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Purpose: The objective of this study was to clarify the effect of mechanical loading on the trabecular structure of peri-implant bone and determine its correlation with the implant stability quotient (ISQ) value.Methods: This study used 3 immunologically mature male dogs. Three months after bilateral extraction of the mandibular premolars of the dogs, 4 implants were placed in these sites for each dog. After 3 months to allow healing of the implant sites, superstructures were prepared on the right side (loaded side). The implants on the left side were covered with mucosa (non-loaded side). The ISQ values of all implants were measured 3 months after placing the superstructures; subsequently, the animals were sacrificed. After the mandible was excised and fixed, micro-CT images were acquired and three-dimensional analysis, performed.Results: The means and S.D. of the ISQ value for the 12 implants were 69.6±6.2 and 62.9±13.8 for the loaded and non-loaded sides, respectively. No significant difference was noted between the 2 sides. Mean and S.D. of bone volume fraction (BV/TV) were 13.0±6.6 and 9.3±3.8; trabecular thickness (Tb.Th), 97.7±27.7 µm and 91.0 ± 24.0 µm; and trabecular number (Tb.N), 1.24±0.30/mm and 0.99±0.20/mm for the loaded and non-loaded sides, respectively. BV/TV and Tb.N values were higher for the loaded side.Conclusion: Morphological changes occurred in response to functional loading. However, lamellar bone was observed around the implants on both sides. These findings revealed that changes in the bone structure due to functional loading of implants had negligible or no effect on the ISQ value.

Objectives: The purpose of this study was to determine the mechanically appropriate retainer design for unilateral distal-extension removable dentures.Methods: Two models were constructed, each with a different design of retainer placed on the first and second mandibular premolars. Each model was composed of bone, denture underlying mucosa, retainer and denture base. In design A, Akers clasps were set on the first and second premolars, and in design B, an occlusal rest and back-action clasp with mesial rest were set on the first and second premolars, respectively. Loading on the occlusal surface of the denture was performed in the vertical and oblique directions. Load on the abutment tooth and displacement of the denture base were determined by 3-dimensional finite element analysis.Results: Load on the abutment tooth in the vertical direction caused by vertical loading on the denture was lower in design B than in design A. No large difference in displacement of the denture base was observed between design A and B. Load on the abutment tooth both in the vertical and buccolingual direction induced by loading on the denture in the lingual and buccal directions was lower in design B than in design A. However, displacement of the denture base in the vertical and buccolingual directions induced by loading on the denture in the lingual direction was higher in design B than in design A.Conclusion: In this study, displacement of the denture base was smaller in design A than in design B, so design A would be more useful clinically than design B, but the abutment tooth would require greater support.