Self- or dual-curing resin cements may lack color stability due to oxidation of the tertiary amine activator. Objective: To compare color stability after one year of both light-and dual-cured versions of a composite-resin cement (Nexus 3, Kerr) containing a proprietary amine-free activator to more traditional resin cements. Methods: Color changes were evaluated for light- and dual-cured versions of Nexus 3 (Kerr), Calibra (Dentsply), and Variolink II (Ivoclar) resin cements. Thirty cylindrical specimens per each of the three restorative materials (n=10) were prepared using a teflon mold (2mm thick x 8mm diameter). The light-cured (base only) version of the cements was syringed into the mold and light cured for 20 seconds on each side (Bluephase 16i, Ivoclar). The dual-cured version of the cements was mixed according to the manufacturer's instructions (base and catalyst), syringed into the mold, and either light-cured as before or allowed to chemically set (n= 10). Color was measured using a spectrophotometer (VITA Easyshade, Vident) against a white background after 24-hours (baseline), 3- and 12-months of storage in distilled water at 370C. Changes in L*, a*, and b* were calculated between baseline and each time interval. The total color change (Delta E) was used to assess the amount of discoloration. A mean Delta E and standard deviation was determined per cement for each curing condition. Data was analyzed with a repeated-measures ANOVA/Tukey (alpha=0.05) for each curing condition. Results: Significant differences were found between cements per curing condition (p<0.001), however, there were significant interactions (p<0.001). A one-way ANOVA per curing condition at 12 months found significant differences between cements. See table. Conclusions: After one-year of storage, Nexus 3 had the lowest color change values overall (Delta E) although it was not significantly different from Variolink II when light cured or Calibra when dual-cured with no light.
Cement |
Time | Mean Delta E (st dev) | ||
Light Cure | Dual Cure with Light | Dual Cure, No Light | ||
Nexus 3 | 3 months | 1.8 (0.8) | 1.5 (0.5) | 4.5 (0.8) |
12 months | 1.2 (0.9) a | 0.9 (0.5) a | 5.5 (1.7) a | |
Calibra | 3 months | 2.0 (0.7) | 4.1 (2.6) | 4.2 (1.9) |
12 months | 3.6 (1.9) b | 7.5 (0.8) c | 7.2 (1.4) a | |
Variolink II | 3 months | 1.2 (0.3) | 3.9 (1.7) | 14.6 (6.9) |
12 months | 1.3 (0.2) a | 4.6 (1.5) b | 22.1 (5.3) b | |
Groups with the same letter by column are not significantly different (p>0.05) | ||||