Potassium Oxalate and Potassium Nitrate and Post-bleaching Sensitivity
Condition: Medicaments Substances in Therapeutic Use
MeSH terms: Hypersensitivity
Study type: Interventional

Summary: 
      Objectives: This study will determine the effectiveness of the use of desensitivity gels
      prior in office bleaching on risk and intensity of tooth sensitivity caused by in-office
      bleaching using 35% hydrogen peroxide. Materials and Methods: Fourty seven patients will be
      selected for this triple-blind, randomized, cross-over, placebo-controlled clinical trial. 10
      minutes prior to bleaching procedure, patients will receive the the potassium nitrate 2% and
      potassium oxalate 5% desensitivity gel application on vestibular surface. The whitening
      treatment with 35% hydrogen peroxide will be carried out in two sessions with a 7-day
      interval. Tooth sensitivity will be assessed before, during and 24 hours after the procedure
      using analog visual and verbal scales. Color alteration will be assessed by a bleach guide
      scale and Vita Easy shade spectrophotometer 7 days after each session. Relative risk to
      sensitivity will be calculated and adjusted by session; while comparison of overall risk will
      performed by McNemar's test. Data on the sensitivity level for both scales and color shade
      will be subjected to the Friedman, Wilcoxon and Mann-Whitney tests, respectively (α = 0.05).
    

Detailed description: 
      Methods & Materials:

      This clinical trial was approved by the Scientific Review Committee and by the Committee for
      the Protection of Human Subjects of the local university (CAAE 60259316.2.0000.5546).

      Trial design:

      This study will be a randomized, triple-blinded, placebo-controlled clinical trial, and split
      mouth study design.

      The patients included will be submitted to two in-office bleaching sessions receiving the
      potassium nitrate 2% and postassium oxalate 5% desensitivity gel application on vestibular
      surface, for 10 minutes. A delay of 1 week between the sessions will be established. The
      study will be conducted at the clinic of the School of Dentistry of the local university from
      November 2016 to October 2017.

      Participants:

      Patients included in this clinical trial will be at least 18 years old with good oral health.
      Patients with any of the six upper anterior teeth with caries, restoration, severe
      discoloration (e.g., stains caused by tetracycline), enamel hypoplasia, gingival recession,
      dentin exposure, pulpitis, or endodontics will be excluded. Participants submitted to
      previous bleaching procedures, presenting prior tooth sensitivity, known allergy to any
      component of medication used in the study, pregnant or breastfeeding will be also excluded.
      Only patients presenting all six upper anterior teeth with shade mismatching with 2.5 M2
      (Vita Bleachguide 3D-Master scale, Vita-Zahnfabrik, Bad Sackingen, Germany) or darker will be
      included.

      Sample Size Calculation:

      The sample calculation will be based on the primary binary outcome (sensitivity risk 24 hours
      after the procedure) for superiority trial. Power of the test will be set at 80%, considering
      a type I error of 0.05; risk to tooth sensitivity of 63% (potassium nitrate) and 35%
      (potassium oxalate), while a reduction around 55% with the treatment will be expected. The
      calculation resulted in fourty seven patients.

      Randomization:

      A randomized list will be computer-generated by a person not involved in intervention or
      evaluation. The participants were defined as blocks in the randomization process, where the
      sequence of treatment (placebo or etodolac) will be randomly set for each block by using
      computer-generated tables (www.sealedenvelope.com). The sequence will be inserted into sealed
      envelopes numbered from 1 to 47 that were opened by the operator only at the moment of the
      intervention. The patients were numbered according to the sequence of enrollment. Neither the
      participant nor the operator knew the group allocation determining blinding to the protocol.

      Baseline evaluation:

      Prior to bleaching procedure, the teeth will be cleaned using rubber cups associated to
      pumice and water. The shades of six upper anterior teeth will be assessed on a baseline using
      the bleach guide scale and for CIE L*a*b* measurement, ΔE will be calculated by the following
      equation: ∆E= [(∆L)2 + (∆a)2 + (∆b)2]1/2, while ∆L = L1 - L0; ∆a = a1 - a0; e ∆b = b1 - b0.

      Intervention:

      Prior to each bleaching session, the patients will receive the potassium nitrate 2% (active
      comparator) on one half (anterior superior teeth) and potassium oxalate 5% desensitivity gel
      on the other half (anterior superior teeth) application on vestibular surface, for 10
      minutes.

      Neither the operators responsible for intervention and evaluation nor the patients knew the
      content which treatment will be done.

      A light-cured resin dam will be applied (Top Dam, FGM, Joinville, SC, Brazil) on the gingival
      tissue corresponding to the teeth to be bleached. A 35% hydrogen peroxide based bleaching
      agent (Whiteness HP MAxx Intermixx, FGM, Joinville, SC, Brazil) will be mixed and applied on
      the vestibular surface of teeth, remaining for 40 minutes. After this time, the bleaching
      agent will be removed. A second session will be carried out after 1 week following the same
      procedures.

      Evaluations:

      The tooth sensitivity reported by patients will be assessed using a visual analog scale (VAS)
      and verbal rating scale (VRS). The VAS consisted of a scale 10 cm in length ranging from
      green (absence of pain) to red (unsupportable pain). The patient set his or her level of
      sensitivity by pointing to the color corresponding to this level, while the distance from
      this point to the green border will be recorded. For VRS, the patient reported his or her
      level of sensitivity based on scores: 0 = none, 1 = light, 2 = moderate, 3 = considerable and
      4 = severe. The tooth sensitivity will be assessed during the bleaching, immediately after
      bleaching agent removal and after 24 hours. For this last assessment, only the VRS will be
      used. Tooth sensitivity will be measure: baseline, at 40 minutes during the bleaching
      procedure, after the bleaching procedure and 24 hours after. One week after each session the
      tooth color will be evaluated again using the same procedure described previously.

      Statistical Analysis:

      The demographic data from patients will be analyzed to determine age, gender, and anxiety
      level for each allocation sequence. Comparisons between the allocation sequences will be
      performed by the Mann-Whitney test (age) and Fisher's exact (gender) and chi-square (anxiety
      level) tests.

      Based on presence of any tooth sensitivity (scores different from 0 for VRS), the absolute
      risk, odds ratio and relative risk will be calculated regarding the treatments for each
      moment of evaluation/session of bleaching, as well as its confidence intervals (95%). For
      each moment, differences on presence/absence ratios will be analyzed by Fisher's exact test.
      For the overall risk related to each treatment, the odds ratio will be adjusted to
      independent variable "session of bleaching" using the Mantel-Haenszel statistic. The
      homogeneity of odds ratios will be analyzed by the Breslow-Day and Tarone's tests. Following,
      the odds ratio estimated will be converted to relative risk and the overall presence/absence
      ratios will be analyzed by the McNemar's test, considering the study design (cross-over).

      For VRS, the data from scores observed in each time of evaluation/session of bleaching will
      be submitted to the Mann-Whitney rank sum test. Despite the measurement of tooth sensitivity
      using VAS giving a continuous outcome, data assessed with this scale did not show a normal
      distribution (Shapiro-Wilk's test). Thus, data from VAS will be also analyzed by the
      Mann-Whitney rank sum test, while one test per time of evaluation will be carried out.

      For color evaluation, comparisons between the sequences of treatment will be performed using
      the Mann-Whitney rank sum test. The Friedman test followed by Dunn's post hoc test will be
      used to analyze the difference between the moments of evaluation for each sequence of
      treatment. All statistical analyses will be performed adjusting the initial significance
      level (α = 0.05) by Bonferroni correction.
    

Intervention name(s): Potassium nitrate 2% gel; Potassium oxalate 5% gel
Intervention type(s): Device; Device
Intervention description(s): Teeth will be cleaned using rubber cups associated to pumice and water;
Relative isolation with roller cotton will be done;
Prior to each bleaching session, the patients will receive the potassium nitrate 2% desensitivity gel application on vestibular surface, for 10 minutes.
Gingival dam will be performed using a fluid resin (Top Dam, FGM, Brazil)
A 35% hydrogen peroxide based bleaching agent will be mixed and applied on the vestibular surface of teeth, remaining for 40 minutes.; Teeth will be cleaned using rubber cups associated to pumice and water
Relative isolation with roller cotton will be done;
Prior to each bleaching session, the patients will receive the potassium OXALATE 5%
Gingival dam will be performed using a fluid resin (Top Dam, FGM, Brazil) desensitivity gel application on vestibular surface, for 10 minutes.
A 35% hydrogen peroxide based bleaching agent will be mixed and applied on the vestibular surface of teeth, remaining for 40 minutes.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Treatment