Existence of linearity in soft to hard tissue changes following orthognathic surgery

Ramdas Balakrishna; Tanmoy Nath

Volume : VI, Issue : X, October - 2017

Existence of linearity in soft to hard tissue changes following orthognathic surgery

Ramdas Balakrishna, Tanmoy Nath

Abstract :

Introduction: Profile prediction is crucial to planning prior to orthognathic surgery. Today computerized simulation softwares have replaced acetate tracings, which are based upon mean ratios of soft tissue change following skeletal movements linearly. The aim of this study is to evaluate the soft tissue changes with skeletal movements following orthognathic surgery. Method: Lateral cephalograms of 24 patients were taken preoperatively at least 2 months before (T1) and, postoperatively (T2) 6 months after the surgery and acetate paper tracings were done. The sample was divided into two groups (maxillary & mandibular) depending upon type of surgery. Five pairs of soft and hard tissue landmarks were studied pre and postoperatively. Paired t test was used to compare the corresponding soft tissue and hard tissue change in both the groups. Scatter plots were used to explore the relationships of the corresponding soft– and hard–tissue movements for both the groups. The Pearson correlation coefficient (r) was calculated for each pair of tissue movements in both the groups. Result: The changes in soft tissue were closely correlated with hard tissue movement following orthognathic surgery. All the corresponding soft and hard tissue landmarks showed a linear relationship except for Sn–ANS pair. Conclusion: Linear ratios can be safely used for a wide range of mandibular orthognathic surgeries. However for maxillary surgeries, simulation softwares using nonlinear ratios should be beneficial.