Effect of fracture strength of primer-adhesive mixture on bonding effectiveness.
OBJECTIVE
The purpose of this study was to measure the micro-tensile bond strength (microTBS) of two adhesives to dentin and to correlate this microTBS with the micro-tensile fracture strength (microTFS) of primer-adhesive mixtures of the two adhesives.


METHODS
The three-step etch&rinse adhesive OptiBond FL (Kerr) and the two-step self-etch adhesive Clearfil SE Bond (Kuraray) were used to bond Filtek Z100 (3M ESPE) to twenty mid-coronal dentin surfaces. The microTBS was determined at 1 and 24 h after light-curing. In addition, the microTFS of primer-adhesive mixtures (primer:adhesive=1:3 by weight) and of the pure adhesives (controls) were measured after the same time intervals.


RESULTS
The microTBS to dentin of OptiBond FL at 24 h was significantly higher than at 1 h and than the microTBS of Clearfil SE Bond at 24 h. The mean microTFS of the primer-adhesive mixtures was always lower than the microTFS of the respective adhesives. The highest reduction in microTFS due to mixing primer with the adhesive resin was measured for Clearfil SE Bond. Both the microTFS of the primer-adhesive mixtures and the pure adhesives of OptiBond FL and Clearfil SE Bond increased with time.


CONCLUSIONS
The early 1 h microTBS to dentin was lower than the 24 h microTBS for OptiBond FL, but not for Clearfil SE Bond. Differences in polymerization efficiency as well as in the resulting interfacial strength may explain such varying early bond strengths to dentin.
Ikeda
Takatsumi
T
Leuven BIOMAT Research Cluster, Department of Conservative Dentistry, School of Dentistry, Oral Pathology and Maxillo-Facial Surgery, Catholic University of Leuven, Kapucijnenvoer 7, B-3000 Leuven, Belgium.
De Munck
Jan
J
Shirai
Kenichi
K
Hikita
Kazuhiro
K
Inoue
Satoshi
S
Sano
Hidehiko
H
Lambrechts
Paul
P
Van Meerbeek
Bart
B
D003188:Composite Resins; D001840:Dental Bonding; D003799:Dental Stress Analysis; D003804:Dentin; D017220:Dentin-Bonding Agents / Q000528:radiation effects; D006801:Humans; D008422:Materials Testing; D044367:Phase Transition; D019279:Resin Cements / Q000528:radiation effects; D012822:Silicon Dioxide; D013718:Tensile Strength; D019237:Tooth Cervix; D015040:Zirconium
C438313:Clearfil SE Bond; D003188:Composite Resins; D017220:Dentin-Bonding Agents; C469607:OptiBond FL; D019279:Resin Cements; C083568:Z100 composite resin; D012822:Silicon Dioxide; D015040:Zirconium