Micro-tensile bond strength of adhesives bonded to Class-I cavity-bottom dentin after thermo-cycling.
A widely used artificial aging methodology is thermo-cycling. The ISO TR 11450 standard (1994) recommends 500 cycles in water between 5 and 55 degrees C. Recent literature revealed that more cycles are needed to mimic long-term bonding effectiveness. Furthermore, the artificial aging effect induced by thermo-cycling is not clearly established. Two underlying mechanisms can be advanced: (1) hot water may accelerate hydrolysis and elution of interface components and (2) repetitive contraction/expansion stress can be generated.


OBJECTIVE
The purpose of this study was to evaluate the relative contribution of both chemical (hydrolysis and elution of interface components) and mechanical (repetitive contraction/expansion stress) degradation pathways on the thermo-cycling-induced artificial aging of dentin-adhesive interfaces at the bottom of class-I cavities.


METHODS
The micro-tensile bond strength (muTBS) of contemporary adhesives (a three-step etch and rinse, a two-step and a one-step self-etch adhesive) bonded to class-I cavity-bottom dentin was determined after 20,000 cycles as well as after 20 days of water storage (control). Restored class-I cavities (repetitive contraction/expansion stress) as well as prepared micro-specimens (diffusion-dependent hydrolysis and elution) were subjected to the thermo-cycling regimen.


RESULTS
Thermo-cycling did not enhance chemical or mechanical degradation of the bonds produced by a two-step self-etch and a three-step etch and rinse adhesive to dentin. The one-step self-etch adhesive tested was, however, not able to withstand polymerization shrinkage stress, nor thermo-cycling, when applied in class-I cavities.


CONCLUSIONS
Thermo-cycling results in combined contraction/expansion stress and accelerated chemical degradation. However, the relative contribution of each is strongly dependent on the specific test set-up and the adhesive used.
De Munck
Jan
J
Leuven BIOMAT Research Cluster, Department of Conservative Dentistry, School of Dentistry, Oral Pathology and Maxillo-Facial Surgery, Catholic University of Leuven, Kapucijnenvoer 7, 3000 Leuven, Belgium.
Van Landuyt
Kirsten
K
Coutinho
Eduardo
E
Poitevin
André
A
Peumans
Marleen
M
Lambrechts
Paul
P
Van Meerbeek
Bart
B
D000704:Analysis of Variance; D003188:Composite Resins; D001840:Dental Bonding; D003737:Dental Cavity Preparation; D003799:Dental Stress Analysis; D003804:Dentin; D017220:Dentin-Bonding Agents; D006801:Humans; D006868:Hydrolysis; D008422:Materials Testing; D044367:Phase Transition; D011897:Random Allocation; D019279:Resin Cements; D012822:Silicon Dioxide; D018709:Statistics, Nonparametric; D013718:Tensile Strength; D015040:Zirconium
C503075:Clearfil Protect Bond; D003188:Composite Resins; D017220:Dentin-Bonding Agents; C469607:OptiBond FL; D019279:Resin Cements; C083568:Z100 composite resin; C477386:iBond; D012822:Silicon Dioxide; D015040:Zirconium