Abstract
Objective: This study compared different composites for color stability after exposure to at home and in-office bleaching gels. Material and Methods: Composite resin specimens (6mm diameterx2mm thickness) were manufactured according to the following groups (n=20): RC- Conventional; BF-Bulk Fill; RF-Flow; BFF-Bulk-Fill Flow. The surfaces were stained with coffee solution for 36hrs. A spectrophotometer was used to record the initial color (L*a*b*). Half of the specimens from each group underwent bleaching with 35% hydrogen peroxide (in-office) in three 45-minute applications. New color measurements were performed after 7, 14 and 21 days. The other half of the specimens underwent bleaching with 22% carbamide peroxide (at home) in 14 1-hour applications. Further color measurements were performed after 7 and 14 hours. For comparison between the color coordinates in different periods, ANOVA for repeated measures was applied (?=5%). The color variation (?E) was calculated for each group. Results: For in-office bleaching, there were no significant differences between the periods b* coordinate of the RF group, and for L* and b* coordinates of the BFF group. For at home bleaching the groups BF and BFF showed no differences for the L* coordinate. For the other coordinates, there was difference between the initial periods and after 14 days. The ?E variation presented higher values for the at home bleaching groups. For both whiteners the bulk-fill resins presented the greatest color variations. Conclusions: Bulk Fill resins do not guarantee greater color stability than the other composite resins tested, including conventional flow resin. The conventional composite resin showed the lower ?E.
Highlights
Composite resins have been favored as restorative material over the years because they have advantageous properties for use in clinical practice, such as the coefficient of thermal-linear expansion, which is highly compatible with dental structure, higher compressive strength values, acceptable modulus of elasticity and hardness, as well as an excellent aesthetic result. [1]
The results presented refer to the measurements obtained by the color readings of the samples with spectrophotometer, corresponding to the values of ΔL - luminosity: difference between white and black, Δa - change between red and green, and Δb - change from yellow to blue
The data obtained for the 35% Hydrogen Peroxide subgroup is shown in Table 1, where the values of the CIEL* a* b* system coordinates can be observed for each experimental group, indicating that there were significant differences between the periods for all the groups, except for the b* coordinate of the RF group, and for the L* and b* coordinates of the BFF group
Summary
Composite resins have been favored as restorative material over the years because they have advantageous properties for use in clinical practice, such as the coefficient of thermal-linear expansion, which is highly compatible with dental structure, higher compressive strength values, acceptable modulus of elasticity and hardness, as well as an excellent aesthetic result. [1]. In addition to making the restorative procedure faster, the development of bulkfill resins resulted in the addition of a high percentage load (approximately 60% of the volume) in a combination of nanoparticles and larger particles This structural change results in less polymerization contraction and stress induction; its polymerization has been shown to be more efficient, increasing its mechanical properties and reducing the cytotoxicity related to the lack of conversion of monomers to polymers. Bleaching procedures were performed in 3 sessions with a 7-day interval between them At these times and before the beginning of the tests the samples were immersed in distilled water and stored in a bacteriological oven at 37oC.
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