Influence of Abutment Selection in Maxillary Kennedy Class II RPD on Elastic Stress Distribution in Oral Mucosa: An FEM Study

PURPOSE: The aim was to study the influence of abutment selection on elastic stress distribution in oral mucosa in a maxillary removable partial denture (RPD) by means of 3-dimensional finite element models. MATERIALS AND METHODS: Four RPD framework models of an equal size (by area) and underlying oral mucosa were produced for a Kennedy Class II arch. Each framework included an occlusal rest as part of a clasp assembly on one of four abutments (canine, first, and second premolars, and first molar) on the side contralateral to the edentulous ridge (tooth-supported side). Movement of the alveolar surface of the mucosa and the occlusal rest on the abutment adjacent to the ridge were fixed in a vertical direction. Movement of the rest on the tooth-supported side was restricted in all directions. Vertical or buccally oblique biting force was applied simultaneously on each of the locations representing three missing teeth. RESULTS: The frameworks with the contralateral side rest on the canine or the first premolar were less resistant to lateral forces than other framework designs, showing greater saddle displacements under the oblique force than the vertical force. The framework with the rest on the second premolar demonstrated relatively good resistance to deflection; however, both vertical saddle intrusion and the maximum equivalent stress in mucosa shown in all the models were within small ranges. CONCLUSION: The saddle movement was influenced by the abutment selection on the tooth-supported side, although resultant stress in the mucosa was insensitive to the abutment location.