Tensile and bending fatigue of the adhesive interface to dentin.

Abstract

OBJECTIVES:

The aim of this study was to evaluate the fatigue limits of the dentin-composite interfaces established either with an etch-and-rinse or an one-step self-etch adhesive systems under tensile and bending configurations.

METHODS:

Flat specimens (1.2 mm×5 mm×35 mm) were prepared using a plexiglass mold where dentin sections from human third molars were bonded to a resin composite, exhibiting the interface centrally located. Syntac Classic and G-Bond were used as adhesives and applied according to the manufacturer's instructions. The fluorochrome Rhodamine B was added to the adhesives to allow for fractographic evaluation. Tensile strength was measured in an universal testing machine and the bending strength (n=15) in a Flex machine (Flex, University of Antwerp, Belgium), respectively. Tensile (TFL) and bending fatigue limits (BFL) (n=25) were determined under wet conditions for 10(4) cycles following a staircase approach. Interface morphology and fracture mechanisms were observed using light, confocal laser scanning and scanning electron microscopy. Statistical analysis was performed using three-way ANOVA (mod LSD test, p<0.05).

RESULTS:

Tensile and bending characteristic strengths at 63.2% failure probability for Syntac were 23.8 MPa and 71.5 MPa, and 24.7 MPa and 72.3 MPa for G-Bond, respectively. Regarding the applied methods, no significant differences were detected between adhesives. However, fatigue limits for G-Bond (TFL=5.9 MPa; BFL=36.2 MPa) were significantly reduced when compared to Syntac (TFL=12.6 MPa; BFL=49.7 MPa). Fracture modes of Syntac were generally of adhesive nature, between the adhesive resin and dentin, while G-Bond showed fracture planes involving the adhesive-dentin interface and the adhesive resin.

SIGNIFICANCE:

Cyclic loading under tensile and bending configurations led to a significant strength degradation, with a more pronounced fatigue limit decrease for G-Bond. The greater decrease in fracture strength was observed in the tensile configuration.

• Authors: Renan Belli, Luiz Narciso Baratieri, Marc Braem, Anselm Petschelt, Ulrich Lohbauer
• Journal: Dental materials : official publication of the Academy of Dental Materials (Dent Mater) Vol. 26 Issue 12 Pg. 1157-65 (Dec 2010) ISSN: 1879-0097 [Electronic] England
• PMID: 20869109 (Publication Type: Comparative Study, Evaluation Study, Journal Article)
• Copyright: Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Chemical References

• Composite Resins
• Dentin-Bonding Agents
• G-Bond
• Methacrylates
• Resin Cements
• Syntac dentine adhesive

Topics

• Analysis of Variance
• Composite Resins
• Dental Bonding
• Dental Stress Analysis (methods)
• Dentin
• Dentin-Bonding Agents
• Humans
• Materials Testing (instrumentation)
• Methacrylates
• Microscopy, Confocal
• Microscopy, Electron, Scanning
• Pliability
• Resin Cements
• Stress, Mechanical
• Survival Analysis
• Tensile Strength