Evaluation of In-office Vital Tooth Whitening Combined with Different Concentrations of At-home Peroxides: A Randomized Double-blind Clinical Trial

1. INTRODUCTION

Vital Tooth Whitening (VTW) is a widely documented non-invasive technique that improves the aesthetic for discolo-red teeth [1-10]. At - home VTW with custom or prefill trays is usually done daily for several hours per week with low concentrations (10% to 20% resulting in 3.35 - 7% hydrogen peroxide) of Carbamide Peroxide (CP) [11-13]. The 10% CP is considered as the “gold standard” for VTW, since it presents great results with lower risk and intensity of Dental Sensitivity (DS) for the patients [3, 7, 13-17]. Despite its advantages, some patients request quicker results, therefore in-office, VTW using higher concentrations (20 -40%) of Hydrogen Peroxide (HP) is an alternative [18-20]. Both techniques have shown favorable effectiveness in color changes [1, 3, 5, 9, 11, 13, 14, 19-23].

In order to overcome the drawbacks of each procedure, the combination of both methods has been widely accepted, resulting in achieving fast effects with less gingiva irritation and DS [8, 12, 22, 24]. However, Machado et al. [22], found that the combined technique produced greater DS and the same whitening results when compared to the at-home technique. Vaez et al. [19], concluded that the combined technique reduced the time necessary to obtain satisfactory tooth color compared with at-home bleaching, but increased the risk and level of DS.

Longer contact time and higher peroxide concentrations provide faster result, though a medium to severe intensity of DS has been reported [2, 4, 11, 21, 23, 25]. To decrease DS in at-office protocols, it has been suggested that a single application of the VTW gel is applied, since the amount of product that reaches the pulp might be reduced, although Reis et al. [18], showed that one 45 minutes application reduces the whitening speed and increases the DS intensity, compared to 3- 15 minutes protocol. In order to decrease the interaction with high Hydrogen Peroxide concentration, Rodriguez et al. [4], evaluated the combined technique with two in-office sessions, showing that both protocols result in acceptable color and same DS, in this order Kose et al. [10], found that a single 15 minutes session produced less DS but reduced the whitening effect. Roderjam et al. [21], concluded that calcium-containing gel could cause less pulp damage and DS. Obtaining acceptable results in terms of satisfactory color modification with none or minimal DS has been the main objective of clinical researchers, this is why continuing modifications in the VTW protocols is still proposed.

To the best of authors’ knowledge, no clinical study has evaluated the whitening effect of the combined technique with shortened application. Therefore, the purpose of this randomized double-blind clinical trial was to evaluate the effect on color change and DS when decreasing the application time of in-office VTW combined with different concentrations of at-home products.

2. MATERIALS AND METHODS

This clinical trial was approved by UNIBE’s Ethics Committee (CEI) No. CEI2013-07 and The National Committee for Health Bioethics (CONABIOS) No.024-2013 [26]. The clinical trials identifier is: NCT02682329 [27]. This report follows the protocol established by CONSORT Statement. The study design was a randomized double-blind clinical trial (Fig. 1).

2.3. Study Intervention

2.3.1. In-office VTW Procedure

All patients included in the study were subjected to an initial in-office VTW with 40% HP (Opalescense Xtra Boost Ultradent, USA) without light activation as recommended by the manufacturer. The VTW procedure was performed up to the second premolar of both dental arches (first molar could be included in case of absence of the second premolars). A light-cure resin dam was applied to the gingival tissue to isolate and protect it. The in-office VTW was applied for 20 minutes single application. The manufacturer's recommendation is 45 minutes application in three consecutive 15-minutes intervals. After finishing the process; the teeth were rinsed with copious water. The in-office VTW was performed in two sessions, with an interval of 8 days between them, during which time home bleaching was done.

2.3.2. At-home VTW Procedure

For groups 1, 2 and 3 alginate impressions (Tropicalgin - Zhermark) of both arches were made. The stone molds were produced to fabricate the whitening trays with reservoirs. The patients were instructed to place a small drop of the gel into each tooth of the tray; then after insertion, the excess of gel must be wiped away from the gingiva with a quick tip. Group 4 used prefabricated trays. The patients were advised to use the in-home VTW daily for 1 hour according to the allocation: group 1 for 7 days; group 2 for 5 days; group 3 and 4 for 2 days.

Table 1.

Material	Brand	Composition	Mode of Application
Opalescence® Boost (HP40%)	(Ultradent Products Inc, South Jordan, US)	40% hydrogen peroxide, chemical activator, 1.1% fluoride, 3% potassium nitrate.	In-office bleaching agent. Three applications of 20 minutes. Remove it with a soft pellet; rinse twice with copious water. Repeat the procedure in 2 other applications with 3-day interval between each one.
Opalescence® 10% (CP10%)	(Ultradent Products Inc, South Jordan, US)	10% carbamide peroxide, Carbopol, glycerin, flavoring.	​To the patient: Express one continuous bead of gel approximately halfway up the facial side of your tray. Place the tray over your teeth and gently press. Wear for 8-10 hours, or overnight. After whitening, remove the tray and use a soft toothbrush, or your finger, to clean any excess gel off your teeth.
Opalescence® 15% (CP15%)	(Ultradent Products Inc, South Jordan, US)	15% carbamide peroxide, Carbopol, glycerin, flavoring.	To the patient: Express one continuous bead of gel approximately halfway up the facial side of your tray. Place the tray over your teeth and gently press. Wear for 6-8 hours. After whitening, remove the tray and use a soft toothbrush, or your finger, to clean any excess gel off your teeth.
Opalescence® 20% (CP20%)	(Ultradent Products Inc, South Jordan, US)	20% carbamide peroxide, Carbopol, glycerin, flavoring.	To the patient: Express one continuous bead of gel approximately halfway up the facial side of your tray. Place the tray over your teeth and gently press. Wear for 2-4 hours. After whitening, remove the tray and use a soft toothbrush, or your finger, to clean any excess gel off your teeth.
Opalescence® TresWhite Supreme (HP10%)	(Ultradent Products Inc, South Jordan, US)	10% Hydrogen peroxide, glycerin, flavoring	Remove the tray and align it correctly over your teeth. Gently suck on the tray to create suction, so that the tray will adhere to your teeth. Detach the external part of the tray. Tap gently on the remaining part of the tray to ensure that it is securely attached to your teeth. Leave it in place for 30 to 60 minutes. Remove the tray from your mouth and cleanse your teeth of the excess gel by brushing as necessary.

Analgesic, anti-inflammatory or desensitizing gels were indicated to the patient with moderate and severe tooth sensitivity [4].

2.3.3. Visual Analysis of Color Change

The visual analysis of color change was recorded for each volunteer in four intervals: 1. At baseline, 2. Immediately after in-office session, 3. After the conclusion of at-home treatment and 4. Final color tooth measurement, using a shade guide (Vita Classical, Vita Zahn Fabric) organized by scores from B1 (1) to C4 (16). The middle third of the canines of both dental arcades were analyzed for the degree of color change. Two calibrated examiners performed the evaluations; the final color was determined based on a consensus of both.

2.3.4. Dental Sensitivity Analysis

DS was analyzed after the at-office and at-home VTW treatment. The visual analogue scale method was used, with a scale 0 to 3, with 0 indicating no sensitivity, 1low sensitivity, 2 medium sensitivity and 3 indicating severe sensitivity.

Table 2.

Group	Products	Use
1	CP 10%/ HP40%	6 hours/ 7 days
2	CP 15% /HP40%	6 hours/ 5 days
3	CP 20% /HP40%	6 hours /3 days
4	HP 10% /HP40%	1 hour / 2 days

2.3.5. Statistical Analysis

The data collected from 83 patients was registered. The mean and standard deviation were calculated for each group at each evaluation intervals. The two- way ANOVA and Tukey for pairwise comparison (p<. 05) were used. The means of DS were analyzed using one-way analysis of variance (ANOVA) to evaluate the color change between groups at each interval. The means of dental sensitivity were compared using the One- way ANOVA and Tukey test (p<0.05) for each whitening protocol. All results were analyzed using the SPSS version (23) (SPSS inc, Chicago, IL, USA).

3. RESULTS

A total of 120 patients were included in this clinical study, where 83 completed the whitening protocol and attended recalls appointment, 37 volunteers did not complete the treatment or missed appointments for evaluation.

The baseline tooth color in the superior arch was 4.76 +/-3.53 and 6.89 +/- 2.78 in the inferior arch. The mean color change results for each group are described in Table 3 and 4. Analysis of variance (ANOVA) and HSD Tukey test detected that there was no statistical significance for the color change in the superior/ inferior arc for de 4 experimental groups (p= 0.183/ p=0.374). All in-office combined with different in-home gels were effective for color change for vital tooth whitening (Tables 4-5). No statistically significant differences were found in tooth color change between subjects, p= 0.065 and within subjects, p= 0.187

The final DS mean of each group are described in Table 6. No statistically significant differences were found in dental sensitivity between subjects, p=0.268 (Table 7).

4. DISCUSSION

The whitening effect is related to the concentration and application time [10, 13], all the techniques investigated in this randomized double-blind clinical trial showed significant color change with no statistical differences between the groups, regardless of in-home concentration, from 10 to 20% and application protocol, from 2 to 7 days. This has an important clinical implication: reducing the in-office time to half, from 40 minutes, indicated by the manufacturer, to 20 minutes in two sessions, combined with at-home products for just 2 days (group 4) could be effective in better tooth whitening results.

Long chair-time, usually 40 - 45 minutes in two or three different appointments and high risk of TS are most common complains about in-office VTW [2, 10, 13]. The main concern regarding in-home whitening is the longer time required to obtain a satisfactory color. Two combined protocol have been suggested, a whitening treatment in a single 40 minutes in-office session as a jump-start for the initial effect and shortening the time required for at-home procedure [19]. Rodriguez et al. [4], concluded that the combined protocol using a tray for 1week after the in-office VTW could increase the TS when compared to two in-office sessions.

In this study, group 4 used in-home HP 10% bleaching with a prefabricated tray for just 2 days reporting the same results compared with the other combinations evaluated. This also has a significant clinical inference: favors the clinician’s preference to simplification: This product requires no impression, plaster cats or costume made tray, reducing the treatment time. Carlos et al. [17], found no significant differences among the acceptance of prefill and custom-made trays. Also, aggressive bleaching protocols can cause pulp damage resulting in a rebound effect of the bleached teeth due to the production of reactional dentin [4].

The DS, a common side effect of whitening treatments, is the principal concern related to this procedure reported by patients, especially in-office treatments [2, 16, 28]. The hydrogen peroxide has a rapid diffusion into enamel prism due to its low molecular mass reaching the pulp chamber through the dentinal tubules. Although the majority of people are able to tolerate tooth whitening, sensitivity is a major problem. In this study, there was no statistical difference in sensitivity between the groups (p=0.268). Basting et al. [3], found that 13.8% participants experienced extreme sensitivity that forces them to quit the study, also Briso et al. [15], reported spontaneous low to moderate TS during all treatment periods, equal to the findings in this study.

Vaez et al. [19], found a greater risk of DS with the combined protocol compared with in-home techniques with 10% carbamide peroxide. Kose et al. [10], suggested that a multiple appointment with a single 15 minutes applications can reduce the pulp tissue damage with satisfactory results. Moghadam et al. [29], founded no differences in TS between in-office and in-home VTW techniques. Patients with darker teeth and those who used in-home VTW presented lower intensity and risk TS [23].

The method used to assess the color change in this study was the Vital Classical shade scale, as other clinical trials [3, 11, 18, 22, 28] frequently used to show the beginning and final color to the patient in dental office [17]. Two trained examiners measured the color after each session protocol was blinded to the experimental conditions. Despite the subjectivity of visual assessment, this method is easy, fast, and satisfactory with good reliability [18, 22].

In recent studies, the impact on the quality of life and the patient’s level of satisfaction related to the color of their teeth before and after the bleaching treatment has been considered [9, 11, 14, 16, 19]. In the present study, the combination of an initial 20 minutes in-office therapy with different in-home protocol and a final 20 minutes whitening showed that the color change process was gradual, the initial color was between A3 - A3.5 decreasing to a final color between A1 to B1, reducing the number of days and application time, indicating that the participants were satisfied with the results. Rezende et al. [23], explained that regardless of the VTW technique used by the clinician, the baseline color showed a significant effect on overall whitening efficacy, especially in younger patients or with darker teeth.

The concentration agent and the bleaching technique are one of the principal factors to be considered in the effectiveness of the whitening procedure. Also Torres et al. [1], exposed that the efficacy of VTW is directly proportional to the pH, additionally the application time, safety, side effects evolved and patient’s preferences must be taken into consideration [3]. The outcomes of this study showed that reducing in half the application time of in-office bleaching combined with at-home products results in positive VTW color changes, however further studies considering the patients' level of satisfaction could increase the evidence. Another limitation of this study was that final color was evaluated immediately after the second VTW application; Correa et al. [28], suggest longer periods of follow-up to allow color stabilization because teeth appear whiter immediately after the VTW procedure due to dehydration and demineralization caused by the acidity of the agent [4].

CONCLUSION

Within the limitation of this study, it was determined that the reduction in the application time of in-office whitening with different at-home products was effective in color change for VTW, the result was the same for all groups. As for the matter of post-treatment sensitivity, all the VTW combinations were identical.

REFERENCES