Jianping Geng’s research while affiliated with Zhejiang University and other places

As the Finite Element (FE) method requires a huge amount of computation, its application should be supported by advanced of computer technology. Many computer softwares have been developed and commercialised for workstation and Personal Computers (PC) in recent years. Most of the FE softwares are developed for general applications in solids, fluids, and electrical and magnetic field. There are also some FE software designed for a specific type of analysis. The FE software used for dental implant simulation is the one for general applications.

The use of numerical methods such as FEA has been adopted in solving complicated geometric problems, for which it is very difficult to achieve an analytical solution. FEA is a technique for obtaining a solution to a complex mechanics problem by dividing the problem domain into a collection of much smaller and simpler domains (elements) where field variables can be interpolated using shape functions. An overall approximated solution to the original problem is determined based on variational principles. In other words, FEA is a method whereby, instead of seeking a solution function for the entire domain, it formulates solution functions for each finite element and combines them properly to obtain a solution to the whole body. A mesh is needed in FEA to divide the whole domain into small elements. The process of creating the mesh, elements, their respective nodes, and defining boundary conditions is termed “discretization” of the problem domain. Since the components in a dental implant-bone system is an extremely complex geometry, FEA has been viewed as the most suitable tool to mathematically, model it by numerous scholars.

Part of the new series, Advanced Topics in Science and Technology in China, this book is designed to give the necessary theoretical foundation to new users of the finite element method in implant dentistry, and show how both the implant dentist and designer can benefit from finite element analysis. The first part deals with the theory of the finite element method. containing the necessary mathematical theory but written so that readers from a dental background can easily understand. Then basic knowledge of implant dentistry is introduced to readers from an engineering background. Next, dental implant applications, and the critical issues of using finite element analysis for dental implants are discussed, followed by aspects of dental implant modeling. Finally, two popular commercial finite element software programs, ANSYS and ABACUS, are introduced for dental finite element analysis. Dr J.P. Geng is a professional implant dentist and has been an implant designer for 15 years.

The finite element method may be applied to all kinds of materials in many kinds of situations: solids, fluids, gases, and combinations thereof; static or dynamic, and, elastic, inelastic, or plastic behaviour. In this book, however, we shall restrict the treatment to the deformation and stress analysis of solids, with particular reference to dental implants.

Although the precise mechanisms are not fully understood, it is clear that there is an adaptive remodelling response of surrounding bone to stresses. Implant features causing excessive high or low stresses can possibly contribute to pathologic bone resorption or bone atrophy. This chapter reviews the current applications of FEA in Implant Dentistry. Findings from FEA studies will then be discussed in relation to the bone-implant interface; the implant-prosthesis connection; and multiple implant prostheses.

Dentistry aims at replacing missing teeth since it was first recognized as a profession. For centuries, dental practitioners have relied on their own skills and various artifacts to develop esthetic and functional alternatives to minimize sequelae that occur as a result of edentulism. Partial, complete, fixed, or removable dentures are by far the most commonly used forms of tooth replacement applied. In other words, these devices have been incorporated into the oral cavity anchored on either remaining teeth and/or other anatomical structures. Only scarce archeological reports have demonstrated attempts of incorporating prosthetic devices into the jaws as more natural and functional replacements. However, predictability of these methods was not achieved until recently. (Table 2.1)

This paper presents a new method for 3D shape reconstruction in computer-aided dental prosthetics. A specklegram is projected onto the tooth to be measured. This shadow speckle image is recorded and then processed by a digital image correlation method, which enables the computation of 2D shapes based on the similar principle of shadow moiré method. By repeating the procedure for all the sides, i.e., one crown and several side surfaces, local 2D shapes can be measured precisely. Afterwards, these local 2D profiles are merged to form a 3D model, during which certain constraints such as the widths along perpendicular directions are introduced to guide the process. As the height information within an entire image field is recorded instantly, it has the potential to be employed in an intra-oral environment, which would make the patient feel more comfortable during the restoration process. In vitro experiments were carried out on gypsum teeth models and the results proved the effectiveness of the proposed method.

This study presents a method of using shadow-speckle correlation to reconstruct a 3-dimensional (3D) tooth model. Compared with other methods based on laser or optical geometric measurements, the shadow-speckle method overcomes their limitations by using a digital image correlation to reconstruct a 3D tooth model. Using plaster models 4 times the normal tooth size showed that the accuracy of the reconstructed model was estimated at roughly 30 microm, which potentially could be used in direct intraoral applications.