Evaluation of Ultraviolet light (UV) and Light emitter diode (LED) on Toothbrushes Decontamination : An Experimental in vitroStudy
Regular plaque removal by effective tooth cleaning using a toothbrush is the most common and effective device that removes the bacterials from the oral cavity, reducing the risk for decay and periodontal diseases . However, these devices may become heavily contaminated with microorganisms, implicating in the possibility of reinfection of a patient and resulting in simple or more complexes systemic diseases, namely in immunologically compromised and hospitalized patients [2-4].
Procedures for the decontamination of toothbrushes would prevent the risks of reinfection or infection by other pathogenicmicrorganisms from the enviromment . Several chemical agents have been tested to reduce the toothbrush bacterial contamination, including chlorhexidine, essential oils and dentifrices [3-7]. However, because these methods are time consuming and may result in unwanted product residues , other household methods, such as microwave  and ulraviolet (UV) light [1,4,9-11] are been researched, showing conflicting results. It seems that low-intensity UV rays are not effective against certain microbes and molds. Then machines using other light sources must be tested.
Few works analyzed the extent of bacterial decontamination using the UV light in a clinical trial and no studies evaluated theeffect of light emitter diode (LED) on toothbrush decontamination. Then, the following experiment compared the efficacy of these physical methods as toothbrush sanitization machine.
Materials and Methods
The University’s Ethics Committee approved the research protocol (Report Coética no. 783575/2014, University of Fortaleza).
Thirty patients (15 male and 15 female aged 20-55 years) were enrolled in this study. All subjects had at least 20 naturalteeth, presenting gingivitis but no signs of periodontitis, had no caries or extensive dental restorations and had not been exposed to systemic antibiotic treatment during past 6 months. Volunteers with medical disorders, using mouthwashes, smokers and pregnant women were excluded from the trial.
On day 0, each participant received a “kit” with a toothbrush (Leader®, Facilit Odontológica e Perfumaria Ltda., Rio de Janeiro,Brasil) and a fluoride dentifrice (Freedent®, Indústrias Raymond’s São Paulo, Brasil). The participants were instructed to brush their teeth using their habitual technique, during one minute, three times a day, for one week. After tooth brushing the volunteers were instructed to rinse the brush heads under running tap water for ten seconds and hold the toothbrush at room temperature. Verbal and written instruction about the home procedures were given to all subjects. After seven days, the volunteers should return the toothbrushes to proceed for the laboratorial phase.
The toothbrushes were designed to each group, by random allocation using a computer-generated random table made by a person not participant of the study: Control (n=10) – the toothbrushes were not decontaminated; LED (n=10): application of light emitter diode during 05 minutes (Foto Optilight LD Max, Gnatus®, 450 nm, 600mW); UV (n=10): application of ultraviolet light during 05 minutes (“Esterilizador de Escovas Portátil”®- Modelo RM-TS101, 270 nm, 3W).
After the decontamination process, the brush heads were covered with the plastic caps, identified according the group and sent to Microbiology’s Laboratory for microbiological analysis. The brush heads were immersed in test tubes containing Brain Heart Infusion – BHI for 30 seconds and after this, they were putted in a stove at 37°C for 24h. The level of contamination by McFarland scale and morphological characteristics of the microorganisms was performed.
ANOVA and Student Newman-Keuls analysis were performed to evaluate statistical differences among groups (α=.05). Formorphological analysis the chi-square test was used (α=.05). However, for illustrative purposes the results are showed asmeans, medians and standard deviations.
All groups showed higher levels of bacterial contamination and not presented statistically significance difference among them (p>0.05) (Tables 1 and 2). In the control group gram + and gram- cocci were present in all toothbrushes and gram – cocci were absent in the other groups (p<0.05). In the LED and UV groups gram+ cocci and gram + bacilli were predominant, but no statistically significance difference was observed among them (p>0.05) (Table 3; Figure 1).
Table 1. Mean, Medians and standard deviation of the level of turbidity in the different groups.
*Values followed by same letters (a) in a same line did not differ statistically (p>0.05).
Table 2. Mean, Median and standard deviation of the level of sediment in the different groups.
*Values followed by same letters (a) in a same line did not differ statistically (p>0.05).
Table 3. Percentage distribution among different morphotypes in the different groups.
*Different letters showed significant statistically difference among groups (p<0.05).
Figure 1. Percentage distribution among different morphotypes in the groups
Failure in maintaining adequate oral health status in the hospital environment can negatively affect the quality of life of patients and new condition can onset, such as pulmonary infection by microrganisms of the oral cavity . Besides,contaminated toothbrushes contributed to the persistence of group A beta-hemolytic streptococci in the oropharynx and to the failure of penicillin therapy in some cases of pharyngotonsillitis .
To minimize this risk, toothbrushes are commonly used in hospital settings for oral care by nurses and may harbor potentiallyharmful microorganisms [14,15]. Even so, tooth brushing alone or in combination to chorhexidine showed no additionalbenefits for the prevention of nosocomial pneumonia . So, is that the toothbrushes are not acting as agents of recontamination? Is that the problem is not the lack of decontamination of dental brushes before each use in these very contaminated environment?
In fact, a peer-reviewed literature review revealed that toothbrushes of oral diseased adults become contaminated with pathogenic bacteria from the dental plaque, environment, or a combination of factors. Surfaces in close contact with thepatient such as bed frames, countertops, sinks and bedside tables may act as fomites. Some commonly observed nursingpractices include storing the toothbrush in the bath basin with other bathing/personal supplies. These practices may impact the contamination of toothbrushes [16,17].
The higher levels of contamination of the control group showed that one-week contamination was sufficient for promotes the bacterial growth in the toothbrush head , including gram-negative bacilli, which are microorganisms very common in the oropharyngeal area of the hospitalized patients . Microorganisms present on a contaminated toothbrush can remain viable for a period ranging from 24 h to 7 days; this fact shows the importance of the researches that evaluate decontamination methods to avoid in the spreading these microorganisms within the oral cavity . Then, the present work was designed to evaluate the effect of the UV light on toothbrush decontamination in comparison to LED.
The toothbrushes of the UV group had the same level of turbidity and sediment than other groups, even though that showedlower percentage of bacterial morphotypes comparing to no decontaminated toothbrushes. In a similar study, toothbrushesdecontamination using UV light for seven minutes was effective and showed a lower aerobic bacterial in relation to controlgroup. This may be due to the length UV light exposure the toothbrushes received during the sanitization process.However, in the same way, LED showed similar results, even presented wavelength greater than UV light. Up to now, there are no studies evaluating the effect of LED on toothbrushes decontamination, so it is unable the data comparison with the current literature.
One of the possible reasons for the divergence of the results with UV light was the contamination time, which was just 48hours in that study . Other works showed positive results using UV in the decontamination process [9,11]. The toothbrushsanitization machines for household was used diary, in which lower bacterial contamination is present, and it could explain the difference with our study.
Previous studies have revealed that the longer exposure to UV light is necessary to ensure a complete inactivation of all microorganisms[18,19], by damaging the DNA and disrupting the chemical bonds that hold the atom of DNA together in the microorganism . Indeed, even using the double of the time recommended by the manufacturer, UV light did not significantlyreduce the bacterial contamination on the brush heads when compared to microwave . A previous literature review ,has questioned the potential of low-intensity UV radiation in microbial inactivation. Furthermore, tightly packed bristles could not be in direct exposure to UV light and may explain these inexpressive results .
The American Dental Association (ADA) Council on Scientific Affairs’ encourages patients to select a toothbrush sanitizer that is cleared by the Food and Drug Administration (FDA). Furthermore, the ADA invites consumers and professionals to critically review the claims made by manufactures of the toothbrush sanitizer which usually refer to sanitizing (not sterilizing) or reducing bacterial contamination on toothbrush . In the present study, in spite of the manufacture indicates that the sanitizer machine was a “sterilizer device”, it did not match this claim.
It seems that UV light and LED are not efficient in contaminated highly toothbrushes, such as that are used by patients withperiodontal diseases and hospitalized patients, although they had affected the composition of the flora of the mouth, reducingthe quantity of pathogenic gram-negative bacteria. Then, it is suggested that companies in the industry dental focus morefrequent and comprehensive manner this issue by developing products more efficient to toothbrushes decontamination,specifically for hospitalized patients under intensive care, in which the level of contamination of the oral cavity is higher and more complex.
Ultraviolet light and light emitter diode had a limited benefit on toothbrushes decontamination.
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