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Abstract: Objectives: Since photoinitiator systems for dental resins based on camphorquinone (CQ) present color disadvantages, trimethylbenzoyl-diphenyl-phosphine oxide (TPO) has been proposed as an alternative. However, there are remaining considerations about its curing efficiency. The aims of the present investigation were: to characterize the relationship between the photoinitiator absorption spectra and the light spectrum emitted from a QTH light (absorbed power density, PDabs); to evaluate the kinetics of polymerization, and the depth of cure for filled dimethacrylate resins formulated with different photoinitiator systems. Methods: CQ+EDMAB (control); TPO and TPO+EDMAB were used in 50:50 Bis-GMA/TEGDMA resins. Photoinitiator absorption and QTH-light emission were evaluated using a spectrophotometer and kinetics of polymerization with differential scanning calorimetry (DSC) (n =3). Depth of cure was analyzed by the scraping method (n =5), as recommended by ISO4049. One-way ANOVA/Tukey''s (p <0.05) was used to analyze the results. Results: CQ presented higher PDabs than TPO (364 and 223mW/cm3, respectively). The DSC revealed that TPO and TPO+EDMAB produced a faster reaction than CQ+EDMAB. Composite formulated with CQ+EDMAB produced higher depth of cure (6.3±0.4mm) than those with TPO (4.3±0.1) or TPO+EDMAB (4.2±0.3). Significance: Although CQ presented higher PDabs than TPO, formulations containing TPO exhibited higher reactivity than that with CQ. On the other hand, materials formulated with TPO demonstrated lower depth of cure than that with CQ. Therefore, its use as an alternative photoinitiator requires further investigation, with higher concentrations. [Copyright &y& Elsevier]

Abstract: Objectives: To evaluate the effect of amine ratio (ethyl 4-dimethylaminobenzoate, EDMAB) on the maximum rate of polymerization (), degree of conversion (DC), Knoop hardness (KH), water sorption (Wsp), water solubility (Wsl) and color changes (ΔE) over time of resin composites formulated with the photoinitiators camphorquinone (CQ), phenylpropanedione (PPD) and CQ-PPD in combination. Materials and methods: Experimental resin composites were made with photoinitiator:amine ratios of 2:1, 1:1, 1:1.5 and 1:2 by weight. was evaluated with differential scanning calorimetry (DSC), DC with DSC and Fourier transformed infrared (FTIR) spectroscopy, KH with Knoop indentation, Wsp and Wsl adapted from ISO 4049; and color with a chromameter. The results were analyzed with two-way ANOVA/Tukey’s multiple comparison test (p <0.05). Results: The higher the amine ratio in the composite, the higher was DC, , and KH, and the lower was Wsl, regardless of the photoinitiator type. The use of PPD alone resulted in poorer properties than CQ and CQ-PPD. Many factors seem to affect the color changes and the b-axis data revealed that the higher the amine ratio, the higher was the +b value (yellowing) for CQ and CQ-PPD formulations. Conclusions: Higher amine ratios led to improved polymer properties, but also produced more yellowing in resin composites with CQ and CQ-PPD. The use of PPD alone was not advantageous for producing good final properties when compared to CQ and CQ-PPD. [Copyright &y& Elsevier]

Abstract: Objectives: To evaluate the degree of conversion (DC), maximum rate of polymerization (), Knoop hardness (KHN) and yellowing (b-value) of resin composites formulated with phenylpropanedione (PPD), camphorquinone (CQ), or CQ/PPD at different concentrations. The hypotheses tested were (i) PPD or CQ/PPD would produce less and yellowing than CQ alone without affecting DC and KHN, and (ii) , DC, and KHN would be directly related to the absorbed power density (PDabs). Methods: CQ/amine, PPD/amine and CQ/PPD/amine were used at low, intermediate and high concentrations in experimental composites. Photoinitiator absorption and halogen-light emission were measured using a spectrophotometer, R p with differential scanning calorimetry (DSC), DC with DSC and FTIR, KHN with Knoop indentation; and color with a chromameter. The results were analyzed with two-way analysis of variance (ANOVA)/Student–Newman–Keul''s test (p <0.05). Correlation tests were carried out between PDabs and each of DC, and KHN. Results: The PDabs increased with photoinitiator concentration and PPD samples had the lowest values. In general, maximum DC was comparable at intermediate concentration, while and KHN required higher concentrations. DC was similar for all photoinitiators, but was lower with PPD and CQ/PPD. PPD produced the lowest KHN. Yellowing increased with photoinitiator concentration. PPD did not reduce yellowing at intermediate and/or high concentrations, compared to CQ-formulations. PDabs showed significant correlations with DC, and KHN. Conclusion: PPD or CQ/PPD reduced in experimental composites without affecting the DC. The use of PPD did not reduce yellowing, but reduced KHN. DC, and KHN were dependent on PDabs. [Copyright &y& Elsevier]

Objectives: The aim of this study was to formulate materials with high color stability and reduced degradation by using photoinitiator systems derived from phosphine oxides alternative to the traditional camphorquinone (CQ)/amine system. Methods: Materials were formulated with the monomers BisGMA and TEGDMA as organic matrix. The photoinitiators tested were CQ+ amine (EDMAB), phenylbis(2,4,6-trimethylben-zoyl)phosphine oxide (BAPO), BAPO + EDMAB, diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide (TPO) and TPO + EDMAB. A 60% mass of silanated glass filler particles was added. Degree of CC conversion was evaluated by Fourier-transformed infrared spectroscopy 10 min after photopolymerization. The color properties were evaluated by a digital spectrophotometer, applying the CIELab parameters, either before photoactivation, immediately after photoacti-vation, 24 h after dry storage, and one month after water immersion. Water sorption and solubility were assessed by mass gain or loss after storage in water for 30 days. Data were analyzed using ANOVA and Tukey's test (5%). Results: Degree of conversion did not differ statistically among all the tested formulations. Regarding color, only groups with TPO presented satisfactory color stability after one month of water storage (ΔE < 3.3). Water sorption and water stability did not differ among the groups. Conclusions: Degree of conversion, water sorption and water solubility did not differ among all the tested groups. The TPO-based groups were the only materials with satisfactory color stability after one month of water storage. [ABSTRACT FROM AUTHOR]

Objective To establish the relationship between photoinitiator system and nanofiller size on the optical properties and cure efficiency of model composites. Methods Model composites based on BisGMA/TEGDMA (60:40 mol%) were loaded with 40 wt% of 7 nm or 16 nm-sized filler particles. One of the following photoinitiator systems was added: camphorquinone (CQ) associated with an amine (EDMAB), monoacylphosphine oxide (TPO), or bysacylphosphine oxide (BAPO). The optical properties of disk-shaped specimens were measured 24 h after curing and repeated after storage in water for 90 days and coffee for 15 days. A large spectrum LED unit (Bluephase G2, Ivoclar Vivadent) was used for photoactivation. CIE L * a * b * parameters, color difference (Δ E ), and translucency parameter (TP) were calculated. Knoop hardness readings were taken at top and bottom composite surfaces. Cure efficiency was determined by bottom/top hardness ratio. Data were statistically analyzed at α = 0.05 significance level. Results Composites formulated with 16 nm particles had higher CIE L * than those with 7 nm particles in all storage conditions. BAPO-based composites generally had lower CIE a * than the other composites. The group TPO + 16 nm before storage and all groups with 16 nm-sized particles after storage had lower CIE b * (i.e. lower degree of yellowing) than the other groups. TPO-based materials had higher color stability. The cure efficiency was not significantly affected by photoinitiator system or particle size. CQ + 7 nm had the lowest and BAPO + 16 nm the highest hardness values. Significance Combination of photoinitiator system and filler particle size might affect the optical properties of composites, with low influence on cure efficiency. [ABSTRACT FROM AUTHOR]