Effect of Curing Mode on Microtensile Bond Strength to Dentin of Two Dual-cured Adhesive Systems in Combination with Resin Luting Cements for Indirect Restorations

Abstract

SUMMARYThis study evaluated the microtensile bond strength (µTBS) of dual-cured adhesive systems when the different components were either light activated or left in the uncured state prior to cementation of an indirect composite restoration. Occlusal dentin surfaces of 40 human third molars were flattened. The teeth were randomly assigned to 8 groups (n=5) according to the dualcured systems (bonding agents/resin cements) and curing modes: All Bond 2/Duolink (AB2-BISCO Inc) and Optibond Solo Plus Dual Cure/Nexus 2 (SOLO-Kerr). Resin cements were applied to pre-cured resin composite discs (2 mm thick/Z-250/3M ESPE), which were fixed to dentin surfaces containing adhesive resin in either cured (LP) or uncured states (SP). The restored teeth were light activated according to the manufacturers' instructions (LRC-XL3000/3M ESPE) or allowed to self-cure (SRC). The restored teeth were water-stored at 37°C for 24 hours. They were then both mesial-distally and buccal-lingually sectioned to obtain bonded specimens (1.2 mm 2 ). Each specimen was tested in tension at a crosshead speed of 0.6 mm/minute until failure. Data (MPa (SD)) were analyzed by two-way ANOVA and Tukey's post-hoc test (p<.05). AB2/SP exhibited higher µTBS than AB2/LP (p=.00001); however, no significant differences were noted between SOLO/LP and SOLO/SP. Results suggested that dual-cured adhesive systems were as strong or even stronger when they were left in the uncured state prior to indirect resin composite cementation.

Activation Mode Effects on the Shear Bond Strength of Dual-cured Resin Cements

“…14 The resin composite was inserted in 1 mm-thick increments, and each increment was polymerized for three minutes in a laboratory light-curing unit, Edglux (EDG Ltda, São Carlos, SP, Brazil). After light-activation of each increment, the resin composite cylinder was submitted to additional light-activation for seven minutes.…”

Effect of Temperature on the Degree of Conversion and Working Time of Dual-Cured Resin Cements Exposed to Different Curing Conditions

“…[3][4][5] In these detrimental clinical conditions, dual-cured resin cements may present lower hardness, higher solubility, lower flexural and compressive strengths, and lower bond strength values to dentin when compared to resin cements that are directly light cured. [6][7][8][9][10][11][12][13] Compromised light delivery to dual-cure cements is a common clinical reality, as only 10% to 15% of light remains after passing through a 2-mm-thick indirect restoration, with shade varying from A2 to A4. 3,9,14 One possible explanation for the lower effectiveness of self-curing components in dual-cured resin cements is related to the slow rate of polymerization activation and subsequent propagation of radicals in comparison to a directly photoactivated product.…”

Pre-heated dual-cured resin cements: analysis of the degree of conversion and ultimate tensile strength

“…2,3,5 In such detrimental clinical conditions, most RCs present lower hardness, higher solubility, lower flexural and compressive strength values than properly cured RCs, resulting in lower bond strength values to dentin. 3,[6][7][8][9] Some studies have shown that pre-heating the resin composite to 50º C or 60º C increases its degree of conversion (DC). 10,11 As a result, increased hardness and fracture strength, increased flexural strength and modulus, and increased resistance to wear are expected.…”