Investigation of the effects of changes in hard tissue on soft tissue after orthognatic surgery

Aim: The aim of this study is to evaluate the correlations and the rates of hard and soft tissue changes after orthognatic surgery in class III malocclusion patients. Materials and methods: A total of 31 individuals with skeletal class III malocclusion were included in the study, 7 individuals undergoing mandibular set-back surgery were group 1, and 24 individuals undergoing double jaw surgery were group 2. The lateral cephalometric X-rays of the patients taken preoperatively (T1) and at least 6 months postoperatively (T2) were drawn digitally using Dolphin 11.5 software. The mean and standard deviations of the difference between T1, T2 and 2 times of the cephalometric variables were evaluated and the significance of the difference was evaluated and the correlation and movement rates between the hard and soft tissue changes were determined. Results: In group 1, there was a significant increase in overjet, facial convexity˚, ANB˚, Wits measurements, and significant regression in SNB˚, mentolabial˚ and mandibular landmarks. Soft tissue hard tissue movement rates in sagittal plane were found to be; Li/ L1 84%, B '/ B 103% and Pg'/ Pg 102%. In Group 2, there was a significant increase in overjet, facial convexity˚, ANB˚, SNA˚, Wits measurements; there was a significant decrease in SNB˚, mentolabial˚; significant improvement was found for maxillary landmarks and significant decline was found in mandibular landmarks in sagittal direction. For group 2, soft tissue-hard tissue movement rates in the sagittal plane were found to be; Pr / ANS 41%, Sn / A 62%, Ls / U1 61%, Li / L1 85%, B '/ B 100% and Pg'/ Pg 104%. Conclusion: In the sagittal direction, movements compatible with the surgical direction of maxilla and mandible were observed. There was an increase in hard-soft tissue correlation and follow-up rates from nasal tip to jaw tip. Soft tissue changes are more predictable for the mandible. Keywords: orthognatic surgery, class III malocclusion, soft and hard tissue changes