Bacteriologic Study of Primary Endodontic Infections

Primary endodontic infections are generally caused by microorganisms which inhabit the root canal environment in mixed infections dominated by anaerobic bacteria. Objectives: The aim of this study was to analyse the microflora isolated from infected root canals of symptomatic or asymptomatic teeth, with periapical radiolucent areas. Methods: Microbial samples were taken from root canals of 90 teeth with necrotic dental pulp. Strict anaerobic techniques were used for serial dilution, plating and incubation. Microbial colonies were then purified, characterized and identified by established methods The clinical aspects of each case were observed: spontaneous pain (n=54), tenderness to percussion (n=58), pain on palpation (43), caries (n=45), swelling (n=33), exudate (n=40), abscess (n=56), absence of simptomatology (n=20). Results: A total of 400 cultivable isolates were recovered from 69 different microbial species and 22 different genera. Root canals from symptomatic teeth harboured more obligate anaerobes and a bigger number of bacterial species than the asymptomatic teeth. About 80% of the total bacterial isolates were strict anaerobes. The most frequently found strict anaerobes were: Fusobacterium nucleatum (n=35), Prevotella intermedia (n=21), Anaerococcus prevotii (n=19), Prevotella oralis (n=19), Peptostreptococcus micros (n=18), Fusobacterium necrophorum (n=16), Veillonella spp. (n=16), Eggertella lenta (n=12), Porphyromonas gingivalis (n=11). ‘Black pigmented bacteria’ were found in 45% of the root canals analysed. Statistical analysis used a Pearson x2 test or a one-sided Fisherxs Exact test, as appropriate. Conclusions: Our results suggested that specific bacteria are associated with endodontic symptoms of infected teeth. Moreover, the majority of the bacteria associated with simptomatology was the strict anaerobes. (Supported by FAPESP 00/13689-7, 02/08167-7; CNPq- 520277/99-6 & CAPES – BEX 2528/02-9)