Effect of an educational intervention on manual toothbrush bristle wear: A light microscopic study : Journal of Indian Society of Periodontology

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Original Article

Effect of an educational intervention on manual toothbrush bristle wear: A light microscopic study

Bhole, Siddhi Shekhar; Vibhute, Nupura A.; Belgaumi, Uzma; Kadashetti, Vidya; Bommanavar, Sushma; Kamate, Wasim

Author Information
Journal of Indian Society of Periodontology: Nov–Dec 2022 - Volume 26 - Issue 6 - p 604-608
doi: 10.4103/jisp.jisp_50_21
  • Open



Oral health is a reflection of the general health and wellbeing of an individual. The single most important contributor in this maintenance of oral and dental health is the habit of daily tooth brushing. From the “chewing sticks” in ancient civilizations to the modern electric toothbrushes,[1] the toothbrush has been the most popular agent used for effective plaque removal and thereby instrumental in the prevention of plaque-related diseases.

Usage of a toothbrush with the most appropriate bristle type and a correct brushing technique are the most important factors in determining the thoroughness of plaque control.[2] Regarding the condition of the toothbrush bristles, the American Dental Association has recommended that the bristle end should be free of sharp, jagged edges and endpoints.[3] This is important as toothbrush with hard, stiff bristles and pointed edges can cause cervical abrasion and gingival recession.[3] Recent studies confirm that bristles with rounded tips cause minimal soft tissue trauma and abrasions and are graded as acceptable.[4]

The use of an appropriate brushing technique is also of paramount importance amongst all the plaque control measures. Application of excessive pressure during brushing and employing an incorrect brushing technique are factors affecting the wear of the toothbrush bristles.[2] Though there are numerous tooth brushing techniques employed by the general population, the most widely acceptable technique with minimal oral tissue damage and maximum plaque removal efficiency is the Modified Bass technique.[5]

An important part of dental practice is contributing to public awareness and patient education regarding the correct tooth brushing techniques and other oral hygiene measures for the prevention of oral diseases. In this regard, the dental professional is expected to be well versed with the correct tooth brushing technique and contribute to oral hygiene maintenance. Hence, this study was conducted to assess the efficacy of an educational module on tooth brushing habits for the newly admitted budding dental professionals by assessing the bristle wear of their toothbrushes.


The present study was conducted in a tertiary health care institute in Maharashtra, India. The study was conducted after ethical clearance (KIMSDU/IEC/08/2019) from the institutional ethical clearance committee as per the ethical principles of the World Medical Association – Declaration of Helsinki and Good Clinical Practice (GCP) guidelines. The estimated sample size for this mono-centric randomized study was calculated from a pilot study on five volunteer participants with the power of the study at 80% and a-value of 0.05 to estimate the difference in means for the outcome variables and was determined to be 25 participants which was further rounded to 30 (n = 30). Forty dental student volunteers were screened and 30 participants meeting the inclusion criteria of the study were recruited. A computer-generated list of random roll numbers was used for selection. The random selection sequence was concealed from both the enrolling participants and the examiner.

The inclusion and exclusion criteria for the study were as follows: To qualify for inclusion, the participants had to be ≥18 years of age, to have a minimum of 5 teeth per quadrant and to have no systemic diseases. Exclusion criteria were open caries, orthodontic appliances, or removable partial dentures.

All the participants were elaborately explained about the purpose, importance, and procedure of the study, and informed written consent was obtained from them after assuring anonymity and confidentiality.

Sixty new toothbrushes with medium bristles from a single brand having the same batch number and date of manufacture were utilized in the study to maintain uniformity. All the participants also received a nonabrasive toothpaste from a single company to avoid any bias.

For pre interventional evaluation, each of the 30 participants was given one toothbrush for use for 3 months using their routine tooth brushing technique. The participants were asked to brush twice a day, for 3 min each as per the guidelines recommended for ideal brushing by the Indian Dental Association under its National School Oral Health Program.[6]

The brush bristle end morphology of these 30 toothbrushes was examined under light microscope after use for 3 months by the participants. For educational intervention, a power-point presentation was used to impart knowledge on the correct Modified Bass tooth brushing technique to all the participants. Models and live demonstration were also done for better understanding followed by practice of the technique on educational models by the participants was carried out. The educational intervention was carried out by a single trained examiner under the supervision of senior faculty from the Department of Periodontology to remove bias. The examiner was calibrated against Professor (gold standard) in the Department of Periodontology with inter-examiner reliability k =0.85. To ensure compliance the students were encouraged to give periodic feedback both in-person and telephonically. They were also provided access to the senior faculty in case of any doubts or further queries. A reminder message was sent to all the participants on a private social media group to encourage active participation and ensure complete compliance.

For postinterventional evaluation, each of the 30 participants was given a new toothbrush for use for 3 months. After use for 3 months by the participants following the correct brushing technique as directed in the educational intervention, the brush bristle end morphology was examined under light microscope.

For all the examinations, bristles from a single tuft approximately situated in the middle of the toothbrush head were selected and removed using surgical scissors under magnifying loupes as per methodology by Balan et al.[7] The cut portion of the bristle was marked using an indelible marker to eliminate the error of visualizing the wrong end. The bristle was then mounted on a glass slide and the toothbrush bristle end morphology was assessed using Light Microscope under × 40 [Figure 1].

Figure 1:
Compound light binocular microscope

For all the examinations, the shape of the bristle tips was recorded and assessed for the wear index (WI) and wear rate (WR) as follows.

For evaluation of WI, as suggested by Rawls et al.[89] five measurements as indicated in were made as indicated in Figure 2.

Figure 2:
Calculation of wear index measurements of toothbrush bristles as per Rawls et al.[8] FLL: Free long length is the extent that the bristles splay, which is the maximum width of the side of the toothbrush. BLL: Base long length is the width of the side of the toothbrush at the part that is fixed to the plastic. FFL2: Front free length is the extent that the bristles splay, which is the maximum width of the front of the toothbrush. BFL: Base free length is the width of the front of the toothbrush at the part fixed to the plastic. BRL: Bristles’ length is the maximum length of the toothbrush bristles

Free long length (FLL) is the extent that the bristles splay, which is the maximum width of the side of the toothbrush.

Base long length (BLL) is the width of the side of the toothbrush at the part that is fixed to the plastic.

Front free length (FFL) is the extent that the bristles splay, which is the maximum width of the front of the toothbrush.

Base free length (BFL) is the width of the front of the toothbrush at the part fixed to the plastic.

Bristles’ length (BRL) is the maximum length of the toothbrush bristles. The larger the measured value, the higher the WI.

All toothbrushes were measured and the WI was calculated according to the formula suggested by Rawls et al.[8]

For evaluation of WR, the evaluation criteria established by Rawls et al.[8] was used. The scoring was done from 0 to 3; where 0: No spreading in the bristles; 1: Few bristles spread; 2: Bristle spreads with multiple overlaps with each other and 3: Most bristles are tangled and tilted.

Bristle end morphology was categorized as acceptable or non-acceptable based on Silverstone and Featherstone.[10] Classification in which the bristle ends with round tips without any sharp point has been categorized into acceptable and bristle ends with sharp tips, jagged and un-uniformed margins are categorized as nonacceptable as indicated in Figure 3. The observed values were further converted into percentages.

Figure 3:
Acceptable and non-acceptable morphology according to Silverstone and Featherstone[10]

Data was summarized into number, percentage, mean, and standard deviation. Mann–Whitney U-statistics test and unpaired t-test were used to compare measurements of acceptable percentage and gender wise, respectively. The difference was said to be significant at P < 0.05.


Total 30 participants in this study included 15 male and 15 female students. Each toothbrush was assessed for bristle wear morphology as indicated in Figure 2.

The data from all the toothbrushes were tabulated and WI and WR were calculated.

Table 1 shows WI and WR indices before and after intervention. The mean WI before intervention was 0.29 ± 0.122 and after intervention was 0.23 ± 0.07, while the mean WR before intervention was 1.6 ± 0.167 and after intervention was 1.17 ± 0.46. Thus, both the WI and WR decreased after intervention and the difference for both was found to be statistically significant with P < 0.05.

Table 1:
Evaluation of wear index and wear rate

Table 2 shows that the mean score of acceptable % of bristle end morphology before intervention was 52.5 ± 10.064 and after the intervention was 64.5 ± 5.625 with the difference being statistically significant with P < 0.05.

Table 2:
Comparison of acceptable percentage of toothbrush bristle end morphology

Results of the Acceptable Percentage Distribution of bristle end morphology according to the gender showed an increase from 52.33 ± 10.83 before intervention to 65 ± 5.35 after intervention in males and 2.67 ± 9.612 before intervention and 64 ± 6.04 after intervention for females [Table 3].

Table 3:
Acceptable percentage distribution of bristle end morphology according to gender

However, the difference in acceptable percentage according to gender amongst the before and after intervention groups was not found to be statistically significant with P > 0.05.


Undergraduate course in dentistry is the first step in the direction to provide the future dental healthcare professional with solid foundation of learning on which to base one’s clinical experience and patient care. Previous studies have examined the oral health knowledge and oral hygiene practices amongst university students in different countries and found poor tooth brushing outcomes among university dental students in different cultures across Africa, Asia, and the Americas.[11]

Similar findings were echoed by Yao, K in their study in China when they found that the oral health behavior, consciousness, and status of the 1st, 3rd year medical and dental students were not optimistic. They found the third-year students had better knowledge and practice compared to the first-year students in regards to the correct tooth brushing technique as well as duration and frequency of daily tooth brushing.[12]

The correct tooth brushing technique is generally not taught for the first-year undergraduate dental students at the preclinical stage in the undergraduate course in India. A comparison of the dental curriculum in India with that of developed countries shows the need for the incorporation of early clinical experiences to thoroughly map theoretical aspects of learning with practical aspects of dentistry.[13]

Hence, this group of the population was chosen in our study to study the efficacy of an educational intervention of correct tooth brushing technique by assessing their toothbrush bristle wear.

To assess the efficacy of any educational intervention, it is important to assess the baseline findings of the preinterventional practices. Hence, in the first part of our study, examination of toothbrush bristle wear was carried out with the participant’s current tooth brushing techniques while removing all confounders by standardizing all other variables including duration and frequency of brushing as well as the dentifrice and toothbrush used.

Tooth brushing is the most fundamental and efficient way in the prevention of serious oral pathological diseases including dental caries and periodontal disease.[14] A correctly employed tooth brushing technique ensures adequate plaque removal and gum massage to maintain optimum oral health and hygiene.

In the present study, the toothbrush bristle end morphology was assessed by light microscopy. Previously other techniques like stereo-microsopy or scanning electron microscopy (SEM) have been used. However, SEM is technique sensitive, and “ametallization” process is required which can cause the bristles to become deformed, thereby altering their bristle end morphology.[15] The use of light microscope helps in avoiding this undesirable complication.

Studies have shown that the ability to manage the plaque decreases in a worn toothbrush in comparison new toothbrushes making it easier for the bacteria to thrive as a consequence of the splayed bristle tips of toothbrushes with worn bristles.[1617] Bristle splaying is evident when the bristles spread apart and take on a permanent curvature.[18] The worn toothbrushes progressively lose their ability to clean as the bristles further abrade and become curled and matted.[8]

This decrease in plaque removal ability is especially seen in the proximal areas and appears irrespective of the type of toothbrush used including manual and powered as shown by a study by Conforti et al. in 2003.[19]

The findings of the present study indicate that the correct tooth brushing technique educational intervention resulted in a statistically significant decrease in both WR and WI (P < 0.05). This is important as the decreased wear of toothbrushes positively reflects on increased plaque removal efficacy and decreased deleterious effect on the oral soft and hard tissues. There is the paucity of literature regarding the effect of an educational intervention of proper tooth brushing technique on tooth bristle wear. Although some studies have assessed the effect on the duration of use on the tooth bristle wear, the data are inconsistent as there are many variables including the number of times brushed per day varying from one to three or study population being either school children, adolescents, or adults.[2021]

For a toothbrush to be least damaging to the oral structures, the acceptable bristle end morphology should be higher than nonacceptable. In our study, we found that there was a statistically significant increase in the acceptable percentage of bristle end morphology of the toothbrushes after the educational intervention (P < 0.05).

Differing toothbrushing techniques and forces amongst individuals result in considerable variation in the degree of wear.[18] Several studies indicate that the individual tooth brushing technique warrants more importance than the duration of brush usage in causing the wear.[1822]

Thus, this early intervention for the students will also be important not only for themselves but also when they embark on their clinical interactions and educate the patients regarding the same.


Though the present study is the first of its kind to evaluate the effect of an educational intervention on toothbrush wear, the study had some limitations.

  • The WR index used by Rawls et al. index is a subjective tool[8]
  • Other oral deleterious habits including “chewing” the brush head whilst brushing may also aggravate the tooth bristle wear[23]
  • Though the participants in the study were instructed to brush for 3 min per session, the same could not be ascertained as it relied on self-reporting by the client. Overestimation or underestimation of the self-reported brushing time by the participants could affect the wear of the toothbrush bristles. For greater accuracy and validity, future studies can control this variable rather than relying on participant self-reporting.

In future, similar studies could be carried out with a different type of toothbrush product regarding the brand, model, toothbrush head design, as well as variations in bristle filament dimensions, number, and material.[23] In the present study, the efficacy of educational intervention of correct tooth brushing technique was assessed by examination of toothbrush wear, however further longitudinal studies can expand the scope of study to also include the effect on teeth and soft tissues.


Thus, the results from this study provide further support to the hypothesis that the correct tooth brushing technique has a significant effect on the toothbrush bristle wear. These results are important as worn toothbrush bristle is known to cause gingival and tooth surface wear. The early educational intervention of correct oral hygiene measures is especially prudent for the budding dental professional for future healthcare delivery to the general population. This is important from a public health point of view, especially in developing countries, where the dissemination of preventive techniques will contribute significantly in reducing the oral disease burden.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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Bristle wear; dental students; intervention; knowledge; toothbrush

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