Objective: This study aimed to investigate the mechanical properties of three composite resins using 2nd and 3rd generation LED-based light-curing devices. Material and Methods: Sixty specimens distributed according to the type of resin(Group Z350 - nanoparticle composite resin [Filtek Z350 / 3M ESPE]; Group AP - microhybrid composite Amelogen Plus/Ultradent; Group DF - Group composite resin Durafil l/Heraeus Kulzer), and the light-curing device(Group 2ndG - 2nd generation LED-based curing unit at power density of 500 mW / cm2; Group 3rdG - 3rd generation LED-based curing unit at power density of 1100 MW/cm2).The specimens were stored in a dark, dry container at 37 °C in an incubator for 24 h and submitted to the mini-flexural test on universal test machine (EMIC) to determine the elastic modulus and flexural strength using a three-point test.The data were submitted to two-way ANOVA (Resin Composite X LED) and Tukey test (5%).Results: Concerning to flexural strength (in MPa), ANOVA showed significant in Tukey test for the interaction between the factors: Group Z350/3rdG - 105.36a; Group AP/3rdG – 81.49ab; Group DF/3rdG – 66.43bc; Group AP/2ndG – 66.13bc; Group DF/2ndG: 60.61bc; Group Z350/2ndG: 47,19c. With regard to the modulus of elasticity (in GPa), the results obtained were: Factor resin composite - Group Z350 (8.85a) > Group AP (7.61b) > Group DF (1.94c); Factor LED - Group 3rdG (7.13a) > Group 2ndG (5.14b). Conclusion:It was concluded that the 3rd generation LED (1100 mw/cm2) significant increased the means of the flexural properties of composites. It was also concluded that the result of flexural properties of compositesdepends on the resin material tested. Keywords: Composite resin; Flexural strength; Modulus of elasticity.
Impact of photoinitiator quality on chemical-mechanical properties of dental adhesives under different light intensitiesImpacto da qualidade de fotoiniciadores nas propriedades químico mecânicas de adesivos dentais sob diferentes intensidades de luz
Objective: The objective of this study was to evaluate the bond strength of resin-modified glass ionomer cement (RMGIC) to composite resin considering the use of conventional and self-etching adhesive systems. Material and Methods: 60 RMGIC blocks (Riva, SDI) measuring 4 x 4 x 4 mm. were constructed. On the blocks, the application of different protocols of adhesive systems (n = 10) was carried out: Group 1 (Control) - without application of adhesive agent; Group 2 - 37% phosphoric acid + conventional adhesive agent Single Bond 2; Group 3 - conventional adhesive agent Single Bond 2; Group 4 – conventional adhesive agent Scotch Bond Multi-Purpose; Group 5 - self-etching adhesive Clearfil SE Bond; Group 6: self-etching adhesive Optibond Allin-One. Next, resin composite blocks measuring 4 x 4 x 4 mm were constructed (Venus, Heraeus Kulzer). The specimens were cut to obtain sticks which were submitted to microtensile bond strength test in a universal testing machine. The data were submitted to ANOVA and Tukey test (5%). Results: ANOVA showed a value of p < 0.05, which indicated significant differences between the groups (in Mpa): Group 2 - 32.83; Group 5 - 31.2; Group 3 - 25,15b; Group 6 - 22.92; Group 4 - 22.15; Group 1 - 13.84. The analysis of fracture mode demonstrated that there was a predominance of adhesive and mixed fractures for all groups. Conclusion: The protocols of acid etching + conventional adhesive system Single Bond 2 (Group 2) or self-etching adhesive system Clearfil SE Bond (Group 5) increased the bond strength of RMGIC to the composite resin. The presence of an adhesive layer between the two materials tended to improve the bonding of RMGIC to composite resin.
Impact of photoinitiator quality on chemical-mechanical properties of dental adhesives under different light intensitiesImpacto da qualidade de fotoiniciadores nas propriedades químico mecânicas de adesivos dentais sob diferentes intensidades de luz
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