RESUMEN
Background and Aims: . Retrieval of separated rotary file may not be possible many times. Then sealing of coronal root canal system depends on sealing ability of root canal sealers. The type of seal to be obtained should be bacterial-tight seal. Hence it is important to evaluate the sealing ability of obturation with different newer sealers with separated file in apical 3rd of root canals with bacterial penetration method using e.fecalis. Methods: Forty six human mandibular molars extracted for periodontal reasons were collected. After Decoronation of teeth Protaper rotary S1 files (Dentsply Maillefer) were intentionally separated in apical third of canal and obturated with gutta-percha (Prime Dental Products, India) along with zinc oxide eugenol sealer (Dental products of India-Mumbai) in Group I, Nano Zinc oxide eugenol (Nano Research Lab, Jharkand, India) in Group II and MTA sealer (Angelus, Londrina, Brazil) in Group III. Samples were assessed for bacterial leakage with E fecalis for 48 hours. The number of colony forming units was assessed. Results: The values obtained were subjected to one way ANOVA test and significance level was set to 0.05. Group I scored the highest mean value of (6.58), followed by Group II (3.91). The lowest Mean value was with Group III (2.91). However there was no statistical significant difference in Mean values among groups with (p-value 0.05). Conclusion: The mean value of colony forming units in Group III was 2.91, in Group II 3.91 and 6.58 in Group I. None of the groups demonstrated complete bacteria-tight seal.
RESUMEN
AIM: The aim of the study is to compare the maximum stress distribution on the rotary retreatment instruments within the root canal at cervical, middle, and the apical one-third during retreatment of gutta-percha. MATERIALS AND METHODS: A human mandibular premolar was scanned, and three-dimensional geometry of the root was reconstructed using finite element analysis (FEA) software package (ANSYS). The basic model was kept unchanged; tooth models were created using the same dimensions and divided into two groups as follows: Group I: ProTaper Universal retreatment system and group II: Mtwo rotary retreatment system. The stress distribution on the surface and within the retreatment files was analyzed numerically in the FEA package (ANSYS). RESULTS: The FEA analysis revealed that the retreatment instruments received the greatest stress in the cervical third, followed by the apical third and the middle third. The stress generated on the ProTaper Universal retreatment system was less when compared with the Mtwo retreatment files. CONCLUSION: The study concludes that the retreatment instruments undergo higher stress in the cervical third region, and further in vivo and in vitro studies are necessary to evaluate the relationship between instrument designs, stress distribution, residual stresses after use, and the torsional fracture of the retreatment instrument. CLINICAL SIGNIFICANCE: The stress developed on the rotary retreatment instruments during retrieval of gutta-percha makes the instrument to get separated. There is no instrument system, i.e., suitable for all clinical situations and it is important to understand how the structural characteristics could influence the magnitude of stresses on the instrument to prevent its fracture in use.