Effects of the acetone content of single solution dentin bonding agents on the adhesive layer thickness and the microtensile bond strength.
OBJECTIVE
This study investigated the hypothesis that varying the acetone content of single solution dentin bonding agents may affect the adhesive layer thickness and microtensile bond strength (MTBS) of the bonded complex, and explored whether the adhesive layer thickness is a valid predictor for MTBS.


METHODS
Experimental dentin bonding agents containing (27, 37, 47, 57, or 67) mass fraction% acetone were used to bond composite resin onto occlusal dentin surfaces of extracted human molars. The adhesive layer thickness was determined by digitized image analysis. MTBS was measured after 48 h. The fracture surfaces were observed using SEM.


RESULTS
With increasing acetone content, MTBS varied from 38 MPa (67% acetone) to the highest MTBS of 64 MPa (37% acetone), while the adhesive layer thickness decreased linearly. Both dependent variables demonstrated moderate inverse correlation with the acetone content (p<0.0001), but were not correlated with each other (p>0.05). Ninety-four percent of the specimens showed fractures within the adhesive layer extending toward the interfaces with the hybrid layer or the composite resin. In the groups containing 57 and 67% acetone, cracks were observed at these interfaces.


CONCLUSIONS
Rather than the adhesive layer thickness, interfacial cracks in specimens with acetone-rich bonding agents may have caused lower MTBS. Within the scope of this investigation, lower acetone concentrations, as could be anticipated from solvent evaporation during clinical use of the bonding agent, did not seem to lower MTBS, but rather improved the integrity of the dentin/adhesive bond.
Cho
Byeong-Hoon
BH
Department of Conservative Dentistry and Dental Research Institute, College of Dentistry, Seoul National University, Seoul, South Korea.
Dickens
Sabine H
SH
D000096:Acetone / Q000737:chemistry*; D000269:Adhesives; D003188:Composite Resins; D001840:Dental Bonding; D003799:Dental Stress Analysis; D003804:Dentin; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D019279:Resin Cements / Q000737:chemistry*; D013718:Tensile Strength; D014783:Viscosity; D014835:Volatilization
D000269:Adhesives; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D019279:Resin Cements; D000096:Acetone