Stress Distribution Analysis in Aramany Class VI Maxillary Defect Obturator

Objectives: The purpose of the study was to evaluate the biomechanical effects of an obturator prosthesis in an Aramany class VI defect compared to a removable partial denture (RPD) prosthesis.
Methods: 3D geometric skull model was developed through CBCT data using modeling software. Aramany class VI defect anterior to the right and left second premolars was created. A partially edentulous maxillary model with the same missing teeth but without bone defect was also created as control. A maxillary obturator prosthesis and an RPD prosthesis were virtually constructed for their respective models in a similar framework design (Visual-Mesh). Static load of 100 N was applied to marginal ridges of incisors and canines, and to triangular ridges of buccal and palatal cusps of premolars in a 45° oblique direction. Maximum von-Mises stress and displacement values were analyzed and compared for each model (Visual-Crash).
Results: The maximum von-Mises stress value for the metal framework of the obturator prosthesis (216.3 MPa) was lower than that of the RPD prosthesis (315.9 MPa). PMMA resin showed similar maximum stress values (4.3 MPa) for both models. Moreover, the maximum stresses on the surveyed crowns of each model were almost the same (149.4 MPa on the right side and 93 MPa on the left side in the obturator model, and 154.2 MPa and 99.4 MPa, respectively, in the RPD model). The obturator model had significantly higher maximum von-Mises stresses on the periodontal ligament of the remaining teeth compared to the RPD model. Moreover, the prosthesis displacement distribution pattern of each model was also significantly different.
Conclusions: Aramany class VI obturator prosthesis had a significant biomechanical impact on the remaining abutment teeth rather than on bone or prosthesis itself. Therefore, attention should be paid to the prosthesis framework design and the maintenance of supporting dental tissues for the long-term prognosis of obturator prostheses.