RESUMO
PURPOSE: To evaluate the effect of light guide distance and the different photoactivation methods on the degree of conversion (DC) and microleakage of a composite. METHODS AND MATERIALS: Three photoactivation protocols (600 mW/cm2 x 40 seconds; 400 mW/cm2 x 60 seconds or 200 mW/cm2 x 20 seconds, followed by 500 mW/cm2 x 40 seconds) and three distances from the light source (0, 3 or 7 mm) were tested. Cylindrical specimens (5 mm diameter; 2 mm tall; n=3) were prepared for the DC test (FT-Raman). Class V cavities were made in 90 bovine incisors to conduct the microleakage test. The specimens were conditioned for 15 seconds with phosphoric acid (37%), followed by application of the adhesive system Prime & Bond NT (Dentsply/Caulk). The preparations were restored in bulk. The specimens were stored for 24 hours in distilled water (37 degrees C) before being submitted to the silver-nitrate microleakage protocol. The restorations were sectioned and analyzed under 25x magnification. RESULTS: Statistical analyses (two-way ANOVAs and Tukey test, alpha=0.05) found significance only for the factor distance (p=0.015) at the top of the composite for the DC test. Conversion was statistically lower for the 7 mm groups compared to the 0 and 3 mm groups, which were equivalent to each other. At the bottom of the specimens, none of the factors or interactions was significant (p<0.05). The Kruskal-Wallis test showed that, in general, the soft-start method led to lower microleakage scores when compared to the continuous modes, mainly when associated with a distancing of 7 mm (p<0.01). With the exception of specimens irradiated with 400 mW/cm2 that did not demonstrate variations on scores for the distances tested, higher microleakage was observed for shorter distances from the light source. CONCLUSIONS: Soft-start methods may reduce microleakage when the light guide distancing provides a low level of irradiance, which also causes a discrete reduction in the DC.
Assuntos
Resinas Acrílicas , Resinas Compostas , Infiltração Dentária , Restauração Dentária Permanente , Cura Luminosa de Adesivos Dentários , Poliuretanos , Resinas Acrílicas/química , Animais , Bovinos , Resinas Compostas/química , Técnicas In Vitro , Incisivo , Poliuretanos/químicaRESUMO
PURPOSE: To investigate the in vitro performance of three one-bottle adhesives by measuring their dentin microtensile strength. MATERIALS AND METHODS: Extracted human molars had the dentin exposed on the occlusal surface. The teeth were randomly assigned to three dentin adhesives: Group 1 - Prime & Bond 2.1; Group 2 - Prime & Bond NT; and Group 3 - Experimental (unfilled NT). All materials were applied as recommended by the manufacturer. A high-density resin composite (Surefil) was packed on the bonding area in five increments. Specimens (sticks) were obtained using a diamond disc and were stored in distilled water for 24 hrs. The microtensile bond strengths were measured with a universal testing machine. RESULTS: Group 1: 54.3+/-15.6 MPa; Group 2: 62.0+/-17.6 MPa; Group 3: 54.6+/-16.8 MPa. Although no statistically significant difference was found between pairs of means, Prime&Bond NT showed a tendency for higher bond strengths.
Assuntos
Colagem Dentária , Adesivos Dentinários/química , Acetona/química , Condicionamento Ácido do Dente , Análise de Variância , Resinas Compostas/química , Análise do Estresse Dentário/instrumentação , Dentina/ultraestrutura , Humanos , Teste de Materiais , Dente Molar , Ácidos Polimetacrílicos/química , Resistência à Tração , Fatores de Tempo , ÁguaRESUMO
PURPOSE: To evaluate microleakage at enamel and dentin margins of Class V resin-based composite (RBC) restorations using five simplified adhesive systems, one self-etching adhesive, three commercial one-bottle adhesives and one experimental one-bottle adhesive. MATERIALS AND METHODS: Class V cavities (3 mm x 2 mm x 2 mm) were prepared in sound human molars with occlusal margins in enamel and gingival margins in dentin/cementum. Etch & Prime 3.0 (Degussa), Single Bond (3M), PQ1 (Ultradent), Prime & Bond NT (Dentsply) and Experimental BEH (Dentsply DeTrey) were applied strictly according to manufacturers instructions. All adhesive systems were applied on etched substrates, except for the self-etching adhesive Etch & Prime 3.0. Cavities were restored with Z100 RBC. After finishing and polishing, teeth were thermo-cycled (x 700, 5-55 degrees C, 60 s dwell time). Specimens were coated with nail varnish, immersed in silver nitrate for 2 hours and sectioned longitudinally with a diamond disc. The extent of leakage was measured and ranked using a 0-4 scale. RESULTS: Statistical analysis using Kruskal-Wallis test revealed significantly higher leakage scores (P < 0.001) for Etch & Prime 3.0 on enamel when compared to all other adhesive systems. Regarding dentin margins none of the systems completely eliminated microleakage. PQ1 had significantly lower scores (P < 0.05) when compared to Etch & Prime 3.0 and Single Bond. No statistically significant difference was observed for the other groups.