Effizienz der Revision von Wurzelkanalfüllungen nach Obturation mit fünf verschiedenen Techniken mittels maschineller Wurzelkanalinstrumente

Background and Aims Endodontic retreatment is indicated when clinical or radiographic signs of an apical periodontitis are present on teeth that have already previously been treated endodontically. The aim of endodontic retreatment is the restitution of the integrity of healthy periapical conditions and the therapy or prevention of clinical symptoms by a repeated chemomechanical instrumentation and irrigation of the root canal system followed by a hermetic seal of both the root canal system and the access cavity. This study ought to assess the efficiency of step-wise endodontic retreatment of root canal fillings performed by different cold and warm obturation techniques using D-RaCe-NiTi- rotary files. Therefore, the retreatment efficiency and the retreatment time were measured. Methods For this in vitro study 75 extracted human single-rooted teeth were decoronated. The specimens were instrumented by means of BioRaCe files to an apical size .04/#35. Following the separation of the roots in longitudinal direction using a diamond-coated disc, halves of roots were re-assembled within Biresin polyurethane blocks. Then, a final instrumentation to size .04/#40 was performed to obtain circular canals. The specimens were randomly assigned to 5 groups and subsequently obturated with the dedicated root filling technique. The investigated obturation techniques were: lateral compaction, die non compaction technique and die single cone technique for cold obturation, and the Thermafil technique and warm vertical compaction technique for warm obturation. Finally, all specimens were retreated. The first retreatment step was performed using D RaCe instruments of sizes .10/#30 and .04/#25, as well as BioRaCe file of size .04/#40. For the second retreatment step, a Rondo Instrument (custom made) of size .04/#45 and in the final retreatment step a BioRaCe instrument of size .04/#50 was used. After each retreatment step the specimens were microphotographed by means of a light microscope (Leica) using 4x and 16x magnification and calculated with Image Tool software. Statistical analysis was performed with SPSS 19.0. Results The analysis of the specimens revealed a clear result. Cold obturation showed less amount of gutta-percha than sealer. In contrast, warm obturation techniques yielded only little amounts of residual sealer and significantly more gutta-percha. In general, retreatment and canal enlargement was quite efficient. Regarding retreatment time root fillings performed using the single cone technique were easy and fast to retreat. In opposition, retreatment of Thermafil was less effective and significantly more time consuming. Practical Conclusions The results of the present study show the efficiency of step-wise enlargement of the root canal during endodontic retreatment. The instrumentation size should exceed the original size of the root canal by at least 2 instrument sizes in order to remove a maximum of sealer and gutta-percha from the root canal walls. Especially regarding retreatment of Thermafil obturations requires more time compared with the other obturation techniques.