marginal microleakage of a resin-modifi ed glass-ionomer restoration:interaction effect of delayed light activation and surface pretreatment

background: despite widespread clinical uses of resin-modifi ed glass-ionomers (rmgis), their sealing ability is still a concern. this study evaluated the effect of delayed light activation (dla) of rmgi on marginal sealing in differently pretreated cavities. materials and methods: in this in vitro study, two standardized class v cavities were prepared on the buccal and lingual surfaces of 56 sound maxillary premolars at the cementoenamel junction. the cavities were randomly divided into eight equal groups. in groups 1-4 (immediate light activation [ila]), no pretreatment (negative control [nc]) and three surface pretreatments were used, respectively as follows: cavity conditioner, vitremer primer, cavity conditioner plus and casein phosphopeptideamorphous calcium phosphate (cpp-acp). fuji ii lc (gc, japan) was prepared and placed in the cavities and immediately light-cured according to manufacturer’s instructions. in groups 5-8 (dla), the same pretreatments were applied, respectively. after placing fuji ii lc in the cavities, the restorations were light-cured after a 3-min delay. after fi nishing the restorations, the specimens were placed in water for 1-week and thermocycled. microleakage scores were determined using the dye penetration technique. kruskal–wallis test and mann–whitney u-test were used to analyze the obtained data (α = 0.05). results: at the dentin margins, dla resulted in a lower microleakage for no treatment (nc), cavity conditioner and cavity conditioner plus acp-cpp pretreatments groups (p ≤ 0.004); however, no difference was observed for vitremer group (p > 0.05).at the enamel margins, no difference was observed between dla and ila for all groups (p > 0.05); only nc group exhibited a lower microleakage in case of dla (p = 0.007). conclusion: delayed light activation of rmgi may lead to different effects on marginal sealing, depending on pretreatment procedures used in the cavity. it might improve dentin sealing when no treatment and conditioner alone or with ccp-acp is used. key words: casein phosphopeptide-amorphous calcium phosphate, delayed, light activation,marginal sealing, resin-modifi ed glass-ionomer