ABSTRACT
OBJECTIVE: This study aimed to evaluate the efficacy of low intensity (0.1-0.8 Watt/cm2) pulsed ultrasound on chondrocyte cell proliferation and migration. METHODS: Low-intensity pulsed ultrasound (frequency 3 MHz, duty cycle 25%, and pulse repetition frequency 150 Hz) for 5 minutes at different spatial average intensities was applied on chondrocyte cells. First, the optimum dose with significantly increased proliferation was determined to be 0.5 W/cm2 for 5 minutes of duration. Then, 0.5 W/cm2 ultrasound intensity was applied for durations of 2.5, 5, 7.5, and 10 minutes, and healing was assessed by monitoring cell migration and proliferation. RESULTS: At the intensity of 0.5 W/cm2 48 hours after the application, a statistically significant increase in proliferation (p = .0089) was observed in chondrocyte cells compared to the control group. Proliferation was analyzed at 4, 8, 24, and 48 hours after applying 0.5 W/cm2 ultrasound for durations of 2.5, 5, 7.5, and 10 minutes. Statistically significant increases were observed at 4 hours (p = .009), 8 hours (p = .032), 24 hours (p = .0084), and 48 hours (p = .00098) with 10 minutes of exposure. For 7.5 min of exposure duration, significant increases were observed at 48 hours (p = .045). In migration for all parameters, no statistically significant improvement (p > .05) was observed. CONCLUSION: It was shown that low intensity pulsed ultrasound induces cartilage cell proliferation; therefore, it may have a disease-modifying effect in the treatment of osteoarthritis. However, no positive effect was observed on cartilage cell migration.
ABSTRACT
OBJECTIVE: A long-term clinical study previously stated that adhesively luted resin-bonded fixed partial dentures (RBFPDs) with two retainers exhibited two complications (loss of adhesion or fracture between retainer and pontic) when compared to RBFPDs with a single retainer. The reasons for these complications were not reported. The aim of this study was to evaluate the stress distribution of two-retainer and singleretainer zirconium dioxide RBFPDs by using three-dimensional finite element analysis (3D FEA). METHOD AND MATERIALS: Two different 3D finite element models were created. Each model contained cortical bone, cancellous bone, periodontal ligament, cement, and enamel. Additionally one of the models contained a two-retainer zirconium dioxide RBFPD while another contained a single-retainer zirconium dioxide RBFPD. A 100 N force was applied at 45 degrees 2 mm below the incisal edge of the palatal surface of the pontic. In each model, Von Mises stress distribution was evaluated. RESULTS: Maximum Von Mises stress values in RBFPD with a single retainer and two retainers were 1.13 MPa and 1.23 MPa, respectively. Von Mises stress was concentrated at the interface between pontic and retainer for RBFPD with two retainers. CONCLUSION: Zirconium dioxide RBFPD with a single retainer and two retainers exhibited similar stress concentrations between pontic and retainer. However, the use of a single retainer for RBFPDs prevented stress concentration at the interface between retainer and pontic.
