Chin Volume Asymmetry Score Changes After Class III Orthognathic Surgery

Objectives: The objective of this study was to investigate the asymmetric changes in chin volume over 12 months after orthognathic surgery using three- dimensional stereophotogrammetry. The analysis of soft tissues over time was conducted using 101 healthy Caucasian patients with a skeletal Class III malocclusion (age range 19–53 years, mean age 28.6 years).
Methods: Three-dimensional facial images were acquired using the 3dMDtrio (3dMD, Atlanta, GA) stereophotogrammetric system and recorded: before surgery (T0), 6 months (T1) and 12 months (T2) after surgery. The 21 anthropometric landmarks were digitally marked on each 3-D facial surface and evaluated at 3 time points. The chin area asymmetry was assessed and classified as: 0–2 mm (mild); 2–5 mm (moderate); > 5 mm (severe). The Chin Volume Asymmetry score (CVAS) was used. All patients were divided in two groups depending on the type of surgery: single jaw (LeFort I-21 (20.8%)) and both jaw (bimaxillary- 79 (78.2%)) surgery group.
Results: The Chin Volume Asymmetry score showed statistically significant difference between T0 (median 1.11 mm; IQR (1.04; 1.19)) and T1 and T2 (median 1.08 mm for both; IQR (1.04; 1.13); P < 0.001), but not difference between T1 and T2 (P> 0.05). No differences in the CVAS was found between both surgical groups at any time point (p>0.05). With the CVAS, the right side of the face was larger before surgery (51.48% of cases); while in 19.8% of cases, the sides changed after surgery, but the right side remained dominant. A statistically significant difference was observed in moderate asymmetry group between T0 (median: 1.16) and T1 (median: 1.07) (p<0.01).
Conclusions: It is concluded that with the CVAS the most statistically significant changes were found in the first 6 months after the surgery. Furthermore, there was no statistically significant change in chin asymmetry 12 months after surgery.