Evaluation of thermal cycling and mechanical loading on bond strength of a self-etching primer system to dentin.
OBJECTIVE
The aim of this study was to evaluate the in vitro durability and fracture modes of the tooth-resin interface following thermal cycling, fatigue load cycling (FLC) and micro-tensile bond strength testing (MTBS).


METHODS
Twenty-four human molars were divided into two groups. In group A, coronal dentin was ground flat with #600-grit SiC paper, Clearfil Linerbond.2V (LB.2V) adhesive was applied and a crown fabricated with Clearfil AP-X resin composite. Samples were loaded in the FLC simulator and thermal cycle device. In group B, Class I cavities were prepared with a diamond bur and the cavity restored with LB.2V/AP-X. Samples were simultaneously subjected to FLC and thermal cycling. After storage of the specimens in water for 1 week, MTBS tests were performed, and fracture modes examined by SEM.


RESULTS
For group A, MTBS were approximately 40 MPa with cohesive failures in the bonding resin of all specimens. Neither thermal nor mechanical stressing altered bond strengths on flat dentin surfaces. In group B, MTBS in the unstressed control group was 21 MPa with cohesive failures in the resin. As both thermal and mechanical stresses increased, there was a significant decrease in bond strength (16 MPa, P<0.05) and the fractures were seen in the resin-dentin interface and hybrid layer.


CONCLUSIONS
Surface preparation, C-factor, cavity depth, the dentin substrate and character of the smear layer strongly influence the bond strength values after thermal and fatigue loading. The FLC simulator in combination with MTBS testing provides meaningful in vitro evaluation of dentin bonding durability.
Nikaido
T
T
Cariology and Operative Dentistry, Department of Restorative Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, Japan. nikaido.ope@tmd.ac.jp
Kunzelmann
K-H
KH
Chen
H
H
Ogata
M
M
Harada
N
N
Yamaguchi
S
S
Cox
C F
CF
Hickel
R
R
Tagami
J
J
D000134:Acid Etching, Dental / Q000379:methods; D000268:Adhesiveness; D000704:Analysis of Variance; D017554:Carbon Compounds, Inorganic; D003188:Composite Resins / Q000737:chemistry; D003442:Crowns; D001840:Dental Bonding; D003737:Dental Cavity Preparation / Q000145:classification / Q000295:instrumentation; D003793:Dental Restoration, Permanent; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D018130:Diamond; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D010710:Phosphates / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D017655:Silicon Compounds; D016369:Smear Layer; D013223:Statistics as Topic; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013816:Thermodynamics; D013997:Time Factors; D014867:Water / Q000737:chemistry; D016474:Weight-Bearing
D017554:Carbon Compounds, Inorganic; C112828:Clearfil AP-X; C112274:Clearfil Liner Bond 2; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D008689:Methacrylates; C093719:Panavia TPN-S; D010710:Phosphates; D019279:Resin Cements; D017655:Silicon Compounds; D014867:Water; D018130:Diamond; C022088:silicon carbide