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Dental Tribune Middle East & Africa No. 4, 2017

12 ORAL HEALTH Dental Tribune Middle East & Africa Edition | 4/2017 Interview: The natural oral microbiome is not associated with oral disease By Kristin Hübner, DTI As Professor of Oral Microbiology at the University of Leeds, Philip Marsh has received national and interna- tional awards for his research in the fi eld and is a regular conference speaker. At the Australian Dental Congress, where he recently pre- sented three lectures on the topics of dental biofi lms and oral microbial ecology , Dental Tribune had the op- portunity to speak with him about the relationship between lifestyle factors and the microbial compo- sition and how to best maintain a healthy bacterial balance in the mouth. The microbial balance of the oral cavity is essential for dental (and overall) health. Could you briefl y explain this relationship? Humans and micro-organisms have evolved to have a close and impor- tant symbiotic relationship, to the extent that we are 50 per cent mi- crobial! These micro-organisms [the human microbiome] are natural and deliver essential health benefi ts. In ADC speaker Prof. Philip Marsh. (Photograph: Australian Dental Association) the mouth, the normal oral microbi- ome prevents colonisation by exter- nal microbes—some of which would be potentially pathogenic—and con- tributes to the development of our host defences and cardiovascular system. The natural oral microbiome is closely linked to oral health and is not associated with oral disease. The oral microbiota is vulner- able to disruption by lifestyle and environmental changes. The oral microbiota is natural and benefi cial and therefore needs to be managed and maintained at levels compatible with oral health. Oral care products are designed and evaluated to support the patient in maintaining an appropriate level of oral micro-organisms, so if they are used as intended, there is little danger of negatively disrupting the oral microbiota. In contrast, the long- term use of broad-spectrum anti- biotics can lead to the suppression of signifi cant numbers and types of benefi cial oral bacteria, and this can result in overgrowth by yeasts or en- vironmental microbes. Bacteria play an important role in the development of diseases such as periodontitis or caries. Are there ways to manage harmful colonisa- tion other than with dental hygiene measures, for example with vac- cines, or will there be in the future? New strategies to promote benefi - cial oral bacteria and/or to suppress the likelihood of disease are being developed. These strategies include the development of oral probiotic bacteria to prevent dental disease and the use of prebiotics, which are supplements designed to boost the growth of benefi cial bacteria. Novel anti-infl ammatory agents are be- ing evaluated that would promote wound healing and reduce the tissue damage caused by a subverted host response to subgingival dental bio- fi lms. Molecules that reduce biofi lm formation or inhibit species impli- cated in dental disease are under ac- tive investigation. Some snack foods and drinks contain sweeteners that cannot be metabolised into acid by oral bacteria. Is dentistry experiencing greater challenges with re- gard to biofi lms and bacterial shifts today than in the past, and if so, why? The main differences today com- pared with the past probably sur- round the increased amounts of sugar in snack foods and drinks. Also, people are living longer and are re- taining their teeth into later life, so the dentition is vulnerable to dental disease for longer, and this is cou- pled with the fact that a side-effect of many medications taken by the elderly is a reduction in salivary fl ow. What strategies for keeping a healthy balance in the mouth can dentists teach patients? The main strategies are for patients to practise effective oral hygiene and thereby reduce biofi lm accumula- tion and to appreciate the impact of sugar in their diet on their risk of dental caries. It may be helpful if pa- tients realise the relationship and di- rect link between their lifestyle, their oral microbiome, and their oral and general health and well-being. Thank you very much for the inter- view. What exactly can cause a shift and what are potential consequences? The symbiotic relationship between the oral microbiota and the host is dynamic and can alter if the oral en- vironment undergoes a substantial change, often as a consequence of an altered lifestyle. A clear example is when salivary fl ow is reduced or when an individual more regularly consumes sugar-containing foods and beverages. In this situation, the dental biofi lm spends more time at an acidic pH. This leads to an enrichment of acid- producing and -tolerating bacteria at the expense of benefi cial organ- isms and increases the risk of dental caries. Similarly, the host mounts an infl ammatory response if biofi lm accumulates around the gingival margin. If this fails to reduce the mi- crobial load, then the protein-rich gingival exudate that delivers the host defences inadvertently acts as a novel supply of nutrients for the proteolytic and obligately anaero- bic bacteria in subgingival biofi lms. These bacteria subvert the host re- sponse and continue to drive infl am- mation; this exaggerated response is responsible for host tissue damage. Is the composition of the oral microbiota mainly based on heredity or can it be managed through external factors? Some elements of the make-up of the oral microbiota are linked to he- redity, but the general composition and activity of these microbes can be managed by effective oral hygiene and an appropriate lifestyle, for ex- ample reducing the amount and frequency of intake of fermentable sugars in the diet, avoidance of to- bacco-smoking, etc. An unintended side-effect of some medications can be a reduction of salivary fl ow; this would disturb the natural balance of the oral microbiota and increase the risk of dental caries. Dental care products aim to reduce harmful bacteria while maintaining the good ones. Is there a danger of using too much product and thereby de- stroying the oral fl ora?

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