Effect of four different dentifrices applied by customized automated brushing device on enamel surface abrasion: An in vitro profilometric study.

AIM: The aim of this study is to evaluate the enamel surface abrasion using four different dentifrices and a customized automated brushing machine under a profilometer.
MATERIALS AND METHODS: A total of 30 enamel blocks (9 mm × 9 mm × 2 mm) were prepared from freshly extracted maxillary central incisors which were randomly divided into five equal groups (Group 1: specimens brushed with Colgate Total, Group 2: specimens brushed with Colgate Lemon and Salt, Group 3: specimens brushed with Colgate Visible White, Group 4: specimens brushed with Colgate Sensitive, and Group 5: intact enamel surface). Samples were brushed using a customized automated toothbrushing machine for 60 min. A profilometric read out (Ra value) was taken for each group subjected to brushing and also for the control group. STATISTICAL ANALYSIS: Statistical analysis used in this study was one-way analysis of variance followed by post hoc Tukey's test.
RESULTS: Statistically significant differences (P < 0.05) were observed in the values of enamel abrasion (Ra) among Group 1-Group 4 whereas Group 5 (control group) had no significant difference in enamel abrasion (P > 0.05).
CONCLUSION: The highest enamel abrasion was observed in the group with Colgate Visible White toothpaste, and the least enamel abrasion was seen in the group with Colgate Sensitive Plus.

INTRODUCTION

Effective plaque control is critical to the maintenance of oral health because dental plaque is the primary etiological factor in the initiation and development of both caries and periodontal disease.[1] The toothbrush is the principal instrument in general use for accomplishing plaque removal as a necessary part of disease control.[2] However, toothbrush alone does not suffice, and dentifrices have been used in conjunction with toothbrushes since a long time because of its positive chemical effects and delivery of various therapeutic agents which enhance the mechanical plaque control. The ideal dentifrice should provide the greatest possible cleaning action on tooth surfaces with the lowest possible abrasion rates.

Among the components of toothpaste formulations, abrasive agents are important for a given toothpaste to be effective as a dental stain and plaque removing agent. In fact, toothbrushing compliance is reduced under the use of an abrasive-free formula, due to the poor cleaning capacity of the toothbrush alone in removing pellicle, resulting in increased tooth staining and rapid dental biofilm regrowth.[3] However, too much abrasivity can cause dentin abrasion, tooth hypersensitivity, and esthetic problems and eventually damage the masticatory system.

Buccal surfaces of teeth are more prone to abrasion due to overzealous brushing.[4] Abrasion is most commonly associated with toothbrushing on the cervical margins of teeth.[56]

An upper limit of 250 for relative dentin abrasivity (RDA) or 40 for relative enamel abrasivity for a toothpaste is considered safe for everyday use in adults’ International Organization for Standardization (ISO).[7]

To evaluate toothpaste abrasivity, many different techniques have been used, for example, the RDA method, weight, and volume loss techniques which are quantitative techniques, measuring the amount of abraded material removed, as well as profilometer and light reflection techniques, which are qualitative techniques measuring the roughness of the abraded material.[8910]

The aim of this study was to evaluate the enamel surface abrasion using four different dentifrices and a customized automated brushing machine under a profilometer. The four different dentifrices that were used for the study are the ones that are commercially available from Colgate Palmolive India Ltd.

The alternative hypothesis of the study was that differences in the enamel surface abrasion are expected by the different dentifrices.

MATERIALS AND METHODS

Thirty intact freshly extracted maxillary central incisors were taken for the study from the oral surgery department. Teeth were extracted due to periodontal cause and had no caries, cracks, discolorations, or enamel defects.

Infection control protocol

Immediately after extraction, the soft tissue attached to the tooth surface was carefully removed with wet cotton. Occupational safety and health administration (OSHA) and the Centers for Disease Control and Prevention (CDC) recommendations and guidelines were followed. After collection, the samples were transferred to 100 ml of 5.25% sodium hypochlorite solution (Prime Dental Products Pvt. Ltd, Thane, India) stored in amber-colored bottle. The solution was discarded after 30 min, and the teeth were transferred into separate jars containing artificial saliva (Wet Mouth, ICPA Health Products Ltd, Ankleshwar, India. Batch No: C30101) to simulate the oral environment with added 0.1% thymol as antifungal agent. The samples were removed with cotton pliers and rinsed in tap water. The samples were dried by placing them over paper towels and blotted for a few minutes before using them for study .

The teeth were decoronated with the help of diamond disc. Enamel blocks of 9 mm × 9 mm × 2 mm were prepared from the labial surface of the teeth samples. The enamel blocks were embedded in self-curing acrylic resin (DPI-RR Cold Cure Powder and Liquid; Dental Products of India, Mumbai. Batch No.: 101417) of 10 mm × 10 mm × 4 mm dimension [Figure 1a and 1b].

Figure 1

(a and b) Decoronation of the tooth samples and acrylic mounting of the samples. (c) Customized automated brushing machine. (d and e) Profilometric analysis

Construction of automated customized toothbrushing machine

The customized brushing model comprising a direct current motor, handle, and a wooden base was constructed. This device was electrically operated. The apparatus had a screw and wedge design that facilitated easy to-and-fro motion of the toothbrush. Medium bristle toothbrush (Colgate ZigZag, Medium, Colgate Palmolive India, Batch No.: BO4 CP) was used in this in vitro study. The samples were placed below the brush head of the automated customized toothbrushing machine. The bristles of the toothbrush were aligned without pressure contacting the specimen surface in perpendicular fashion, and a linear cleaning movement of 3-cm length was selected for the experiments with manual toothbrush to simulate the most natural brushing method used by patients, which is simple horizontal motion (Scrub Technique) [Figure 1c].

A force of 2 N was chosen for brushing. The cleaning force was generated using a compressing spring and an extending screw.

Specimens were randomly allocated to four groups (Groups 1, 2, 3, and 4) and one control group based on the toothpaste used. The sample size calculation was done by keeping a significance level of 0.05 and a power of 80% to have a chance of detecting a difference as statistically significant. Each group comprised six mounted specimens as follows: [Figure 2].

Figure 2

Group distribution

The dentifrices used in the experiment along with their composition are mentioned in Table 1.

Table 1

Ingredients of the dentifrices used in this study

Toothpaste	Ingredient list
Colgate Total	Water, hydrated silica, glycerin, sorbitol, PVM/MA copolymer, sodium lauryl sulfate, flavor, cellulose, gum, sodium hydroxide, 0.32% wt %, sodium fluoride, sodium saccharin, triclosan
Colgate Lemon and Salt	Calcium carbonate, sorbitol, silica, sodium lauryl sulfate, flavor, sodium silicate, sodium carboxymethylcellulose, sodium monofluorophosphate, sodium bicarbonate, sodium chloride, benzyl alcohol, sodium saccharin, xanthan, lemon oil, D-limonene in aqueous base
Colgate Visible White	Silica, sorbitol, glycerin, polyethylene glycol, sodium tripolyphosphate, tetra potassium pyrophosphate, sodium lauryl sulpate, flavor, cocamidopropyl betaine, sodium carboxymethylcellulose, sodium saccharin, sodium fluoride, xanthan, sodium hydroxide, blue poly 50, titanium dioxide in aqueous base
Colgate Sensitive Plus	Active ingredients: Arginine 8%Other ingredients: calcium carbonate, aqua, sorbitol, bicarbonate, sodium lauryl sulfate, sodium monofluorophosphate (1450 ppm F), aroma, cellulose gum, sodium bicarbonate, tetrasodium pyrophosphate, titanium dioxide, benzyl alcohol, sodium saccharin, xanthan gum, limonene

PVM: Copolymer of methyl vinyl ether, MA: Maleic anhydride

Toothbrushing procedure

Slurry of the dentifrice was prepared according to EN ISO 11609:2010 standard (Dentistry-Toothpastes: Requirements, test methods, and marking). Water and toothpaste were mixed in a ratio of 1:3 by weight and spread over the mounted enamel specimens using a measuring scoop before toothbrushing. Every time of brushing equal amount of slurry was applied. It was placed over the enamel surface and gently spread over the surface using the toothbrush bristle tips.

The average time taken to brush by a person daily is 120 s. Based on this estimation, the maximum contact time for one tooth surface per day is 5 s.[11] Thus, the total brushing time was calculated to be 60 min, which is equivalent to 1 year of brushing.

As literature suggests that a toothbrush should be replaced after 45 days, and thus, after every 4 min of experimentation, the toothbrush used in the apparatus was changed.[12]

Each sample was subjected to 7200 brushing strokes at a rate of 120 strokes/min.[12]

Profilometric analysis

A noncontact type optical three-dimensional (3D) profilometer (R Tech Universal 3D profilometer, Nipkow confocal technologies, Japan) was used for taking profilometric readout for each group subjected to brushing and also for the control group. Before each measurement, the sample's surface was covered with distilled water for 30 s.[12] Excess of water was blotted with absorbent tissue without touching the specimen surface and checked for any remnants macroscopically [Figure 1d and 1e].

The Ra value (μm) reading was recorded using a profilometer with 0.8 mm cutoff and 0.25 mm/s speed. The procedure was performed in three different places which resulted in an average final Ra value.

Statistical analysis

Statistical analysis was performed with the help of Epi Info (TM) 3.5.3. (Centre for Disease Control and Prevention, Kolkata, West Bengal, India) Epi Info is a trademark of the CDC. Descriptive statistical analyses were performed to calculate the means with corresponding standard deviations.

One-way analysis of variance (ANOVA) was done to compare the mean values across the five groups for numerical data (using the F distribution) followed by post hoc Tukey's test which was performed with the help of critical difference or least significant difference at 5% and 1% levels of significance to compare the mean values.

The P value corresponding to the F-statistic of one-way ANOVA [Table 2] is lower than 0.05, suggesting that the one or more treatments are significantly different.

Table 2

The one-way analysis of variance table

Source	SS	Degree of freedom (v)	MS	F statistic	P
Treatment	0.1457	4	0.0364	251.9412	<0.05
Error	0.0036	25	0.0001
Total	0.1493	29

SS: Sum of squares, MS: Mean square

To know the significant mean surface roughness difference among the study groups, post hoc Tukey's (honestly significant difference) [Table 3] comparison test was conducted.

Table 3

Post hoc Tukey test

Treatments pair	Tukey HSD P	Tukey HSD inference (P)
A versus B	0.0010053	<0.01**
A versus C	0.0010053	<0.01**
A versus D	0.0010053	<0.01**
A versus E	0.0010053	<0.01**
B versus C	0.0010053	<0.01**
B versus D	0.0010053	<0.01**
B versus E	0.0192340	<0.05*
C versus D	0.0192340	<0.05*
C versus E	0.0010053	<0.01**
D versus E	0.0010053	<0.01**

HSD: Highly significant difference, **: P<0.01 at confidence interval 99%, *: P<0.05 at confidence interval 95%

DISCUSSION

Brushing associated with dentifrices continues to be the most commonly used and efficient procedure in the practice of oral hygiene in most countries. However, besides having potential benefits of dental plaque biofilm removal and improving oral health, the injudicious use of toothpaste and toothbrush in causing injuries to dental hard and soft tissues has also been documented.[13] Different factors such as brushing technique, force of brushing, duration and frequency of brushing, and type of brush, in particular filament stiffness, influence toothbrush abrasion.[14] The present study was done using Colgate Total, Colgate Lemon and Salt, Colgate Visible White, and Colgate Sensitive Plus. These four toothpastes are indigenous and marketed in India. This is a maiden study using all four toothpastes in these parameters.

In the present study, the brushing technique, brushing force, and duration and frequency of brushing were kept constant by construction of a customized brushing apparatus.

Brushing force is a crucial factor for the development of abrasions.[15] For manual toothbrushes, brushing forces ranged from 1.6 to 3.23 N.[16] Thus, an average of 2 N was selected, which is based on figures existing in available literature. Horizontal brushing movements were executed in the automated toothbrushing machine using a manual toothbrush to simulate the “scrub technique” as it is the most widespread brushing technique among children and adults.[17]

Toothbrushes per se do not cause significant differences in abrasion of human enamel. However, increasing the abrasivity of the toothpaste caused an increase in surface loss of enamel samples.[18] It is well recognized that the capacity of a dentifrice to abrade can be attributed to the nature and size of its particulate abrasive component ranging from 5 to 15 μm. The components of a typical dentifrice include an abrasive (calcium carbonate, calcium phosphate, hydrated alumina, sodium bicarbonate, or a mixture of them), detergent (sodium lauryl sulfate), colorant, flavoring agent, humectant, water, binder, fluorides, tartar control agents, and desensitizing agents.

The particle size and the type of abrasive in each of the dentifrice might have caused the difference in the results among the four experimental groups. All four dentifrices selected were aqueous based to keep the vehicle constant to avoid any discrepancy in the result obtained. Among the constituents mentioned by the manufacturer, silica particles present in Colgate Visible White might have resulted in the highest enamel abrasion which is statistically significant (P < 0.05), followed by Colgate Lemon and Salt and Colgate Total. Colgate Sensitive Plus has sodium bicarbonate and calcium carbonate instead of silica which may have resulted in minimum abrasiveness which is in variance with results obtained by Silva et al. and Ferreira et al.[1920]

Recent studies have demonstrated that radioactive dentin abrasion (RDA)[21] and profilometry are more accurate for evaluation of the abrasivity of toothpastes. The accuracy of profilometry compared to other methods and not damaging the surface during the measurement are among the most important advantages.[2223]

In vivo clinical studies on tooth abrasion are not feasible because of the need for patient follow-up and multi-factorial nature of abrasion and not having fixed reference points in the oral environment. Thus, this in vitro study was conducted using enamel specimens to simulate clinical setting conditions as much as possible.[24]

Limitations

Enamel samples obtained from different age groups could be experimented with which might give differences in abrasion results using different dentifrices

A larger sample size could be taken into consideration in future studies.

CONCLUSION

Within the limitations of this study, the highest enamel abrasion was observed in the group with Colgate Visible White toothpaste, and the least enamel abrasion was seen in the group with Colgate Sensitive Plus.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.