ABSTRACT
Objectives@#The purpose of this study was to compare differences in facial soft tissue thickness in three-dimensional (3D) images before and after orthognathic surgery in patients with skeletal Class III malocclusion and to obtain a better understanding of the relationship between hard and soft tissue changes after surgery.Materials and method: The present retrospective study included 31 patients with skeletal Class III malocclusion with mandibular chin deviation greater than 4 mm who had undergone cone-beam computed tomography before and 6 months after surgery. Seven bilateral points were established. Measurements were taken from software-generated multiplanar reconstructions. The predictor variables were timing (pre- and postoperatively) and side (deviated vs.nondedicated). A regression model and correlation analysis were conducted for statistical analysis. @*Results@#The difference of bilateral facial soft tissue thickness was statistically significantly different between deviated and nondeviated sides (P < 0.05), with lower values observed on the deviated side. The soft tissue thickness has become nearly symmetric at local regions of the lower thirds of the face after orthognathic surgery. However, most measurements showed a negative correlation between changes in soft tissue thickness and changes in bone tissues. @*Conclusions@#Skeletal Class III malocclusion with facial asymmetry is accompanied by differences in soft tissue thickness when comparing Dev and N-Dev sides of the posterior region of the mandible, where soft tissues are thinner on the Dev side. Soft tissue thickness can compensate for or camouflage the underlying asymmetric mandible. In addition, the asymmetric soft tissue thickness on the lower third of the face can be partially improved by orthognathic surgery, but the amount of soft tissue thickness change is not consistent with that of hard tissue positional change.
ABSTRACT
<p><b>OBJECTIVE</b>To determine the biomechanical characteristics of mandibular fractures in different site.</p><p><b>METHODS</b>Nine adult mandibular specimens were measured precisely. The data was used to establish a three-dimensional model. When mandibular was under functional loading, the bending and torsion moment as well as shear force of angle, body and symphyseal fracture was calculated. The data were analyzed by Origin 6.0 software.</p><p><b>RESULTS</b>Angle fracture had relatively high positive bending moment and high shear force. Body fracture had positive as well as negative bending moment and the highest torsion moments. Symphyseal fracture had only negative bending moment and relatively low shear force.</p><p><b>CONCLUSION</b>Angle, body and symphyseal fractures each have a biomechanics characteristic. These biomechanics characteristic should have an important meaning in the treatment of mandibular fractures and instructing patient how to bite correctly.</p>