Polymerization efficacy of an all-in-one adhesive using a self-curing activator

All-in-one adhesives combined with chemically/dual curable resins may impede proper resin polymerization, as unpolymerized acidic adhesive monomers (p acceptor) and the basic tertiary amine catalyst (p donor) may form charge-transfer complexes preventing the amine from generating free-radicals that are necessary to induce polymerization. Objectives: To determine the effect of the addition of a self-curing activator (arylborate salt-Aurora) in the spatially resolved extent of photopolymerization (EP) and the final volumetric contraction (VC) of an all-in-one dental adhesive (Xeno IV). Methods: 1H Stray-Field magnetic resonance (STRAFI-MRI) profiles were obtained from Xeno IV, with and without the addition of the self-curing activator, before and after solvents removal. The influence of a pre-curing period on Xeno IV and Aurora mixture (1, 18 and 24h post-mixing) was also evaluated. Data were obtained in the presence of oxygen from the atmosphere. Results: Upon curing, a decrease of profile integral, but not intensity, should be only assigned to solvent evaporation; loss of profile intensity may be due to solvent evaporation and/or mobility loss due to the viscosity increase that goes along with ongoing curing reactions. High VCs were observed for Xeno IV and Xeno IV+Aurora mixtures; these data are directly related to the evaporation rate of the solvent fraction of the adhesive and self-curing agent. 1H STRAFI-MRI profiles obtained for the experimental groups show that the decrease in signal intensity is very small, in agreement with a low EP. The incorporation of the self-curing agent did not affect EP. Conclusions: The one-step system has shown high VC, mainly due to evaporation effects. In this condition, and regardless the incorporation of the self-curing activator, the curing appears to be low (intensity remains very similar after the curing period), as it occurs with other simplified dental adhesives. Acknowledgements: CICYT/FEDER MAT2004-06872-C03-02. Dentsply/Caulk USA (Research agreement #2496). FCT/FEDER (PDCT/SAU-BMA/55935/2004).