Effect of prolonged application times on the durability of resin-dentin bonds.
OBJECTIVE
To examine the effect of prolonged application time on the early and 3-year resin-dentin microtensile bond strength.


METHODS
Water/ethanol (Single Bond [SB]) and acetone-based systems (One Step [OS]) were employed. A flat superficial dentin surface was exposed in third human molars by wet abrasion. The adhesives were applied to a delimited area of 52 mm2 on wet surfaces, for 40, 90, 150 and 300 s. Four teeth were assigned for each experimental condition. Composite build-ups were constructed incrementally. After water storage at 37 degrees C for 24 h, teeth were sectioned to obtain sticks with cross-sectional areas of 0.8 mm2 to be tested in tension (0.5 mm/min) either immediately (IM) or after 3 years (3Y) of water storage. The microtensile bond strength (microTBS) values were analyzed by two way repeated measures ANOVA and Tukey's test (alpha=0.05).


RESULTS
The 90- and 150-s groups achieved the highest IM microTBS for OS (p<0.01). For SB, the highest IM microTBS values were observed after 300-s application (p<0.01). Significant decreases in microTBS were observed for OS in the 40- and 90-s groups after 3Y, except for the 150-s group. With regard to SB, after 3Y significant drops in microTBS values were observed for the 40- and 150-s groups, except for the 300-s group.


CONCLUSIONS
Prolonged application times can increase the immediate microTBS of two-step etch-and-rinse adhesive systems and make the adhesive layer more stable over time.
Reis
Alessandra
A
Department of Dental Materials and Operative Dentistry, University of Oeste de Santa Catarina, Joaçaba, SC, Brazil. reis_ale@hotmail.com
de Carvalho Cardoso
Paula
P
Vieira
Luiz Clovis Cardoso
LC
Baratieri
Luiz Narciso
LN
Grande
Rosa Helena Miranda
RH
Loguercio
Alessandro D
AD
D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D014867:Water / Q000737:chemistry
C103506:Bis-GMA, BPDM, HEMA dental-bonding resin; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D008689:Methacrylates; C115612:single bond; D014867:Water; D017438:Bisphenol A-Glycidyl Methacrylate