Bacteriologic Analysis In Teeth Associated With Different Types Of Pulpal And Periapical Disease

Part I Status of bacterial colonization in teeth associated with different types of pulpal and periapical diseaseObjective To use scanning electron microscopy (SEM) to investigate the status of bacterial colonization in differently infected root canals.Materials and methods Twenty-five freshly extracted teeth were selected for this study (group A:8 teeth with pulpitis; group B:10 teeth with periapical lesions; and group C:7 teeth with failed root canal treatment). After fixation, the roots were longitudinally split into 2 halves. The halves were then dehydrated, sputter-coated with gold, and viewed utilizing SEM, descriptively being divided their lengths into apical, middle, and coronal thirds.Results In group A, bacterial infection was mainly located in the coronal third of the root canals and bacteria failed to penetrate into the dentinal tubules. In group B, bacterial infection was distributed over the entire length of the root canal. The invasion depth of bacteria into the dentinal tubules was approximately 300 μm. In group C, bacterial infection was mainly focused on the apical third of the root canals. Most of the dentinal tubules had collapsed, and the root canal walls were heavily colonized with dense bacterial biofilm, primarily consisting of cocci. Compared to group B, the invasion depths were deeper in the apical thirds of root canals (P<0.05).Conclusion Bacterial infection was lighter in the root canals with pulpitis than in those with apical periodontitis, which might require special considerations regarding different stages of pulp and periapical pathology in root canal treatment.Part Ⅱ Detection and analysis of 4 anaerobic bacteria in teeth associated with different types of pulpal and periapical diseases Objective To detect the 4 anaerobic bacterial colonization in differently infected root canals with 16S rDNA PCR.Materials and methods Thirty freshly extracted teeth were selected for this study (group A:10 teeth with pulpitis; group B:10 teeth with periapical lesions; and group C:10 teeth with failed root canal treatment). After extraction, the periodontal ligament and other attachments were removed with a scalpel and clinical crown was sectioned at the cemento-enamel junction (CEJ) with low speed cutting machine. The root was cut into two sections horizontally (coronal and apical) with the use of sterile diamond disc. The outer surface of the tooth was wiped off repeatedly with a piece of gauze soaked in 0.5% sodium hypochlorite and was then placed in a 2.5% sodium thiosulfate solution. The samples were transferred to a 5ml Cryogenic Vials and then placed in liquid nitrogen for 24 hours. The teeth were wrapped with high density of white cloth sterilization at high temperature and high pressure, and were broken into pieces with the hammer. The powdered root segments were frozen at-80℃. A 16S rDNA polymerase chain reaction method was used to assess the occurrence of four anaerobic bacteria in root canal infections.Results All samples examined showed the amplicon of the ubiquitous bacterial primers. In group A, P.e, F.n and P.i were detected in the coronal and middle segment, the detection rate of P.e was highest. However, P.e was only detected in the apical segment, and the detection rate is relatively low (10%), significantly lower than the coronal and middle section (P<0.05). In group B, the detection rate of P.e, F.n, E.f and P.i (30%,20%,10% and 70%) in the coronal and middle segments and apical segments (40%,40%,10% and 80%) have no significant statistical difference (P>0.05), which the highest detection rate is P.i. In group C, positive rate of E.f in apical segments (60%) than in the coronal and middle segments (10%), which was of statistically significant (P<0.05), and the other three kinds of bacteria detection rates are relatively low.Conclusion Root canal infection is multiple bacterial infection; The 4 strains of bacteria are the dominant bacteria in root canal infections; With pulpitis, the bacterial infection in the crown and middle segments were predominantly porphyromonas endodontalis, and bacteria detection rate of apical segment was very low; With primary periapical, there was no significant difference in the four kinds of bacteria in the middle and apical segments; With secondary periapical periodontitis, the bacterial detection rate is very low in the crown and middle segments, but the detection rate of of enterococcus faecalis in the apical segment was the highest.