# 3D analysis of smile transformation in patients with class III deformities following orthognathic surgery: a stereophotogrammetric study: Original Article

## TL;DR

This study uses 3D imaging to show that orthognathic surgery improves the fullness of smiles in patients with class III deformities, while keeping other smile features stable.

## Contribution

The first study to use 3D stereophotogrammetry to assess smile changes after orthognathic surgery in class III deformities.

## Key findings

- The buccal-corridor ratio decreased by 4.4%, indicating a fuller transverse smile after surgery.
- Upper-lip length and inter-commissural width increased slightly, but vertical smile dimensions remained stable.
- 3D stereophotogrammetry provided reliable and reproducible measurements of soft-tissue changes.

## Abstract

Smile aesthetics are crucial in orthodontic and orthognathic planning, particularly for patients with dentofacial deformities seeking enhanced facial harmony. This study evaluated changes in smile parameters of patients with class III deformities before and after orthognathic surgery using 3D stereophotogrammetry.

Conducted at Başkent University Oral and Maxillofacial Surgery Department, this retrospective investigation comprised 21 patients with class III skeletal deformities who underwent bimaxillary orthognathic surgery. Standardized social-smile photographs and 3D facial scans were obtained preoperatively and at an average 8-month follow-up. Smile parameters, including buccal-corridor ratio, upper-lip length, inter-commissural width, lip thickness, lip asymmetry and volumetric measures were reported. Preoperative and postoperative differences were analyzed with paired T-tests or Wilcoxon signed-rank tests (p < 0.05), 95% confidence intervals, and Cohen’s d for paired samples.

Mean follow-up was approximately 8 months. False-discovery-rate correction identified one significant change: buccal-corridor ratio decreased by 4.4%, producing a visibly fuller transverse smile (d = 0.66). Upper-lip length and inter-commissural width increased by about 1.0 mm and 1.6 mm, respectively (both d ≈ 0.5). Vertical smile dimensions, incisor display, and global facial height and width remained stable (|d|≤0.18). Measurement reliability ranged from good to excellent (ICC = 0.60–0.93(Intraclass Correlation Coefficient).

Orthognathic surgery improved transverse smile fullness in patients with class III skeletal deformities while preserving vertical dental display, affirming the value of 3D assessment.

Three-dimensional stereophotogrammetry offers objective, reproducible documentation of soft-tissue changes and should be integrated into routine orthognathic evaluations. Unlike previous studies relying on cephalometry and photographs, this is the first study to utilize 3D stereophotogrammetry for assessing smile parameters.