effect of different polishing methods and storage media on discoloration of resin composites

Statement of Problem: Accumulation of plaque and staining due to a rough surface, and penetration of colourant agents from food and beverages in to the resin composite results in an incomplete polymerization. There is a little information on the effect of finishing and polishing techniques on the discoloration of nanohybrid and microhybrid composites when exposed to staining solutions

Objectives: To determine the degree of surface staining of nanohybrid and microhybrid composites after polishing and immersion in distilled water and two commonly used staining solutions

Materials and Methods: A nanohybrid [Ice; SDI] and microhybrid [Gradis direct; GC] composites were used. Disc-shaped specimens were prepared and treated with either a matrix finish or polished using Sof-Lex discs [3M/ESPE] and Enhance point [Dentsply]. After 24 h immersion in distilled water at 37[degree sign]C the specimens were polished and colour coefficients [CIE L[asterisk] a[asterisk] b[asterisk]] was measured by a spectrophotometer. All specimens were immersed in 37[degree sign]C distilled water in an incubator for 7 days and colour coefficients were measured again. The colour change [[DELTA]E] was calculated using the following formula: [Delta]E = [[[Delta]a][2]+[[Delta]b][2]+[[Delta]L][2]] [1/2]. The data were analyzed using three-way ANOVA, one-way ANOVA/Tukey HSD and Student's t-test

Results: There was a significant interaction between resin composites, polishing systems and staining solutions [p < 0. 05]. ANOVA and Tukey's tests showed that Ice had a significantly lesser colour change than Gradia direct and matrix finish revealed the smoothest surface followed by Sof-Lex discs and Enhance point. Distilled water and cola caused no perceptible colour change [[Delta]E < 3.3]. The effect of surface polish on staining was statistically significant [p < 0 .05]

Conclusions: Sof-Lex discs in comparison to Enhance point stimulated greater staining resistance for both composites. The nanohybrid exhibited less colour change than microhybrid composite. Coffee was the only storage media that induced a perceptible colour change [[Delta]E > 3.3] compared to cola and distilled water

influence of surface polish and beverages on the roughness of nanohybrid and microhybri resin composite

Statement of the Problem: Surface roughness is a key factor in the aesthetics of restorative dentistry as it can determine the clinical quality and success of restorative materials. The chemical process of dissolution in the presence of mechanical forces can accelerate the surface roughness of tooth-coloured restorative materials

Objectives: To determine the degree of surface roughness of a microhybrid and a nanohybrid resin composite after polishing and immersion in various solutions

Materials and Methods: Two resin composites were used: a microhybrid [Gradia direct, GC], and a nanohybrid [Ice, SDI]. A total of 54 disc-shaped specimens were prepared for each composite and immersed in distilled water incubated at 37[degree]C for 24 hours. After 24 h, the baseline measurement for surface roughness [Ra] was performed and the specimens were divided into 3 groups of 18 and tested with unpolished or after polishing with Sof-Lex disc and Enhance point systems. Specimens in each group were subdivided into 3 subgroups [n = 6] and immersed in 3 solutions [distilled water, coffee, and cola] for 7 days incubated at 37[degree]C. After 7 days, the specimens were rinsed with tap water for 10 seconds, dried with paper towel and Ra was measured again. Two randomly selected specimens of each group were sputter coated with gold and examined using a Field-Emission Scanning Electron Microscope [SEM]

Results: Gradia direct showed a greater R[a] than ice in all solutions for all polishing systems [p < 0.001]. Specimens polished with Enhance point revealed a significantly greater roughness than Sof-Lex discs and both showed greater R[a] than unpolished specimens. Specimens immersed in coffee exhibited significantly greater surface roughness than that of distilled water [p < 0.05] and cola [p < 0.001]

Conclusions: Nano-hybrid composite showed a significantly smoother surface than microhybrid. Coffee exhibited the highest R[a] compared to distilled water and cola. Enhance point revealed significantly greater R[a] than Sof-Lex discs and unpolished group