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Aim: This study aimed to evaluate the effect of blood and synthetic tissue fluid on marginal adaptation and surface microstructure of Mineral trioxide aggregate (MTA) and Endosequence root repair material (ERRM Putty). Materials and Methods: Sixty human single-rooted teeth were endodontically treated, and root-end cavities were prepared to 3 mm depth. The teeth were divided randomly into three groups (n = 20) based on the contamination, and each group was again divided into two subgroups (n=10) based on the root-end filling material used. Group I (Blood Exposed): The root-end cavities were filled with fresh blood then gently aspirated.  The retro cavities were then filled with MTA and ERRM putty and placed in molds containing heparinized blood. Group II (STF-Exposed): STF was mixed accordingly and  the retro cavities were then filled with STF and then gently aspirated. The cavities were now filled with MTA and ERRM putty and placed in molds containing STF. Group III (Control): The root end cavities were not contaminated with any fluid and were filled with MTA and ERRM putty in this group.   All samples were viewed Under SEM at 2000x magnification and statistically analyzed with Tukey post hoc test. Results: Mean gap width in microns (SEM) was blood with MTA(22.12), followed by blood with ERRM putty (18.89), Control with ERRM putty (14.53), STF with MTA (6.86), Control with MTA (6.85) and  STF with ERRM putty (3.78). A significant difference was observed among the three groups (Blood, STF and Control) with gap width in microns (SEM) at 5% level of significance.  Conclusions: The samples contaminated with blood showed more gap width, and ERRM putty exhibited better marginal adaptation.

Aim: The study aimed to evaluate the number of canals safely enlarged with Protaper instruments before the instrument showed initial signs of failure. Materials and Methods: Freshly extracted 100 human molar teeth with canal curvature < 200 were included in the study. Group 1(PTU SX files) (n=50): Instrumentation was done with Pro taper Universal files, Group 2 (PTG SX files) (n=50): Instrumentation was done with Pro taper gold rotary files. The total number of root canals considered for instrumentation in each group was 150. After the access opening of all teeth, canal patency was checked and the SX files of PTU were instrumented in 50 teeth, and the SX files of PTG were instrumented in another 50 teeth. The SX files were checked for any signs of failure after each use under the Dental operating microscope. The number of canals enlarged before showing the signs of failure was noted. Statistical Analysis: The data were analyzed with the independent t-test. Results: The difference was statistically significant with a p value of 0.006 in the number of canals enlarged by PTU SX files and PTG SX files without showing any signs of failure. The mean number of canals enlarged using PTG SX files was 10 ± 1.054 compared to PTU SX files (8.6 ± 0.966). Conclusions: PTG SX files were used in more canals than PTU SX files, before showing initial signs of failure thereby showing the more efficiency of gold files.