Oral microbiology: current concepts in the microbiology of dental caries and periodontal disease.

The microbial flora of the mouth is highly complex, containing a wide variety of bacterial species. The most common types of oral disease, dental caries and periodontal disease, are both related to dental plaque and seem to occur when the normal balance between the microorganisms and the host is disturbed in some way. Dental caries is usually associated with increased numbers of mutans streptococci and lactobacilli at the sites of disease; estimation of salivary levels of these organisms may be useful for assessing caries risk in patients and for monitoring their response to preventive measures. A large number of 'candidate pathogens' have been identified as potential aetiological agents in different types of periodontal disease, although the 'specific plaque hypothesis' may still be controversial. Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, together with the poorly understood spirochaetes, have most frequently been reported as significant periodontopathogens and a number of possible virulence factors have been described. Application of modern molecular techniques to the study of the microbiology of oral diseases should allow rapid further progress to be made and will lead, hopefully, to improved methods of diagnosis, risk assessment and treatment.