Color Stability Behavior of Resin-Composites polymerized with QTH and LED

Color stability behavior of resin composites is dependent on aspects relative to material composition, extent of polymerization, water sorption and others.

 

Objective: To evaluate polymerization-dependant color change and shade stability of methacrylate-based resin-composites polymerized with quartz-tungsten-halogen (QTH) and light-emitting diodes (LED).

Methods: Five discs (H=1.0 x D=5.0mm, shade A3) were made from Estelite Sigma Quick (Tokuyama Dental); Supreme Plus (3M-ESPE); Heliomolar, TetricEvoCeram (Ivoclar-Vivadent); Premise (Kerr); Vit-l-escence (Ultradent); Beautifil (Shofu) and Artiste (Pentron). The composite was placed in a polytetrafluoroethylene mold and pressed between two glass microscope slides to the thickness of the mold. The discs were polymerized with Quartz Tungsten Halogen (QTH) or Light Emitting Diode (LED) with exposure times of 40s and 20s respectively to attain comparable radiant exposure. Color measurements were made with colorimeter (Chroma Meter, Minolta) before polymerization, immediately after polymerization, at 24h, one week, one month and three months of dark storage (100% humidity at 37°C). Values ΔE*≥3.3 were considered clinically unacceptable. Data was analyzed with a three-way ANOVA and Student-Newman-Keuls with a significance level of p<0.05.

Results: Composite, testing time and their interaction demonstrated a significant effect on the color change (p<0.001). Specimens polymerized with LED exhibited greater color change than QTH, but the differences remained not significant (p=0.163). When the data was not stratified, mean color change values at the different testing periods were: 4.15 (baseline), 3.85 (24h), 0.87 (1week), 1.07 (1month) and 1.19 (3months).  Overall, color change values at baseline and 24h were significantly larger than those observed after 1 week, 1 month and 3 months (p<0.001).

Conclusion: Color change beyond the clinically acceptable level was observed for all brands of composites and light curing units. These changes were greater immediately after polymerization and at 24h. Clinicians should be aware of these clinical changes.