This study discusses the stresses in alveolar bones with various thicknesses of cortical layer around the implanted fixed partial denture subject to occlusion or external load. The stresses induced by occlusion and external loads can vary with the condition of the bone. For verification, a physical model with identical shape to the digital model and with similar material properties, loads, and boundary conditions was built. The data obtained from the physical model agreed well with that obtained from the simulations performed on the digital model. After the reliability of the finite element method (FEM) digital model had been confirmed, stresses induced by occlusion and external loads were studied. The induced stress level on the cortical bone increased with the decrease in the cortical layer. When the cortical layer vanished, the induced stress level significantly dropped. The soft cancellous bone supported the implanted complex completely once the cortical layer had gone. However, the induced displacement continued to increase more rapidly as the cortical layer thickened or vanished. A lateral load applied to the complex was also studied. The movement between the natural bone and the implant increased with the decrease in the cortical layer. This could lead to the stability problem of the implant denture and osseointegration. The results indicate that patients with thinner cortical bone carried a higher risk of failure during the restoration.

Traditionally, three CT markers are attached to a surgical guide of dental implant surgery to correlate the implant positions in CT images and the drill positions of a drill press. To allow the drill press to know the positions of the CT markers, users need to use the press to probe the positions of them manually. This process is inaccurate and time-consuming. The objective of this research was to develop a new process to eliminate the traditional probing process. This new process uses two identical pairs of locating pins both in the plaster mold cavity and on the fixture of a CNC drill press, respectively. Since the position of the drill bit relative to the locating pins and the positions of the locating pins relative to the CT markers are designed by us, the drill press knows the positions of the CT markers without probing them. According to the preliminary evaluation results, the mean errors of the location and angle of the drilled holes were 0.696 mm and 1.23°, which indicate that this innovative idea presented in this paper is feasible and promising.

The purpose of this study was to verify the stresses induced by dental restoration on bi-material FEM alveolar bone model. Implanting induced stresses over the alveolar bone are studied during the past decades. With the improving computing technology, computer simulations with FEM( Finite Element Method) software are employed on investigating the stresses after the cure. An important issue about FEM calculations is the discretelized model. Single material bone model were adopt in the early stage studies. Due to the nature of human bone structure, the assumption of homogenous material over the bone is not an adequate one nowadays. Bi-material bone structure has become the mainstream of the numerical studies these years. The bones are modeled with a cancellous core surrounded by a dense cortical layer. Forces, stresses, deformations and strains are calculated by performing FEA on those digital bone models. However, the reliability of bi-material bones digital models is not verified. We built a bi-material prototype and an identical digital implanted bone model. Same boundary conditions and loads are applied on both models. The induced strains measured by strain gage agree with the computer calculated results well.