Inflammatory parameters and color alterations of dental bleaching in patients wearing fixed orthodontic appliance: a randomized clinical trial

BACKGROUND

Many orthodontic patients request dental bleaching during orthodontic treatment to achieve a faster aesthetic resolution, however, no attention has been paid to the inflammatory processes that can occur when both therapies are indicated together. So, this clinical trial evaluated the inflammatory parameters and color alterations associated with dental bleaching in patients wearing a fixed orthodontic appliance.

METHODS

Thirty individuals aged between 18 and 40 years were equally and randomly allocated into three groups: FOA (fixed orthodontic appliance), BLE (dental bleaching), and FOA + BLE (fixed orthodontic appliance + dental bleaching). The orthodontic appliances and the bleaching procedures were performed in the maxillary premolars and molars. For dental bleaching a 35% hydrogen peroxide was used. The gingival crevicular fluid (GCF) and nitric oxide (NO-) levels were evaluated at different time-points. Color evaluation was performed using an Easyshade spectrophotometer at baseline (FOA, FOA + BLE, BLE), one month after (FOA + BLE) and 21 days after appliance removing (FOA + BLE and FOA groups), in each tooth bleached. The ANOVA and Tukey's tests, with a significance level of 5%, were used for statistical analysis.

RESULTS

The GCF volume in the FOA + BLE and FOA groups significantly increased at the time points evaluated (p < 0.001); however, this did not occur in the BLE group (p > 0.05). On the other hand, NO- levels significantly decreased during dental bleaching with or without fixed orthodontic appliances (FOA + BLE and BLE groups; p < 0.05), while no significant changes were observed in the FOA group (p > 0.05). Significant changes in color were observed in the FOA + BLE and BLE groups compared to in the FOA group (p < 0.01). However, the presence of fixed orthodontic appliance (FOA + BLE) negatively affected the bleaching efficacy compared to BLE group (p < 0.01).

CONCLUSIONS

Dental bleaching did not increase the inflammatory parameters in patients wearing fixed orthodontic appliance. However, in the presence of orthodontic appliances, the bleaching efficacy was lower than that of bleaching teeth without orthodontic appliances.

TRIAL REGISTRATION

RBR-3sqsh8 (first trial registration: 09/07/2018).

Effect of Prior Application of Desensitizing Agent on the Teeth Submitted to In-Office Bleaching

This study aimed to quantify the penetration of hydrogen peroxide, color change evaluation, surface morphology, and composition after application of desensitizing agents before in-office bleaching. Fifty premolars were sectioned, an acetate buffer was placed in the pulp chamber and divided into five groups (n=10). In the positive control group, only the in-office bleaching gel was used, and in the negative control group, no treatment was used. Three different desensitizing agents were applied: Desensibilize KF2%® group; Mi Paste® group, and Desensibilize Nano-P® group. The bleaching procedure was carried out with 35% HP. The absorbance of the resulting solution was determined in a spectrophotometer. Color change was assessed by using a digital spectrophotometer. Four additional premolars were assigned to the same groups above for analysis under scanning electron microscope, as well as to evaluate the elemental composition with X-ray dispersive energy spectrometry. Data were subjected to ANOVA and Tukey's test (α=0.05). All products reduced the penetration of HP in the pulp chamber. Mi Paste and Nano P were the products that yielded the lowest HP penetration, which was similar to the negative control group (p<0.001). No significant difference was detected in color change (p<0.001). Concerning enamel morphology, the groups that were analyzed after bleaching were observed a greater deposition of desensitizing agents on the surface. The use of desensitizing agents before tooth bleaching seems to be an alternative to reduce adverse effects of the tooth.