Impact of needle insertion depth on the removal of hard-tissue debris.

Aim To evaluate the effect of depth of insertion of an irrigation needle tip on the removal of hard-tissue debris using micro-computed tomographic (micro- CT) imaging. Methodology Twenty isthmus-containing mesial roots of mandibular molars were anatomically matched based on similar morphological dimensions using micro- CT evaluation and assigned to two groups ( n = 10), according to the depth of the irrigation needle tip during biomechanical preparation: 1 or 5 mm short of the working length ( WL). The preparation was performed with Reciproc R25 file (tip size 25, .08 taper) and 5.25% Na OCl as irrigant. The final rinse was 17% EDTA followed by bidistilled water. Then, specimens were scanned again, and the matched images of the canals, before and after preparation, were examined to quantify the amount of hard-tissue debris, expressed as the percentage volume of the initial root canal volume. Data were compared statistically using the Mann-Whitney U-test. Results None of the tested needle insertion depths yielded root canals completely free from hard-tissue debris. The insertion depth exerted a significant influence on debris removal, with a significant reduction in the percentage volume of hard-tissue debris when the needle was inserted 1 mm short of the WL ( P < 0.05). Conclusions The insertion depth of irrigation needles significantly influenced the removal of hard-tissue debris. A needle tip positioned 1 mm short of the WL resulted in percentage levels of hard-tissue debris removal almost three times higher than when positioned 5 mm from the WL. [ABSTRACT FROM AUTHOR]