Fractographical analysis of resin-dentin bonds.
OBJECTIVE
To characterize resin-dentin bond structures of three adhesive resin systems using fractographic analysis to measure the area of failure at the fractured surface.


METHODS
Flat dentin surfaces were ground perpendicular to the long axis of the tooth. The prepared dentin surfaces were treated by one of three adhesive resin systems (Mac Bond II, One-Step, and Single Bond). The samples were sectioned perpendicular to the adhesive interface to produce a square bar-shaped specimen (adhesive area: 0.9 mm2) using a diamond saw. A micro-tensile test was then conducted at a crosshead speed of 1.0 mm/min. The mean tensile bond strengths were statistically compared using one-way ANOVA and Fisher's PLSD test (P< 0.05). The fractured surfaces of all specimens were examined using SEM and the area of failure was measured using an image analyzer on SEM microphotographs.


RESULTS
No significant differences in tensile bond strength were observed between Single Bond (62.1+/-18.2 MPa) and One-Step (53.8+/-13.1 MPa) (P > 0.05). However, the bond strength of Mac Bond II (36.5+/-13.7 MPa) was significantly lower than that of One-Step or Single Bond (P< 0.05). At the fractured surface, except for the cohesive failure of the bonding resin and resin-based composite, different failure patterns were observed for each resin system as follows: the failure of the hybrid layer and demineralized dentin was observed in the two wet bonding systems (One-Step and Single Bond) and of the hybrid layer but not the demineralized dentin in the self-etching primer system (Mac Bond II). The results demonstrated that the integrity of the hybrid layer depends on the adhesive system.
Hashimoto
M
M
Department of Pediatric Dentistry, School of Dentistry, Hokkaido University, Sapporo, Japan. masanori-h@mue.biglobe.ne.jp
Ohno
H
H
Kaga
M
M
Endo
K
K
Sano
H
H
Oguchi
H
H
D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins; D001840:Dental Bonding; D003804:Dentin / Q000648:ultrastructure; D003806:Dentin Permeability; D017220:Dentin-Bonding Agents; D019544:Equipment Failure Analysis; D024022:Fibrillar Collagens / Q000648:ultrastructure; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates; D008855:Microscopy, Electron, Scanning; D019279:Resin Cements; D013499:Surface Properties; D013718:Tensile Strength
C103506:Bis-GMA, BPDM, HEMA dental-bonding resin; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D024022:Fibrillar Collagens; C452442:Mac Bond II; D008689:Methacrylates; D019279:Resin Cements; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate