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Mammalian cells are sensitive to extracellular microenvironments. In order to precisely explore the physiological responses of cells to tensile loading, a stable and well-defined culture condition is required. In this study, a high-throughput perfusion-based microbioreactor platform capable of providing dynamic equibiaxial tensile loading to the cultured cells under a steady culture condition was proposed. The mechanism of generating tensile stimulation to cells is based on the pneumatically-driven deformation of an elastic polydimethylsiloxan (PDMS) membrane which exerts tensile loading to the attached cells. By modulating the magnitude and frequency of the applied pneumatic pressure, various tensile loading can be generated in a controllable manner. In this study, the microbioreactor platform was designed with the aid of the experimentally-validated finite element (FE) analysis to ensure the loading of tensile strain to cells is uniform and definable. Based on this design, the quantitative relationship between the applied pneumatic pressure and the generated tensile strain on the PDMS membrane was established via FE analysis. Results demonstrated that the proposed device was able to generate the tensile strain range (0~0.12), which covers the physiological condition that articular chondrocytes experience tensile strain under human walking condition. In this study, moreover, the effect of tensile loading on the metabolic, biosynthetic and proliferation activities of articular chondrocytes was investigated. Results disclosed that the dynamic tensile loading of 0.12 strain at 1 Hz might significantly up-regulate the synthesis of glycosaminoglycans while such stimulation was found no significant influence on the metabolic activity, the synthesis of collagen, and the proliferation of chondrocytes. Overall, this study has presented a high throughput perfusion micro cell culture device that is suitable for precisely exploring the effect of tensile loading on cell physiology.

The purpose of this study was to relate the proportions of bone-supported root length of a 2D view into the amount of a 3D bone-attached root surface area (BA-RSA) by using a dental laser scanner examination. White-light 3D scanning technology was used to probe 36 maxillary and 35 mandibular single-rooted premolars. The bone-supported height (BSH) and BA-RSA at designated levels (95–25%) were compared using statistical t tests. The 100% BSH and BA-RSA of the maxillary/mandibular premolars were 12.6 ± 1.60 mm/13.45 ± 1.47 mm (p < 0.05) and 220.78 ± 35.31 mm2/199.51 ± 26.33 mm2 (p < 0.01), respectively. Approximately 79–80%, 59–60%, and 35–36% premolars 2D BSH remained in comparison to 75%, 50%, and 25% 3D BA-RSA preservation, respectively. However, corresponding to a 75%, 50%, and 25% 2D BSH reserve, premolars retained 67–68%, 39–41%, and 15–17% 3D BA-RSA, respectively. When taking 1.0 mm connective tissue attachment into account, 60% 3D BA-RSA and 50% 2D BSH loss were noted at the 5.1–5.4 mm clinical attachment level. Assigning a periodontal prognosis and determining the severity of periodontitis for premolars with alveolar bone loss based on 3D’s or 2D’s measurement is inconsistent.

This study investigates micro-crack propagation at the enamel/adhesive interface using finite element (FE) submodeling and element death techniques. A three-dimensional (3D) FE macro-model of the enamel/adhesive/ceramic subjected to shear bond testing was generated and analyzed. A 3D micro-model with interfacial bonding structure was constructed at the upper enamel/adhesive interface where the stress concentration was found from the macro-model results. The morphology of this interfacial bonding structure (i.e., resin tag) was assigned based on resin tag geometry and enamel rod arrangement from a scanning electron microscopy micrograph. The boundary conditions for the micro-model were determined from the macro-model results. A custom iterative code combined with the element death technique was used to calculate the micro-crack propagation. Parallel experiments were performed to validate this FE simulation. The stress concentration within the adhesive occurred mainly at the upper corner near the enamel/adhesive interface and the resin tag base. A simulated fracture path was found at the resin tag base along the enamel/adhesive interface. A morphological observation of the fracture patterns obtained from in vitro testing corresponded with the simulation results. This study shows that the FE submodeling and element death techniques could be used to simulate the 3D micro-stress pattern and the crack propagation noted at the enamel/adhesive interface.