O uso do gel de glicerina melhora a estabilidade de cor de resinas compostas? / Does the use of glycerin gel improve the color stability of composite resins?

Introdução: A camada superficial de resina composta não polimerizada, em função da presença do oxigênio, ocasiona problemas clínicos, como alteração de cor por absorção de pigmentos. Objetivo: Determinar o efeito de diferentes técnicas usadas no controle da formação da camada de dispersão sobre as propriedades ópticas de uma resina composta comercial. Material e método: Espécimes foram produzidos com a resina composta Estelite Sigma. A fotoativação foi conduzida com uma fonte de luz LED Bluephase G2 (1.200 mW/cm2 por 40 s). Os grupos foram determinados em função de três técnicas distintas: 1) sem tratamento (controle); 2) fotoativação com gel de glicerina; 3) polimento com lixa abrasiva após a fotoativação. A estabilidade de cor (ΔE) e o parâmetro de translucidez foram determinados pelo método de espectroscopia de reflectância (Easyshade Compac, Vita) empregando o parâmetro CIELab. As análises foram realizadas imediatamente após a fotoativação e repetidas após 7 dias de armazenamento em água ou em café. Os resultados foram submetidos à análise de variância e ao teste de Tukey (α = 0,05). Resultado: Não houve diferença para ΔE nos grupos envelhecidos em água. Quando armazenados em café, o grupo controle apresentou o maior valor de ΔE, enquanto o grupo polido gerou a menor alteração de cor. A aplicação do gel de glicerina produziu resultados intermediários. O parâmetro de translucidez não foi afetado pelos tratamentos testados. Conclusão: O uso do gel de glicerina minimiza a alteração de cor nas regiões de difícil acesso aos instrumentos de acabamento e de polimento.

Introduction: The resin composite superficial layer not polymerized due to the presence of oxygen leads to clinical problems as color alteration by the absorption of pigments. Objective: Evaluate the effect of different techniques to control the formation of the composite resin dispersion layer on the optical properties of a commercial composite. Material and method Resin composite Estelite Sigma specimens were made. The specimens were light-cured with the LED Bluephase G2 device (1200 mW/cm2 - 40 s). The groups were determined according to three different techniques: 1) no treatment (control); 2) light-curing through a glycerin gel layer on the surface; 3) polishing with abrasive discs after light-curing. The color stability (ΔE) and the translucency parameter were determined by the spectroscopy method (Easyshade Compact Vita) as a function of the CIELab parameter. The analyzes were performed immediately after photoactivation and repeated after 7 days of storage in water or 7 days in coffee. The results were submitted to ANOVA and Tukey test (α = 0.05). Result : No difference was found for ΔE in groups aged in water. When stored in coffee, the control group had the highest value of ΔE while the polished group generated the lowest color change. The glycerin gel groups promoted intermediated results. The translucency parameter was not affected by the treatments tested. Conclusion: The glycerin-based gel layer minimizes the color change in those regions that the finishing and polishing instruments are difficult to access.

Influence of chemical degradation and abrasion on surface properties of nanorestorative materials

Aim: The aim of this in vitro study was to investigate the synergistic effect of chemical degradation (erosion) and three-body abrasion (mechanical degradation) on the surface roughness (Ra) and hardness (KHN) of two nanorestorative materials and two conventional materials. Methods:Disc-shaped specimens (5 mm in diameter, 2 mm thick) of Filtek Z350TM and TPH SpectrumTM composites and Ketac NanoTM and VitremerTM light-curing glass ionomer cements, nanomaterials and conventional materials were prepared according to the manufacturer's instructions. After 24 h, polishing procedures were performed and initial measurements of Ra and KHN were taken in all specimens. The specimens were divided into 12 groups (n = 10) according to material and storage media: artificial saliva, orange juice, and Coca-Cola(r). After 30 days of storage, the specimens were submitted to mechanical degradation and re-evaluated for Ra and KHN. Data were tested for significant differences by repeated-measure three-way ANOVA and Tukey's tests (p<0.05). Results:Erosion and abrasion wear significantly decreased hardness of all materials. Only Filtek Z350 roughness, however, was not affected by erosion and abrasion. All materials showed a significant increase in surface roughness after erosion and abrasion, except for Filtek Z350. After chemical and mechanical degradation, the KHN of all samples had decreased significantly. After mechanical degradation, the acidic drinks (Coca-Cola(r) and orange juice) were more aggressive than artificial saliva to all materials. Conclusions:A synergistic effect was observed by the increase in roughness for all materials, except for Filtek Z350; hardness values decrease for all materials, regardless of whether they were nanofilled or not. The RMGICs were more susceptible to degradation than the composites, considering both hardness and roughness surface parameters.