Interaction of different concentrations of 10-MDP and GPDM on the zirconia bonding.

OBJECTIVES: To analyze the influence of different concentrations of 10-MDP and GPDM used, combined or not, on the bonding to zirconia. METHODS: Specimens of zirconia and a resin-composite (7 mm length, 1 mm width, and 1 mm thick) were obtained. The experimental groups were obtained according to the functional monomer (10-MDP and GPDM) and the concentrations (3 %, 5 %, and 8 %). For the groups with combined 10-MDP and GPDM, the agents were used with a proportion of 50 %/50 % wt until reaching the 3 %, 5 % and 8 % concentrations. All monomers were diluted in ethanol to obtain the primers. Two control groups were established: ethanol (negative control) and a commercial reference Monobond N (positive control). The zirconia surface treatment was performed with the primer application followed by the bonding to a resin-composite sample with a light-curing resin cement. Twenty-four hours after the adhesive procedure, a microtensile test was performed and the failure pattern of each sample was analysed with a stereoscopic magnifying glass. Data were analysed by a two-way ANOVA and Dunnet test. RESULTS: All experimental primers presented a higher bond strength than the negative control (ethanol). Excepting the 8 % GPDM primer, all groups presented statistically similar bond strength compared to the positive control, with a predominance of adhesive failure. SIGNIFICANCE: 10-MDP, GPDM, and the combination of both for the concentrations tested promote an effective chemical bonding to zirconia. However, using 10-MDP and GPDM in the same primer has no synergistic effect.

Increased rates of photopolymerisation by ternary type II photoinitiator systems in dental resins.

To evaluate the effects of Type I and Type II photoinitiator systems on curing efficiency, degree of conversion (DC) and chemico-physical properties of resin based materials. A comonomer base containing 50%wt 2.2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (bis-GMA) and 50%wt triethyleneglycol dimethacrylate (TEGDMA) was formulated with either 0.5 or 1mol% of Type II camphoroquinone (CQ), Type I monoacylphosphine oxide (MAPO) or bis-acylphosphine oxide (BAPO) photoinitiators. The Type II system was either a binary (1: 2 CQ:amine) or ternary system (1: 2 CQ:amine + 0.5 mol% DPI). Degree and rate of polymerization was measured by Fourier Transform Infrared Spectroscopy (FTIR). Knoop micro-hardness prior to and following ethanol immersion was assessed. Flexural strength and modulus was measured under three-point bend test. Water sorption and solubility was also evaluated. The photoinitiator absorption spectra and the total absorbed energy per unit volume (Eabs) for 0.5mol% photoinitiator in each material was calculated. Despite the reduced total absorbed energy per unit volume for CQ based systems, ternary Type II system significantly improved curing efficiency (P < 0.05) compared to both Type I photoinitiators and degree of conversion compared to MAPO only, whilst exhibiting comparable mechanical and physical properties compared to both Type I based materials at equivalent molar concentrations of photoinitiator (P > 0.05). Ternary Type II systems is an efficient alternative to improve the polymerization of resin materials, promoting similar or even better properties than Type I initiators. DPI can increase the reactivity of CQ systems and promote polymerization rates superior than Type I photoinitiators.