Effects of demineralization depth on microtensile bond strength to human dentin.
OBJECTIVE
To evaluate the effect of different phosphoric acid concentrations (10% and 37%) on the microtensile bond strengths (microTBS) of three dentin adhesive systems with different solvents (ethanol, acetone, or none).


METHODS
Eighteen third molars divided into six groups were ground flat to expose superficial dentin, which was polished to 600-grit. The bonding procedure was initiated using either of two phosphoric acid gels (10% and 37%). Three adhesive systems - Single Bond (SB), Prime & Bond NT (NT), and One Coat Bond (OC) - with different solvents (ethanol, acetone, or none, respectively) were used. After adhesive application, a cylinder of composite resin was built up. After 24 h water storage, each tooth was serially sectioned into thin rectangular sections (or "sticks") parallel to the long axis and with a mean cross-sectional area of 0.4 mm2. microTBS were determined using an Instron universal testing machine. Data were analyzed using two-way ANOVA and Duncan's test.


RESULTS
Mean bond strengths ranged from 66.1 MPa for 10%/ H3PO4 and SB to 43.8 MPa for 37% H3PO4 and OC. SB and OC tended to have slightly higher bond strengths when 10% H3PO4 was used. NT with 37% H3PO4 had a significantly higher microTBS (54.6 MPa) than NT with 10% H3PO4 (44.4 MPa).


CONCLUSIONS
Etching dentin with 37% H3PO4 resulted in a significantly higher mean microTBS for the acetone-based adhesive NT. For both the ethanol- and water-based adhesive (SB) and the solvent-free adhesive (OC), acid concentration did not significantly affect bond strength.
Nunes
M F
MF
Department of Operative Dentistry, University of North Carolina at Chapel Hill, 27599-7450, USA.
Swift
E J
EJ
Perdigão
J
J
D000096:Acetone / Q000737:chemistry; D000134:Acid Etching, Dental / Q000379:methods*; D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000187:drug effects / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry; D006801:Humans; D008689:Methacrylates / Q000737:chemistry; D008964:Molar, Third; D010756:Phosphoric Acids / Q000008:administration & dosage / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013223:Statistics as Topic; D013718:Tensile Strength; D013997:Time Factors; D014867:Water
D003188:Composite Resins; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D010756:Phosphoric Acids; D011109:Polymethacrylic Acids; C103500:Prime & Bond; D012997:Solvents; C090969:Tetric; C115612:single bond; D014867:Water; D000096:Acetone; D000431:Ethanol; D017438:Bisphenol A-Glycidyl Methacrylate