A finite element analysis of stress distribution on maxillofacial skeleton and temporomandibular joint articular disc under intermaxillary loading after simulated bone anchored maxillary protraction.

INTRODUCTION: Bone-anchored maxillary protraction (BAMP) is an effective therapeutic approach for managing developing skeletal Class III malocclusion. This study aimed to determine the stress distribution in the circum-maxillary sutures, temporomandibular articular disc and mandibular condyle, as well as the displacement of key craniofacial landmarks during BAMP.

METHODS: A three-dimensional linear finite element (FE) model of the skull, articular disc and anchor plate was developed. Using this model, Class III intermaxillary loads of 150g, 250g and 400g were applied through anchorage plates at angulations of 10°, 20° and 30°. Stress distribution in the circum-maxillary sutures, articular disc and condylar head was evaluated. Additionally, displacement of the anterior nasal spine (ANS), posterior nasal spine (PNS), pogonion and condylion in the anteroposterior and vertical directions was assessed.

RESULTS: Increasing force magnitude and angulation resulted in greater maxillary displacement and elevated stresses at circummaxillary sutures. Von Mises and principal stress analyses demonstrated that moderate forces (150-250g) produced favourable displacement with comparatively lower stress concentrations in the TMJ region, whereas higher forces (400g) generated increased stresses at the condylar head and articular disc.

CONCLUSION: Within the limitations of a linear static model, moderate force levels and smaller angulations appear to offer a biomechanically favourable balance between skeletal advancement and TMJ loading during BAMP therapy. These findings represent immediate mechanical responses and should be interpreted cautiously. Future studies incorporating muscle forces, soft tissues, and time-dependent remodelling are warranted.