Influence on periapicai tissues of indigenous oral baclteria and necrotic pulp tissue in monkeys. Scaad. J. Bent. Res. 1981: 89: 475-484. Abstract -Ia nine monkeys (Macaca fascicularis) the pulps of 78 teeth were aseptlcaUy necrotized. Twenty-six of the pulp chambers were kept bacteria-free by scaling, while 52 were infected by the indigenous oral flora. The results were recorded clinically, radiograp hie ally and micro biologic ally at the beginning of the experiment and after 6-7 months. The fmal examination also included histologic recordings. The initially noninfected root canals were all sferile at the flnal samplings, indicating that the risk of contamination (including ihematogenouis) of root canals of this anim.al is verv^ slight. It was shown that noninfected necrotic puip tissue did not induce inflammatory reactions in the apical tissues., By contrast, teeth with infected pulp tissue showed inflammatory reactions clinically (12/52 teeth) aod radiographically (47/52 teeth). Facultatively anaerobic streptococci, coliform rods and o^bligately anaerobic bacterial strains were most frequently foiand. In the final samples the number of obligately anaerobic straims increased. Some microorganisms which were isolated in the initial samples were not detected in the final samples. All infected teeth histologically examined showed strong inflaiomatory reactions in the periapical region.

– The present study deals with the ability of 11 bacterial strains, in various combinations, to induce periapical reactions. The indigenous oral bacteria were originally isolated from an experimental apical periodontitis in monkey. Eight of the strains were a complete collection isolated from one root canal. These strains were inoculated together, in equal proportions, into 12 root canals. In addition, 63 canals were inoculated with other combinations or separate strains. At the end of the experimental period it was found that in the mixed infections the Bacteroides oralis strain predominated in most root canals. In contrast, this Bacteroides strain was not reisolated in any of nine root canals when inoculated in a pure culmfe. Enterococci, however, survived as pure cultures in all canals. The mixed infections showed the greatest capacity ofindticing apical periodontitis, as revealed by radiography, and most pronounced was the “eight‐strain collection”. The facultatively anaerobic streptococci induced only weak periapical reactions.

The pulps of 24 root canals, eight in each of three monkeys, were mechanically devitalized and exposed tO' the mouth flora for about I week and thereafter sealed. Microbiologic sampling and analysis was performed in 16 teeth (tM' O of the monkeys) after 7 d of closure (initial samples). The teelli ofthe three monkeys represented obsen-ation times of 90, 180 and 1060 d. At the end of each observation period final samples were taken. Final sampling included samples from the main root canal, the dentin, and the apical region at the same sampling session. All microbiologic analyses were carried out quantitatively. Final root canal samples from the apical region showed a predominance of obligately anaerobic non-sporuiating bacteria, in fact 85-98% of the bacterial cells were anaerobic. The most frequently found species were Bacteroides and Gram-positive anaerobic rods. Alower proportion of facultatively anaerobic bacteria was found. This was most pronounced for coliform rods in comparison with strains of B. melaninogenicus.

The purpose of this study was twofold: first, to determine the influence on the healing of the periapical tissues when selected bacterial strains and combinations thereof remain after root canal treatment; and, second, the relationship to healing of the quality of the root filling. In eight monkeys, 175 root canals, previously infected with combinations of four or five bacterial strains and with radiographically verified apical periodontitis, were endodontically treated, bacteriologically controlled, and permanently obturated. After 2-2.5 yr, the periapical regions were radiographically and histologically examined. Of these teeth, 48 root canals were also examined for bacteria remaining after removal of the root fillings. When bacteria remained after the endodontic treatment, 79% of the root canals showed non-healed periapical lesions, compared with 28% where no bacteria were found. Combinations of residual bacterial species were more frequently related to non-healed lesions than were single strains. When no bacteria remained, healing occurred independently of the quality of the root filling. In contrast, when bacteria remained, there was a greater correlation with non-healing in poor-quality root fillings than in technically well-performed fillings. In root canals where bacteria were found after removal of the root filling, 97% had not healed, compared with 18% for those root canals with no bacteria detected. The present study demonstrates the importance of obtaining a bacteria-free root canal system before permanent root filling in order to achieve optimal healing conditions for the periapical tissues.

Once established, nonmutans streptococci, enterococci and lactobacilli appear to survive commonly following root-canal treatment of teeth with clinical and radiographical signs of apical periodontitis.