page_title: Plaque hypotheses
section_title: Caries
hierarchical_section_title: Plaque hypotheses / Ecological plaque hypothesis / Caries
caption_attribution_description: English: The ecological plaque hypothesis and the aetiology of dental caries. The diagram shows a dynamic relationship whereby an environmental change in the biofilm (e.g. low pH) drives a shift in the balance of the resident microflora, thereby shifting the balance towards enamel demineralization. Caries could be controlled by inhibiting the putative pathogens, e.g. mutans streptococci (MS) or other acid producers, by interfering with the environmental changes driving the ecological shift, e.g. by reducing the acid challenge by the use of sugar control, saliva stimulation and/or biofilm removal. Adapted from Marsh,P.D.(1994).Microbialecology of dental plaque and its significance in health and disease. Adv.Dent.Res. 8, 263–271.
context_page_description: Plaque hypotheses are theories to explain the role of plaque bacteria in dental caries and in periodontitis. They rely heavily on the postulates of Koch and on the work of Louis Pasteur. Changing perceptions have altered treatment models.
  The hypotheses have sought to establish both in caries and in periodontitis a relation between pathogen virulence, environmental considerations, plaque biofilm structure and the host response.
context_section_description: The ecological plaque hypothesis, a combination of the two previously mentioned hypotheses, suggests that there are certain species responsible for pathology, but are present in insufficient quantities to cause damage to a healthy individual. Thus biofilm derived diseases are the result of an imbalance in the normal oral ecology.
  The most commonly recognised bacteria that are responsible for initiating the biofilm formation that can eventually lead to caries are streptococcus mutans and lactobacillus. The key factors for virulence include their ability to metabolise glucose and similar sugars, their tolerance for a low pH environment and their acidogenicity. The presence of streptococci encourage adherence of more cariogenic bacteria, which in turn increases the likelihood for caries. Although factors such as the quality of saliva, using fluoridated toothpaste and chewing gum after meals can inhibit the growth of these bacteria and change the biofilm environment. Saliva containing more buffering agents such as calcium and phosphate ions alter the internal environment of dental plaque to become less acidic, favouring the growth of less cariogenic organisms. The fluoride components of fluoridated toothpaste can be bacteriostatic to cariogenic bacteria, decreasing their acidogenicity and proliferation. Chewing gum can disturb the mature and fairly stable acid producing plaque to alter the bacterial composition of the biofilm. In turn the disease causing organisms may still be present, but are so in reduced numbers. Chewing gum containing sufficient levels of xylitol also has the ability to reduce the number of streptococcus mutans present in the saliva as well as the mechanisms for the bacteria to adhere to tooth tissue, which reduces the chance for reinfection.
caption: Ecological plaque hypothesis and the aetiology of dental caries
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