Effects of diphenyliodonium salt addition on the adhesive and mechanical properties of an experimental adhesive

ObjectivesThe aim of this study was to assess the microtensile bond strength (μTBS), nanoleakage (NL), nano-hardness (NH) and Young's modulus (YM) of resin-dentine bonding components formed by an experimental adhesive system with or without inclusion of diphenyliodonium salt (DPIH) in the camphorquinone-amine (CQ) system.MethodsOn 12 human molars, a flat superficial dentine surface was exposed by wet abrasion. A model simplified adhesive system was formulated (40 wt.% UDMA/MDP, 30 wt.% HEMA and 30 wt.% ethanol). Two initiator systems were investigated: 0.5 mol% CQ + 1.0 mol% EDMAB and 0.5 mol% CQ + 1.0 mol% EDMAB + 0.2 mol% DPIH. Each adhesive was applied and light-cured (10 s; 600 mW/cm2). Composite build-ups were constructed incrementally and resin-dentine specimens (0.8 mm2) were prepared. For NL, 3 bonded sticks from each tooth were coated with nail varnish, placed in the silver nitrate, polished down with SiC papers and analysed by EDX-SEM. NH and YM were performed on the hybrid layer in 2 bonded sticks from each teeth. The remaining bonded sticks were tested on μTBS (0.5 mm/min). The data from each test were submitted to a Student t-test (α = 0.05).ResultsNo significant difference was found for μTBS between groups (p > 0.05). Significant lower NL and higher NH and YM were found in the hybrid layer and adhesive layer produced with the iodinium salt-containing adhesive (p < 0.05).ConclusionsThe inclusion of the DPIH to the traditional CQ is a good strategy to improve the adhesive and mechanical properties of a simplified etch-and-rinse adhesive system.