Effect of curing units on color stability of composite resins

Objectives: This study investigated the effects of two different light curing units and two staining solutions on the color stability of a microhybrid and a nanohybrid composite. Methods: Thirty specimens were fabricated for each of the composite resins, Clearfil AP-X and Filtek Supreme. The specimens were randomly divided into two groups according to the curing unit being used: Group I specimens(n=15) were cured with a quartz-tungsten-halogen light for 40 s, and Group II specimens(n=15) were cured with a light-emitting diode unit in standard mode for 40 s. Baseline color values(L*,a*,b*) of each specimen were measured with a spectrophotometer. After baseline color measurements, five randomly selected specimens from each group were immersed in one of two staining solutions(tea or coffee) or distilled water(control). After 1, 7 and 30 days of immersion, the color values of each specimen were remeasured and the color change value(ÄE*ab)was calculated. Results: Polymerization with QTH or LED did not cause any significant difference in the color stability of Clearfil AP-X or Filtek Supreme. While there were no significant differences between the staining solutions in Clearfil AP-X specimens cured with LED after 1 and 7 days of storage and 1 day of storage in QTH cured specimens, significant differences were observed between water and coffee after 7 days of storage. In Filtek Supreme specimens cured with QTH or LED, there were statistically significant differences between the staining solutions for 1 and 7 days of storage. After 30 days of storage, no significant difference was found between tea and coffee in either composite resin cured with QTH or LED. Conclusion: Polymerization with QTH or LED did not cause any significant difference in the color stability of Clearfil AP-X, or Filtek Supreme. The effect of staining solutions on color changes in composites was immersion-time and resin-material dependent.