RESUMO
PURPOSE: The purpose of this study was to evaluate the effect of the zirconia surface architecturing technique (ZSAT) on the bond strength between veneering porcelain and zirconia ceramic. MATERIALS AND METHODS: 20 sintered zirconia ceramic specimens were used to determine the optimal surface treatment time, and were randomly divided into 4 groups based on treatment times of 0, 1, 2, and 3 hours. After etching with a special solution, the surface was observed under scanning electron microscope, and then the porcelain was veneered for scratch testing. Sixty 3 mol% yttria-stabilized tetragonal zirconia polycrystal ceramic blocks were used for tensile strength testing; 30 of these blocks were surface treated and the rest were not. Statistical analysis was performed using ANOVA, the Tukey post-hoc test, and independent t-test, and the level of significance was set at α=.05. RESULTS: The surface treatment of the zirconia using ZSAT increased the surface roughness, and tensile strength test results showed that the ZSAT group significantly increased the bond strength between zirconia and veneering porcelain compared to the untreated group (36 MPa vs. 30 MPa). Optimal etching time was determined to be 2 hours based on the scratch test results. CONCLUSION: ZSAT increases the surface roughness of zirconia, and this might contribute to the increased interfacial bond strength between zirconia and veneering porcelain.
Assuntos
Cerâmica , Porcelana Dentária , Resistência à TraçãoRESUMO
Introduction: The challenge of restoring patient's function that presented some loss of an organ or tissue encourages the Tissue Engineering and Biotechnology to develop materials that promote bone regeneration. Poly(lactic-co-glycolic acid) (PLGA) copolymer is among of the most biomaterials used. Objective: To evaluate the tensile strength of PLGA membranes at different conditions of humidity and temperature. Material and methods: PLGA membranes were hourglass-shape cut and prepared at three different conditions of temperature and humidity (n = 10): (I) dry membrane at environment temperature of about 20ºC (control group), (II) moist membrane plasticized at 55ºC, (III) moist membrane plasticized at 55ºC, which subsequently underwent cooling. Subsequently, the membranes were subjected to tensile tests in a universal testing machine (DL-2000, EMIC) at 1.0 mm/min. Data was submitted to ANOVA and Tukey's test (p < 0.05). Results: Group I showed the highest tensile strength mean (16.7 ± 1.9a MPa, p = 0.0022). There was no statistically significant difference between the means of groups II (14.6 ± 1.4 MPab) and III (13.9 ± 1.7 MPab). Conclusion: The dried PLGA membranes showed higher tensile strength than the membranes that were only either plasticized or cooled.
RESUMO
Anastomosis of rat common carotid artery was performed by applying four crossed-fixing sutures and by mantling with human fibrinogen-thrombin glue. There was a 97% patency rate 24 hours after surgery, and the anastomosed vessels were still patent on the 7th and 30th postoperative days. Aneurysm formation was absent but stenotic change was seen to 1 case of 8 angiographic studies. Histopathological studies of microvascular anastomosis showed that this surgical technique of anastomosis has certain advantages, namely that it reduces the number of sutures needed, is less traumatic to the vascular wall, ensures elastic vascular junction, and the glue used possess high biological inertness that provides a better physiological connection of vessels than conventional suturing. The duration of the clipping and the operation is significantly reduced. A tensile strength test 24 hours following operation and 1 week later showed that this anastomosis was significantly better than that achieved with the usual manual suture method. The author therefore concludes that this new surgical technique of microvascular anastomosis may be valuable in microvascular neurosurgery.