Document Type


Date of Degree

Spring 2017

Degree Name

MS (Master of Science)

Degree In

Operative Dentistry

First Advisor

Kwon, So Ran

Second Advisor

Wertz, Philip

First Committee Member

Dawson, Deborah V.

Second Committee Member

Vargas, Marcos A.


Objectives: To measure the level of hydrogen peroxide penetration into the pulp chamber and to evaluate its whitening efficacy when the tooth is treated with an innovative double layer of potassium nitrate desensitizing agent and hydrogen peroxide whitening gel.

Methods: Extracted human molar teeth (n=160) were collected. Roots were trimmed 3 mm apical to the cemento-enamel junction, the pulp was removed and a cavity prepared, leaving a standardized wall of 2 mm thickness, which retained 100 µL of acetate buffer solution. A standardized whitening area of 6 mm in diameter was established buccally by painting the rest of the tooth with gray nail varnish. The teeth were randomly assigned into four groups. Group 1: no treatment (glycerin gel, negative control); Group 2: double layer of 20 L 5% potassium nitrate (Relief ACP, Philips Oral Healthcare) and 100 L 25% hydrogen peroxide (Zoom Chairside Whitening Gel, Philips Oral Healthcare); Group 3: double layer of 40 L 5% potassium nitrate and 100 L 25% hydrogen peroxide; and Group 4: 100 L 25% hydrogen peroxide (positive control). All groups received three 45-minute sessions of in-office whitening with light activation at 3-day intervals. Hydrogen peroxide penetration was assessed spectrophotometrically using leucocrystal violet and horseradish peroxidase. Color measurements were assessed with VITA Easyshade at baseline, 1-day, and 1-month post-whitening. Tooth color change was measured per Commission Internationale de l'Eclairage methodology. One-way ANOVA with Tukey multiple comparisons adjustment was performed to compare group differences in overall tooth color change (Delta E*) and hydrogen peroxide penetration (type I error = 0.05).

Results: Hydrogen peroxide penetration levels were not significantly different between Group 2 and Group 4; however, the levels were significantly higher than Group 1 and Group 3 (p< 0.0001). Groups 2, 3 and 4 showed no differences for overall tooth color change but differed significantly from the negative control group (Group 1) at 1-day and 1-month post-whitening.

Conclusions: Hydrogen peroxide penetration was affected when pretreated by potassium nitrate desensitizer; however, the double layer technique did not adversely affect the whitening efficacy.

Public Abstract

Tooth whitening is a conservative and effective treatment for discolored teeth. The main active ingredient of tooth whitening is hydrogen peroxide. Tooth-whitening-induced sensitivity (TWIS) is the most frequently reported side effect associated with all the whitening modalities and may be related to the penetration of hydrogen peroxide into the pulp chamber.

Potassium nitrate as a desensitizer is used widely to treat TWIS by decreasing dentinal sensory nerve activity. A double layer technique has been recently proposed which involves the application of an initial potassium nitrate layer and a hydrogen peroxide layer on top.

This study aimed to measure the levels of hydrogen peroxide penetration into the pulp chamber and to evaluate the whitening efficacy when teeth are treated with a double layer of potassium nitrate desensitizer and hydrogen peroxide whitening gel.

Overall this research demonstrates that the use of potassium nitrate desensitizing agent and hydrogen peroxide whitening gel in a double layer technique affected hydrogen peroxide penetration. However, the double layer technique did not adversely affect the whitening efficacy. Further research is required to confirm these effects for, and a safety protocol should be established before the technique is applied to clinical treatment. In a broader sense, this research further suggests that this technique may reduce tooth-whitening-induced sensitivity.


double layer technique, hydrogen peroxide penetration, potassium nitrate, tooth color change, tooth whitening


xiv, 124 pages


Includes bibliographical references (pages 111-124).


Copyright © 2017 Watcharaphong Ariyakriangkai