Fatigue of dentin-composite interfaces with four-point bend.
OBJECTIVE
The objective was to determine the fracture and cyclic fatigue properties of composite-dentin beams bonded with a self-etching adhesive in four-point bend.


METHODS
Beams of rectangular cross-section were shaped to a size of approximately 0.87mmx0.87mmx10mm and placed in a four-point bending apparatus, with the loading points 1.8 and 7.2mm apart, with the interface centered between the inner rollers. Cyclical loading was performed in Hanks' Balanced Salt Solution at 25 degrees C, with forces between 54% and 99% of the bending strength of the bonded beams.


RESULTS
Solid dentin and solid composite beams [n=6] had bending strengths of 164.4 and 164.6MPa, respectively, under monotonically increasing loads. Bonded beams [n=6] had strengths of 90.6MPa. No significant difference was found between solid composite and solid dentin beams, the bonded beams were different (ANOVA, p<0.0001) With long-term cycling, stresses below 49MPa were tolerated for 10(6) cycles, but with increasing stress up to 90MPa, beams failed earlier, demonstrating that subcritical fatigue cycling will eventually cause failure.


CONCLUSIONS
Fatigue may be a significant mechanism of dentin-composite bond degradation.
Staninec
Michal
M
Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, CA 94143, USA. michal.staninec@ucsf.edu
Kim
Paul
P
Marshall
Grayson W
GW
Ritchie
R O
RO
Marshall
Sally J
SJ
D000134:Acid Etching, Dental; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D018583:Pliability; D011108:Polymers / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors
C438313:Clearfil SE Bond; D003188:Composite Resins; D003764:Dental Materials; D017220:Dentin-Bonding Agents; C444701:Filtek Z250; D011108:Polymers; D019279:Resin Cements