These results suggest that the increased prostaglandin E2 concentration, caused by endodontic treatment of teeth with large restorations, is well correlated with the intensity of postoperative pain.

Under the conditions of our study, it may be concluded that the Acroseal sealer presented the behaviour more like epoxy-based material, AH Plus, than calcium hydroxide sealer, Apexit.

Introduction. Mechanical instrumentation of the complex root canal system is very demanding procedure which requires use of the various manual and rotary instruments. The aim of this study was to assess the frequency and to verify the possible deformation of the working part of endodontic instruments after their multiple clinical use. Material and Methods. New sets of the manual endodontic instruments (reamers, K-files and Hedstroem) used in routine clinical use (44 instruments) and for root canal instrumentation of extracted teeth (44 instruments) were included in the study. Instrumentation was performed by Step-Back technique and constant irrigation with 0.5% NaOCl solution, 10 ml for each root canal. All the instruments were used 10 times and after use sterilized in a dry sterilizer or autoclave. The working parts of deformed instruments were analyzed using optimagnetic print. Results. The results obtained after clinical use showed deformations of the working part of the reamers in 50%, K-files in 43% and Hedstroem in 66.7% of used instruments. After instrumentation the canal of the extracted teeth, deformations were observed in 87.5% of the reamers, in 50% of the K-files and in 62.5% of Hedstroem files. The difference in frequency of the deformations was not statistically significant. On the instruments used for the preparation the canals of the extracted teeth and sterilized in autoclave, malformations were observed in 86.4%, comparing to the instruments sterilized in a dry sterilizer where malformations of the working part were registered in 59.1% of the cases. That difference was statistically significant (χ2=5.250; p=0.072). Conclusion. Multiple use of the manual endodontic instruments in clinical conditions leads to increased frequency of malformations of the working part in all types of manual endodontic instruments