Critical analysis of the influence of different parameters on the microtensile bond strength of adhesives to dentin.
OBJECTIVE
To evaluate how six different test parameters (TP) of the microtensile bond strength (microTBS) methodology influence the test outcome.


METHODS
The microtensile bond strength of adhesives bonded to dentin was measured, and the resultant failure patterns and stress-time graphs were analyzed, varying the microTBS specimen-fixation mode (TP1), the microspecimen geometry (TP2), the microspecimen bond surface area (TP3), the remaining dentin thickness of the microspecimens (TP4), the procedure employed to glue the microspecimen to the microTBS jig (TP5), and the microTBS crosshead speed (TP6).


RESULTS
The orientation of the microspecimens to the actual interface primarily influenced the resultant microTBS value and the eventual failure pattern. A notched jig consistently yielded significantly higher mciroTBS values than samples fixed onto a flat jig or following a "top-bottom" design (TP1). A higher bond strength, a lower standard deviation/coefficient of variation, a failure closer to the interface, and a more representative number of specimens per tooth were obtained for nontrimmed, square microspecimens (TP2). The most reproducible results were obtained using square specimens of 1 mm2 (TP3), which could also be most easily prepared. The remaining dentin thickness (TP4) was an influential factor as well, whereas the microspecimen gluing protocol (TP5) and the crosshead speed (TP6) appeared less influential.


CONCLUSIONS
As several test parameters significantly influenced the microTBS outcome, sufficient attention should be paid to these methodology variables with regard to the microTBS-test reliability and reproducibility.
Poitevin
André
A
Leuven BIOMAT Research Cluster, Department of Conservative Dentistry, School of Dentistry, Oral Pathology and Maxillofacial Surgery, Catholic University of Leuven, Leuven, Belgium.
De Munck
Jan
J
Van Landuyt
Kirsten
K
Coutinho
Eduardo
E
Peumans
Marleen
M
Lambrechts
Paul
P
Van Meerbeek
Bart
B
D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods; D008855:Microscopy, Electron, Scanning; D019279:Resin Cements / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors; D015040:Zirconium / Q000737:chemistry
C438313:Clearfil SE Bond; D003188:Composite Resins; D017220:Dentin-Bonding Agents; C469607:OptiBond FL; D019279:Resin Cements; C083568:Z100 composite resin; D012822:Silicon Dioxide; C041330:Scotchbond; D015040:Zirconium