Shear Bond Strength of Liner Materials to Caries-Free and Caries-Affected Dentin
Dental liners are used on caries-free dentin to attenuate postoperative sensitivity and caries-affected dentin to promote remineralization and for antibacterial effects. The shear bond strength of liners to caries-affected and caries-free dentin is a significant clinical property in the restoration of teeth with large caries lesions. Objective: The aim of this in vitro study was to compare the shear bond strengths (SBS) of different liners to caries-free and caries-affected dentin. SBS specimens were prepared according to ISO 29022:2013(E) (n=10/ group). Caries-free dentin specimens were ground to superficial dentin. For caries-affected dentin, grinding to proximity of carious dentin was performed, remaining caries-infected dentin was removed with a polymer bur, and sanding to 320 grit was conducted to achieve a flat surface. 150-micron thick tape was centered over caries-free or caries-affected dentin, and five different liners (new RMGI-based calcium silicate liner [RMGI/ CS], Biodentine, Lime-Lite Enhanced, TheraCal LC, Vitrebond Plus) were applied to dentin and leveled with the tape. Specimens were treated with adhesive, cured, and bonded with resin composite using the Ultradent fixture. Specimens were stored in 37°C water for 24 ± 2 hours and debonded at 1 mm/min. SBS was analyzed by two-way analysis of variance (ANOVA) and the Tukey post hoc test. There was a significant difference in SBS among materials for both caries-affected and caries-free dentin (p<0.01). Tukey post hoc analysis grouped materials into significantly different groups for caries-free dentin (Lime-Lite Enhanced, Biodentine < TheraCal LC < Vitrebond Plus, RMGI/CS) and caries-affected dentin (Lime-Lite Enhanced, Biodentine, TheraCal LC < Vitrebond Plus, RMGI/CS). There was no difference in SBS to caries-free and caries-affected dentin for Lime-Lite Enhanced (p=0.359), Biodentine (p=0.522), Vitrebond Plus (p=0.406), or RMGI/CS (p=0.165). SBS was significantly greater to caries-free dentin with TheraCal LC (p<0.01). RMGI/CS and Vitrebond Plus produced higher SBS to caries-free and caries-affected dentin than the three other materials. There was a higher bond to caries-free dentin than caries-affected dentin for TheraCal LC, but not for any of the other liners tested. Clinicians should balance biologic advantages of liner materials with a decrease in bond strength.SUMMARY
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Specimen preparation for caries-affected dentin specimens. (A) Specimen wet ground to exposure of a caries lesion. (B) Removal of caries-infected dentin with a polymer bur. (C) Exposure of caries-affected dentin. (D) Specimen gently ground flat even with the depth of exposed caries-affected dentin. (E) Masking tape placed with hole centered over caries-affected dentin. (F) Liner placed level with the upper surface of the tape (150 μm).
Representative image of a specimen secured in the Ultradent SBS bonding clamp apparatus for resin composite placement following application of Scotchbond Universal Plus to the liner surface.
Debonding of a specimen secured to a testing clamp using a circular notched-edge blade mounted to a universal testing machine.
Representative image of an adhesively debonded dentin surface. There is an outer layer of tape and an inner ring of residual liner enclosing a flat circle of exposed dentin. This failure implies that the bond between the liner and the tooth structure is weaker than the bond between the liner and the overlying resin composite.
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