Effect of Pregabalin Gel in Controlling Cervical Dentin Hypersensitivity

To obtain the experimental pregabalin gel, a carbopol 940 gel base was used. To prepare the base gel for the formulation, each component was weighed on an analytical balance and, after 24 hours, the components were taken to a mechanical shaker, rotating at 1000 rpm for 10 minutes. 50% triethanolamine was added to adjust the pH to ±6 and complete gel formation. The concentrations of the components of the initial base formula were adjusted to obtain a homogeneous, transparent gel with good consistency. A PG solution (10 mg/ml) was prepared by diluting the drug, which is presented as a white, crystalline powder (Vardhman Chemtech Ltd, Punjab, India), with purified water. The solution was stirred for 10 min in a water bath (Taitec) and centrifuged at 4°C for 10 min. The supernatant obtained was collected and then incorporated into the 1% carbopol-based gel.

This formulation has already been evaluated in a previous study regarding quality standards, physical/chemical characterization, cytotoxicity and subjected to stability analyzes (preliminary and accelerated). Its characteristics indicate that it is a favorable formulation for clinical application.

This randomized clinical study will follow the guidelines for clinical trials recommended by CONSORT (Consolidated Standards Of Reporting Trials) and will be submitted to the Human Research Ethics Committee of the Institute of Health Sciences at the Federal University of Pará (CEP-ICS/UFPA). All selected participants who agree to participate in the research will be informed about the benefits, risks, methods, and goals of the study before consenting to their participation through the Informed Consent Form declaring that the participants agree with all the steps to be taken. The participants can withdraw from the research at any time, following the principles of the Declaration of Helsinki.

This randomized clinical trial will be parallel, double-blind, placebo-controlled and all clinical interventions will be conducted in the clinics of the Faculty of Dentistry of the Federal University of Pará (FOUFPa). The research will consist of three groups: a placebo control group (CG) with gel without any active ingredient, a group with potassium nitrate gel (Ultradent, South Jordan, UT, USA) (GNK), and an experimental group with gel 10% Pregabalin (GPG). Applications will be carried out in 3 sessions with an interval of 72 hours between each one. Sensitivity recording will be performed at T0 (baseline), T1 (after the first session), T2 (after the second session), T3 (after the third session), T4 (7 days after the last session), and T5 (one month after the last session) and T6 (3 months after the last session).

A questionnaire (QEDH-15) will be applied to evaluate the impact of desensitizing treatment on improving the participants' oral health-related quality of life (HRQoL). The questionnaire will be applied at baseline (T0) and the last sensitivity record (T6). Higher QEHD-15 scores indicate a negative impact on the oral health-related quality of life (OHRQoL) of research participants.

The sample size was determined using the GPower 3.1 program (Heinrich-Heine-Universität Düsseldorf, Germany), based on a comparison of intergroup means. According to previous studies, the minimum expected difference is 2.26, and a standard deviation of 2 between groups. An alpha of 5%, power of 80%, and a 20% increase in possible loss of participants were considered. The final sample size determined was 63 teeth in total, 21 sensitive teeth per group.

To evaluate the painful sensation of hypersensitivity, a Visual Analogue Scale (VAS) will be used. The initial mark "0" represents no pain and the opposite mark "10" represents extreme pain.

The participant will be asked to signal the number compatible with the painful sensation after applying the evaporative stimulus, by applying a jet of air from a triple syringe for two seconds, at room temperature, perpendicular to the buccal surface of the tooth at a distance of 1cm, and also by tactile stimulation, where a cross-shaped exploring probe will slide into the cervical region of the hypersensitive teeth, vertically in the cervical-incisal direction and horizontally in the mesiodistal direction. These stimuli will be performed after relative individual isolation with isolation tape (Isotape, Septodont, Louisville, USA) and cotton rolls (Dental Cremer, SC, Brazil).

Random distribution between the groups will be carried out in a block, through a numerical draw that allows each participant to be allocated into one of the three groups (GC, GNK and GPG) using Biostat 5.3 software (Instituto Mamirauá, PA, Brazil). The confidentiality of the allocation will be maintained throughout the sample formation process, through a numerical draw with numbered and coded papers. All participants and the clinical operator will not know the group's codes.

This double-blind study guarantees the confidentiality of the interventions since both the research participant and the main researcher will not be able to differentiate the procedure applied. The placebo gel, the experimental desensitizing gel, and the potassium nitrate gel will be inserted into a dappen jar and delivered immediately before the clinical interventions by a research collaborator. The gels have a similar texture, color and odor to prevent identification. The evaluator will also not be aware of the group the participant belonged to, as the clinical operator will not participate in the randomization process. The research will have a single operator to carry out the clinical part.

The data will be analyzed for normality of distribution, using the Shapiro-Wilk test. If it presents a normal distribution, the ANOVA parametric analysis will be used to verify the existence of differences between the group means and the Student-Newman-Keuls post-hoc test will be used to verify the differences between the times. In case of abnormal distribution, the Friedman repeated measures test and the Tukey post hoc test will be used. To analyze differences in quality of life-related to oral health at T0 and T6, the Friedman test will be used. Data analysis will be performed using the freely available statistical software Jamovi (Version 2.3). The significance level α will be set at p\<0.05.