The effect of bleaching agents on the color stability of ceromer and porcelain restorative materials in vitro.
OBJECTIVE
The aim of this in vitro study was to determine the color changes of five different restorative materials after exposing these materials to two different home bleaching agents.


METHODS
This study applied bleaching agents to an ultralow-fusing porcelain, a low-fusing porcelain, two types of heat-pressed glass ceramics, and a ceromer. A total of 24 disc-shaped specimens were fabricated (with a diameter of 10 mm and a thickness of 2 mm) from each material (n=12). The initial color measurements were taken with a spectrophotometer. The first set of specimens were bleached with 10% hydrogen peroxide (HP) for one hour daily for 10 days. The other set of specimens were bleached with 10% carbamide peroxide (CP) bleaching gel for eight hours daily for 14 days. Data were analyzed with the one-way analysis of variance and Kruskal-Wallis statistical test. The difference in the prebleaching and postbleaching color of each material was considered to be statistically significant at p < 0.05.


RESULTS
The study found a statistically significant difference among the color changes of the test groups after exposing them to both bleaching agents (p<0.05). Appreciable color change was observed in the Estenia (ΔE=3.99) specimens that were bleached with the HP, and noticeable color changes were observed in the Estenia (ΔE=1.89) and IPS Empress 2 (ΔE=1.66) groups when they were treated with the CP.


CONCLUSIONS
Restorations (especially polymer-containing restorative materials) should be protected before any bleaching procedure due to the high risk of color change.
Haluk Baris Kara, Faculty of Dentistry, Medipol University, Istanbul, Turkey. halukbaris@yahoo.com
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D000704:Analysis of Variance; D000077463:Carbamide Peroxide; D002516:Ceramics; D003116:Color; D003124:Colorimetry; D003188:Composite Resins; D003776:Dental Porcelain; D003793:Dental Restoration, Permanent; D006861:Hydrogen Peroxide; D018020:Lithium Compounds; D008422:Materials Testing; D008689:Methacrylates; D010545:Peroxides; D011140:Polyurethanes; D017797:Prosthesis Coloring; D013053:Spectrophotometry; D018709:Statistics, Nonparametric; D058205:Tooth Bleaching Agents; D014508:Urea / Q000031:analogs & derivatives
D003188:Composite Resins; C118557:Empress 2; D018020:Lithium Compounds; D008689:Methacrylates; D010545:Peroxides; D011140:Polyurethanes; D058205:Tooth Bleaching Agents; C111841:ceromer; C091839:urethanetrimethacrylate; D003776:Dental Porcelain; D000077463:Carbamide Peroxide; C037884:finesse; D014508:Urea; D006861:Hydrogen Peroxide