Effect of dentine depth on the fracture toughness of dentine-composite adhesive interfaces.
OBJECTIVE
The fracture toughness test was recently introduced as a clinically relevant method for assessing the fracture resistance of the dentine-composite interface. The objective of this study was to evaluate the effect of dentine depth on the interfacial fracture toughness test of several dentine-composite interfaces using some new proprietary dentine bonding agents.


METHODS
Miniature short rod fracture toughness specimens containing a chevron-shaped dentine-composite-bonded interface were prepared for each group (n = 12). Six different dentine bonding agents and two dentine depths were the variables assessed at the dentine-composite interfaces. After 24 h at 37 degrees C in water, the specimens were tested by loading at 0.5 mm/min in the Instron Universal Testing Machine. The interfacial KIC results were analysed by ANOVA, unpaired Student's t-tests and Fisher's LSD test (P < 0.05).


RESULTS
The interfacial KIC results in MN.m-3/2 (S.D.) on superficial and deep dentine, respectively, were: All-Bond 2, 0.80 (0.21), 0.44 (0.13); Bond-lt, 0.75 (0.20), 0.38 (0.19); Prime and Bond, 0.56 (0.11), 0.28 (0.10); Scotchbond Multi-Purpose, 0.45 (0.23), 0.26 (0.15); One-Step and OptiBond, insufficient results due to premature specimen failures.


CONCLUSIONS
The results from this study should contribute to the development of the fracture toughness test as a method for assessing the integrity of the dentine-composite interface. The interfacial fracture toughness test determined significant differences among the different dentine bonding agents and between the superficial and deep dentine substrates. The dentine bonding agents showed significantly reduced interfacial fracture toughness results when bonding to deep versus superficial dentine.
Tam
L E
LE
Department of Restorative Dentistry, University of Toronto, Canada.
Yim
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D000269:Adhesives / Q000737:chemistry*; D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D003804:Dentin / Q000293:injuries / Q000503:physiopathology / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006358:Hot Temperature; D006801:Humans; D008689:Methacrylates / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014082:Tooth Fractures / Q000503:physiopathology*; D014867:Water
D000269:Adhesives; C103506:Bis-GMA, BPDM, HEMA dental-bonding resin; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D008689:Methacrylates; C092987:Optibond; D011109:Polymethacrylic Acids; C103500:Prime & Bond; D019279:Resin Cements; C084018:Scotchbond Multi-Purpose; D014867:Water; C100742:All-Bond 2; D017438:Bisphenol A-Glycidyl Methacrylate