Sean M. Horan

Date of Graduation


Document Type


Degree Type



School of Dentistry



Committee Chair

Elizabeth C Kao

Committee Co-Chair

Jerry E Bouquot

Committee Member

Larry K Hildebrand

Committee Member

Bryan Weaver


Introduction.;After proper chemomechanical disinfection and obturation of a root canal system, the next important goal in endodontic therapy is obtaining an adequate coronal seal. If the coronal seal becomes compromised, it is difficult to decide whether the root canal system should be re-treated. This decision should be made based on the ability of the root canal filling to resist bacterial contamination and on the length of time the seal has been compromised.;The root canal system should be filled in three dimensions, typically with a combination of gutta percha and sealer. One obturation method that has seen a revival in recent years is the single-cone technique. Newly developed sealers claim to create an effective seal through adhesive bonding to the gutta percha and/or dentin. The objective of this study was to evaluate the sealing ability of three currently available endodontic sealers used in a single-cone technique with a bacterial leakage model. A pilot study was also conducted in an attempt to better quantify and localize the bacteria in the obturated experimental teeth.;Materials and Methods.;Fifty extracted human maxillary anterior teeth were decoronated and root length was standardized. Each tooth was instrumented and irrigated. The teeth were randomly divided into three experimental groups (n = 12) and two control groups (5 positive and 5 negative). The final four teeth were used in the pilot study. Obturation of the three experimental groups, EndoSequence BC Sealer, ThermaSeal Plus Ribbon Sealer, or GuttaFlow 2, was performed with a single-cone technique using a ProTaper master cone. A bacterial leakage experimental apparatus was constructed to evaluate the seal created by each of the experimental groups.;For the pilot study, four teeth were obturated with varying levels of gutta percha and evaluated in the same experimental apparatus. A solution of a bioluminescent bacterium, Staphylococcus aureus Xen36, was used to inoculate each tooth. Scans of the teeth were taken with an In Vivo Imaging System (IVIS) at Days 0, 3, 7, and 10 to show whether bacteria could be detected at varying levels in the teeth.;The remaining forty-six apparatuses were evaluated with a more traditional bacterial leakage method, where Difco Purple Broth Base was placed in the lower chamber of the apparatus so that 2 mm of the root end was submerged. A solution of S. aureus Xen36 was used to inoculate the top chamber of the apparatus, and the apparatuses were incubated for up to 50 days. The apparatuses were checked daily to monitor for bacterial contamination.;Results and Conclusion.;The pilot study was unable to provide accurate information on the localization and quantification of bacteria in the four sample teeth. For the traditional bacterial leakage study, each of the experimental groups had a noticeable amount of early leakage, and after one week, all three groups had a survival rate of 58.3%. After 50 days, the ThermaSeal Plus Ribbon Sealer group had a survival rate of 8.3%, while the EndoSequence BC Sealer and GuttaFlow 2 groups had a survival rate of 25.0%. The log-rank test showed no statistically significant differences between the three groups with respect to leakage over time (p = 0.665). The results of the present study showed that in the absence of a coronal seal, the single-cone method of root canal obturation does not provide long-term sealing ability in many teeth. Further studies should be piloted to see if the IVIS could be beneficial for analyzing obturated teeth.