05) Fifteen days after bleaching, the ��E values were very simil

05). Fifteen days after bleaching, the ��E values were very similar in comparison with the postbleaching values, without statistically significant differences among the materials, in comparison with the previous treatment (P>.05). Table 2. Means (standard deviation) of ��E of aged samples (2-way ANOVA, Bonferroni, P<.05). Surface roughness The results after AAA (Table 3) indicated that there was no selleck chem statistically significant difference (P>.05) in roughness for any of the tested materials. When the materials were compared among them, there was statistically significant difference (P<.05) only for Heliomolar. After bleaching, Filtek Supreme and Heliomolar presented an increase in surface roughness values, with statistically significant difference (P>.05) in comparison to the post AAA values.

Fifteen days after bleaching, there was not statistically significant difference (P>.05) in comparison with the post bleaching situation. Table 3. Means (standard deviation) of surface roughness (Ra) of aged samples (2-way ANOVA, Bonferroni, P<.05). Microhardness As regards the microhardness values (Table 4), a large increase was verified after AAA, results differing statistically from the initial values (P<.05). After bleaching, there was an increase in the microhardness of Heliomolar (P<.05). For the other composites, there was a decrease, with statistically significant results (P>.05). After 15 days, there were no significant alterations (P>.05). Table 4. Means (standard deviation) of microhardness (KHN) of aged samples (2-way ANOVA, Bonferroni, P<.05).

DISCUSSION There is a consensus among researchers that direct composite resin restorations undergo color alteration with the passage of time,21�C28 and that one of the greatest challenges in modern dentistry is to find a material that has a color stability similar to that of the dental structure; and that this stability can be maintained in the oral environment as the years pass.29�C30 As regards the color stability, this study tested the hypothesis that the bleaching agent would promote bleaching of the studied composites. The results demonstrated that the color of composites could be significantly altered by AAA31 and bleaching, and this alteration is material dependent, results that are similar to other studies.7,32 This susceptibility to color alteration can be attributed to the composition of the resin matrix and the type and volume of load particles of the composite.

7 When bleached, the aged specimens did not presented significant alteration for ��E (P>.05), with the exception of the Cilengitide composite Charisma, and the same behavior was maintained 15 days after bleaching. This fact demonstrated that the action of the bleaching agent was more effective on the aged specimens, allowing one to agree with the tested hypothesis. After being bleached, the specimens remained without significant color alteration (P>.05). This may have occurred due to the stability of bleaching agents and their prolonged action.

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