[Stress distribution of surgically assisted tooth-borne rapid maxillary expansion via three different types of osteotomies].

PURPOSE

To investigate the stress distribution of craniofacial bones during surgically assisted tooth-borne rapid maxillary expansion (SARME) via three different osteotomies.

METHODS

Three-dimensional finite element model of craniofacial bones with a tooth-borne appliance was generated. According to the different osteotomies, the models were categorized as three groups: Type I-isolated midpalatal osteotomy, Type II-Le Fort I and midpalatal osteotomies, Type III-Le Fort I and midpalatal osteotomies and bilateral pterygomaxillary disjunction. In all three models, with 4 different displacements, von-Mises stress was measured and analysed at 11 anatomical structures of the craniofacial bones.

RESULTS

An obvious reduction of the stress was observed followed by the larger extent of the surgery. The maximum stress of the bones was only noticed in Type I model. Stress on lamina of the pterygoid acutely increased in the Type II model compared with the Type I model. In Type III model, after separation of the pterygomaxillary junctions, stress on lamina of the pterygoid decreased rapidly and meanwhile stressed on the majority of the midfacial bones also decreased. In Type III osteotomies, anatomical structures of the upper craniofacial bones suffered from an increase of the stress.

CONCLUSIONS

Surgical procedures would be of great help to reduce the stress on the craniofacial region in the rapid maxillary expansion postoperatively. Fractures of the cranial base may occur at a greater chance because of stress focusing on lamina of the pterygoid. So, separation of the pterygomaxillary junctions during the operation is suggested. Increasing stress on the upper craniofacial bones can be observed after separation of the pterygomaxillary junctions due to changes of stress transduction pathways.