RESUMO
Abstract Objective The rDNA-based method is unable to distinguish between alive and dead cells. Alternatively, bacterial viability can be assessed by molecular methods based on ribosomal RNA (rRNA). Therefore, this study aimed to detect viable streptococci in root canal samples using rRNA-based reverse transcription polymerase chain reaction (RT-PCR), compared to an rDNA-based PCR assay. Methodology Microbiological root canal samples were obtained from 32 teeth with primary endodontic infections before (S1) and after chemomechanical preparation (S2), and after removal of intracanal medication (S3). RNA and DNA were extracted, and complementary DNA (cDNA) was synthesized from RNA using RT reaction. cDNA and genomic DNA were subjected to PCR with primers complementary to the 16S rRNA sequences of Streptococcus spp. McNemar's test was used to compare the detection rate of both assays (P<0.05). Results Streptococci were detected in 28.12% (9/32) and 37.5% (12/32) of S1 samples using rRNA- and rDNA-based PCR assays, respectively. In contrast, they were detected in only 6.25% (2/32) of S2 samples using rRNA-based RT-PCR, compared to 15.62% (5/32) using rDNA-based PCR. Finally, in S3 samples, streptococci were not detected by rRNA, whereas rDNA-based PCR still detected the bacteria in 12.5% (4/32) of the samples. The total number of PCR-positive reactions in the rDNA-based PCR was higher than in the rRNA-based assay (P<0.05). Conclusions The rRNA-based RT-PCR showed a lower detection rate of streptococci when compared to the rDNA-based PCR, suggesting that the latter may have detected dead cells of streptococci in root canal samples.
Assuntos
Humanos , Streptococcus/isolamento & purificação , DNA Ribossômico/isolamento & purificação , RNA Ribossômico/isolamento & purificação , Reação em Cadeia da Polimerase/métodos , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodos , Cavidade Pulpar/microbiologia , Tratamento do Canal Radicular/métodos , Streptococcus/genética , DNA Bacteriano/isolamento & purificação , DNA Bacteriano/genética , DNA Ribossômico/genética , RNA Bacteriano/isolamento & purificação , RNA Bacteriano/genética , RNA Ribossômico/genética , Reprodutibilidade dos TestesRESUMO
O objetivo deste trabalho foi de realizar uma revisäo de literatura sobre cisto radicular, procurando elucidar a etiologia e formaçäo, o diagnóstico diferencial com o granuloma, a classificaçäo e as opçöes de tratamento. Baseada nesa revisäo, como clínica e radiograficamente o diagnóstico diferencial näo é possível em virtude das características serem muito semelhantes entre si, o tratamento inicial proposto é o endodôntico. Se a terapia endodôntica for bem conduzida, tanto o granuloma como o cisto baia deveräo ser reparados, enquanto o cisto verdadeiro necessitará ser removido cirurgicamente, pois é pouco provável que haja reparo somente com o tratamento endodôntico