The photoelastic analysis for obturator of unilateral maxillary defect

Purpose: To photoelastically evaluate load transfer of RPD obturator in radical maxillectomy defect with attachment as the major retainer. Methods: A life sized photoelastic model was made of a radical maxillectomy defect model. Individual simulants were used for tooth structure, periodontal ligament, and alveolar bone. Two obturators were fabricated as follow:1) Traditional obturator framework with 4 casting circumferential clasp on the posterior abutments of healthy side.2) A continuous lingual guide plane of 0.5mm thickness was bonded on all of the remaining teeth, with Mini-SG/F attachment on the mesial surface of the central incisor. The obturator prostheses with casting palatal plate were constructed according to the lingual guide plane and the condition of the maxillary defects. Simulated posterior occlusal loads were applied to the obturators. Frozen photoelastic analysis was used to evaluate the load distribution on the bone and the abutment. Results: Comparing the traditional design, attachment restoration shows no significant difference stress distribution was seen on the abutment teeth. The stress patterns on the posterior teeth are quite even, with no different strips on both buccal and lingual side. More stress stripes were seen near the teeth cervical. Stress was a little concentrated on the anterior part of the palate, with stress values being lower on the anterior teeth compared to the posteriors. High stress was also observed on the cervical of the lateral incisor and central incisor. The mesial alveolar of the central incisor also express high stress stripes. Conclusions: The application of a resin-bonded extracornal attachment for obturator retention is in accord with the design principles for the restorative treatment of maxillary defects. Benefit can be gained by splinting the two incisors. Enough thickness of the alveolar bone adjacent to the defect should be saved during surgery to prolong the life of the incisor.