| Summary: | 博士 === 國立成功大學 === 生物醫學工程學系 === 101 === Hydrodynamic theory is the most widely accepted theory explaining dental pain. An external stimulus on teeth during daily activities or clinical dental treatments may cause fluid flow in the dental pulp and induce dental pain. This study used the fluid-structure interaction (FSI) to simulate the fluid flow in dental pulp when teeth are subjected to external stimuli. This study was divided into four parts. Firstly the fluid flow behavior in the pulp chamber resulting from external mechanical stimulus was evaluated through in-vitro, and compared with the corresponding FSI simulation. In the experiment the root of one molar tooth was removed. The pulp chamber was filled with water and connected to a capillary. Vertical forces, 5N, 100N and 150N respectively were given on tooth crown. The fluid movement in the capillary was observed. Corresponding 3D model was created in FSI simulation to compare with experimental results. The second part of this study created an intact premolar tooth FSI model. Various loading rates of vertical, along occlusion direction, transient forces, from 0 to 100 N, were applied on the occlusal surface to simulate the fluid flow responses. The third part, using the same premolar model simulated dental intrapulpal responses under transient force, from 0 to 100 N, with various directions. The fourth part investigated the effects of food property, elastic modulus, and chewing speed on the dentinal fluid flow during mastication.
The results showed that FSI simulation results are similar as that of the experimental results. The external compression loading resulted in pulp fluid outflow. The force magnitude influences the fluid outflow volume, while the loading rate affects the fluid flow velocity, at both coronal pulp wall and radicular pulp. For the effect of force direction, the horizontal force not only increases the risk of tooth structure failure but also enhances the fluid flow velocity at the coronal pulp, which increasing the possibility of tooth pain. This should due to the large bending effect generated by this horizontal force. Masticating hard food, high elastic modulus, would induce high stress and large deformation on the tooth structure which transferred a high reaction force on the bone. This would cause faster dentinal fluid flow within the pulp. Combining with the fast chewing speed, the hard food particles can easily cause the fluid flow velocity in the radicular pulp reaching the tooth pain threshold, triggering dental pain. In conclusion, it is demonstrated, for the first time, that the FSI simulation can provide more complete information for the evaluation of dental biomechanics.
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