HUMAN ROOT CARIES - MICROBIOTA IN PLAQUE COVERING SOUND, CARIOUS AND ARRESTED CARIOUS ROOT SURFACES

The plaque microbiota covering sound or carious root surfaces were stu died and compared with that covering arrested root caries lesions, Fro m each of these categories five extracted teeth were examined. The exp erimental design of the study allowed us to relate the qualitative and quantitative microbial composition to the degree of integrity of the root surface. Plaque was sampled by a newly developed 'mowing' techniq ue, Plaque samples were cultured anaerobically on nonselective Columbi a blood agar plates supplemented with 5% hemolyzed human blood and on media selective for Lactobacillus spp, and streptococci of the mutans group, The cultivable microbiota were quantitatively speciated using R apid ID 32A, Rapid ID 32 Strep, API 20 Strep, API ZYM, and API 50 CH t ests and SDS-PAG electrophoresis, Regardless of the state of mineraliz ation, the microbiota on all surfaces resembled marginal plaque associ ated with gingivitis. In addition to the gram-positive predominant fac ultative anaerobic genera Streptococcus, Staphylococcus, Lactobacillus and Actinomyces, gram-negative anaerobes, predominantly Bacteroides, Prevotella, Selenomonas, Fusobacterium, Leptotrichia and Capnocytophag a, showed the highest isolation frequencies. On all surfaces Actinomyc es spp, predominated, with streptococci and lactobacilli forming a min or part of the microbiota. With respect to the detected proportions of anaerobes, microaerophiles, Actinomyces naeslundii, Prevotella buccae and Selenomonas dianae, significant differences were observed between the three categories of root surfaces. The total CFU's on both caries -free and caries-active surfaces were significantly higher than on arr ested lesions, In general, the results support a polymicrobial etiolog y for caries initiation on root surfaces, with A, naeslundii, Capnocyt ophaga spp., and Prevotella spp, malting specific contributions to the processes of cementum and dentin breakdown.