Esthetic Dentistry

Effect of potassium nitrate and fluoride on carbamideperoxide bieachingLaura Tarn, DDS,

Ob]ectivesr The purpose ot this study was to assess the ettecl on tooth sensitivity when potassium nifrateand fluoride were added to a 10% carbamide peroxide bleaching gel. Method and materials: Seventeenmaxiliary and four mandibuiar arches were bieached using the at-home bleaching technique. Thebleaching treatment consisted of the simultaneous use of a 10% carbamide peroxide gel containing3% potassium nitrate wt/voi and 0.11 fiuoride ion wVvol on one side ol the midiine and a 10% carbamideperoxide gel oniy (controi) on the other side ot the midline for 14 nights. A visual analog scaie tor each sideof the dental arch was used by the patients to assess tooth sensitivity and tcoth whitening. Preoperativeand postoperative photographs were also taken. Results: The addition ot potassium nitrate and fluondesignificantly decreased the totai tooth sensitivity reported by the patients. The addition did not signiticantlychange the whitening efticacy of the carbamide peroxide bieach. Conclusion: A 10% carbamide peroxidebleaching gel containing potassium nitrate and tiuoride produced iess tooth sensitivity than did the controibleaching gel during a 2-week at-home bieaching treatment. (Quintessence int 2001:32:766-770)

Key words: at-home tooth bleaching, carbamide peroxide, desensitization, tiuoride, potassium nitrate,

tooth sensitivity

CLINICAL RELEVANCE: The addition ot potassiumnitrate and tiuoride to a carbamide peroxide bleach canreduce the tooth sensitivity experienced during at-homebieaching, increasing the patient's comtort and encourag-ing compliance during treatment.

Tooth sensitivity is the most significant problemassociated with the at-home bleaching technique.

The incidence of tooth sensitivity for this bleachingmethod ranges from 9% to 100%'-^ but more com-monly is in the 60% range. - The degree of tooth sen-sitivity can vary from mild to severe. Although thetooth sensitivity that occurs during at-home vital tooth

'Associate Professor. Restorative Dentistry. Depaitment of ClinicalSciences, Faculty ol Denlistry, University ot Toronto. Tofonto. Ontario,Canada

Reprint requests: Dr La j i a Tam, Associate Protessor, RestorativeDentistry. Department of Clinical Sciences, Faculty of Dentislry, Universityof Toronto, 124 Edward Street, Toronto, Ontario, Canada, M5G 1G6,E-mail: laura.iamSutoronto.ca

bleaching has not been associated with pulpal prob-lems after the cessation of bleaching, tooth sensitivitycan affect a patient's compliance by preventing thepatient from completing the full course of treatment.

A common recommendation for treatment of thetooth sensitivity is to reduce the frequency or durationof bleaching applications. Another treatment method isapplication of topical fluorides or desensitizing pastes.Several manufacturers have added potassium nitrateand/or fluoride to their bleach formulations in anattempt to reduce tooth sensitivity problems. However,there have been no independent studies to determinethe effect of such additives on tooth sensitivity.

The purpose of this research was to assess the effecton tooth sensitivity when potassium nitrate and fluo-ride (PF) were added to a 10% carbamide peroxidebleaching gel. The effect of the PF bleach was com-pared with that of a control 10% carbamide peroxidebleaching gel in a double-blind prospective clinicalstudy format. The null hypothesis for this study wasthat there would be no significant difference in thedegree of tooth sensitivity experienced by patientsusing the carbamide peroxide bleach either with orwithout potassium nitrate and fluoride.

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METHOD AND MATERIALS

Patients who were seeking hleaching treatment andwho met the selection criteria were considered forinclusion in the study. The patients had to be oldertban 18 years, not pregnant, and not lactating; bad tobave no bistory of previous bleaching treatment; andbad to bave vital anterior teeth with no or minimalintact restorations, A total of 21 dental arches (17maxillary and four mandibular arcbes) were treatedindividually on patients wbose average age was 31 ±10 years {range: 20 to 53 years), Tbere were 10 femaleand 7 male patients. None of the patients reported tohave used a desensitizing toothpaste in the last 4weeks. All of the patients had been regularly using afluoridated toothpaste tbat was available over tbecounter, Tbe selection of the patient population, theconsent form, and the study protocol were approvedby the University of Toronto, Office of ResearchServices, Human Subjects Review Committee,

The bleaching treatment consisted of the applica-tion of a lO /o carbamide peroxide ge! with 3% potas-sium nitrate wt/vol and 0,11 fluoride ion wt/vol onthe incisors and premolars on one side of the midline,and the application of a 10% carbamide peroxide gelonly (control) on the incisors and premolars on theother side of the midline. The carbamide peroxide gelformulations were manufactured specifically for thisstudy (Ultradent) and were packaged identically forthis double-blind study, Tbe syringes were randomlynumbered and selected for use on eitber tbe left orright side of each patient's dental arch,

A preoperative photograph was taken of thepatient's teeth under standardized lighting conditionsusing the same camera and dental operatory light,with and without a matching Lumin Vacuum {VitaZahnfabrik) sbade guide tab.

An alginate impression was taken of each patient'sdental arcb for fabrication of stone casts, LC Block-Out Resin {Ultradent) was applied to tbe facial sur-faces of the incisors and premolars to be bleached toan approximate tbicloiess of 0,5 mm. The bieachingtrays {0,9-mm-thick, Sof-Tray Sheets, Ultradent) werevacuum formed to the stone casts and trimmed alongthe gingiva! margins. The bleaching trays werechecked for fit and to ensure that they did not impingeon the soft tissue.

Patients were shown how to load the bleachingtrays. The patients were given verbal and writteninstructions for which teeth and which side receivedwhich numbered syringes. The patients wereinstructed to wear the loaded bleach trays overnightfor 14 consecutive nights. However, if the patientexperienced tooth sensitivity, he or she was advised tocontinue bleaching if the tooth sensitivity was mild or

Toolli colorgeneralized coior change; iocaiized color change; white spols

A. BTooth sensilwity

rare; occasional; frequent; constant; mild; moderate; severe;spontaneous; elicited by hot; elicited by cold

Fig 1 Visual analog scales for looth coior and tooth sensiliuity.Patients were asked to mark an X on each line to represent Ihedegree of tooth color and tooth sensitivity presen! for that day,in the evening, before they began the next day's bleachingtreatment. On the tooth color soale, A represented "as dark aspossible" and B represented "as light as possibie" on the linescale. On the tooth sensitivity scale, A represented "no sensitivity"and 6 represented "extreme sensitivity " Patients were aiso askedto circle as many descriptors as applied, and space was given tcrecord other comments or notes.

moderate or to skip 1 or 2 days of bleaching if he orshe felt a higher degree of tooth sensitivity. The patientcould elect to discontinue the home hleaching treat-ment at anytime,

A daily log form was provided to patients to recordtreatment variables. Patients were asked to monitortheir perception of tooth whitening and tooth sensitiv-ity on a daily basis (immediately after removal of thebleaching tray) on a 100-mm visual analog scale foreacb side of the dental arch (Fig 1), Patients could fur-ther characterize their tooth whitening and tooth sen-sitivity by circling descriptors tbat, for example, coulddetail the frequency or location of tbe tootb sensitivity,or by offering comments.

At tbe end of the bleacbing treatment, a postopera-tive photograph was taken under standardized lightingconditions using the same camera and dental opera-tory light, with and without a matching preoperativeand postoperative Lumin Vacuum shade guide tab.The daily log sheets were collected.

The daily entries for whiteness and tooth sensitivitywere measured from the visual analog scales to thenearest millimeter Wilcoxon Signed Ranks Tests for aPaired Difference (P < .05) were performed on all therecorded visual analog scores to compare the overalltooth sensitivity and tooth whiteness results betweenthe control and PF groups and case by case to com-pare the tooth sensitivity and tooth wfiiteness by theindividual patient and by day.

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Fig 2 Mean visual analog score (VAS) tor tooth sensitivity by day.(PF] Potassium nitrate-fiuoride group.

Fig 3 Mean visuai anaiog score (VAS) lor tooth coior by day. (PF)Potassium nitiate-liuoride group.

RESULTS

The average daily treatment time was 7,1 + 1.2 hours.One patient chose to discontinue treatment after 9days because of tooth sensitivity on the control side. Atotal of 9 treatment days (out of a potential total of294 treatment days) were missed by the patients,either because of general tooth sensitivity or for per-sonal reasons (eg, forgot or too tired).

The mean visual analog tooth sensitivity scores foreach day for both groups are shown in Fig 2, Toothsensitivity generally increased during the courseof treatment for both the control and PF groups.However, two patients reported no tooth sensitivitythroughout the course of treatment, and severalpatients reported reductions or fluctuations in toothsensitivity, as opposed to a steady increase, during thecourse of treatment. The range of tooth sensitivity wasfrom 0 for both the control and PF groups to a visualanalog score of 82 for the control group and 96 for thePF group.

Overall, the addition of PF significantly decreasedtotal tooth sensitivity compared with the control. TheWilcoxon Signed Ranks Tests showed a significantreduction in tooth sensitivity for the PF group com-pared with the control group on days 3, 9, 10, U, and

13, There were no days on which the mean tooth sen-sitivity score for the PF group was significantly higherthan that for the control group. For eight of thepatients, the PF-treated side was signiflcantly less sen-sitive than the control side during the course of treat-ment. For two of the patients, the control side was sig-nificantly less sensitive than the PF-treated side duringthe course of treatment. No patient reported sensitivityproblems after the cessation of bleaching treatment.

The mean visual anaiog tooth whiteness scores foreach day for both groups are shown in Fig 3, Sub-jectively, tooth whiteness generally increased duringthe course of treatment for both the control and PFgroups. The range of tooth whiteness was from 0 forboth the control and PF groups to a visual analogscore of 95 for the control group and 97 for the PFgroup.

Overall, the addition of PF did not significantlychange the perception of tooth whiteness during thecourse of bleaching compared with the control. Therewere no speciflc days during the course of treatmenton which perception of tooth whiteness between thePF and control groups was significantly different.During the postoperative visit and on photographs, noobvious clinical differences between the control andPF sides were detected.

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DISCUSSION

The incidence and severity of tooth sensitivity duringthe course of an at-home bleaching treatment varies.The possible risk factors and causes of tooth sensitivityinclude the patient's inherent sensitivity, the pH of thewhitening solution, the concentration of the activehleaching ingredient, and the daily frequency of bleacbapplication,'-'' Tooth sensitivity has heen attributed totbe penetration of hydrogen peroxide into the pulpchamber,^-" It is speculated that reducing the hydro-gen peroxide concentration or the duration of bleachapplication could reduce tooth sensitivity but wouldalso likely reduce the tooth whitening as well. Henceother desensitizing agents, such as potassium nitrate,have heen added to carbamide peroxide bleach formu-lations in an attempt to decrease the tooth sensitivityexperienced by the patient without reducing the con-centration of tbe active bleaching ingredient.

Both potassium nitrate and fluoridated materialshave been used to treat tbe problem of dentin hyper-sensitivity not related to tooth bleaching. It has heensuggested that potassium nitrate reduces tooth hyper-sensitivity hy preventing nerve repolarization after ini-tial depolarization, thereby reducing puipal or dentinalsensory nerve activity.'-'^ Several desensitizing tooth-pastes contain potassium nitrate at a 5% concentration.

Fluoride, in pastes, gels, or varnishes, has also heenused hy dentists to reduce tooth sensitivity. The pro-posed mechanism of action is the occlusion of denti-nal tuhules by fluoride precipitates. Calcium fluorideand fluorapatite are the major products deposited onenamel and dentin surfaces after tbeir exposure tohigh- and low-concentration topical fluoride vehicles,respectively,"*-' A favorable condition for formation offluorapatite in sound enamel is a constant low con-centration (1 ppm) of fluoride for at least 24 bours,'^

The patients in this study concurrently used a fluo-ridated toothpaste. The low 0.11% fluoride ion con-centration in the PF group is similar to that found inregular home-use toothpastes and some rinses fordaily use. The added benefit specifically provided bythe fluoride in the PF test material on tooth sensitivityis unknown.

This study was not designed to differentiate which,if either, of the two ingredients, potassium nitrate orfluoride, was primarily responsible for the reduction intooth sensitivity. Another study showed that both 5%potassium nitrate and 1,000 ppm sodium fluoridereduced tooth sensitivity when applied for 10-30 min-utes before and/or after bleacbing.'' In this study, therewas a significant reduction in reported tooth sensitivityon day 3, and the mean tooth sensitivity scores for thecontrol and PF groups begin to diverge thereafter.Generaüy, brushing with a potassium nitrate-contain-

ing toothpaste will reduce sensitivity in 2Similarly, prolonged use of a fluoride gei (up to 4weeks) is necessary to achieve satisfactory dentinaldesensitization,^" However, the duration of daily expo-sure to potassium nitrate and fluoride in the PF mater-ial during a bleaching treatment approximates severalhours, whereas the duration of daily exposure topotassium nitrate and fluoride from brushing withdesensitizing and fluoride pastes would approximateseveral minutes at most. Case reporis of the use ofpotassium nitrate-containing dentifrices in a tray wornfor several hours a day suggested that relief from toothsensitivity could be achieved after one week, '

Tbe split-mouth design allowed for simultaneoususage of both materials and a paired study design.Patients were asked to indicate if a speciflc tooth inthe arch was more or less sensitive than the othersduring the hleaching treatment. There was no evi-dence of less sensitivity for the central incisor on thecontrol side or more sensitivity for the centra! incisoron the test side of the arch. Similarly, there was noevidence of less whitening for the central incisor onthe control side or more whitening for the centralincisor on the test side of the arch. Such findingswould have indicated significant spillover of the con-trol and test materials across the midline.

Reduced overall tooth sensitivity is a benefitbecause it could improve patient compliance andpatient comfort during tbe bleaching treatment. Theaddition of potassium nitrate and fluoride to a car-bamide peroxide bleach material reduced the totaltooth sensitivity experienced during at-home bleach-ing. The subjective and clinical evaluation of toothwhitening suggested that the potassium nitrate andfluoride did not significantly affect the bleacbing effi-cacy of the bleaching gel v/ithin the parameters of thisstudy. The lack of a stafistically significant differencein perceived whiteness hetween the control and PFgroups does not necessarily indicate that there wereno differenees hut does suggest that the two bleacbingmaterials exbibited comparable efficacy.

CONCLUSION

1. A lO /o carbamide peroxide bleaching gel contain-ing potassium nitrate and fluoride produced lesstooth sensitivity than did the control 10% car-bamide peroxide bleaebing gel without potassiumnitrate and fluoride during a 2-week at-homebleaching treatment.

2. There was no stafisfically significant difference inthe degree of perceived whitening caused by tbe10% carbamide peroxide bleaching gels with orwithout potassium nitrate and fluoride.

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