Abstract
AIM: To evaluate the impact of different light-curing times on dentin microtensile bond strength of two restorative systems after 24 h and 6 months of water storage. METHODS: Standardized Class II preparations were performed in 56 freshly-extracted human molars (n = 7), restored with methacrylate- or silorane-based restorative systems, and light-cured using a light-emitting diode at 1390 mW/cm2 by the recommended manufacturers' time or double this time. After storage for 24 h at 37 oC, the teeth were sectioned to yield a series of 0.8-mm thick slices. Each slab was trimmed into an hourglass shape of approximately 0.64 mm2 area at the gingival dentin-resin interface. Specimens were tested using universal testing machine at crosshead speed of 0.5 mm/min until failure, after 24 h and 6 months of storage. Data were statistically analyzed by three-way ANOVA and Tukey's test (α = 0.05). RESULTS: The highest bond strength values were recorded for the groups restored with methacrylate system (p<0.001) as well as for extended light-curing time (p = 0.0034). There was no statistically significant difference between 24 h and 6 months storage on bond strength (p>0.05). CONCLUSIONS: Bond strength was influenced by the material and light-curing time, but the 6-month storage did not affect the bond strength of restorations.
Highlights
Received for publication: June 26, 2014 Accepted: September 02, 2014Correspondence to: Anderson CatelanDepartamento de Odontologia Restauradora Faculdade de Odontologia de Piracicaba - UNICAMPAv
Polymerization of methacrylate-based composite is characterized by volumetric shrinkage[1]
Polymerization stress may result in cuspal deflection[4], de-bonding at composite-dentin interface, post-operative sensitivity[5,6], microleakage[5], secondary caries formation, marginal staining, restoration and dental fractures[6], all reducing the longevity of the restoration
Summary
Received for publication: June 26, 2014 Accepted: September 02, 2014Correspondence to: Anderson CatelanDepartamento de Odontologia Restauradora Faculdade de Odontologia de Piracicaba - UNICAMPAv. Polymerization of methacrylate-based composite is characterized by volumetric shrinkage[1] Silorane presents a cationic ring-opening polymerization mechanism instead of the free radical cure of methacrylate monomers[4] and an exended light-curing time to form cations is necessary to initiate the polymerization reaction[1,4]. It exhibits lower polymerization shrinkage[4,8] and mechanical properties comparable to that of methacrylate dental composites[7]
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