Sorption, Solubility and Dentin-sealing Ability of Adhesives Containing Alternative Photo-initiators

Objectives: The aim of this study was to evaluate the water sorption (WS), solubility (WSL) and dentin sealing ability (DSA) of experimental adhesives containing alternative photo-initiators light activated by monowave (MWL) or polywave (PWL) LED light-curing units (LCU).
Methods: Experimental hydrophobic adhesive resins containing BisGMA/HEMA as organic matrix were manipulated, with different photoinitiator content: CQ/DMAEMA [G1], PPD/DMAEMA [G2], CQ/PPD/DMAEMA [G3], BAPO/DMAEMA [G4], BAPO [G5], CQ/BAPO/DMAEMA [G6], PPD [G7] and one commercial hydrophobic resin (Bond, Adper Scotchbond Multi-Purpose, 3M ESPE) [CONTROL]. For WS and WSL, resin discs were prepared (n=5) using a PVS mold (Express XT, 3M ESPE) with sample dimensions of 5.0 x 0.5mm. Samples were light cured using a MWL (Radii-Cal, SDI) or PWL (Bluephase G2, Ivoclar Vivadent) LED LCU, delivering 48J of energy through a polyester strip. After proper desiccation, specimens were stored in distilled water for 7 days and, again desiccated, in order to evaluate WS and WSL. For DSA, middle-dentin discs were prepared from sound extracted human third molars and maximum permeability was measured after EDTA treatment (10psi). Adhesive systems were applied to dentin, light-cured, and DSA was re-evaluated. DSA was expressed in terms of dentinal sealing percentage. Data were submitted to two-way ANOVA and Tukey’s test at a pre-set alpha of 0.05.
Results: All experimental adhesives showed similar WS values, except for G4 when light-cured with MWL. For WSL, control group showed lower mean values when compared to experimental adhesives. For DSA, all groups demonstrated same dentin permeability behavior, except for G4 light-cured with PWL that showed higher DSA.
Conclusions: CQ could be replaced by BAPO and PPD in hydrophobic adhesive resins, showing similar DSA and WBS. However, WS is increased in BAPO containing formulations.