Recently, whitening systems used by patients at home have become increasingly popular.^10–13 However, tooth-whitening procedures may adversely affect both hard^14–16 and soft^17–20 tissues in the oral cavity, as well as the dental pulp,^21–23 although when they are performed properly, their effects generally are mild and transient. Mucosal irritation often is related to tray design or improper application of bleaching agents. Adjustment of the tray or modification of the technique used to apply the agent generally eliminates the irritation.

One commonly reported potential side effect of home-use whitening systems is tooth sensitivity, which usually is mild and transient, but occasionally may cause significant discomfort. To date, only anecdotal reports and retrospective studies have addressed tooth sensitivity after whitening treatment.^13,18,20,21 We conducted a randomized prospective double-blind study to determine the incidence of tooth sensitivity after home whitening treatment. We hoped that data obtained as a result of this investigation could enhance dental practitioners’ ability to more knowledgeably discuss the risks and benefits of home bleaching with their patients.

	MATERIALS AND METHODS

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
This clinical investigation was approved by the scientific review committee and by the committee for the protection of human subjects at the Naval Medical Center, San Diego. Subjects were recruited from among patients receiving care at the dental department at the Naval Medical Center. After a pilot study in which three of 10 subjects engaged in home whitening treatment experienced moderate sensitivity, we determined the appropriate sample size using power analysis ( = .05). One hundred adult dental patients participated in the study. As recommended by the manufacturer, pregnant patients were not enrolled as subjects.

After obtaining written informed consent from each subject, the principal investigator (W.C.) performed the clinical examination, fabricated a custom bleaching tray with reservoirs and instructed the subject on use of the system and on the data collection method. Subjects were instructed to apply only enough gel to fill the buccal reservoir space in the tray and to wear the tray for one three- to four-hour period daily.²⁴ Parameters recorded at baseline included the subject’s age, sex, plaque index score,²⁵ gingival recession status, caries status, dentifrice being used and history of tobacco use. Subjects were instructed to continue their customary oral hygiene regimen and to continue using their current dentifrice. The associate investigator (M.J.) dispensed kits containing either bleaching gel (Opalescence F1 [5 percent carbamide peroxide with 0.11 percent—1,100 parts per million—weight/weight fluoride ion], Ultradent Products Inc., South Jordan, Utah) or identically packaged placebo gel (glycerin, U.S.P.) obtained from the manufacturer. Using a computerized randomization program (dBase randomization program, manufactured at the time of the study by Borland Software Corp., Scotts Valley, Calif., now manufactured by dBase Inc., Vestal, N.Y.), we randomly determined the contents of the kits. We evaluated sensitivity by interviewing each subject on a weekly basis for four weeks and recorded it using the following scale:

– no changes noted;

– 1 = mild sensitivity—slight change noted, no interference with function, well-tolerated;

– 2 = moderate sensitivity—definite change noted, some interference with function, necessity of avoiding certain foods;

– 3 = severe sensitivity—subject considered discontinuing treatment, major interference with function, necessity of avoiding many foods.

The principal investigator conducted all weekly evaluations; neither the subject nor the principal investigator was aware of the nature of the gel being used. After data collection was completed, the code was broken, and the principal investigator issued bleaching gel to subjects who had used a placebo, so that they might accomplish tooth whitening.

	RESULTS

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Demographic and baseline data. Subject demographics and baseline data are summarized in the table. Fifty-seven women and 43 men ranging from 19 to 55 years of age took part in the study.

Gingival recession status. Twenty-eight subjects had no gingival recession; 52 subjects had at least one tooth with 1 millimeter of gingival recession; 16 subjects had at least one tooth with 2 mm of gingival recession; four subjects had at least one tooth with 3 mm of gingival recession. We saw no recession greater than 3 mm. The magnitude (0–3 mm) and distribution of recession was similar for the carbamide peroxide and placebo groups.

Dental caries status. We detected no dental caries in any subject.

Dentifrices used. Fifteen different dentifrices were recorded, all containing some type of fluoride; seven subjects reported using a tooth-whitening dentifrice.

Tobacco use. Fourteen subjects reported a history of tobacco use (eight subjects from the carbamide peroxide group, six subjects from the placebo gel group).

Sensitivity status. No existing tooth sensitivity was reported at baseline.

Figures 1 through 4 summarize the findings from weekly follow-up evaluations. All subjects (50 using carbamide peroxide gel and 50 using a placebo gel) completed the study, and all reported using the gel provided as directed.

View larger version (34K): [in this window] [in a new window]   Figure 1. Subjects’ self-rated tooth sensitivity after one week of whitening or placebo gel. 0: No sensitivity. 1: Mild sensitivity. 2: Moderate sensitivity. 3: Severe sensitivity.

View larger version (34K): [in this window] [in a new window]   Figure 2. Subjects’ self-rated tooth sensitivity after two weeks of whitening or placebo gel. 0: No sensitivity. 1: Mild sensitivity. 2: Moderate sensitivity. 3: Severe sensitivity.

View larger version (33K): [in this window] [in a new window]   Figure 3. Subjects’ self-rated tooth sensitivity after three weeks of whitening or placebo gel. 0: No sensitivity. 1: Mild sensitivity. 2: Moderate sensitivity. 3: Severe sensitivity.

View larger version (36K): [in this window] [in a new window]   Figure 4. Subjects’ self-rated tooth sensitivity after four weeks of whitening or placebo gel. 0: No sensitivity. 1: Mild sensitivity. 2: Moderate sensitivity. 3: Severe sensitivity.

After two weeks of treatment (Figure 2), 27 (54 percent) subjects using the carbamide peroxide gel and 24 (48 percent) subjects using the placebo gel reported mild sensitivity. Three (6 percent) subjects using the carbamide peroxide gel and no subjects using the placebo gel reported moderate sensitivity. No subjects in either group reported severe sensitivity after two weeks. Twenty (40 percent) subjects using the carbamide peroxide gel and 26 (52 percent) of those using the placebo gel reported no sensitivity.

After three weeks of treatment (Figure 3), 18 (36 percent) subjects using the carbamide peroxide gel and 14 (28 percent) subjects using the placebo gel reported mild sensitivity. One (2 percent) subject using the placebo gel and no subjects using the carbamide peroxide gel reported moderate sensitivity. No subjects in either group reported severe sensitivity after three weeks. Thirty-one (62 percent) subjects using the carbamide peroxide gel and 36 (72 percent) of those using the placebo gel reported no sensitivity.

At the conclusion of the study, after four weeks of treatment (Figure 4), four (8 percent) subjects using the carbamide peroxide gel and three (6 percent) subjects using the placebo gel reported mild sensitivity. No subjects in either group reported either moderate or severe tooth sensitivity after four weeks. Forty-six (92 percent) subjects using the carbamide peroxide gel and 47 (94 percent) of those using the placebo gel reported no sensitivity.

Statistical analysis. We applied multiple logistic regression analysis to baseline parameters and sensitivity data. We found no significant differences between sensitivity associated with 15 percent carbamide peroxide gel and that associated with placebo gel. We did see a significant correlation between gingival recession and sensitivity (P < .003, P < .001, P < .001 and P < .002 at one, two, three and four weeks, respectively). Figure 5 illustrates the percentage of patients reporting sensitivity based on the amount of gingival recession recorded at baseline. No other recorded parameters showed statistically significant correlations to sensitivity.

View larger version (35K): [in this window] [in a new window]   Figure 5. Percentage of patients reporting sensitivity based on gingival recession.

	DISCUSSION

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

Tooth-whitening treatment has become very popular in recent years. Before deciding to proceed with treatment, patients considering home whitening should be informed of its potential risks and benefits. Dentist-supervised home-use whitening systems have been shown to be safe and effective, resulting in only mild, transient changes in gingival and pulpal tissues. An agent commonly used for home whitening is carbamide peroxide in concentrations of 10 to 20 percent. Adverse effects of this treatment may include gingival irritation and tooth sensitivity. Gingival irritation can be minimized by reducing contact of the bleaching gel with gingival tissue. This is best accomplished by adding a thin layer of acrylic to the facial surfaces of teeth on the plaster cast before adapting the tray material, thereby creating a reservoir for the gel (Figure 6). This is one important reason why custom bleaching trays provided by a dentist are safer and more effective than over-the-counter trays. In addition, when the whitening process is supervised, patients can be trained to avoid using excessive gel and consequently minimize gingival irritation further.¹¹

View larger version (118K): [in this window] [in a new window]   Figure 6. A thin layer of acrylic is added to facial surfaces of teeth before the bleaching tray is adapted, thus creating a reservoir for the bleaching gel.

It is possible that subjects in this study, including those using the placebo gel, performed overzealous tooth brushing as a result of the Hawthorne effect: people participating in clinical trials may brush more often and more vigorously, and this may have contributed to the sensitivity reported by both the test and control subjects. With the exception of one subject who reported moderate sensitivity with the placebo gel on one occasion, moderate or severe sensitivity was associated only with the carbamide peroxide gel and likely was related to the bleaching agent. The subsequent decrease in sensitivity as treatment progressed may have been due to the fluoride content of the bleaching gel, since topical fluoride has been shown to reduce sensitivity²⁹ and this reduction in sensitivity tends to occur after a week or more of application.³⁰

All subjects in this study completed the four-week course of treatment, after which only 8 percent of subjects using the carbamide peroxide gel and 6 percent of subjects using the placebo gel reported mild sensitivity. This is in agreement with previous reports indicating that home whitening treatment supervised by a dentist may result in sensitivity but that this side effect does not prevent the patient from successfully completing the full course of treatment. In comparing various parameters with reported tooth sensitivity, we found that only gingival recession had a statistically significant relationship (Figure 7). This is in contrast to a report by Haywood,¹¹ but is consistent with findings by Addy and colleagues,³¹ who found a significant correlation between gingival recession and sensitivity in a clinical study of pre-existing dentinal hypersensitivity. It would seem prudent to advise patients who have gingival recession and are contemplating home whitening treatment that they may be more likely to experience sensitivity than would people without gingival recession.

View larger version (43K): [in this window] [in a new window]   Figure 7. A patient who underwent dentist-supervised home-use whitening, before (A) and after (B) treatment. This patient reported moderate tooth sensitivity during the first two weeks of daily application of 15 percent carbamide peroxide gel with 0.11 percent fluoride ion. Patients with gingival recession, as seen here in multiple sites, were more likely to report tooth sensitivity.

Single-episode tooth whitening procedures performed in the dental office have become popular during the past few years.³² Currently, limited data exist regarding the incidence and severity of tooth sensitivity after this one-time treatment.^33,34 Further clinical investigation of in-office whitening procedures could provide additional information that would be valuable to patients who are considering various treatment options.

	CONCLUSIONS

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Home whitening treatment supervised by a dentist using a gel containing 15 percent carbamide peroxide and 0.11 percent fluoride delivered via custom bleaching trays with reservoirs may cause transient mild tooth sensitivity in 54 percent of patients, transient moderate tooth sensitivity in 10 percent of patients and transient severe sensitivity in 4 percent of patients. Patients with gingival recession appear to be more likely to experience tooth sensitivity during home whitening treatment. Tooth sensitivity tends to decrease as treatment progresses and is not likely to prevent patients from successfully completing a full course of home whitening treatment.

View larger version (137K): [in this window] [in a new window]   Dr. Jorgensen is an associate professor of clinical dentistry, Division of Primary Oral Health Care, University of Southern California, School of Dentistry, 925 W. 34th St., Los Angeles, Calif. 90089-0641, email "jorgensm{at}usc.edu". Address reprint requests to Dr. Jorgensen.

View larger version (134K): [in this window] [in a new window]   Dr. Carroll is a captain, Dental Corps, U.S. Navy, and the director, General Practice Residency, Naval Medical Center, San Diego, Calif.