Physical properties of dual-cured luting-agents correlated to early no interfacial-gap incidence with composite inlay restorations

Abstract

Objectives: The aims of this investigation were to investigate dual-cured luting-agents as to whether their bond strength, dimensional change and flexural modulus influence no interfacial-gap incidence parameters of composite inlay restorations during the early stages. The correlations of interest were between: (a) their shear bond strength to dentin, (b) their dimensional change on setting, (c) their flexural modulus, and (d) no interfacial-gap incidence with indirect restorations.

Methods: Seven dual-cured luting-agents, one self-adhesive resin cement, six resin cements and one resin-modified glass-ionomer for luting, were investigated with specimen sub-groups (n=10) for each property measured. The principal series of experiments were conducted in dentin cavities with interfacial polishing either immediately (3 min) after setting or after 1-day water-storage. After the finishing procedure, each tooth was sectioned in a buccolingual direction through the center of the restoration, and the presence or absence of interfacial-gaps was measured (and then summed for each cavity) at 14 points (each 0.5mm apart) along the composite inlay restoration interface (n=10 per group; total points measured=140), and was expressed by percentage of measured total points. The shear bond strengths to dentin, setting shrinkage-strain and flexural modulus were measured. To estimate the dimensional change of luting-agents, the maximum marginal gap-width and the opposing-width that occurred with luting-agents in a Teflon mold were measured. Moduli were measured in 3-point bending.

Results: For all composite inlay restorations, polished immediately after setting, an incidence of summed no-gaps of 69-88% was observed. For specimens polished after 1 day, a significantly (p<0.05) decreased number of 91-96% summed no-gaps occurred. After 1-day storage, shear bond strengths to dentin and flexural modulus increased highly significantly (p<0.001) for many materials, whereas dimensional changes in the Teflon mold were non-significantly different (p>0.05). There was a highly significant correlation between no interfacial-gap incidence and shear bond strength (r=0.702, p=0.002, n=16). As the dimensional change (shrinkage) within Teflon molds increased, the no interfacial-gap incidence of dentin/inlay interfaces with 'no-gaps' decreased (r=-0.574, p=0.02, n=16). Flexural moduli significantly correlated with no interfacial-gap incidence in the composite inlay restorations (r=0.695, p=0.003, n=16).

Significance: For three classes of luting-agents during the early stage of setting (<1 day), the shear bond strength to dentin, the dimensional change measured by marginal gaps in Teflon mold and flexural moduli correlated with no interfacial-gap incidence in the composite inlay restoration.