An retrospective study of soft tissue changes of lip and chin morphology in skeletal Class III adult patients with orthognathic surgery

Objective To observe the morphology characteristics of lips and chin in skeletal Class Ⅲ malocclusion patients and the soft tissue changes after different orthognathic surgery patterns. Methods The 94 adult surgery patients with skeletal Class Ⅲ malocclusion were selected, which comprised of 31 mandible-only cases, 10 maxilla-only cases and 53 two-jaw cases. The gender difference on soft tissue morphology and changes of lips following different orthognathic surgeries were evaluated by cephalometric analysis. Results The gender differences were found only on the length of upper lip, the depth and degree of mentolabial fold. In the mandible-only group, the Li-LL、B'-B、LLL、B'-(LL-Pog')、B'-LL-FH、LL-B' -Pog'、UL-SnPog'、LL-SnPog'、B'- SnPog'、Sn-H line、Li-H line、Sm-H line、Ns-H line、Ls-NsPog' in both gender have changed significantly. In maxilla-only group, the depth of the upper lip and ULL、A'-(Sn-UL)、Cotg-Sn-Ls、A'-UL-FH、B' -LL-FH and the distance from some points to different reference lines have changed significantly. And in the two-jaw group, besides the differences observed in mandible-only group, the Cotg-Sn-Ls、A'-UL-FH also have a significant change. Conclusions The gender difference is not significant in skeletal Class Ⅲ patients in the thickness of lip soft tissue, but is significant in the length of lips and the morphology of lips and chin. Two-jaw surgery is good at improving lip and chin morphology and is better for patients with unsatisfied nasolabial and mentolabial morphology both. Key words: Skeletal Class Ⅲ; Orthognathic surgery; Lip morphology