Chemomechanical preparation is intended to clean, disinfect, and shape the root canal. This step is of utmost importance during treatment of infected teeth with apical periodontitis, because treatment outcome depends on how effectively the clinician eliminates bacteria, their products, and necrotic tissue that would serve as substrate for bacterial regrowth. Nonetheless, curvatures and complex internal anatomical variations of the root canal system can pose a high degree of difficulty in reaching these goals. In infected teeth, bacteria may persist not only in difficult-to-reach areas such as isthmuses, ramifications, dentinal tubules, and recesses from C-shaped or oval/flattened canals, but also in areas of the main canal wall that remain untouched by instruments. If bacteria withstand chemomechanical procedures, there is an augmented risk for post-treatment apical periodontitis. This article discloses the reasons why some areas remain unprepared by instruments and discusses strategies to circumvent this issue and enhance infection control during endodontic treatment/retreatment of teeth with apical periodontitis.

Evidence suggests that diabetic patients are more significantly affected by problems of endodontic origin. This study sought to radiographically and histologically examine the development of periradicular inflammation in control and in diabetic rats after induction of pulpal infection. The pulps of the mandibular first molars of normal and streptozotocin-induced diabetic rats were exposed and left in contact with their oral cavities for 21 and 40 days. Afterwards, the animals were sacrificed, the mandibles were surgically removed, fixed in formalin and then radiographed in a standardized position. The radiographic images of the periradicular lesions were scanned and computerized images were evaluated for the total area of the lesions using a specific software. Representative specimens were also prepared for histopathological analysis. Radiographic analysis revealed that diabetic rats presented significantly larger periradicular lesions when compared with control rats, regardless of the experimental period (p<0.05). Histopathological examination of representative specimens revealed larger periradicular lesions and more severe inflammatory exudate in the group of diabetic rats when compared with the control group. Data from the present study indicated that diabetic rats can be more prone to develop large periradicular lesions, possibly due to reduction in the defense ability against microbial pathogens.

Fusobacterium nucleatum is a Gram-negative, non-spore-forming, nonmotile, obligatory anaerobic rod that is normally isolated from the oral cavity. Epidemiological studies have shown that this species is one of the most prevalent in primary root canal infections. The purpose of this study was to compare the effectiveness of bacteriological culture, 16S rDNA directed polymerase chain reaction and checkerboard DNA-DNA hybridization for detection of F. nucleatum strains in infected teeth associated with periradicular lesions. Thirteen single-root teeth from adult patients, all having carious lesions, necrotic pulps, and radiographic evidence of periradicular bone loss were included in this study. Combining all methods, the results indicated that F. nucleatum was present in approximately 31% (4 of 13) of the specimens. Incidence of F. nucleatum in root canal infections, as evaluated in this study by polymerase chain reaction, culture, and DNA-DNA hybridization, was 15.4%, 15.4%, and 10.0%, respectively. Our data demonstrated that no method used herein could be considered superior for detecting F. nucleatum directly from clinical samples. However, the small number of samples examined and the low prevalence that was observed should be considered.

The aim of this study was to describe a 16S rDNA-based nested polymerase chain reaction (nPCR) assay to investigate the occurrence of Campylobacter gracilis in oral infections. Samples were collected from ten infected root canals, ten cases of acute periradicular abscesses and eight cases of adult marginal periodontitis. DNA extracted from the samples was initially amplified using universal 16S rDNA primers. A second round of amplification used the first PCR products to detect C. gracilis using oligonucleotide primers designed from species-specific 16S rDNA signature sequences. The nPCR assay used in this study showed a detection limit of 10 C. gracilis cells and no cross-reactivity was observed with nontarget bacteria. C. gracilis was detected in the three types of oral infections investigated - 4/10 infected root canals; 2/10 acute periradicular abscesses; and 1/8 subgingival specimens from adult periodontitis. The method proposed in this study showed both high sensitivity and high specificity to directly detect C. gracilis in samples from root canal infections, abscesses, and subgingival plaque. Our findings confirmed that C. gracilis may be a member of the microbiota associated with distinct oral infections, and its specific role in such diseases requires further clarification.

RÔÇAS, I. N.; SIQUEIRA Jr., J. F.; FAVIERI, A.; SANTOS, K. R. N. Detecção de Treponema denticola em casos de abscesso perirradicular agudo. Pesqui Odontol Bras, v. 14, n. 3, p. 209-212, jul./set. 2000.Nosso objetivo foi detectar Treponema denticola em casos de abscesso perirradicular agudo. O DNA extraído das amostras de pus foi examinado pelo método da "Polymerase Chain Reaction" direcionada para o gene do RNAr (fração 16S). A amplificação usando o "primer" da espécie Treponema denticola permitiu detectá-la em 5 dos 6 casos de abscessos examinados. Apenas uma banda de tamanho esperado foi observada para as amostras positivas para esta bactéria, o que foi confirmado pela comparação com o DNA de referência do Treponema denticola (controle positivo). Até o momento, este é o primeiro relato da presença desta espiroqueta, considerada um importante patógeno periodontal em infecções endodônticas. Os resultados sugerem que Treponema denticola também pode ser um importante patógeno endodôntico.UNITERMOS: Abscesso periapical; Treponema; Reação em cadeia por polimerase. INTRODUÇÃOAs lesões perirradiculares são alterações patológicas que ocorrem em decorrência da necrose e da infecção pulpar. O dano aos tecidos perirradiculares pode ser provocado pela ação direta ou indireta das bactérias que colonizam o sistema de canais radiculares. Fatores de virulência liberados por bactérias, como enzimas, exotoxinas e produtos metabólicos, agem diretamente nesses tecidos. Componentes da própria estrutura bacteriana, como lipopolissacarídeos, peptidoglicano e ácido lipoteicóico, podem desencadear as respostas de defesa do hospedeiro, as quais podem gerar o dano tecidual. Esta última ação caracteriza um dano tecidual indiretamente causado por bactérias 10