The influence of the modification of etched bovine dentin on bond strengths.
OBJECTIVE
The aim of this study was to modify demineralized bovine dentin surfaces by application of either 12.5% sodium hypochlorite (NaOCl), or 0.1% (w/w) Type I collagenase, after conditioning with phosphoric acid, to observe the demineralized surface and to investigate the effect on tensile bond strength.


METHODS
The NaOCl was applied to etched dentin for 30 s, 1 or 2 min and the collagenase for 1, 3 or 6 h. A control group was used without NaOCl or collagenase treatment. Prior to bonding, treated surfaces were examined using an Atomic Force Microscope (AFM). A 2.3 mm diameter area of dentin was conditioned, treated and bonded with either One Coat Bond or Single Bond following each manufacturer's instructions, and a resin composite rod attached. Bonds were stressed in tension at a rate of 1 mm/min until failure. Mean bond strengths were calculated (MPa) and mode of failure was determined by observation at 20x magnification. Results were analyzed using multiple regression analysis and LSD test at the 95% level of confidence (n = 12).


RESULTS
AFM results showed progressive changes of the surface collagen as the treatment time of NaOCl or collagenase increased. For both bonding systems, the bond strengths of 1 min NaOCl and 3 h collagenase treatments were significantly higher than the control or other treatment groups (p < 0.05). Bond failure consisted of mostly adhesive failure between dentin and resin combined with small regions exhibiting cohesive failure of resin.


CONCLUSIONS
Bond strengths were not dependent on the thickness of the hybrid layer, but rather quality of the hybrid layer.
Phrukkanon
S
S
School of Dental Science, University of Melbourne, 711 Elizabeth Street, Melbourne, Vic. 3000, Australia.
Burrow
M F
MF
Hartley
P G
PG
Tyas
M J
MJ
D000134:Acid Etching, Dental / Q000379:methods*; D000268:Adhesiveness; D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002417:Cattle; D017364:Collagenases / Q000494:pharmacology; D003188:Composite Resins / Q000737:chemistry*; D016001:Confidence Intervals; D001840:Dental Bonding; D003804:Dentin / Q000187:drug effects / Q000648:ultrastructure*; D008422:Materials Testing; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D010756:Phosphoric Acids / Q000008:administration & dosage; D012044:Regression Analysis; D012822:Silicon Dioxide; D012973:Sodium Hypochlorite / Q000494:pharmacology; D012997:Solvents / Q000494:pharmacology; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors; D015040:Zirconium
D003188:Composite Resins; D010756:Phosphoric Acids; D012997:Solvents; C083568:Z100 composite resin; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide; D015040:Zirconium; D012973:Sodium Hypochlorite; D017364:Collagenases