In Part I, the effects of irrigant delivered via a 31-gauge irrigation needle to E. faecalis infected teeth instrumented to different apical sizes with six different nickel titanium (NiTi) rotary instruments were examined in an in-vitro model using 165 single canaled extracted teeth. In Part II, the accuracy and deformation of NiTi rotary files before and after use were examined via SEM imaging and ImageJ software. Statistical analysis was done using r-ANOVA and Tukey's test for Part I, and proportional odds model and Mantel-Haenszel row mean score for Part II. Smaller preparation sizes showed higher likelihood of having a larger bacterial count compared to larger preparation sizes. Most files' nominal diameter and taper did not conform to their advertised size showing a lack of standardization between manufacturers. Pilot tip lengths vary greatly between different rotary files.