Clinical Studies

Toothbrush contamination: a potential health risk?

• Richard T. Glass, D.D.S., Ph.D.*

• Mary Martin Lare, R.D.H., D.D.S.**

Introduction

Studies have been conducted to determine the level of bacteria following oral hygiene procedures. A study by Sconyers et al. of toothbrushing in clinically healthy patients found no circulating bacteria in any of the 50 persons tested.1 In a study of similar design, Silvers et al. tested 36 subjects, 3 of whom exhibited detectable bacteremias.2 Both studies relied on 10 ml blood samples taken from the disinfected anticubital fossa during the last 30 seconds of brushing, and in both studies aerobic and anerobic cultures were obtained. Sconyers used an electric toothbrush for four minutes and Silver used a manual sulcular brush for two minutes. Only the Sconyers study, however, obtained a 10 ml prebrushing control blood sample. These studies were conducted to determine the level of risk involved in normal oral hygiene procedures for high risk patients, such as rheumatic fever or congenital heart defects, or those with intracardiac and vascular prostheses. The relationship of bacteremia to toothbrushing in patients with periodontitis was also studied.3 Thirty periodontal patients were selected for the brushing study. As a baseline study, nine patients who were having extractions participated. Blood samples were drawn during the fourth minute of brushing and immediately after extraction procedures. Bacteria found in blood samples from the brushing group were compared with the bacteria cultures from the extraction group. Bacteremia was found in 5 of the 30 brushing patients and in all nine extraction cases.

     In the above mentioned studies, emphasis was placed on the disease or clinical condition in the patient's mouth as the factor affecting the bactermia. As early as 1920, Cobb cited the toothbrush as a cause of repeated infections of the mouth and reported on a significant case.4 Svanberg found that toothbrushes and toothpaste can be heavily infected with Streptococcus mutans for 24 hours after usage (the longest period tested was 24 hours). Svanberg also suggested that brushing with a contaminated brush introduces new microorganisms while simultaneously reducing existing normal flora.5

     Discussion of the modern toothbrush has suggested the problem of toothbrush construction as a factor of toothbrush contamination. The nylon multi-tuft toothbrush has been cited for its design of tufts set too closely to accommodate easy cleaning.6 With natural toothbrushes, the bristles can harbor inherent microorganisms. The natural toothbrush bristle has a central core or medulla running throughout the length of the bristle. When the brush is trimmed, the end of the bristle has an irregular shaped lumen. Fluids can be drawn into this core by capillary action, allowing for bacterial growth. the bristles also split longitudinally, further increasing the bacterial contamination.7

     The handles of modern toothbrushes are usually made of thermoplastic material, most commonly cellulose acetate, styrene acrylonitrile, or cellulose propionate. Nylon is almost universally used for filaments. The filaments are collected into bundles, bent in half with a metal anchor in the center, and driven into premolded holes in the toothbrush head at high speed. Nickel silver is used as anchor material because it is resistant to corrosion from toothpaste materials and from saliva residues. Despite the name "nickel silver," the alloy contains only nickel and copper.

     Several years ago, we observed that patients who had oral inflammatory disease tended to respond better to therapy if they had their old toothbrush replaced with a new one on a regular basis (e.g. replacement every two weeks). Further, when the inflammatory disease involved the tongue, necessitating tongue brushing, separate toothbrushes were used for the teeth and tongue. This observation prompted the following study to determine if toothbrushes harbor pathogenic microorganisms and if there is a correlation between contaminated brushes and the presence of disease.

Materials and Methods

The data for this study were collected from 30 synthetic toothbrushes. Ten new brushes from two manufacturers were cultures to determine whether microorganisms were present with a packaged brush. Ten brushes were cultured from clinically healthy patients and ten from patients with oral disease. A patient was considered "clinically healthy" if there were no caries, no mucosal abnormalities, and no gingival or periodontal inflammation. A patient was considered to have oral disease if he demonstrated large and/or numerous carious lesions, periodontal disease or mucosal disease (e.g., lichen planus, desquamative gingivitis, benign mucous membrane pemphigoid, burning mucosa, geographic tongue).

     The patients were asked to bring their toothbrushes to their dental examinations. Consent was obtained, a screening examination was performed, and significant data (toothbrush environment, oral health status, etc.) were collected.

     The toothbrush heads were transferred to sterile tubes (15 ml, orange-top centrifuge tubes with screw caps*) with an aseptic technique. Toothbrush handles were severed with end-cutting nippers which had been stored in Cidex (Formula 7).** Brushes were collected only during morning clinic hours to avoid drying of bristles. In oral-diseased patients, the specifically involved areas were also swabbed, and the specimens were immediately carried to the pathology lab for culture procedures.

     In order to again decrease the chances of contamination from brush transfer, the brushes and swabs remained in the sterile tubes, and brain-Heart Infusion Broth* was added. the borth was incubated at 37C until a turbid state existed. the following six plates were then inoculated and incubated at 37C:

1. Sabouraud Dextrose Agar (Emmonds) with yeast extract (SAB)
2. Blood Agar
3. Chocolate Agar
4. Reducible Blood Agar
5. Reducible Colistion Nalidixic Acid Blood Agar (CNA)
6. Reducible Laked Blood Agar with Kanamycin and Vancomycin (LKV)

     The aerobic plates were allowed to incubate for a minimum of 24 hours, while the anaerobic plates were given a minimum of 48 hours. Yeasts were not rules out for two weeks.

     The predominant colonies were identified on each plate and pure cultures were obtained. Analytical Profile Index Strips* were utilized to identify yeasts, streptococci, enterics, anaerobes, and actinomyces.

Table 1   Data obtained from laboratory reports

N  = Normal

Table 2   Data obtained from laboratory reports

P   = Periodontal Disease
M  = Mucosal inflammatory disease

Analysis

All data from laboratory reports were collected and recorded in a tabulary form (Tables 1 and 2). The used toothbrushes collected from patients were considered contaminated if microorganisms were detected in pure culture quality from the initial plating or if known pathogens were present. Gram positive Streptococci and Staphylococcus epidermidis were considered normal findings on used brushes. A correlation between he contaminated toothbrushes and the presence of oral disease was considered positive of common organisms or pathogens were found on the brush and oral swab. The finding of any microorganism on packaged (new) toothbrushes was considered contamination.

Results

It does appear that toothbrushes can harbor pathogenic microorganisms. A correlation is suggested between contaminated brushes and oral disease; however, the number of brushes tested as inadequate for statistical analysis (Tables 1 and 2). The length of use of the toothbrush did not seem to correlate with the presence of microorganisms. The time span was from two days to 24 months, with the mean of 23 weeks. However, the results do suggests that contamination occurs after four weeks.

     There was no strong correlation between health history and the organism present on the toothbrush. Of the 20 patients, 6 had negative health histories; 9 had minor systemic disease (maxillary sinus disease, menstrual irregularity, etc.) and 5 had a history of systemic disease (rheumatic fever, hepatitis, hypertension). Thus, the patient population can be considered fairly representative of the general population.

     All but one toothbrush was stored in the open air. All patients used the brushes at least once a day, and some as many as three times a day. The presence or absence of fluoride in the toothpaste did not seem to affect the bacterial growth. The 13 male and 7 female participants ranged from 21 to 75 years (a mean age of 39 years), with neither age nor sex having an effect on either the types of microorganisms. A wide range of socioeconomic levels were present in the study with no apparent relevance.

     New toothbrushes, directly from their packages, were also studied. Of 5 new toothbrushes from one company, 4 were contaminated with Staphylococcus epidermidis, while 5 of 5 from another company showed no growth (Table 3). Therefore, even though 12 of 20 of our used brushes demonstrated Staphylococcus epidermidid, it cannot be determined at this point whether or not the brushes were contaminated when "new".

Table 3   Contamination of packaged brushes

Discussion

In this day of organ transplants and alteration of the immune system, it is important to consider the toothbrush as a cource of potential pathogens. Given the fact that very often people will traumatize themselves with their toothbrush, this trauma may become a potential portal of entry for organisms.
     In our study, there was no clear-cut time of contamination; however, there was a suggestion that contamination occurs sometime after one week but before one month. An exception did occur with on patient demonstrating a contaminated brush after only two days. Conversely, one brush was not contaminated by pathogens after one year.
     The data suggest that further study is indicated to determine the length of time it takes for brushes to become contaminated, to consider the range of microorganisms that might be found on a toothbrush, and to determine whether there is a correlation between either local or systemic disease and the microorganism in the toothbrush. Ultimately, studies need to be conducted to develop a mechanism for sterilization using materials and methods found in the home such as chemicals or microwave ovens.89

Summary

Toothbrushes can be contaminated after approximately one month of use. These contaminated brushes may play a role in systemic or localized disease. We recommend that patients about to undergo major surgery procedures and debilitated or immunosuppressed patients be considered candidates for disposable brushes. Further, we recommend that for the general population, toothbrushes be changed at least once a month and after any illness.

Acknowledgments

The authors wish to that Louise Comfort DeWitt, Diana Harris, Donna Russell, and Elaine Taylor for their assistance with this study.

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