A Clinical Study to Determine the Tooth Hypersensitivity Reduction in Subjects Who Brushed with the New Colgate 360° Sensitive Toothbrush

John Gallob, DDS;¹ Pejmon Amini, DDS;² Jimmy Qaqish, BS;³ Pat Chaknis, BS;⁴ James H. Kemp, BA;⁵ and William DeVizio, DMD6

¹Biosci Clinical Research—America, Las Vegas, Nevada

²Biosci Clinical Research—America, Las Vegas, Nevada

³Biosci Clinical Research—America, Las Vegas, Nevada

⁴Colgate-Palmolive Technology Center, Piscataway, New Jersey

⁵Colgate-Palmolive Technology Center, Piscataway, New Jersey

⁶Colgate-Palmolive Technology Center, Piscataway, New Jersey

Dentin sensitivity is a common condition that has been reported to affect between 8% and 35% of the population.¹ One theory suggests that open tubules are a prerequisite for dentin sensitivity. That theory, the Brannstrom hydrodynamic model, suggests that exposed root surfaces may contain open/exposed dentin tubules that provide a conduit for fluid movement. The rapid fluid movement in response to certain stimuli may cause distortion of intradental nerves and generate a pain response.² Current hypersensitivity treatments concentrate on occluding the tubules and blocking neural transmission. It generally is accepted that occluding dental tubules will reduce dentin permeability and sensitivity. Most treatments for dentin sensitivity attempt to inhibit sensitivity, either by sealing the tubules as a result of altering their contents or by creating insoluble calcium complexes thus forming mechanical or chemical plugs.^3,4

Dentin is a calcified tissue, covered by enamel on the crown and cementum on the root and surrounds the entire pulp. By weight, 70% of dentin consists of the mineral hydroxylapatite; 20% is organic material and 10% is water.⁵ Dentin consists of microscopic channels, called dentinal tubules, which radiate outward through the dentin from the pulp to the exterior cementum or enamel border. These tubules contain fluid and cellular structure and, as such, have a degree of permeability that can increase the sensation of pain. Dentin formation begins before enamel forms and is initiated in the late stage of tooth development when the cells of the inner enamel epithelium induce the cells of the dental papilla to differentiate into odontoblasts. Odontoblasts are large columnar cells arranged in an epithelioid sheet along the junction between dentin and pulp down to the root apex. On initial dentin formation, odontoblasts move pulpally away from the primitive amelodentinal junction, leaving behind a tubular structure known as the odontoblast process. A pulpal nerve fiber wraps around the base of this process. The odontoblast process, among other functions, aids in the secretion of tubular dentin and maintains the dentinal tubule and dentinal fluids.⁵ The number of tubules per unit area vary depending on location because of the decreasing area of the dentin surface in a pulpal location. In humans, there are some 65,000 tubules per mm² near the pulp but only 15,000 tubules per mm2 near the periphery of the tooth.⁶ The tubules follow a sinuous course from the amelodentinal junction and the cementodentinal junction and are conical, being wider at the pulpal end than at the periphery. A recent study indicated that the mean number of tubules in the middle part of the root was significantly lower than in the middle part of the crown.⁷

To summarize, the hydrodynamic theory proposes that dentin could be thought of as composed of hollow tubules containing fluid or semifluid material. This fluid follows the same physical laws as fluid in capillary tubes. If the fluid is displaced rapidly enough, a shift of fluid in either direction could deform the odontoblast layer or stimulate nerve fibers and give rise to pain.

Although certainly not the only cause, frequent, overzealous toothbrushing (excessive force on the gums) may remove periodontal tissue mechanically, thus exposing the tubules and eventually resulting in dentin sensitivity.⁸

The Colgate® 360°® toothbrush (Colgate-Palmolive Co, New York, NY), which has been commercially available for the past 4 years, has been clinically proven to be effective in removing harmful desquamated epithelial cells and harmful bacterial in the mouth.^9-11 It also has been clinically proven to improve bad breath, remove plaque, reduce gingivitis, and remove dental stain.^12-15 In addition to the benefits of the original Colgate 360° toothbrush, a newly designed Colgate® 360°® Sensitive toothbrush (Colgate-Palmolive Co) has been shown in vitro to reduce tooth sensitivity.16 The Colgate 360° Sensitive toothbrush has gentle-cleaning ultrasoft multifunctional bristles that have been proven to be 48% softer than a leading soft manual toothbrush.¹⁷ It also has unique rubber cups that, when combined with the soft bristles, result in less wear on exposed root surface.¹⁸ A recent in situ and in vitro dentin disc study showed that brushing with this toothbrush altered the surface morphology of the dentinal surface by occluding the dentinal tubules, thereby causing a reduction in both dentin permeability and sensitivity.¹⁹

The objective of this monadic clinical study was to evaluate the ability of this toothbrush in vivo to reduce tooth tactile and thermal (air-blast) sensitivity in patients who used the Colgate 360° Sensitive toothbrush (Figure 1) during an 8-week period. The study protocol was submitted to and approved by an Institutional Review Board in compliance with international regulations.

Materials and Methods

This clinical study used a monadic, longitudinal study design. Adult men and women from the Las Vegas, Nevada area were enrolled in the study based on the following criteria:

• Participants had to be between the ages of 18 and 70 years and generally healthy, as well as having used only a nondesensitizing dentifrice for 3 months before entry into the study.

• Participants needed to be available for the duration of the study and to sign an informed consent form.

• Participants were required to present, at baseline, two teeth anterior to the molars that exhibited both tactile and thermal sensitivity (a tactile sensitivity score of at least 50 and a thermal sensitivity score of at least 2) and demonstrate cervical erosion/abrasion or gingival recession.

• Those were excluded from the study if they presented any gross oral pathology, chronic disease, or history of allergy to the test products; had advanced periodontal diseases or treatment for periodontal diseases (including surgery) within the past 12 months; presented any sensitive teeth with a mobility score greater than 1; presented teeth with extensive or defective restorations (including prosthetic crowns), suspected pulpitis, caries, cracked enamel, or used as abutments for removable partial dentures; currently used anticonvulsants, antihistamines, antidepressants, sedatives, tranquilizers, anti-inflammatory drugs, or daily analgesics; had participated in a desensitizing dentifrice study or reported regular use of a desensitizing dentifrice within the past 3 months; were currently enrolled in any other clinical study; were pregnant or lactating; or presented any medical condition that prohibited not eating or drinking for 2 hours.

• Those with allergies to oral care products, personal care consumer products, or their ingredients also were excluded from the study.

Prospective study participants reported to the clinical facility, having refrained from all oral hygiene procedures and gum-chewing for 4 hours, and from eating, drinking, and smoking for 2 hours before their examinations. All prospective subjects who met the inclusion/exclusion criteria received a baseline examination for tactile and thermal tooth sensitivity, along with an oral soft- and hard-tissue assessment. To qualify for further participation in the study, subjects needed to present two teeth that were sensitive to both sensitivity stimuli.

Qualifying patients were provided with a supply of a nondesensitizing dentifrice (Colgate® Cavity Protection Great Regular Flavor Fluoride toothpaste, Colgate-Palmolive Co) and with the test toothbrush: a toothbrush designed to aid in the relief of tooth sensitivity (Colgate 360° Sensitive).

The study toothbrush was supplied in a plain white box with the words Colgate 360° on the toothbrush. The toothpaste was overwrapped in white and labeled with toothbrushing instructions. Patients were instructed to brush their teeth for 1 minute, twice daily (morning and evening), using only the toothbrush and dentifrice provided and to refrain from any other oral hygiene procedures throughout the duration of the study. There were no restrictions regarding diet or smoking habits during the course of the study.

After 4 weeks and again after 8 weeks of product use, patients returned to the dental clinic for follow-up examinations of tactile and thermal sensitivity of the baseline-designated sensitive teeth. Examinations of the oral soft and hard tissues also were performed at these follow-up visits. All examinations were performed by the same dental examiner using the same procedures as at baseline. At the 4-week and 8-week examinations, patients also were interviewed with respect to the presence of adverse events.

Clinical Scoring Procedures

Tactile Sensitivity

Tactile sensitivity was assessed by the use of the Yeaple Probe (Model 200A Electronic Force Sensing Probe, XiniX Research, Inc, Portsmouth, NH) using a No. 19 explorer tip (Figure 2). The probe was calibrated at least once daily. Teeth that had been identified by the patient as sensitive and had demonstrated accompanying abrasion, erosion, and/or gingival recession were evaluated by stroking the probe across the buccal surface at the cementoenamel junction, perpendicular to the tooth. The preset force exerted by the probe initially was set to 10 g and was increased progressively in 10-g increments, until the patient first reported experiencing discomfort. At each examination for sensitivity, the testing for tactile sensitivity preceded the testing for thermal sensitivity.^20,21

At the baseline examination for sensitivity, any tooth for which no indication of discomfort had been elicited upon application of a 50-g force was deemed to be nonsensitive and was ineligible for further inclusion in the study. For each examination, a subjectwise score for tactile sensitivity was obtained by taking the average of the tactile sensitivity scores attained from the two baseline-designated sensitive teeth. Higher scores on this index correspond to lower levels of dentinal sensitivity.

Thermal Sensitivity

Thermal sensitivity was assessed by delivering a 1-second air blast to the buccal surface of the tooth at a pressure of 60 psi (± 5 psi) and temperature of 70°F (± 3°F), using a standard dental-unit air syringe. The tested tooth was isolated from the adjacent distal and mesial teeth by the placement of the examiner’s fingers over those teeth. The patient’s response to the air blast was recorded using the Schiff Air Sensitivity Scale and scored as follows:²²

• 0 = Tooth/subject does not respond to air stimulus.

• 1 = Tooth/subject responds to air stimulus but does not request discontinuation of stimulus.

• 2 = Tooth/subject responds to air stimulus and requests discontinuation or moves from stimulus.

• 3 = Tooth/subject responds to air stimulus, considers stimulus to be painful, and requests discontinuation of the stimulus.

At each examination for sensitivity, the testing for thermal sensitivity was performed approximately 5 minutes after the testing for tactile sensitivity. At the baseline examination for sensitivity, any tooth for which the thermal sensitivity score was less than 2 was deemed to be nonsensitive and ineligible for further inclusion in the study. For each examination, a subjectwise score for thermal sensitivity was obtained by taking the average of the thermal sensitivity scores obtained from the two baseline-designated sensitive teeth.

Oral Soft- and Hard-Tissue Assessment

The dental examiner visually examined the oral cavity and perioral area, using a dental light and dental mirror. These examinations included an assessment of the soft and hard palatal mucosa, gingival mucosa, buccal mucosa, mucogingival fold areas, tongue, sublingual area, submandibular area, salivary glands, and tonsilar and pharyngeal areas.

Adverse Events
Adverse events were assessed based on interviews with the patients and dental examination of the patients by the investigator.

Statistical Methods

Statistical analyses were performed separately for the tactile and thermal sensitivity scores. Paired t-tests were used to evaluate the changes in sensitivity scores between the baseline and follow-up examinations. All statistical tests of hypotheses were two-sided and used a level of significance of α = 0.05.

Results

Of the 44 patients who qualified for participation in this study, 42 completed their 8-week examinations. Table 1 presents a summary of the age and gender of the study population who completed their 8-week examinations. Throughout the study, no adverse effects on the oral soft or hard tissues of the oral cavity were observed by the examiner or reported by the participants when questioned. The patients who did not complete the study dropped for reasons not related to the product.

Tactile Sensitivity

Table 2 presents a summary of the tactile sensitivity scores measured at each of the three study examinations and also provides a summary of the analysis of the changes in scores between the baseline and follow-up examinations. The mean tactile sensitivity score at baseline was 10, indicating that all teeth in all patients responded to the probing at the lowest level of applied force (10 g), therefore, the highest level of sensitivity. At the 4-week examinations, the mean tactile sensitivity score was 20.35, which represented a statistically significant, 10.35-unit increase from baseline, indicative of an improvement in tooth sensitivity. At the 8-week examinations, the mean tactile sensitivity score was 32.73, which represented a statistically significant 22.73-unit increase from baseline, again indicative of evidence of less sensitivity.

Thermal Sensitivity

Table 3 presents a summary of the thermal sensitivity scores measured at each of the three study examinations and also provides a summary of the analysis of the changes in scores between the baseline and follow-up examinations. The mean thermal sensitivity score at baseline was 2.36. At the 4-week examinations, the mean thermal sensitivity score was 1.73, which represented a statistically significant 0.63-unit decrease from baseline, indicative of an improvement in tooth sensitivity. At the 8-week examinations, the mean thermal sensitivity score was 1.40, which represented a statistically significant 0.96-unit decrease from baseline, again indicative of an improvement in tooth sensitivity.

Adverse Events
No adverse events were noted during this study.

Discussion and Conclusion

Dentin sensitivity is a common condition, which can affect anyone and is characterized by a sharp or aching pain of the tooth. It can occur from a variety of stimuli, one of which is a result of exposed dentin because of gingival recession caused by overzealous toothbrushing, especially when using a toothbrush with hard bristles.

The goal of toothbrushing is to provide a clean and healthy mouth. Improper brushing, though, can be destructive, damaging the teeth and gums. Too much force put on the toothbrush while brushing will result eventually in receded gums. When gum recession has occurred, the dentin is exposed, resulting in tooth sensitivity to cold, sweet, or touching. A proper toothbrush and proper toothbrushing is essential to good oral health. The use of a soft-bristled toothbrush and brushing with a light touch with an up-and-down motion against the teeth can minimize dental problems.²³

This monadic longitudinal in vivo clinical study provided an assessment of a newly designed toothbrush with respect to its ability to reduce dentinal hypersensitivity caused by tactile or thermal (air-blast) stimulation. The toothbrush is a new variant of the commercially available Colgate 360° toothbrush. The new brush was designed with ultrasoft tapered bristles—one laboratory test showing 48% softer bristles when compared with a leading soft manual toothbrush¹⁸—and was designed with unique rubber cups that together with the ultrasoft bristles, result in less wear on exposed root surface. The toothbrush also has been proven clinically to remove up to 40% more plaque than a leading soft manual toothbrush and has been shown to affect the surface morphology of dentin. In a similar clinical study, it has been shown to reduce tactile and thermal tooth sensitivity.^16,19,24

The data generated from this clinical study showed that after 4 weeks of brushing with the Colgate 360° Sensitive toothbrush, there was a statistically significant 10.35-unit increase in tactile sensitivity scores and a statistically significant 22.73-unit increase in tactile sensitivity scores after 8 weeks of brushing with the toothbrush. The data also demonstrated that there was a statistically significant 0.63 decrease in thermal (air-blast) sensitivity scores after 4 weeks of brushing with the Colgate 360° Sensitive toothbrush and a statistically significant 1.96 decrease after 8 weeks of brushing with the brush. It, therefore, can be concluded that brushing with a Colgate 360° Sensitive toothbrush can help reduce the painful effects of tooth sensitivity.

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