Does pulp cavity affect the center of resistance in three-dimensional tooth model? A finite element method study

Clinical Oral Investigations - To compare the center of resistance (Cres) of the maxillary central incisor in models with and without the pulp cavity and to evaluate the association of pulp...     

Autoaggregation and coaggregation of bacteria associated with acute endodontic infections

Biofilms and microbial aggregates are a common mechanism for the survival of bacteria in nature. Microbial aggregates have been associated with intraradicular and extraradicular endodontic disease. One objective of this study was to assess bacteria isolated from acute endodontic infections for autoaggregation and coaggregation. Another objective was to use both a conventional visual assay and a novel fluorescent dye-staining technique to study bacterial aggregation. Sixty-two strains of bacteria were isolated from 10 clinical samples of endodontic abscesses or cellulitis. Autoaggregation was detected in 35/62 (56.45%) of the bacteria using the visual assay. Coaggregation of bacteria from each of the samples was demonstrated for 29/183 (15.85%) bacterial pairs using the visual assay and 148/183 (80.87%) using the dye-staining assay. Coaggregation was observed for each of the 15 genera assayed, especially Prevotella, Streptococcus, and Fusobacterium. The dye-staining assay using a confocal microscope was a highly sensitive method to detect aggregation of bacteria.     

Efficacy of calcium hydroxide: chlorhexidine paste as an intracanal medication in bovine dentin

The purpose of this study was to evaluate the antibacterial efficacy of an intracanal medication composed of calcium hydroxide with 2% chlorhexidine. Dentin from 24 bovine incisors was used. The incisors were made into standardized cylindrical segments of dentin and infected with Enterococcus faecalis. They were then treated with an intracanal paste composed of calcium hydroxide and sterile water or an intracanal paste composed of calcium hydroxide and 2% chlorhexidine for 1 week. Dentin shavings were collected, suspended in solution, and spread on brain-heart infusion agar. After incubation, colony-forming units were enumerated. The amount of bacteria per mg of dentin was determined. The calcium hydroxide paste with 2% chlorhexidine was significantly more effective at killing E. faecalis in the dentinal tubules than calcium hydroxide with water.     

Identification of bacteria in acute endodontic infections and their antimicrobial susceptibility

OBJECTIVE: The purpose of the study was to identify the bacterial composition of the microbiota from acute endodontic abscesses/cellulitis and their antimicrobial susceptibilities. STUDY DESIGN: Purulence from 17 patients with acute endodontic abscesses/cellulitis was obtained by needle aspiration and processed under anaerobic conditions. Bacteria were isolated and identified by biochemical or molecular methods. The antimicrobial susceptibility of isolated bacteria was determined by using the Etest. RESULTS: All 17 aspirates contained a mix of microorganisms. A total of 127 strains of bacteria were isolated. Of 127 strains, 80 strains were anaerobes and 47 strains were aerobes. The mean number of strains per sample was 7.5 (range, 3 to 13). The average number of viable bacteria was 6.37 x 10(7) (range, 10(4) to 10(8)) colony-forming units/mL. Strict anaerobes and microaerophiles were the dominant bacteria in 82% (14 of 17) of the cases. The genera of bacteria most frequently encountered were Prevotella and Streptococcus. Prevotella and Peptostreptococcus were frequently found to dominate the mixture. The combination of Prevotella and Streptococcus was found in 53% (9 of 17). The previously reported uncultured Prevotella clone PUS9.180 was frequently identified. The percentage of bacteria susceptible/intermediate for each antibiotic in this study was penicillin V, 81% (95 of 118); metronidazole, 88% (51 of 58); amoxicillin, 85% (100 of 118); amoxicillin + clavulanic acid, 100% (118 of 118); and clindamycin, 89% (105 of 118). CONCLUSIONS: The present results confirm the existence of mixed infection with the predominance of anaerobic bacteria in acute endodontic abscesses/cellulitis. The frequency of uncultured Prevotella clone PUS9.180 suggests the possible key role of this Prevotella species in acute endodontic infections. Penicillin V still possesses antimicrobial activity against the majority of bacteria isolated from acute endodontic infections. However, if penicillin V therapy has failed to be effective, the combination of penicillin V with metronidazole or amoxicillin with clavulanic acid is recommended. Switching to clindamycin is another good alternative.     

Identification of spirochetes (treponemes) in endodontic infections

The purpose of this study was to determine the prevalence of spirochetes in asymptomatic infected root canals and in endodontic abscesses/cellulitis. Aseptic clinical samples were collected using paper points from 54 infected root canals and from aspirates of 84 abscesses/cellulitis. Oligonucleotide primers were produced for PCR identification of Treponema vincentii, T. pectinovorum, T. medium, T. amylovorum, T. denticola, T. maltophilum, and T. socranskii. PCR detected spirochetes in 51 of 84 (60.7%) samples from abscesses/cellulitis and in 20 of 54 (37.0%) samples from asymptomatic infected root canals. T. socranskii was the most frequently detected (44.9%), followed by T. maltophilum (29.7%), T. denticola (28.9%), T. pectinovorum (13.7%), and T. vincentii (5.1%). The number of treponema species detected ranged from 1 to 5 species per sample. The mean numbers of species detected were 2.3 in abscesses/cellulitis and 2.6 in infected root canals. Significant association among species was found between T. maltophilum and T. socranskii, as well as between T. maltophilum and T. denticola by determining the odds ratio (> 2.0).