significantly forward (1.43 mm), while the mandibular central incisors moved backward (-2.61 mm). Upper lip landmarks (1) moved forward significantly, while lower lip landmarks (8, 9, 13, 14, 8', 9', LLP) moved backward significantly. There was also significant downward and backward movement at Pg' and Gn'.

Orthodontic treatment resulted in maxillary incisor proclination and lingual uprighting of the mandibular incisors, with downward and backward movement of Pg' and Gn'. No significant soft tissue changes occurred in the transverse axis. The upper lip moved forward, while the lower lip and chin (Pg', Gn') shifted backward and downward. The subnasale and the area under the nostrils remained relatively stable, while the lip angle moved posteriorly.