Application Tip and Concentration of a Self-mixing Bleach: Hydrogen Peroxide Inside the Pulp Chamber, Color Change, and Amount of Bleaching Gel Used

Abstract

SUMMARY Purpose The objective of this study was to evaluate if the application method (tip with brush or tip without brush) and hydrogen peroxide (HP) concentration (6% or 35% self-mixing) of in-office bleaching gel influences the penetration of HP into the pulp chamber, color change, and the amount of bleaching gel used. Methods Forty healthy premolars were randomly divided into the following five groups (n=8): no treatment; HP6% using a tip with a brush, HP6% using a tip without a brush, HP35% using a tip with a brush, and HP35% using a tip without a brush. After treatments, the HP concentration (μg/mL) within the pulp chamber was determined using UV-Vis spectrophotometry. The color change (ΔEab, ΔE00, and ΔWID) was evaluated using a digital spectrophotometer. The amount of gel used (g) in each group was measured using a precision analytical balance. Data from each test were submitted to parametric tests (α=0.05). Results The tip with a brush resulted in a lower amount of HP inside the pulp chamber and less gel used when compared with the tip without a brush, regardless of HP concentration (p<0.05). However, regarding the tip used, although no significant difference was observed when HP35% was used (p>0.05), a higher whitening effect was observed when the 6% HP was applied without a brush as opposed to with a tip brush (p<0.05). Conclusions The use of a tip with a brush, regardless of the in-office bleaching gel concentration (6% or 35% self-mixing), presented a lower penetration and lower volume of spent gel when compared to a tip without brush. However, the whitening effect depends on the concentration of HP used.

In vitro evaluation of the effect of different bleaching varnishes: Hydrogen peroxide penetration into the pulp chamber and color change

“…HP penetration may be related to tooth sensitivity, as previously described, and may depend on some variables, such as the concentration of the bleaching agent and the application time. 18,19,32 Regarding the bleaching varnishes, note that the AW showed low penetration of HP inside the pulp chamber when applied for 10 min, like that of the control group. This may be related to the viscosity of AW since, from the clinical point of view, it is the most viscous varnish among those evaluated.…”

“…Consequently, the lower HP release of the material could be responsible for the lower HP inside the pulp chamber. 19,32 As pointed out previously, not only the viscosity can affect the amount of hydrogen peroxide released, but also solvent, matrix composition, and type of application could be considered as potential factors to influence the kinetics of release of hydrogen peroxide. 25 Unfortunately, only a few studies evaluated the viscosity of bleaching gels, which did not allow the authors give more explanations.…”

“…13,26 It is worth mentioning that, except for AW applied for 10 min, all the values of HP penetration observed in the present study are in accordance with the previous literature. 18,32,34 When different application times were compared, an increase in the amount of HP inside the pulp chamber was registered for three of the four bleaching varnishes when applied for 30 min. The longer the bleaching agent remains in contact with the tooth surface, the greater penetration has been observed when peroxide is still available, 22,27 which can be explained by HP's diffusion dynamics in the dental tissues.…”

“…25 this is the most used to measure the amount of HP inside the pulp chamber. [9][10][11]18,19,22,23,[27][28][29]32,33,[41][42][43] According to the Beer Law, absorbance directly corresponds to the concentration. Therefore, the concentration of HP (μg/mL) was determined by comparing it with the calibration curve previously obtained.…”

“…Also, it is easy to use by the patient himself because all commercial brands include an applicator, similar to the brushes used to apply nail polish. It has already been demonstrated that when a brush applicator was used, a thin layer was achieved due to the increase in the contact surface of the HP with the tooth 32,41 . Recently, at least two studies showed that the thinner the bleaching layer, the less penetration of HP into the pulp, 32,41 and this makes the use of bleaching varnishes seemingly promising 33…”