Publication date: Available online 24 December 2018
Source: Journal of Cranio-Maxillofacial Surgery
Author(s): Akihiro Takayama, Koichiro Ueki, Akinori Moroi, Takamitsu Tsutsui, Yuki Saito, Momoko Sato, Kunio Yoshizawa
Abstract
Purpose
The purpose of this study was to examine changes in masseter and medial pterygoid muscles, ramus, condyle and occlusal force after bi-maxillary surgery in class II and III patients.
Subjects
and Methods. The subjects were 42 patients (84 sides) who underwent sagittal split ramus osteotomy with Le Fort I osteotomy (21 class II cases: mandibular advancement and 21 class III cases: mandibular setback). The cross-sectional measurements of the masseter and medial pterygoid muscles, ramus and condyle were measured in horizontal plane images by computed tomography (CT), before and 1 year after the operation. Occlusal force and contact area were also recorded before and 1 year after the operation.
Results
Preoperatively, class II was significantly larger than class III in masseter width (P=0.0068), masseter area (P<0.0001) and medial pterygoid length (P<0.0001). However, class II was significantly smaller than class III in medial pterygoid width (P<0.0001). After 1 year, class II was significantly smaller than class III in masseter length (P=0.0017). Class II was still larger than class III in medial pterygoid area after 1 year (P=0.0343). Class II was significantly larger than class III in condylar angle pre-operatively (P<0.0001) and after 1 year (P=0.0006). After 1 year, class II decreased significantly more than class III in condylar thickness (P=0.0020), condylar width (P<0.0001) and condylar area (P<0.0001).
Conclusion
This study suggested that changes in the cross-sectional measurements of masseter and medial pterygoid muscles and the condyle differed between class II and class III patients, although occlusal force did not significantly change 1 year after surgery in both groups.
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