Study Title:

Candida Biofims on Retainers

Study Abstract

Aims:  The aim of this study was to determine the prevalence and proportions of opportunistic pathogens harboured on orthodontic retainers.

Methods and Results:  First, Staphylococcus spp. and Candida spp. were isolated from the retainer’s inner surface and from other mucosal surfaces of the subject’s mouth by routine bacterial culture. The prevalence and proportions of these micro-organisms on retainers was compared in different areas of the mouth within a group of retainer wearers, and mucosal carriage was compared to a group of nonretainer wearers. Staphylococcus spp. were isolated from 50% of the retainers and comprised on average 8·4% of the viable microbiota. Candida spp. comprised 0·13% of the viable microbiota and were recovered from 66·7% of the retainers. Neither genus was isolated from nonretainer wearers. Second, the two most commonly worn retainers manufactured from different materials were sampled; again Staphylococcus spp. and Candida spp. were recovered; however, no statistical differences were observed between the devices.

Conclusions:  Opportunistic, nonoral, pathogenic micro-organisms were recovered from orthodontic retainers.

Significance and Impact of the Study:  It is possible that an orthodontic retainer could be a reservoir for opportunistic pathogens and act as a source of cross-, self- and re-infection.

From press release:

Insufficient cleaning could allow build-up of microbes on orthodontic retainers, researchers at the UCL Eastman Dental Institute have found. Dr Jonathan Pratten and colleagues looked at the types of microbes which live on retainers. This study, which found potentially pathogenic microbes growing on at least 50% of the retainers, is published March 15 in the Society for Applied Microbiology's journal Letters in Applied Microbiology and could indicate a need for the development of improved cleaning products for orthodontic retainers.

Dr Pratten and his team took samples from the mouths of people without retainers and those wearing either of the two most widely used types. As retainers are frequently removed and then replaced in the mouth, the potential for transmission of microbes is high.

Our mouths are full of different types of bacteria, some of which promote oral health. However, the researchers were looking for microbes which are not normally found in the oral cavity. They were particularly interested in two species of microbes; Candida, a type of yeast, and Staphylococcus including MRSA. Dr Pratten and his team found that species of these microorganisms were present on 66.7% and 50% of retainers respectively regardless of the retainer type. These microbes were also present on the interior cheeks and tongue of retainer wearers.

Candida and Staphylococcus rarely cause problems in healthy individuals but are potentially highly problematic in people with a compromised immune system. The bacteria on the retainers live in biofilms, which are communities of bacteria living together covered in a layer of slime. Once these biofilms form they are very difficult to remove and often have high levels of resistance to antimicrobials.

Dr Pratten says: "With the growing awareness the public has of hospital-acquired infections it is important to be aware of other potential 'hidden reservoirs' of harmful bacteria which could be introduced to environments where we know they can cause problems."

Whilst the researchers are now looking at developing effective methods of cleaning, for now hygiene is the key to reducing the transmission of these bugs. Anyone handling a retainer should wash their hands before and after use. Careful tooth brushing and mouthwash may also help to keep the retainer clean.

Study Information

D. Al Groosh, G.B. Roudsari, D.R. Moles, D. Ready, J.H. Noar, J. Pratten.
The prevalence of opportunistic pathogens associated with intraoral implants.
Letters in Applied Microbiology
2011 March
UCL Eastman Dental Institute


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