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

Pacheco, Rafael Rocha, Eduardo José Carvalho Souza-Junior, Caio Vinicius Signorelli Grohmann, Viviane Hass, Regina Maria Puppin-Rontani, and Mário Alexandre Coelho Sinhoreti

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). 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. 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. 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.