Accuracy of Dynamic Guidance System in Endodontic Access of Anterior Teeth - ex vivo Analysis

Aim: To measure the accuracy, we will be evaluating the position deviations and angular deviations of endodontic access preparations compared with the digital file plan for the guided access. Material and Methods: 24 extracted human anterior teeth (4 maxillary canines, 4 mandibular canines, 8 mandibular incisors, and 8 maxillary incisors) were mounted into acrylic resin to mimic the position in the human jaw. Pre-op CBCT images of the models were acquired and imported into the X-Nav system software. Virtual endodontic files were custom created in the software by adjusting the diameter of the “implant” to 0.5 mm, with lengths ranging from 7-14 mm to allow virtual placement with coronal termination of the file near the natural tooth occlusal surface. The enamel of the path of the access is first removed using a high-speed drill and a #4 round bur and subsequently 34mm size #1 Munce with the 1:1 dental surgical electric handpiece was used to drill through the designed access in the proper orientation. Post-op CBCT images were taken and evaluated for angular deviation via access design and endodontic file placement deviations. Results: Subjective analysis confirmed passive straight line access with a #8 K-file through the access for all canals and CBCT images were captured. Images were repeated with files in the canal after decoronation of teeth. No significant difference was found in file angular deviations. Overall files angular deviation was 2.75 ± 2.21 degrees. There was a significant difference found among maxillary canine vs mandibular canines (1.34 ± 1.32 degrees and 5.61 ± 1.63 degrees, respectively) with a p-value=0.0064. A significant difference was found among each tooth type when comparing the drill depth needed to achieve passive access with endodontic files. There was significant difference found when comparing maxillary canines to mandibular incisors. The average drill depth for maxillary canines was 12.75 ± 2.06mm, maxillary incisors was 12 ± 1.93mm, and mandibular incisors 8.05 ± 0.97mm. Conclusion: The dynamic guide system proved to be highly accurate in accessing root canals of anterior teeth while creating a highly conservative access design. The accuracy was consistent among all anterior teeth without any significant difference. All canals were located after the endodontic access was completed using the software. Further research will be needed to study the practicality of the system in a clinical setting. The system does have a learning curve of 3-4 teeth and the system can be very useful in situations with highly calcified teeth where deep access will be required to locate canals

Oxidative Cleavage of Alkene C=C Bonds Using a Manganese Catalyzed Oxidation with H2O2 Combined with Periodate Oxidation

A one-pot multi-step method for the oxidative cleavage of alkenes to aldehydes/ketones under ambient conditions is described as an alternative to ozonolysis. The first step is a highly efficient manganese catalyzed epoxidation/cis-dihydroxylation of alkenes. This step is followed by an Fe(III) assisted ring opening of the epoxide (where necessary) to a 1,2-diol. Carbon-carbon bond cleavage is achieved by treatment of the diol with sodium periodate. The conditions used in each step are not only compatible with the subsequent step(s), but also provide for increased conversion compared to the equivalent reactions carried out on the isolated intermediate compounds. The described procedure allows for carbon-carbon bond cleavage in the presence of other alkenes, oxidation sensitive moieties and other functional groups; the mild conditions (r.t.) used in all three steps make this a viable general alternative to ozonolysis and especially for use under flow or continuous batch conditions