ABSTRACT
BACKGROUND: Enterococcus faecalis is one of the most commonly occurring organisms retrieved from root canal treated teeth that show refractory apical periodontitis. Though it is well known that the ability of E. faecalis to form a matrix-encased biofilm contributes to its pathogenicity, the role of extracellular dextran and DNA in biofilm formation and its effect on the susceptibility of the biofilm to chlorhexidine remains poorly understood. It was hypothesized that the addition of an Extracellular Polymeric Substance (EPS) degrading enzyme along with a detergent to chlorhexidine may increase the susceptibility of the E. faecalis biofilm. AIM: To evaluate the sensitivity of Enterococcus faecalis biofilms treated with DNase enzyme and their susceptibility to 2% chlorhexidine used alone or in conjunction with a detergent in a dentin disinfection model and examine under confocal laser scanning microscopy (CLSM). MATERIALS AND METHODS: Semi cylindrical shaped dentin specimens were infected with E. faecalis and incubated for 24 hours. Following incubation, the infected dentin specimens were exposed for 3 minutes to the four disinfecting solutions and grouped accordingly. {Group I- Sterile saline, Group II- 2% Chlorhexidine (CHX), Group III- Dnase1 Enzyme + 2% CHX, Group IV- DNase1 Enzyme + 2% CHX & Tween 80. Bacterial viability was then assessed by staining the specimens and examining under CLSM to analyse the proportion of dead and live bacteria within the dentinal tubules. RESULTS: The Groups II, III and IV showed statistically significant (p<0.05) percentage of dead bacteria compared to the control (Group I). However there was no significant difference in the killing effectiveness within the experimental groups (II-IV) at (p<0.05). CONCLUSION: EPS degrading enzyme (DNase I) disrupts the biofilm and increases the susceptibility of E.faecalis when exposed to 2% Chlorhexidine and the use of a surfactant with this combination significantly contributes to improving the antibacterial efficacy.
ABSTRACT
AIM: To compare and assess the fracture resistance of endodontically treated teeth with those that have been subjected to endodontic retreatment. MATERIALS AND METHODS: 30 extracted mandibular premolars were decoronated at cementoenamel junction and randomly divided into 2 groups. In Group I endodontic treatment was performed with ProTaper rotary system till size F2 and obturated. In Group II, cleaning and shaping was done and teeth were subjected to Spiral CT to assess the remaining dentin thickness and obturated. Later retreatment was done using Protaper Universal Retreatment system and final shaping was performed till size F3. Remaining dentin thickness was again assessed using Spiral CT and then obturated. All the specimens were subjected to fracture resistance using universal testing machine. The results were statistically analyzed using Independent Samples t-test for analysis of remaining dentin thickness using SCT within Group II and Paired Samples t-test was used for assessment of fracture resistance between Group I and II (P < 0.05). RESULTS: In Group II, the intra group comparison of the remaining dentin thickness in the coronal third reveals statistical significance, with a significant difference noted in the apical third. Results of the fracture resistance reveal a statistically significant difference (P < 0.05) between Groups I and II with the mean fracture resistance of Group I being higher than Group II. CONCLUSION: Endodontically retreated teeth have shown significantly decreased resistance to fracture and this has a positive correlation to the increased loss of root dentin during the retreatment procedures.
