Efficacy of desensitizing agents on postoperative sensitivity following an in-office vital tooth bleaching: A randomized controlled clinical trial.

AIM: To assess and compare the incidence and intensity of experienced after an in-office vital tooth bleaching in case of dental fluorosis using two different types of desensitizing agents, at different time periods.
MATERIALS AND METHODS: Sixty-nine subjects with mild-to-moderate fluorosis were randomly divided into three groups of 23 each. Group I - control group (placebo), group II-potassium nitrate 5% and sodium monofluorophosphate 0.7% (Sensodent KF), and group III-Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP) (Tooth Mousse). In-office vital tooth bleaching was done using 35% hydrogen peroxide liquid (Pola office) in two sessions. Desensitizing agent was applied for 10 min after each session. Postoperative sensitivity was recorded after 24 h and 7 days. The statistical analysis was done using chi-square test, analysis of variance (ANOVA), and post hoc Tukey's test.
RESULTS: The experimental groups showed significantly less incidence and intensity of sensitivity compared to control group, whereas there was no difference between them.
CONCLUSION: The desensitizing agents used in the study show effective reduction after an in-office vital tooth bleaching.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

The appearance of teeth is very important to patients of all ages and it is often associated with a perception of health and fitness. Tooth discoloration is a great concern and it may be intrinsic or extrinsic in nature. There are various methods employed to treat the discolored teeth such as bleaching; microabrasion; macroabrasion; and restorative treatments such as porcelain veneers, crowns, or composite bonding.[1] Bleaching is considered the most conservative treatment option and it is noninvasive in nature. The American Dental Association defined bleaching as the treatment, usually involving an oxidative chemical that alters light-absorbing and/or light-reflecting nature of the material/structure thereby increasing its value (whiteness).[2]

Basically, there are two techniques for vital tooth bleaching-1. in-office bleaching technique and 2. at-home bleaching technique.[123]

In-office bleaching is popular among patients as it offers convenience of whitening teeth in one or two dental appointments. But in clinical research studies tooth sensitivity during bleaching has been reported in a range of 18-78%.[4] Although it resolves on completion of treatment, it is sometimes responsible for the patient's withdrawal from treatment.

There are several approaches and various methods employed to minimize tooth sensitivity — by reduction in wearing time of bleaching tray and frequency of application;[56] temporary interruption of whitening and also the use of desensitizing paste before or after bleaching;[78] incorporation of desensitizing agent in the bleaching gel itself;[9] and minimizing the time of exposure to bleaching agent or reducing the concentration of bleaching agent, with varying success rate.[10] Recent studies have shown that Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP) is a remineralizing agent that is effective in reducing the tooth sensitivity due to bleaching.[1112]

Literature search revealed no studies related to tooth sensitivity after an in-office vital tooth bleaching in case of dental fluorosis. Hence, the purpose of the present study was to assess the effect of two desensitizing agents (Sensodent KF and Tooth Mousse) after an in-office vital tooth bleaching in the patients with dental fluorosis. Null hypothesis tested was that the desensitizing agents have no effect on the tooth sensitivity developed after an in-office vital tooth bleaching.

MATERIALS AND METHODS

Subjects aged between 18 years and 30 years with mild-to-moderate degree of dental fluorosis (Dean's Index) with yellow or brown discoloration in maxillary anterior teeth were selected. The subjects with sensitive teeth, anterior restorations, nonvital teeth, history of prior tooth-whitening procedures, and bruxism were excluded from the study. Written informed consent was obtained before starting the treatment.

Institutional ethical clearance was obtained to conduct the study. The sample size estimation was done using nMaster software (developed by the Department of Epidemiology, CMC, Vellore). The power of the study was fixed at 80% and alpha error at 5%. The statistical test employed was one sided. The minimum sample size required was 21. Anticipating 10% loss to follow-up, it was decided to select 23 subjects in each group.

The subjects were randomly distributed into three groups of 23 each (N = 23) according to the application of desensitizing agents as follows: Group I — control group (placebo without desensitizing agent, pumice powder); group II — potassium nitrate 5% and sodium monofluorophosphate 0.7% [Sensodent KF, Indoco Remedies Ltd. (Warren) Mumbai, India]; and group III - CPP-ACP (Tooth Mousse, GC Corporation, Japan).

Isolation of the operating field was achieved using rubber dam. Gingival protection was done with gingival barrier (Methacryalte resin, Pola office, SDI Innovative Dental Products, Australia) and cured using LED light (Bluephase, Ivoclar Vivadent, Australia). Discolored maxillary anterior teeth were bleached with 35% hydrogen peroxide (Pola office, SDI Innovative Dental Products, Australia) with three applications for 15 min each in one visit. The desensitizing agent or placebo was applied on the labial surfaces of bleached teeth according to the group specification and the teeth were left for 10 min followed by scrubbing the surface with a rubber cup for 20 s. The procedure was repeated after an interval of 1 week.

Tooth sensitivity following bleaching was recorded using two methods-1. clinical evaluation by a calibrated examiner and 2. visual analogue scale used by the patients on daily basis.

Clinical evaluation of tooth sensitivity

A calibrated examiner who is blinded about the study groups recorded tooth sensitivity perceived by the patient by deploying a blast of air to teeth isolated with cotton rolls, from a distance of 1.0 cm for 1 s, as per the American Dental Association recommended guidelines[4] at two time intervals-24 h and 1 week. Sceffe's scale was used for the measurement of sensitivity:[13]

0 = Absence of pain, but perceiving stimulus.

1 = Slight pain (mild sensitivity).

2 = Pain during the application of stimulus (moderate sensitivity).

3 = Pain during the application of stimulus and immediately thereafter. (severe sensitivity).

Subjective self-assessment of unstimulated tooth sensitivity

The modified visual analog scale (VAS)[14] was used by the subjects for the measurement of tooth sensitivity on daily basis for 7 days after each bleaching session and the subjects were blinded about the study group. The VAS scoring sheet uses a printed continuous scale of 0 through 10 points for each day. A score of 0 referred to the absence of tooth pain at rest and a score of 10 referred to the highest level of tooth pain imaginable. The participants were instructed to mark a point along the scale corresponding to the level of tooth sensitivity perceived on daily basis.

The statistical analysis was done using chi-square test, analysis of variance (ANOVA), and post hoc Tukey's test using Statistical Package for the Social Sciences (SPSS) version 16 software (Chicago, IL, USA). P value was set at P < 0.05.

RESULTS

There were three dropouts, one subject from each group. Subjects from groups I and III dropped out due to severe sensitivity, and one subject from group II dropped out for unknown reasons. The other 66 subjects were available for the recall at 7th, 8th, and 14th day of the study.

Intergroup comparison for objective scale show statistically significant difference at day 1 and 8, with experimental groups showing less incidence and the intensity of the sensitivity [Tables 1 and 3], whereas at day 7 and 14, i.e. after 1 week of each bleaching session, there is no significant difference between them [Tables 2 and 4].

Table 1

Incidence and intensity of sensitivity for experimental and control groups using objective scale at day 1

Table 3

At day 8

Table 2

At day 7

Table 4

At day 14

Table 5 shows the intergroup comparison of the mean scores of sensitivity at different time intervals using VAS scale.

Table 5

Comparison of mean VAS scores between the groups

On day 14, there is statistically significant difference between the experimental groups (groups II and III) and control group. But there is no statistically significant difference observed between the experimental groups. Figure 1 shows the incidence of tooth sensitivity to VAS score.

Figure 1

Incidence of tooth sensitivity for VAS score

DISCUSSION

Tooth discoloration due to dental fluorosis is a developmental disturbance of enamel caused by excessive exposure to high concentrations of fluoride (>1-2 ppm) during tooth development. The various treatment modalities for treating dental fluorosis are microabrasion, macroabrasion, bleaching, veneers, and crowns. Bleaching is considered the most conservative, popular treatment option and it is noninvasive.[1215] Materials, such as hydrogen peroxide and carbamide peroxide, are generally used for in-office vital tooth bleaching.[116] An overall color change of five to eight shade guide units (SGUs) is usually obtained after two bleaching sessions.[67817]

In clinical research studies, tooth sensitivity during bleaching is reported in a range of 18-78%, and it is usually related to the small microscopic enamel defects and subsurface pores, and the rapid transenamel and transdentinal diffusion of hydrogen peroxide to the pulp or other toxic components released with the degradation of the bleaching gels.[131617]

In the present clinical trial, discolored maxillary anterior teeth were bleached with 35% hydrogen peroxide with three applications for 15 min each in one visit, according to the method used by Reis et al.[6] who observed a better bleaching efficacy when compared with the single 45-min bleaching time.

McInnes solution is commonly used in bleaching teeth with fluorosis and is reported by McCoy SE.[18] An in vitro study done by Darshan et al. showed decrease in the enamel microhardness after two cycles of McInnes bleaching.[19] McInnes solution is prepared in a clinic at the time of bleaching, it is neither commercially available nor approved by the FDI. Hence, in this study a commercial brand of 35% of hydrogen peroxide liquid (Pola office, SDI Innovative Dental Products, Australia) that has the material safety certificate from the FDI is used.

The current study used an objective as well as a subjective assessment to evaluate the intensity of the postoperative sensitivity.

According to the objective evaluation, the incidence and intensity of sensitivity was less in the experimental groups after each bleaching session. According to the VAS scale, on day 14, i.e., at the end of evaluation period, significantly less sensitivity was experienced by subjects in the experimental groups. Hence, the null hypothesis is rejected in this study.

Over the years, Potassium nitrate (KNO3) is used as the desensitizing agent to manage tooth sensitivity, with varying reported success.[612] KNO3 has a calming effect on the nerve by preventing the nerve from repolarizing after it has depolarized in a pain cycle. Potassium ions in dentifrice act directly on intradental nerves by raising extracellular potassium ion concentration sufficiently to prevent action potential generation by axonal accommodation. Peacock et al. have shown that a potassium ion concentration above 8 mM to 16 mM (0.08-0.16% as KNO3) around the axons is needed to sustain nerve depolarization.[20]

Fluoride application has also been traditionally used to manage sensitivity, and it is thought to act as tubule blocker to control the pulpal fluid flow. The primary mechanism of action of fluoride is the occlusion of dentinal tubules or an increase in enamel hardness.[8]

In the present study, a combination of KNO3 and sodium monofluorophosphate is used, which is found to be effective in reducing tooth sensitivity after an in-office vital tooth bleaching. Silverman et al.[21] have reported that the use of sodium monofluorophosphate neither enhances nor detracts the desensitizing efficacy of KNO3.

The desensitizing agents were applied on the labial surface of the bleached tooth for a 10-min time period in this clinical trial and the observations are in accordance with Haywood et al. who demonstrated that applying KNO3 -fluoride for 10-30 min could be successful in reducing sensitivity in over 90% of the patients.[22]

CPP-ACP, a remineralizing agent developed by the ADAF to remineralize teeth and reverse early enamel carious lesion, is shown to make teeth less sensitive to hot, cold, air pressure, and tactile stimulation when it is applied topically either by dental professionals or by the patient themselves after tooth bleaching,[1112] and the present study results are similar to them.

CPP-ACP may interfere with the penetration of oxidizing molecule during bleaching procedure as it is a remineralizing agent.[23] Hence, the application of desensitizing agents is considered after the bleaching procedure.

There is only one study where KNO3 and sodium fluoride and amorphous calcium phosphate are compared for reducing the sensitivity due to vital tooth bleaching, and there is no significant difference observed between the desensitizing agents used.[9] This is similar to the observations in our study.

There are very few clinical studies done to evaluate the effect of desensitizing agents on tooth sensitivity following an in-office vital tooth bleaching, and there are no studies cited in the literature in case of dental fluorosis. Therefore, the direct correlation of the present study results is not possible with that of other studies.

Fifty out of the 69 subjects were satisfied with the improvement in the color, and the other 16 subjects opted for further treatments, such as veneers, to improve esthetics.

The use of desensitizing agents, such as Sensodent KF and CPP-ACP, are promising in reducing the incidence and intensity of tooth sensitivity soon after an in-office vital tooth bleaching. However, the toothpaste used by the subjects during the study period is not taken into consideration.

CONCLUSION

Within the limitation and parameters of the present study:

Desensitizing agents show effective reduction in the incidence and intensity of sensitivity after an in-office vital tooth bleaching.

The two desensitizing agents used in the study are equally effective in reducing the sensitivity.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest