Full text
| |
| Author(s): |
Dayane Carvalho Ramos Salles de Oliveira
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | Piracicaba, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba |
| Defense date: | 2016-11-07 |
| Examining board members: |
Mário Alexandre Coelho Sinhoreti;
Luis Felipe Jochims Schneider;
Estevão Tomomitsu Kimpara;
Giselle Maria Marchi;
Vanessa Cavalli
|
| Advisor: | Lourenço Correr Sobrinho; Mário Alexandre Coelho Sinhoreti |
| Abstract | |
The aim of this study was to evaluate the effect of photoinitiators and reducing agents on cure efficiency and color stability of resin-based composites using different LED wavelengths. Then, this study was performed in two parts. First, a total substitution of the conventional photoinitiator system based on camphorquinone was evaluated using alternative photoinitiators, phenil propanedione (PPD), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO). For the conventional system based on camphorquinone, different reducing agents were tested: 2-(dimethylamino) ethyl methacrylate (DMAEMA), ethyl 4-(dimethyamino)benzoate (EDAB) and/or 4-(N,N-dimethylamino) phenethyl alcohol (DMPOH). In the second part of the study, partial substitutions were tested using 75/25, 50/50, 25/75 mol% combination of CQ and TPO. LEDs with blue wavelength (420-495 nm) and/or blue and violet wavelength (380-495 nm) were used for photo-activation. Cure efficiency was evaluated using Fourier transform infrared spectroscopy (FT-IR) and, color and color stability using spectrophotometry. Color stability was evaluated before and after photoactivation and after artificial accelerated aging. Additionally, light-transmittance was also evaluated in order to explain the cure efficiency results in depth. Data were analyzed using analysis of variance and Tukey¿s test for multiple comparisons (?=0.05) and power analysis with 0.8. Regression tests were also performed. In the first part of the study, CQ-based composites showed higher color change after photoactivation. However, this color change occurred specially in the blue-yellow axis. Thus, after photoactivation, the degree of yellow was reduced. It was also observed that despite the lower light-transmittance through the composite containing CQ in comparison to the composites containing alternative photoinitiators, higher light-transmittance change occurred during photoactivation. Consequently, composites containing CQ showed the highest light-transmittance after photoactivation. High correlation was found between color change and light-transmittance change. Due unfavorable results using PPD, this alternative photoinitiator was excluded in the latter tests of the study. Composites containing phosphine oxides showed higher color change after aging in comparison to composites containing CQ. CQ/DMPOH was the formulation with less color change after aging. However, CQ-based composites became more yellow, while BAPO- and TPO-, whitener and less yellow after age. In the second part of the study, for composites containing CQ and TPO, higher TPO concentrations reduced the yellowing and color change of the composite. However, CQ substitution starting at 75 mol% reduced the degree of conversion of the resin-based composites in depth. Thus, it was possible to conclude that total substitution of CQ for phosphine oxides seems not be the more adequate solution to be used in composites, as it can affect degree of conversion in depth. The partial substitution of CQ using phosphine oxides, however, can improve color stability without affecting the depth of cure (AU) | |
| FAPESP's process: | 13/04241-2 - The influence of the photoinitiator system and reducing agents on physical properties of experimental resins photoactivated by LEDs |
| Grantee: | Dayane Carvalho Ramos Salles de Oliveira |
| Support Opportunities: | Scholarships in Brazil - Doctorate |