The Development of the Techniques in Adhesive Interfacial Micro-Mechanical Analysis and Crack Propagation Simulation and Clinical Application to the Cement Incisor Veneer and Orthodontic Bracket Removement

Retention between restorative material and tooth is the major factor affecting the long term survival rate of the dental restoration, it usually primarily depends on the mechanical behavior of the micro interlocking for the resin tag on the enamel/adhesive interface. To date, there is no adequate research method to investigate the micro mechanics of the enamel/adhesive interface. In addition, further recognize the initiation and accumulation of crack processes associated with the resin tags on the enamel/adhesive interface also can improve the interfacial bonding mechanism. Therefore, the aim of this study is attempted to utilize the advanced finite element (FE) methods, such as submodeling and element birth and death approaches to develop the adhesive interfacial micro-mechanical analysis and crack propagation simulation techniques. After the core technique development, two clinical aspects regarding to the ceramic veneer incisor with various cement thicknesses under different occlusal force condition and bracket remove in orthodontic treatment will be investigated to understand the enamel/adhesive interfacial micro mechanics. To develop and validate the core technique, 2D and 3D FE macro-models of the enamel-adhesive- ceramic block will be generated and analyzed to perform the shear bond testing. Stress concentrated area found in the macro-models will be selected to construct total-etch and self-etch micro-models (submodeling) that include different resin tags morphologies based on SEM and Confocal micrographs. Tensile test will be performed to obtain ultimate tensile strengths for total-etch and self-etch cements to determine the material failure parameters. Element birth and death technique provided in FE method is then adopted to simulate the resin tags crack propagation in the micro-models. Parallel in-vitro shear testing and acoustic emissions (AE) fracture experiments on enamel-adhesive- ceramic blocks will be also performed to validate the results of simulations. In veneer restoration applications, 2D and 3D FE macro-models of butt-joint ceramic veneer with different adhesive cement thicknesses (10, 30, 60, 100, 140 μm) will be generated based on anatomy morphology and micro-CT (computed tomography) images. A load is applied at the incisal edge with an angulation of 0°, 60° and 120° respectively to the longitudinal tooth axis to perform the macro simulations. Five total-etch micro-models (based on SEM and Confocal micrographs) corresponding to the macro-models are then constructed at an enamel-adhesive interface where the stress concentrated region to perform the micro interface mechanical analyses. Element birth and death technique will be applied to understand the micro interfacial crack propagation on enamel/adhesive interface in veneer restoration. For orthodontic treatment application, geometries and section contours of premolar and bracket are acquired from Micro-CT to construct the solid models firstly in CAD systems. Solid models are then imported to the finite element (FE) package to generate corresponding FE macro models to perform the macro analysis under different bracket removed forces (direction and location). Micro model based on Confocal micrographs will be construct on the enamel/adhesive interface and the submodeling and element birth and death techniques will be then applied to understand the micro interfacial mechanics and crack propagation. This study has been arranged for three-years, and the specific aims are as follows: First year: core technique development including “Enamel/adhesive interface micro structure observation＂, “Tensile strength testing for adhesive cement＂, “2D adhesive interfacial micro-mechanical analysis and crack propagation simulation＂. Second year: core technique development including “3D adhesive interfacial micro-mechanical analysis and crack propagation simulation＂, “In-vitro shear validated testing on enamel-adhesiveceramic blocks＂, “Acoustic emissions (AE) fracture validated experiment on enamel-adhesiveceramic blocks＂. Three year: clinical applications to understand the enamel/adhesive interfacial micro mechanics including “ceramic veneer incisor with various cement thicknesses under different occlusal force condition” and “bracket remove in orthodontic treatment”.

Project ID:PB9808-2369
External Project ID:NSC98-2320-B010-033-MY3