Three-dimensional dynamic evaluation of facial soft tissue changes following anterior traction in growing Angle Class III malocclusion patients.

BACKGROUND: The aesthetic improvement of the midface is a critical goal in treating growing children with Angle Class III malocclusion. While the skeletal effects of maxillary anterior traction are well-established, predicting the final aesthetic outcome requires a precise understanding of the accompanying three-dimensional (3D) soft tissue response. Current literature lacks detailed, dynamic quantification of these adaptive changes using high-precision methodology. This study aims to address this gap by employing dynamic stereophotogrammetry to sequentially analyze the 3D soft tissue kinematics associated with maxillary advancement.

METHODS: In this study, the three-dimensional dynamic facial imaging system (3dMD) was employed to evaluate the effects of maxillary anterior traction treatment in 28 adolescents and children with Angle Class III malocclusion. Quantitative changes in facial root mean square (RMS) values and landmark displacements were compared across different treatment stages. Key measurements included RMS values at the initial (Ta), middle (Tb), and final (Tc) frames of four facial expression sequences (smile lips closed, smile lips open, lip purse, and cheek puff) along with the corresponding changes in anatomical landmark positions.

RESULTS: Analysis revealed that the RMS values for each sequence frame of facial dynamic expressions increased from baseline (pre-treatment) levels at both the 3-month follow-up (T1-T0) and the end of treatment (T2-T0). RMS values exhibited differential evolution across distinct phases of each facial expression. For the smile lips closed expression, the overall change did not reach statistical significance (p = 0.064). In contrast, the smile lips open expression exhibited statistically significant increases over the full treatment course (p = 0.015). More pronounced changes were observed in the lip purse and cheek puff expressions, both of which exhibited highly significant increases in RMS amplitude across the entire treatment period (p = 0.002 and p < 0.001, respectively). With regards to landmark displacements, statistically significant anterior movements were observed for landmarks b, c, d, e, f and h, while landmark a exhibited a significant posterior displacement. In contrast, no significant positional changes were detected for landmarks i and j.

CONCLUSION: Anterior traction effectively improved the class III facial profile while dynamic 3D assessment revealed a non-linear adaptation pattern with enhanced midfacial convexity. These objective data are crucial for predicting outcomes in early-phase patient management.