Effects of exogenous collagenase and cholesterol esterase on the durability of the resin-dentin bond.
OBJECTIVE
The purpose of this work was to determine microtensile dentin bond strengths (microTBS) of dentin-resin composite bonds after three-month storage in artificial saliva containing either collagenase (COL) or cholesterol esterase (EST). The null hypothesis tested is that the resin-dentin bond strength is equivalent for each storage medium at the tested storage times.


METHODS
Resin composite was bonded to occlusal dentin, and microTBS specimens were formed and stored in the artificial saliva, COL, EST, or synthetic oil. After 24 h and 12-week storage, microTBS was determined and failure modes were characterized by SEM. The interfacial ultrastructure was evaluated by transmission electron microscopy as unstained and stained sections (phosphotungstic acid/uranyl acetate). Statistical analysis was performed by ANOVA and Weibull survival analyses at the 0.05 level of statistical significance.


RESULTS
There were significantly weaker bond strengths after 12 weeks for all experimental storage media (p < 0.001). Artificial saliva containing EST lowered bond strengths to a significantly greater extent than did COL after 12 weeks of storage, while no difference between these groups could be discerned after 24 h. Therefore, the null hypothesis of this experiment is rejected.


CONCLUSIONS
Exogenous enzymatic challenge to resin-dentin bonds decreased bond durability only with EST. However, when further challenges to ideal infiltration of the comonomers into the hybrid layer were carried out using inadequate removal of solvent, additional alterations in hybrid layer ultrastructure were discerned by TEM that may represent different potential degradative processes. The contribution of endogenous enzymatic challenges to the primary degradative process, ie, hydrolysis, is unknown and deserves continued attention.
Armstrong
Steve R
SR
Department of Operative Dentistry, The University of Iowa, Iowa City, Iowa, USA. steven-armstrong@uiowa.edu
Jessop
Julie L P
JL
Vargas
Marcos A
MA
Zou
Yuan
Y
Qian
Fang
F
Campbell
Joshua A
JA
Pashley
David H
DH
D000134:Acid Etching, Dental; D017364:Collagenases / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D019279:Resin Cements / Q000737:chemistry; D012464:Saliva, Artificial / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D002787:Sterol Esterase / Q000737:chemistry*; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors; D015040:Zirconium / Q000737:chemistry
D003188:Composite Resins; D017220:Dentin-Bonding Agents; D019279:Resin Cements; D012464:Saliva, Artificial; C084018:Scotchbond Multi-Purpose; C083568:Z100 composite resin; D012822:Silicon Dioxide; D015040:Zirconium; D002787:Sterol Esterase; D017364:Collagenases