Clin Oral Invest (2000) 4:91–97

© Springer-Verlag 2000

O R I G I N A L A RT I C L E

A.F. Hefti · C. Stone

Power toothbrushes, gender, and dentin hypersensitivity

Received: 19 October 1999 / Accepted: 20 January 2000

Abstract Power toothbrushes require less force for plaque removal than manual brushes. In addition, in vitro studies have indicated that brushing with low force could occlude patent dentin tubules by formation of a smear layer. Hence, lessening the force necessary to remove plaque may reduce dentin hypersensitivity. However, it was recently suggested that the use of an oscillating/rotating power toothbrush could decrease tooth sensitivity as compared to a sonic power toothbrush. Therefore, the objective of the present research was to compare the effect on dentin hypersensitivity of two different types of power brushes, the Optiva Sonicare and the Braun Oral B Ultra Plaque Remover. The null hypothesis was tested in an 8-week, randomized, parallel group, examiner-blind clinical trial. Fifty-nine subjects with a history of dentin hypersensitivity participated. Dentin hypersensitivity-associated pain was elicited using tactile and evaporative stimuli and assessed using a visual analog scale (VAS) instrument. Clinical examinations were carried out at screening and baseline and repeated after 8 weeks of twice daily use of the power brushes. Data analysis was performed on VAS scores obtained at the final visit following adjustment for group differences at baseline. A 35% to 40% reduction in pain as compared to baseline was observed in both treatment groups. Treatment-related differences were not statistically significant. A gender-related effect on dentin hypersensitivity was observed using the tactile stimulus and may merit further investigation. Key words Clinical study · Power toothbrushes · Dentin hypersensitivity · VAS · Plaque A.F. Hefti (✉) College of Dentistry, Ohio State University Columbus, 4133 Postle Hall, 305 West 12th Avenue, Columbus, OH 43210, USA e-mail: [email protected] Tel.: +1-614-292-1421, Fax: +1-614-688-54790 C. Stone Periodontal Disease Research Center, University of Florida, Gainesville, FL 32610, USA

Introduction Dentin hypersensitivity is best described as a short episode of sharp pain that arises from exposed dentin, typically in response to chemical, thermal, tactile, and osmotic stimulation [24, 3]. The prevalence of this painful condition among adults has been estimated at 10–20% [9, 10, 13, 14, 16]. It appears to be higher among females, but the available data are not conclusive [3]. Exposed dentin can result from loss of enamel, removal of cementum, or covering periodontal tissues from roots. Tooth substance loss can be the sequel of attrition, abrasion, dietary erosion, parafunctional habits, or combinations of these factors. Similarly, root exposure has a multifactorial etiology. It can be the clinical manifestation of gingival recession, periodontitis, periodontal therapy, or trauma from habit [12]. In addition, exposed dentin is a frequently observed feature at the cementoenamel junction of newly erupted permanent teeth [30]. Improper, aggressive tooth brushing has been implicated in the etiology of dentin hypersensitivity [4], but in vitro experiments have indicated that tooth brushing also can occlude dentin tubules by creating a smear layer, depending on the amount of force applied [33]. For that reason, tooth brushing could lead to a decrease in dentin hypersensitivity. Breitenmoser et al. [7] have shown that young subjects applied forces between 3 and 5 N to a tooth when cleansing with a standard manual brush. Van der Weijden and coworkers [33] studied brushing forces in subjects using an oscillating/rotating brush. They measured forces of approximately 1.50 N, substantially less than when using manual toothbrushes. An even smaller force of 0.75 N has been recommended for the use of a sonic power brush designed to apply the principle of fluid dynamic action to remove plaque [21, 31]. However, in a recent clinical study of tooth stain removal efficacy [22], some evidence was presented that the use of an oscillating/rotating power brush could decrease tooth sensitivity as opposed to a sonic power brush, which increased the occurrence of sensitive teeth.

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Based upon the above observations, it was of interest to compare the different types of power brushes in a clinical trial designed for the study of dentin hypersensitivity. The Optiva Sonicare (OSC), a sonic power brush, and the Braun Oral-B Plaque Remover (BOB), an oscillating/rotating power brush, were compared in subjects with a history of dentin hypersensitivity. Dentin hypersensitivity elicited by evaporative and tactile stimulation of exposed cervical dentin was used as the primary outcome variable.

Material and methods Protocol The study was conducted according to the Recommendations for Evaluating Agents for the Reduction of Dentinal Hypersensitivity [2] and guidelines published by Kaufman and Kleinberg [18]. The protocol and informed consent form were approved by the University of Florida Health Center Investigational Review Board. All subjects were thoroughly informed about the study’s purpose, risks, and benefits. Study population Demographic information on the sample is presented in Table 1. Subjects were recruited from Alachua County, Florida, using flyers and newspaper advertisements. Informed consent was obtained from all potential subjects. They were considered for study inclusion if they were between 18 and 75 years old, had exposed cervical dentin due to abrasion, erosion, or gingival recession, and complained about dentin hypersensitivity on at least one canine or premolar tooth. At screening, the pain response to both tactile and evaporative stimulation was required to range between 3.0 and 8.0 cm on a 10 cm visual analogue scale (VAS) [28] for at least one tooth per subject. Table 1 Demographic description of the study sample: general assessments Females

Males

BOB

OSC

BOB

OSC

Sample size

19

20

10

10

Mean age Years ±1 SD

33.7 11.26

32.6 10.47

33.1 9.77

33.5 16.67

Nonsmokers

14

17

8

10

5

3

2

0

13 7

7 3

5 5

Smokers

Tooth brushing frequency ≤2× per day 15 >2× per day 4

Number of potential test teeth per subject Mean 11.2 11.0 ±1 SD 1.27 1.41

9.7 2.36

10.8 2.15

Teeth were excluded if they: (1) showed hypersensitivity because of suspected pulpitis, caries, cracked enamel, or large or defective restorations, (2) were used as appliance rests, or (3) were abnormally mobile. Subjects were excluded from participation if they were pregnant or lactating, had a history of hepatitis, diabetes mellitus, tuberculosis, heart disease, and clinically significant medication use that could have interfered with pain perception (e.g., antidepressants, anti-inflammatory drugs, sedatives, and muscle relaxants). Also excluded were subjects exhibiting gross neglect of oral hygiene, rampant caries, advanced periodontitis, history of oral or periodontal surgery within 6 months of baseline visit, and scaling, root planing, or prophylaxis within 6 weeks of baseline visit. Similarly, subjects using nonfluoridated dentifrices or a dentifrice for sensitive teeth, who underwent a desensitizing procedure within 6 weeks of baseline visit, or who had previously used a power toothbrush were excluded. In all, 634 adults were scheduled for a dentin hypersensitivity assessment. At the screening visit, 96 subjects were identified as potential participants. At the baseline visit 2 weeks later, they were reassessed for dentin hypersensitivity. Thirty-four subjects were excluded because they did not meet the inclusion criterion of sustained dentin hypersensitivity at two independent examinations, thus leaving 62 subjects for enrollment. Two subjects were excluded because of protocol deviations, and one was ineligible. No subject withdrew from the study or was excluded for serious adverse events. Therefore, the final sample included 59 subjects for analysis. Test devices, home care instructions Two power brushes were compared: 1. Braun Oral-B Ultra Plaque Remover D9545, Oral-B Laboratories, Belmont, CA, USA 2. Sonicare with quadpacer™, Optiva Corporation, Bellevue, WA, USA Both devices were marketed to the public at the time of study execution. They were maintained according to manufacturers’ guidelines. At the screening, baseline, and 4-week visits, each subject received two tubes of a commercially available dentifrice (Crest Cool Mint Gel), which they used throughout the study. At baseline, standardized brushing instructions were given to each subject. Furthermore, the first tooth brushing session with the assigned device took place in the presence of a dental hygienist who supervised the subject’s brushing technique and made corrections where necessary. Subjects were instructed to brush their teeth twice daily for exactly 2 minutes, using the assigned brush and a timer, and to record date and time of tooth brushing in a diary. The use of mouthwashes or rinsing solutions was prohibited during the study. Besides this restriction, subjects were told to continue their routine oral hygiene procedures. Subjects were asked to refrain from using chewing gum for at least 8 h before reporting to the scheduled

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visits. Similarly, they were asked not to eat or drink for at least 2 h prior to visits and have performed the last tooth brushing at least 1 hour but not longer than 4 hours prior to the examination. Subjects were not allowed to use analgesics 72 hours or less prior to clinical examinations.

fingers and/or cotton rolls. Then, from a distance of 10 mm, a stream of air was directed at an angle of 90° to approximately the same anatomical feature of the tooth as had received the tactile stimulus. The computercontrolled air blast was delivered for 1 s at 50 to 55 p.s.i. pressure and a temperature of 20±2°C.

Visits

Assessment of pain

At the screening visit, each subject completed a medical/dental history. Then, oral soft tissues were examined. Premolars and canines were assessed for dentin hypersensitivity. A full-mouth plaque examination completed the visit. The baseline visit was executed 2 weeks after screening. It started with a review of the medical/dental history. Then, dentin hypersensitivity-associated pain was determined on all teeth that had responded at the screening visit and a full-mouth plaque examination was performed. Subjects were also asked to fill out a Global Dentin Hypersensitivity Experience (GDHE) questionnaire [15]. Only a selection of the total of 18 GDHE questions will be presented here. Finally, subjects were assigned their treatment group and received tooth brushing instructions. Follow-up telephone calls were made 2–3 days following baseline to ensure proper performance and use of the devices. Interim visits were scheduled 4 weeks after baseline visits. Questions or problems the subjects encountered with using the test devices were addressed, and proper device function was assured. Also, correct toothbrush use was checked and reinstructed. The final visit was scheduled to take place 8 weeks after the baseline visit. Examinations were executed as at baseline, strictly observing the same sequence of procedures. Subjects were also requested to return the brushing diaries.

Immediately following stimulation, the subject was asked to gauge pain intensity by directly marking on the VAS, a direct scaling method in which the subject adjusts the length of a line in respect to an anchor point so that line length and pain intensity are proportional. Although simple, the method is reliable [28] and valid [27]. In the present study, the VAS was a 100 mm line with the left and right endpoints indicating “no pain” and “unbearable pain,” respectively. The distance of the mark from the “no pain” anchor was measured to 0.1 mm precision.

Clinical assessments Delivery of tactile stimulus The Yeaple probe [34] with a pointed end tip diameter of 0.3 mm (Williams 14W) was used. It was calibrated prior to each clinical session exactly following the manufacturer’s instructions. Dentin hypersensitivity was elicited by passing the probe tip across the cervical aspect of the tooth just below the cementoenamel junction. The probe force was augmented in 10 g increments, starting at 10 g, until a response was elicited or a force of 50 g was reached, whichever came first. If the subject did not respond at 50 g, the tooth was recorded as negative for dentin hypersensitivity. The force was recorded for each tooth and reproduced at subsequent examinations. Delivery of evaporative stimulus Ten minutes following tactile stimulation, dentin hypersensitivity was elicited using air. Firstly, the examiner isolated the test tooth from the adjacent teeth using the

Assessment of home care Residual plaque was used as a surrogate measure. Plaque levels were determined using the Turesky modification of the Quigley-Hein plaque index [32]. Six sites were evaluated per tooth. Intraexaminer reliability for plaque assessment was studied in a ~10% subsample taken randomly from the study population. The weighted kappa statistic [5] was 0.88, indicating good intraexaminer agreement. The same examiner performed all clinical examinations. Study design and analyses A randomized block design was used. The sample was first stratified according to gender, and blocks of two subjects with similar VAS scores (as obtained at screening using the evaporative stimulus) were formed within each stratum. Then treatments were randomly assigned to subjects within each block. This scheme balanced treatment assignments in each stratum and yielded a balance for gender in each treatment group. Sample size computations assumed type I and type II errors of 0.05 and 0.2, respectively, a minimum important VAS difference of 1.5 between treatments, and a standard deviation of ±2.0. Frequencies and means were used to describe the findings (Tables 2–4). For the analysis of VAS and plaque scores, analysis of covariance (ANCOVA) was used to equate treatment groups on their baseline values and adjust final examination results accordingly. Model assumptions were tested using Levene’s homogeneity of variance test, interaction plots, and residual plots. Furthermore, equality of the slopes of the regression lines for each treatment group was checked using the ANOVA method. Custom hypothesis tests comparing treatment groups at each gender category were performed as indi-

94 Table 2 Description of the study sample: assessment of dentin hypersensitivity at baseline Females

Sample size

Males

BOB

0SC

BOB

OSC

19

20

10

10

Tactile stimulation Number of teeth per subject exhibiting dentin hypersensitivity Mean 6.5 5.7 4.4 6.7 ±1 SD 3.82 3.36 3.31 4.06 Acute pain experience as assessed using a VAS Mean 3.7 4.3 ±1 SD 0.99 1.50

4.5 1.21

3.5 1.46

cated using SPSS’ GLM syntax (see below). Contingency tables were constructed to test the hypothesis that qualitative factors were equally distributed between the treatment groups. The marginal homogeneity test was used to test the equality of paired, ordered responses (Tables 3, 4) obtained using the GDHE questionnaire before and after treatment. Exact P values were computed for nonparametric inference. Data management and analysis were performed using SPSS 8.02 (SPSS, Chicago,Ill., USA) and StatXact 3 (Cytel Software, Cambridge, Mass. , USA).

Results General Information

Evaporative stimulation Number of teeth per subject exhibiting dentin hypersensitivity Mean 5.3 4.9 4.2 5.8 ±1 SD 2.91 2.16 2.04 3.61 Acute pain experience assessed using VAS Mean 5.1 5.6 ±1 SD 1.67 1.53

4.7 1.26

5.1 1.90

Table 3 Severity of dentin hypersensitivity-related pain as reported in questionnaires completed before and after treatment

The data listed in Table 1 show that the two treatment groups were balanced with respect to relevant demographic parameters. At study enrollment, 23 BOB and 25 OSC subjects had experienced dentin hypersensitivity problems for more than 1 year (P=0.750). Despite the seriousness of discomfort, only two subjects from the BOB group and five from the OSC group reported that they had strictly avoided brushing the sensitive sites. Pain occurrence and level were distributed similarly in the two treatment groups (P=0.272 and 0.404, respectively).

Final visit BOB/OSC

Mild

Moderate

Severe Total

BOB: Hypothesis “baseline visit = final visit” P=0.269 Baseline visit

Mild Moderate Severe Total

1 4 1 6

2 10 5 17

1 1 2 4

4 15 8 27

OSC: Hypothesis “baseline visit = final visit” P=0.003 Baseline visit

Mild Moderate Severe Total

Table 4 Frequency of dentin hypersensitivity-related pain as reported in questionnaires completed before and after treatment

1 10 2 13

1 5 4 10

0 2 5 7

2 17 11 30

Home care Historical tooth brushing frequency (Table 1) was not statistically different between treatment groups (P=0.270). Brushing teeth twice a day was standard practice for more than 50% of the sample (BOB: 16, OSC: 17). Most subjects indicated they prefer soft toothbrush bristles to medium or hard bristles. At baseline, the overall mean plaque level was 2.0±0.43. Gender- and treatment group-related differences were best explained by chance (P=0.665 and 0.643, respectively). At the final visit, the overall mean plaque score (1.7±0.45) was 15% lower as compared to

Final visit BOB/OSC

Occasionally

Frequently

Always

Total

1 6 1 8

0 0 1 1

9 14 4 27

0 5 2 7

0 1 5 6

6 15 9 30

BOB: Hypothesis “baseline visit = final visit” P=0.005 Baseline visit

Occasionally Frequently Always Total

8 8 2 18

OSC: Hypothesis “baseline visit = final visit” P=0.002 Baseline visit

Occasionally Frequently Always Total

6 9 2 17

95 Fig. 1 Plaque scores. Turesky modification of Quigley-Hein plaque index (left panel) and VAS scores for dentin hypersensitivity-related pain elicited using a tactile (middle panel) and an evaporative stimulus (right panel). Values are means, SD=1

baseline. The reduction was statistically significant (P=0.001). As a next step, a plaque index was computed for tooth sites that were explored for dentin hypersensitivity. At baseline, this index was significantly smaller than the full-mouth plaque index (1.5±0.68, P<0.001). Treatment- or gender-related differences were not statistically significant. The data gathered at the final visit are presented in the left panel of Fig. 1. Statistical analysis revealed a highly significant (P<0.001) interaction term between treatment and gender, indicating that the treatment difference varied substantially between female and male subjects. Tactile stimulus Overall mean VAS scores at baseline and final examination were 4.0±1.32 and 2.6±1.70, respectively. The 35% decline in VAS between baseline and final examination was statistically significant (P<0.001). VAS scores obtained at baseline (Table 2) were balanced with respect to treatment groups (P=0.597) and gender (P=0.949), but an interaction effect was statistically significant (P=0.038). Clearly, VAS scores assessed in OSC females were higher than in BOB females (4.3:3.7), whereas VAS scores in OSC males were lower than in BOB males (3.5:4.5). A test of the parallelism assumption for ANCOVA demonstrated a significant interaction between gender and the covariate “VAS score at baseline.” For that reason, the subsequent analysis was conducted using a cautious strategy, i.e., independent analyses were performed for each gender stratum. Information on treatment effects for each gender is depicted in the middle panel of Fig. 1. Evaporative stimulus VAS scores obtained at baseline (Table 2) were balanced with respect to treatment groups (P=0.936), gender (P=0.304), and interaction effects (P=0.398). Overall mean VAS scores at baseline and final examination were

5.2±1.59 and 3.1±1.82, respectively. The 40% reduction in VAS between baseline and final examination was statistically significant (P<0.001). The data collected at the final visit did not reveal statistically significant treatment, gender, or interaction effects. The right panel of Fig. 2 offers detailed information on treatment effects for each gender. Questionnaire Fifty-seven of 59 subjects answered both GDHE questionnaires, which were distributed at the first and the final visits. Two questions referred to the subjects’ pain experience, the first addressing severity of pain (Table 3). Twenty-four subjects reported no change between first and final visits (BOB: 13, OSC: 11). Seven subjects noticed more severe discomfort at the end of the study (BOB: 4, OSC: 3). Twenty-six believed that pain severity was lower at the final visit(BOB: 10, OSC: 16). The change between baseline and final visits was statistically significant for OSC (P=0.003) but not for BOB (P=0.269). The second question referred to the frequency of pain experiences (Table 4). Thirty-one subjects experienced no change during the study (BOB: 15, OSC: 16). Two reported more frequent discomfort at the final visit, but 24 indicated they experienced discomfort less frequently (BOB: 11, OSC: 13). The shift was statistically significant (P<0.001) and occurred similarly in both treatment groups.

Discussion Dentin hypersensitivity has been associated with exposed dentin tubules [1, 12]. According to Brännström’s hydrodynamic theory [6], patent dentin tubules play a pivotal role in the transfer of external stimuli to the pulp tissue. Subsequently, Pashley [26] suggested that desensitization could be accomplished by occluding such tubules. The proposed procedure aimed at restoring the original impermeability of dentin. In fact, many of the

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currently advocated therapeutic procedures are based on this paradigm. Some have been shown to be effective in reducing dentin permeability in vitro and dentin hypersensitivity in vivo [4]. While many studies have investigated the effects of desensitizing agents, little attention has been paid to the role of tooth brushing. Recently, Moran et al. [22] observed significantly less dentin hypersensitivity following the 3-week use of an oscillating/rotating power toothbrush when compared to use of a manual or sonic power brush. However, their study was designed primarily to evaluate the stain removal efficacy of toothbrushes, and the effect on dentin hypersensitivity was a secondary finding. In contrast, the present trial was conducted following the American Dental Association’s [2] and Kaufman and Kleinberg’s [18] recommendations for the evaluation of agents for the reduction of dentin hypersensitivity. Using such well-defined conditions, the difference between the power brushes disappeared. In the present study, both treatment groups exhibited less dentin hypersensitivity-related pain at the final visit as compared to baseline. Reductions were 35% and 40% for tactile and evaporative stimulation, respectively. The positive outcome was corroborated by the results of the GDHE questionnaire, in which 46% of all respondents reported less discomfort after using the power brushes for an 8-week period. It may be argued that the reduction observed in dentin hypersensitivity was due to one or several forms of bias. Indeed, caution is recommended before concluding that the pain relief observed in this study is attributable solely to the use of power brushes. No control group was included in this comparative trial, and therefore a placebo effect cannot be ruled out completely. As a matter of fact, placebo-related pain reductions in the range of 30% to 50% of maximum possible pain relief have been reported in many studies [20]. Finally, in studies without control groups, regression to the mean must also be considered as a source of bias. It could have occurred because subjects were required to have a high level of dentin hypersensitivity at screening, and a spontaneous improvement can be expected on purely statistical grounds [11]. Gender differences in the awareness of experimentally induced pain are well-known [29]. In contrast, studies on gender differences in dentin hypersensitivity-related pain are sparse in the peer-reviewed literature. The design applied to the present study used gender as a stratifying variable, which allowed us to analyze the differential effect of gender on treatment within the design. In fact, a subtle and rather unexpected gender difference in response to treatments was observed. Female subjects of the OSC group experienced a statistically significantly greater treatment effect than females of the BOB group as assessed using a tactile stimulus, but such an effect was not seen in male subjects. The outcome was corroborated by the results of the GDHE questionnaire. However, further study will be necessary to establish reliably the relationships between plaque control measures, gender, and dentin hypersensitivity.

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