Tooth sensitivity with a desensitizing-containing at-home bleaching gel—a randomized triple-blind clinical trial

Abstract

Objectives

Desensitizing agents are usually included in the composition of bleaching agents to reduce bleaching-induced tooth sensitivity (TS). This randomized clinical trial (RCT) evaluated the risk and intensity of TS and color change after at-home bleaching with a desensitizing-containing (3% potassium nitrate and 0.2% sodium fluoride) and desensitizing-free 10% carbamide peroxide (CP) gel (Whiteness Perfect, FGM).

Methods

A triple-blind, within-person RCT was conducted on 60 caries-free adult patients. Each participant used the gel in a bleaching tray for 3 h daily for 21 days in both the upper and lower dental arches. The absolute risk and intensity of TS were assessed daily through the 0–10 VAS and NRS scale for 21 days. Color change was recorded using shade guides (Vita Classical and Vita Bleachedguide) and the Easyshade spectrophotometer at baseline, weekly and 30 days after the end of the bleaching. The risk and intensity of TS were evaluated by the McNemar and Wilcoxon Signed Rank tests, respectively. Color change (ΔSGU and ΔE) were evaluated by the Mann-Whitney test and a paired t -test, respectively (α = 0.05).

Results

No difference in the TS and color change was observed (p > 0.05).

Conclusions

The incorporation of potassium nitrate and sodium fluoride in 10% carbamide peroxide at-home bleaching gel tested in this study did not reduce the TS and did not affect color change (RBR-4M6YR2).

Clinical relevance

Bleaching gel composed of 10% carbamide peroxide containing potassium nitrate and sodium fluoride did not have reduced risk and intensity of bleaching-induced tooth sensitivity.

Introduction

The increased search for esthetic procedures may be attributed to advertising and general media that emphasize the need for a pleasing appearance. Consequently, esthetic treatments have become a priority in dental practice, making esthetics as important as function, structure and biology [ ]. This was evident in a survey conducted in Ankara, Turkey [ ]; the authors investigated the factors involved with patient satisfaction and observed that 55.1% of them were dissatisfied with dental discoloration, followed by dental appearance (42.7%) and poor alignment of the teeth (29.9%). When the patients were asked about what kind of treatment they would like to receive, half reported dental bleaching, followed by esthetic restorations (25.4%), orthodontic treatment (24.5%) and prosthetic restorations (16.9%).

Dental bleaching is a very conservative alternative for the treatment of dental discolorations, and among the bleaching protocols, at-home bleaching is the one most commonly used due to its clinical effectiveness, safety and acceptance by patients and professionals [ ].

Although this bleaching protocol requires the use of low-concentrate oxidizing agents, tooth sensitivity (TS) is still present and can be considered the main adverse effect of the bleaching technique [ ]. A recent retrospective study that collected data from eleven RCTs showed that the risk of TS reported by patients who submitted to at-home bleaching is approximately 51% (95% CI 41 to 61%) [ ], and this variation may depend on the active bleaching agent [ ]. Studies that compared different gel concentrations for at-home technique showed higher TS levels for more concentrated gels [ ].

The higher the concentration of the peroxide, the greater the oxidative stress generated in the pulp tissue [ ], which in turn may be the factor responsible for the TS. This oxidative stress generates an inflammatory process with the release of inflammatory mediators, such as adenosine triphosphate and prostaglandins, that excite the nociceptors and trigger the bleaching-induced TS [ ].

Although some studies have shown that the use of desensitizing agents before tooth whitening can minimize the intensity of TS [ ], this technique adds another clinical step to the bleaching process. Theoretically, adding desensitizing agents in the composition of the bleaching gel, such as 3% potassium nitrate and 0.2% sodium fluoride, could be an efficient way to reduce TS without adding an extra step to the protocol. Potassium ions reduce the activation of the sensory nerve by preventing the depolarization of the nerve fiber and fluoride blocks dentin tubules that might be exposed and reducing its fluid flow [ ].

To the extent of the author’s knowledge, few studies have compared desensitizing-containing and desensitizing-free bleaching gels, and they show conflicting results [ ]. Thus, the objective of this study was to compare the risk and intensity of TS in patients who submitted to at-home bleaching and used a desensitizing-containing or desensitizing-free 10% carbamide peroxide gel. The color change was also evaluated.

Material and methods

Ethics approval and protocol registration

The clinical investigation was approved (protocol number 1.762.164) by the scientific review committee and by the committee for the protection of human participants of the local university. It was registered in the Brazilian clinical trials registry (REBEC) under the identification number RBR-4M6YR2. We prepared this article using the protocol established by the Consolidated Standards of Reporting Trials (CONSORT) statement with an extension for within-person designs [ ].

Trial design, settings and locations of data collection

This study was a randomized, within-person, triple-blind clinical trial, in which the patient, operator, and evaluator were masked to the group assignment. A third researcher, who was not involved in the evaluation process, was responsible for the randomization process. All participants were informed about the nature and objectives of the study. The study was performed from November 01, 2016, to March 31, 2017, in the Clinics of the School of Dentistry from the local university.

Recruitment

Recruitment was performed by posting written advertisements on the university walls. All volunteer participants signed an informed consent form before being enrolled in the study.

Eligibility criteria

Based on pre-established criteria, we selected 60 subjects volunteered for this study. Participants included in the present RCT should be at least 18–50 years old and in good general and oral health. The participants were required to have at least six maxillary anterior teeth free of caries and restorations, with canine shade A2 or darker, as judged by comparison with a value-oriented shade guide (VITA Classical Shade, Vita Zahnfabrik, Bad Säckingen, Germany).

Participants with dental prostheses, orthodontics apparatus or severe internal tooth discoloration (tetracycline stains, fluorosis, pulpless teeth, etc.) were not included in the study. In addition, pregnant and lactating women, participants with bruxism or any pathology that could cause sensitivity (such as recession, dentinal exposure and visible cracks in teeth), anti-inflammatory or analgesic drug users, smokers, or participants who had undergone tooth-whitening procedures were also excluded.

Sample size calculation

The primary outcome of this study was the absolute risk of TS. The absolute risk of TS (that is, the number of patients [percent] who reported pain at some point during dental bleaching) was considered for the calculation of the sample size. The absolute risk of TS for at-home bleaching was reported to be 61% in an earlier study [ ]. Using an alpha of 0.05, 90% power and a two-sided test, the minimum sample size in this equivalence trial was 60 patients in order to detect a 30% difference in the risk of TS between groups.

The sample size calculation was performed without accounting for the potential correlation between the paired treatment outcomes. This approach resulted in a larger sample size than if the correlation coefficient between treatment outcomes was not zero. We performed this approach because published within-person trials do not report this correlation coefficient, and thus we opted for being conservative.

Randomization and allocation concealment

A simple randomization process was performed on the website www.sealedenvelope.com . The distribution of the group to be first assigned was recorded on sequentially numbered cards and placed in opaque and sealed envelopes. The information contained in the envelope determined the treatment to be assigned in the upper or lower right arch, while the other arch received the alternate treatment. Once the participant was eligible for the procedure and all initial evaluations were completed, the allocation assignment was revealed by opening the envelope immediately after implementation.

Blinding

This was a triple-blind clinical trial in which the patient and operator were masked to the group assignment. A third researcher, who was not involved in the implementation and evaluation process, was responsible for the randomization process, delivery and guidance on the administration of the gels.

Both bleaching gels (with the desensitizing agent) and the control (without the desensitizing agent) were delivered in identical syringes coded as “A” and “B”. Both gels had similar consistency and color. Only the research coordinator knew the coding system.

Study intervention

The bleaching procedure was done by three clinical dentists with a clinical experience of more than 3 years. We made alginate impressions of each subject’s maxillary and mandibular arch, and these were filled with dental stone. We did not apply block-out material to the labial surfaces of teeth of the stone model teeth. A 1 mm soft vinyl material provided by the manufacturer (FGM Dental Products, Joinville, SC, Brazil) was used to fabricate the custom-fitted tray to hold the bleaching gel. We trimmed the bleaching tray 1 mm beyond the marginal gingiva, and we identified the right and left sides of the bleaching tray. The participant received both bleaching products with the respective instructions on which side each product was to be applied. Both the bleaching product and the corresponding side of the bleaching tray had identical coding to facilitate the patient’s identification, but they were masked to hide the product that was used on each side of the dental arch.

The whitening gel that was used in this study was 10% Whiteness Perfect Carbamide Peroxide (FGM, Joinville, SC Brazil). In the experimental group (desensitizing-containing), the commercial product itself was employed, being composed of 3% potassium nitrate and 0.2% sodium fluoride. In the control group (desensitizing-free), the company manufactured the same bleaching agent but without the desensitizing active agents ( Table 1 ). The wearing instructions are depicted in Table 1 . After each daily use, the patient should remove the bleaching tray, wash it under tap water and brush their teeth routinely.

Table 1
Bleaching gel (manufacturer, composition, groups and application method).
Manufacturer Composition Groups Application method
Carbamide peroxide 10% (Whiteness Perfect, FGM, Joinville, SC Brazil) Carbamide peroxide 10%, neutralized carbopol, glycerin and distilled water Desensitizing-containing (batch number − 091116): The gel contains 3% potassium nitrate and sodium fluoride 0.2% Apply one drop of gel to each tooth in the tray, in the regions corresponding to the buccal surfaces of the teeth to be bleached;
Desensitizing-free (batch number − 210916): The gel did not desensitizing agent Daily use for 3 h for 21 days.

Outcomes

Tooth sensitivity evaluation

The patients were instructed to fill out a form to record the TS daily during bleaching for 21 days. Before starting the bleaching, each patient received a paper form with a mouth drawn on it that contained the teeth of the upper and lower arch and should describe their degree of pain using two pain scales. Using a five-point Numeric Rating Scale (NRS) where 0 = none, 1 = mild, 2 = moderate, 3 = considerable and 4 = severe, the patient was instructed to indicate the numerical value of the degree of sensitivity on each side of the dental arch. Additionally, we instructed them to express their tooth sensitivity degree using the Visual Analogue Scale (VAS). The VAS scale is a 10-cm horizontal line with scores of 0 and 10 at their ends, where 0 = no sensitivity and 10 = severe sensitivity. The patient should mark with a vertical line across the horizontal line of the scale the intensity of the TS. Then, the distance in mm from the zero ends was measured with the aid of a millimeter ruler.

The patients were not instructed to point out the painful teeth in the present study, although they would be able to accomplish this goal if requested. They were told to fill out the form every time they felt pain. We also explained to them that if they did not feel any TS, their intensity would be zero. These forms were returned to the researcher on the next appointment (1 week later).

If the participant scored 0 (no sensitivity) in all time assessments, this participant was considered to be insensitive to the bleaching protocol. In all other circumstances, the participants were considered to have bleaching-induced TS. This dichotomization allowed us to calculate the absolute risk of TS, which is the percentage of patients who reported tooth sensitivity at least once during treatment.

To calculate the TS intensity, we took the worst score from the NRS scale and the highest numerical value obtained in the VAS scale reported by each patient, so that only a single value per patient was taken from the 3-week treatment.

Color evaluation

Two experienced and calibrated dentists (kappa statistics higher than 80% after previous calibration; data not shown) not involved in the randomization procedures performed clinical assessments at baseline, weekly during the 3-week treatment, and 1 month after the bleaching treatment. We performed the color evaluation using the shade guides VITA Classical (Vita Zahnfabrik, Bad Sackingen, Germany) and VITA Bleachedguide 3D-MASTER (BG VITA ZAhnfabrik, Dad Sackingen, Germany), as well as, with the spectrophotometer VITA Easyshade (VITA Zahnfabrik, Bad Säckingen, Germany).

The Vita Classical scale was arranged in 16 tabs from highest (B1) to lowest (C4) value: B1, A1, B2, D2, A2, C1, C2, D4, A3, D3, B3, A3.5, B4, C3, A4 and C4. Although this scale is not linear in the truest sense, color changes were considered as continuous and linear changes as in several clinical studies of tooth whitening [ ]. The VITA Bleachedguide 3D-MASTER contains lighter shade tabs, and it is already organized from highest (0M1) to lowest (5M3) values.

The tooth matching area was the middle third of the buccal surface of the upper canines [ ]. Color changes were calculated from the beginning of the active phase up to the individual recall times by calculating the change in the number of shade guide units (ΔSGU), which occurred toward the lighter end of the value-oriented list of shade tabs. In case of disagreement between operators, they should reach a consensus.

For color measurement with the spectrophotometer, the examiner took an impression of the maxillary arch with dense silicone paste (Coltoflax and Perfil Cub Kit, Vigodent, Rio de Janeiro, Rio de Janeiro, Brazil). The impression was extended to the maxillary canines and served as a standard color measurement guide for the spectrophotometer. For each tooth to be evaluated, we created a window on the buccal surface of the silicone guide using a metal device with a radius of 6 millimeters, which is exactly the diameter of the tip of the spectrophotometer. The tip of the device was then inserted into the silicone guide, and we obtained the L*, a* and b* parameters of color from the spectrophotometer. The L* value represents the luminosity (value from 0 [black] to 100 [white]), a* value represents the measurement along the red-green axis, and b* value represents the measurement along the yellow–blue axis. The color change (ΔE) before (baseline) and after each treatment (in each assessment period) is given by differences between the two colors measured with the spectrophotometer—which is calculated using the formula ΔE = [(ΔL*) 2 + (Δa*) 2 + (Δb*) 2 ] 1/2 .

Statistical methods

The analysis followed the intent-to-treat protocol and involved all participants, who were randomly divided ( Fig. 1 ). The statistician was also blinded to the groups. Each arch was analyzed separately. The absolute risks of TS of both groups were compared by means of the McNemar’s exact test (α = 0.05, test for proportion of dependent data ratio). The relative risk as well as the confidence interval (CI) for the effect size was also calculated.

Fig. 1
Flow diagram of study design phases, including enrollment and allocation criteria.

The TS intensity data sets for both the VAS and NRS scales were plotted in histograms and inspected for normal distributions. As data did not have normal distribution, the groups were compared using the Wilcoxon Signed Rank test (α = 0.05).

The means and standard deviations of color change in ΔSGU and ΔE between baseline vs. 30 days after bleaching were calculated. In order to assess whether the bleaching therapies were effective, data from both groups were compared using the Mann-Whitney test for the ΔSGU data and the paired t -test for ΔE. The level of significance of all tests was set at 5%.

Introduction

The increased search for esthetic procedures may be attributed to advertising and general media that emphasize the need for a pleasing appearance. Consequently, esthetic treatments have become a priority in dental practice, making esthetics as important as function, structure and biology [ ]. This was evident in a survey conducted in Ankara, Turkey [ ]; the authors investigated the factors involved with patient satisfaction and observed that 55.1% of them were dissatisfied with dental discoloration, followed by dental appearance (42.7%) and poor alignment of the teeth (29.9%). When the patients were asked about what kind of treatment they would like to receive, half reported dental bleaching, followed by esthetic restorations (25.4%), orthodontic treatment (24.5%) and prosthetic restorations (16.9%).

Dental bleaching is a very conservative alternative for the treatment of dental discolorations, and among the bleaching protocols, at-home bleaching is the one most commonly used due to its clinical effectiveness, safety and acceptance by patients and professionals [ ].

Although this bleaching protocol requires the use of low-concentrate oxidizing agents, tooth sensitivity (TS) is still present and can be considered the main adverse effect of the bleaching technique [ ]. A recent retrospective study that collected data from eleven RCTs showed that the risk of TS reported by patients who submitted to at-home bleaching is approximately 51% (95% CI 41 to 61%) [ ], and this variation may depend on the active bleaching agent [ ]. Studies that compared different gel concentrations for at-home technique showed higher TS levels for more concentrated gels [ ].

The higher the concentration of the peroxide, the greater the oxidative stress generated in the pulp tissue [ ], which in turn may be the factor responsible for the TS. This oxidative stress generates an inflammatory process with the release of inflammatory mediators, such as adenosine triphosphate and prostaglandins, that excite the nociceptors and trigger the bleaching-induced TS [ ].

Although some studies have shown that the use of desensitizing agents before tooth whitening can minimize the intensity of TS [ ], this technique adds another clinical step to the bleaching process. Theoretically, adding desensitizing agents in the composition of the bleaching gel, such as 3% potassium nitrate and 0.2% sodium fluoride, could be an efficient way to reduce TS without adding an extra step to the protocol. Potassium ions reduce the activation of the sensory nerve by preventing the depolarization of the nerve fiber and fluoride blocks dentin tubules that might be exposed and reducing its fluid flow [ ].

To the extent of the author’s knowledge, few studies have compared desensitizing-containing and desensitizing-free bleaching gels, and they show conflicting results [ ]. Thus, the objective of this study was to compare the risk and intensity of TS in patients who submitted to at-home bleaching and used a desensitizing-containing or desensitizing-free 10% carbamide peroxide gel. The color change was also evaluated.

Material and methods

Ethics approval and protocol registration

The clinical investigation was approved (protocol number 1.762.164) by the scientific review committee and by the committee for the protection of human participants of the local university. It was registered in the Brazilian clinical trials registry (REBEC) under the identification number RBR-4M6YR2. We prepared this article using the protocol established by the Consolidated Standards of Reporting Trials (CONSORT) statement with an extension for within-person designs [ ].

Trial design, settings and locations of data collection

This study was a randomized, within-person, triple-blind clinical trial, in which the patient, operator, and evaluator were masked to the group assignment. A third researcher, who was not involved in the evaluation process, was responsible for the randomization process. All participants were informed about the nature and objectives of the study. The study was performed from November 01, 2016, to March 31, 2017, in the Clinics of the School of Dentistry from the local university.

Recruitment

Recruitment was performed by posting written advertisements on the university walls. All volunteer participants signed an informed consent form before being enrolled in the study.

Eligibility criteria

Based on pre-established criteria, we selected 60 subjects volunteered for this study. Participants included in the present RCT should be at least 18–50 years old and in good general and oral health. The participants were required to have at least six maxillary anterior teeth free of caries and restorations, with canine shade A2 or darker, as judged by comparison with a value-oriented shade guide (VITA Classical Shade, Vita Zahnfabrik, Bad Säckingen, Germany).

Participants with dental prostheses, orthodontics apparatus or severe internal tooth discoloration (tetracycline stains, fluorosis, pulpless teeth, etc.) were not included in the study. In addition, pregnant and lactating women, participants with bruxism or any pathology that could cause sensitivity (such as recession, dentinal exposure and visible cracks in teeth), anti-inflammatory or analgesic drug users, smokers, or participants who had undergone tooth-whitening procedures were also excluded.

Sample size calculation

The primary outcome of this study was the absolute risk of TS. The absolute risk of TS (that is, the number of patients [percent] who reported pain at some point during dental bleaching) was considered for the calculation of the sample size. The absolute risk of TS for at-home bleaching was reported to be 61% in an earlier study [ ]. Using an alpha of 0.05, 90% power and a two-sided test, the minimum sample size in this equivalence trial was 60 patients in order to detect a 30% difference in the risk of TS between groups.

The sample size calculation was performed without accounting for the potential correlation between the paired treatment outcomes. This approach resulted in a larger sample size than if the correlation coefficient between treatment outcomes was not zero. We performed this approach because published within-person trials do not report this correlation coefficient, and thus we opted for being conservative.

Randomization and allocation concealment

A simple randomization process was performed on the website www.sealedenvelope.com . The distribution of the group to be first assigned was recorded on sequentially numbered cards and placed in opaque and sealed envelopes. The information contained in the envelope determined the treatment to be assigned in the upper or lower right arch, while the other arch received the alternate treatment. Once the participant was eligible for the procedure and all initial evaluations were completed, the allocation assignment was revealed by opening the envelope immediately after implementation.

Blinding

This was a triple-blind clinical trial in which the patient and operator were masked to the group assignment. A third researcher, who was not involved in the implementation and evaluation process, was responsible for the randomization process, delivery and guidance on the administration of the gels.

Both bleaching gels (with the desensitizing agent) and the control (without the desensitizing agent) were delivered in identical syringes coded as “A” and “B”. Both gels had similar consistency and color. Only the research coordinator knew the coding system.

Study intervention

The bleaching procedure was done by three clinical dentists with a clinical experience of more than 3 years. We made alginate impressions of each subject’s maxillary and mandibular arch, and these were filled with dental stone. We did not apply block-out material to the labial surfaces of teeth of the stone model teeth. A 1 mm soft vinyl material provided by the manufacturer (FGM Dental Products, Joinville, SC, Brazil) was used to fabricate the custom-fitted tray to hold the bleaching gel. We trimmed the bleaching tray 1 mm beyond the marginal gingiva, and we identified the right and left sides of the bleaching tray. The participant received both bleaching products with the respective instructions on which side each product was to be applied. Both the bleaching product and the corresponding side of the bleaching tray had identical coding to facilitate the patient’s identification, but they were masked to hide the product that was used on each side of the dental arch.

The whitening gel that was used in this study was 10% Whiteness Perfect Carbamide Peroxide (FGM, Joinville, SC Brazil). In the experimental group (desensitizing-containing), the commercial product itself was employed, being composed of 3% potassium nitrate and 0.2% sodium fluoride. In the control group (desensitizing-free), the company manufactured the same bleaching agent but without the desensitizing active agents ( Table 1 ). The wearing instructions are depicted in Table 1 . After each daily use, the patient should remove the bleaching tray, wash it under tap water and brush their teeth routinely.

Jun 17, 2018 | Posted by in General Dentistry | Comments Off on Tooth sensitivity with a desensitizing-containing at-home bleaching gel—a randomized triple-blind clinical trial
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