PLAQUE PH AND MICROFLORA OF DENTAL PLAQUE ON SOUND AND CARIOUS ROOT SURFACES

Given the hypothesis that root caries is the result of acid formation by acidogenic micro-organisms, the present study was performed to rela te sucrose-induced pH response of dental plaque on root surfaces to th e microbial composition of the overlying plaque, Seventeen caries-acti ve elderly Chinese with poor oral hygiene and with both sound and cari ous root surfaces were examined, Plaque pH was measured before and up to one hour after a controlled sucrose mouthrinse, Plaque samples for microbiologic analyses were collected from 2 sound and 2 or 3 carious pH-measurement sites in each subject, The prevalence of the following micro-organisms was assessed as % of total triable counts on Brucella agar: Prevotella intermedia, Prevotella melaninogenica, Fusobacterium nucleatum, Campylobacter rectus, Capnocytophaga spp., Actinomyces visc osus, Actinomyces naeslundi, Streptococcus spp., S. sanguis, S. mitis, S. mutans, S. sobrinus, Lactobacillus spp., and Candida spp. There wa s no difference in plaque pH response on sound and carious root surfac es. The plaque pH response was more pronounced in the maxilla than in the mandible for both sound and carious sites. There was no difference in microbial composition of dental plaque on sound and carious root s urfaces. The pH response to sucrose was the same regardless of the pre sence or absence of mutans streptococci, Our results thus do not readi ly support the traditional concept of caries formation.