Light-Cured Self-Etch Adhesives Undergo Hydroxyapatite-Triggered Self-Cure

Light cure is a popular mode of curing for dental adhesives. however,it suffers from inadequate light delivery when the restoration site is less accessible,in which case a self-cure mechanism is desirable to salvage any compromised polymerization. we previously reported a novel self-cure system mediated by ethyl 4-(dimethylamino)-benzoate (4e) and hydroxyapatite (hap). the present work aims to investigate if such self-cure phenomenon takes place in adhesives that underwent prior inadequate light cure and to elucidate if hap released from the dental etching process is sufficient to trigger it. model self-etch adhesives were formulated with various components,including bis[2-methacryloyloxy)ethyl]-phosphate (2mp) as acidic monomer and trimethylbenzoyl-diphenylphosphine oxide (tpo) as photoinitiator. in vitro evolution of degree of conversion (dc) of hap-incorporated adhesives was monitored by infrared spectroscopy during light irradiation and dark storage. selected adhesives were allowed to etch and extract hap from enamel,light-cured in situ,and stored in the dark,after which raman line mapping was used to obtain spatially resolved dc across the enamel-resin interface. results showed that tpo+4e adhesives reached dc similar to tpo-only counterparts upon completion of light irradiation but underwent another round of initiation that boosted dc to ∼100% regardless of hap level or prior light exposure. when applied to enamel,tpo-only adhesives had ∼80% dc in resin,which gradually descended to ∼50% in enamel,whereas tpo+4e adhesives consistently scored ∼80% dc across the enamel-resin interface. these observations suggest that polymerization of adhesives that underwent insufficient light cure is salvaged by the novel self-cure mechanism,and such salvaging effect can be triggered by hap released from dental substrate during the etching process. © international & american associations for dental research 2016.