Effect of Light-Emitting Diode (LED) Curing Modes on Resin/Dentin Bond Strength

Purpose: This study aimed to compare the effect of three curing modes of a high‐powered curing‐light source on the shear bond strength and marginal gap of light‐ and dual‐cured adhesive resin cements to dentin. Materials and Methods: Twelve freshly extracted intact human mandibular molars were selected for this study and stored in the saline solution. Three of the axial surfaces of the teeth were prepared to obtain flat dentinal surfaces. Thirty‐six ceramic disks (4‐mm diameter, 2‐ mm thick) were constructed from a pressable glass‐ceramic (Vision). The discs were etched with hydrofluoric acid and primed, and then divided into two equal groups, groups I and II (n = 18 each). Two adhesive systems were used following manufacturer's instructions. The discs of group I were bonded to the conditioned dentin surface using adhesive resin (Rely X Veneer), and group II discs were bonded to dentin using Rely X ARC. For each group, the resin was cured using three modes (fast, ramp, pulse). Interfacial gap at the dentin/resin interface was measured at eight predetermined sites for each specimen using a stereomicroscope, and shear bond strength of the bonded specimens was carried out using a universal testing machine. Results: Ramp‐cured specimens recorded significantly higher mean shear bond strengths for both dual‐ and light‐polymerized resins than those with fast and pulse modes. Moreover, fewer interfacial gaps were found at the resin/dentin interface in association with ramp cure modes of both resins. Most failures were adhesive failures at the dentin–resin luting agent (RLA) interface in specimens polymerized using high‐powered LED fast or pulse modes, while a cohesive failure pattern within the resin was associated with the ramp‐curing mode. Conclusion: Within the limitations of this study, the shear bond strength of an RLA to dentin was found to be enhanced with light‐ or dual‐polymerized adhesive resin using an LED light in ramp mode, whereas shear bond strength was significantly lower when polymerized using LED in fast or pulse modes.