$568 Journal of Biomechanics 2006, Vol. 39 (Suppl 1)

4748 We-Th, no. 12 (P62) CAD-based optimum design of functional occlusal surface in accordance with patient's tooth excursions T. Maruyama 1 , '~ Nakamura 2, T. Hayashi 1,2, K. Terada 3, R. Kazama 4, K. Kazumasa 4. 1Graduate School of Science and Technology, Niigata University, Niigata, Japan, 2Department of Biocybernetics, Faculty of Engineering, Niigata University, Niigata, Japan, 3 Niigata University Medical & Dental Hospital, Niigata, Japan, 4Institute of Oral Science, Matsumeto Dental University, Nagano, Japan

Attempts have been made to apply advanced CAD/CAM technology to the design and manufacturing of dental prostheses such as crowns and bridges, in order to simplify production procedure as well as to improve their quality. Presently, several dental CAD systems are available, assisting us to design complicated occlusal surfaces, which should agree with patient's stomatog- nathic functions. In order to avoid occlusal interferences during tooth excur- sions, dental CAD systems usually use patient's functional occlusal impres- sions for the design of occlusal contact points. Previous interfere-free design, however, has been done on a trial-and-error basis by using visual inspection. To improve such time-consuming procedure into a semi-automatic one based on quantitative evaluations, we equipped our CAD system named "Vocs-2" with two difference functions such as (1) a virtual dental articulator, and (2) proximity mapping on the crown surface relative to its opposing occlusal surface. The articulator has several adjustable components as follows: (1) sagittal inclination of the condylar housing, and (2) sagittal and lateral inclinations of the incisal table. These variables are automatically determined in accordance with pa- tient's functional occlusal impressions, employing an advanced 3D-registration- based technique. This procedure is summarized as follows: (1) clinical record- ing of patient's functional occlusal impression; (2) computation of articulator parameter values in order to make the recorded impression surface agree with that obtained from virtual-articulator simulation; and (3) adjustment of virtual articulator. Experiments of designing the crown of a lower first molar demonstrated that a virtual articulator capable of simulating patient's tooth excursions can be implemented in dental CAD system.

5815 We-Th, no. 13 (P62) First step FE-modelling of internal composite behaviour during curing dental restorations C. Koplin, C.R. Jaeger. Fraunhofer-lnstitut f~r Werkstoffmechanik, Freiburg, Germany

Light-curing dental composites have found widespread application in dental restorations due to their tooth-like appearance and easy handling. The devel- opment of ~adhesive dentistry<< (i.e. the use of bonding agents which improve the bond strength between tooth and filling) increased the range application of light curing dental composites e.g. in the area of minimal invasive procedures. Despite intensive research, these composites still introduce internal stresses into the restoration due to the polymerisation shrinkage during curing. These stresses can compromise the marginal integrity and lead to secondary caries, cause initial damage to the material during hardening, and promote chemical and mechanical degradation. The stresses result from a complex interplay between geometry of the cavity, increasing stiffness, decreasing flowability, and changes in the density of the material due to thermal expansion and polymerisation shrinkage. We developed a dedicated mechanical testing set-up which measures stiffness, viscosity, and volume behaviour of the composites during the hardening reaction. The results of the experiments are used in a material model which describes the development of internal stresses for differ- ent composite compositions and allows a comparison of the performance of various dental filling materials. The development of heterogeneous distributed stresses and local flow processes close to the filler particles of two different dental composites are investigated as first step but in detail. High filler loads of 60% (vol.) are accomplished in different composites by differing multimodal filler sizes. We compared older but well-known Tetric Ceram with Heliomolar, that are more dislike in filler-structure but more alike in monomer-mixture, by their tendency to handle critical local stresses during curing.

7096 We-Th, no. 14 (P62) Geometrical modeling, finite element analysis and simulation of operations in the area of the denture T. Charamis, E. Karatsis, I. Chalkidis, G. Athanasiadis. Laboratory efMachine Elements & Machine Design, Department of Mechanical Engineering, Aristotle University of Thessaloniki, Thessaloniki, Greece

From an engineer's point of view, biological systems, such as the denture and the mandible, constitute of a group of assembled parts characterized of different physical and mechanical properties. The aim of the current paper is to introduce a new geometrical modeling method which can be embodied into the typical modeling and finite element analysis process in order to reduce the required time for the creation of a Finite Element Model.

Poster Presentations

Tools with morphing functionality are used in order to create the specific geometry of a patient's part based on a general geometrical model. This makes easy the adaptation of a geometrical model to every patient's specific characteristics changing only the dimensions of its feature parameters. Thus, parts of more than one patient can be simulated, avoiding the iteration of the whole procedure. After the adaptation of the general geometry to the patient's individual data is complete, follows the calibration of the model as well as the definition of the initial and boundary conditions. The procedure allows the simulation of operations such as: - tooth fillings, - tooth replacements using bridges - tooth replacements using implants This innovative modeling procedure combined with a Finite Element Analysis can provide with a preview of the results of an operation and give a clear view of the way the result can be affected by the modification of various parameters. The conclusions extracted from the finite element analysis additionally to the doctor's experience can minimize the possibility of failure and make the whole procedure a powerful tool in biomechanics modeling.

6592 We-Th, no. 15 (P62) FEA and experimental FBG sensing system for the analysis of different dental implant concepts P. Carvalho 1 , I. Abe 2, M.W. Schiller 2, L. Carvalho 3, J.A. SimSes 1 , P. Lopes 1 , J.L. Pinto 1 . 1Departamento de Engenharia Mec~nica, Universidade de Aveiro, Portugal, 2 Departamento de Fisica, Universidade de Aveiro, Portugal, 3Institute Superior de Sa~de do Norte, Gandra, Portugal

Dental implant systems are in constant development to make them functionally more efficient and closer to the physiological human part behavior. This work had as objective the design of a functionally more reliable dental implant system to improve the load mechanism transfer form the implant to the surrounding bone without loosening of long term fixation. Three types of macro models of dental implants concepts were prototyped. The geometry was fixed, but the materials were changed, one using steel alloy, another using a ABS plastic and the third one combining these two materials. The implants were tested and implanted into two different kinds of materials: silicone and fresh bovine cancellous bone. Carvalho et aL [1] have shown that an implant attached to bone, constructed with two different materials, can have the same strain pattern as the natural physiological tooth-bone system. Finite Element models simulating the experimental one were used in this study to design a novel dental implant system that can replicate the mechanical function of the loss periodontal ligament of the natural tooth. Optical fiber Bragg sensors (FBG) have been used to measure statically and dynamically the silicone/bone response to mechanical loads (occlusion loads) on the implant. Good agreement was obtained for both experimental and numerical results. It is possible, with this technique to speculate on the dental implant-bone load transfer mechanism and how different concepts can provoke cancellous stress- strain patterns more closely to the physiological ones.

References [1] Carvalho L., Pereira J., Ramos A., Sim6es J.A. Sistema de implante dent&rio

n&o convencional: um estudo preliminar. In: Metodos Numericos en Ingenieria, J.M. Goicolea, C. Mota Soares, M. Pastor and G. Bugeda (Eds.). 2002; So- ciedade EspaSola de Metodos Numericos en Ingenieria Ingenieria V. p. 74 (in CD-ROM).

7607 We-Th, no. 16 (P62) Continuous clenching analysis of temporomandibular joint: individual model-based analysis for factors inducing joint disorder

M. Tanaka 1 , R. Fujita 1, E. Tanaka 2, T. Matsumoto 1 , H. Naito 1 . 1Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Japan, 2Department of Orthodontics and Craniofacial Developmental Biology, Graduate School of Biomedical Science, Hiroshima University, Minami, Hiroshima, Japan

Temporomandibular disorders (TMD) are very common ailments especially in young women. Disc disorders such as anterior disc displacement (ADD) and disc perforation, which are found in many TMD cases, may be attributed to abnormal mechanical conditions. Bruxism such as clenching or grinding is reported to be associated with TMD as a factor causing lateral pterygoid muscle tonus, ADD, and so on. In particular, the continuous clenching is considered one of the major factors inducing TMD. In this study, we analyzed the biomechanical condition in temporomandibular joint (TMJ) during contin- uous clenching using finite element TMJ models of individual subjects, and investigated mechanical risk factors for TMD. The individual three-dimensional model of TMJ system was developed based on MR slice images and cor- responding cephalometric radiograph. We treated bone components as rigid bodies and soft tissue components of the TMJ disc and surrounding connective