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% NaOCl 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.

Impacto da profundidade da agulha de irrigação na remoção de debris dentinários / Impact of the needle insertion depth on the removal of hard-tissue debris

O presente estudo avaliou o efeito da inserção da agulha de irrigação max-i-probe 30G em duas profundidades diferentes na remoção de debris após a instrumentação endodôntica. Raízes mesiais de molares inferiores com a presença de istmos foram escaneadas em um microtomógrafo de raios-X em uma resolução isotrópica de 14.16 µm. Cada dente foi aleatoriamente designado para um dos dois grupos experimentais (n = 10) de acordo com a profundidade de inserção da agulha durante a irrigação do sistema de canais radiculares: 1 ou 5 mm aquém do comprimento de trabalho. Todas as amostras foram instrumentadas com o sistema Reciproc (VDW, Munique, Alemanha) e o mesmo protocolo de irrigação foi usado, diferindo apenas na profundidade de inserção da agulha. O segundo escaneamento foi realizado após os procedimentos de limpeza e modelagem e, depois disso, as imagens registradas, antes e após o preparo, foram examinadas a partir do nível da bifurcação até o ápice para identificar volumetricamente, medir e mapear a quantidade de debris acumulados. O teste de Mann-Whitney comparou estatisticamente o volume percentual de debris acumulados entre os grupos de irrigação. Os resultados mostraram que a profundidade de inserção da agulha teveinfluência relevante na remoção de debris (P< 0,05). Uma redução significativa na percentagem de debris foi observada quando a agulha foi inserida a 1 mm do comprimento de trabalho (P< 0,05). A profundidade de inserção da agulha de irrigação tem uma marcante influênciasobre o montante final de debris acumulados. Infere-se, desta maneira, que quanto mais próximo ao ápice é levada a agulha de irrigação, menor é a quantidade final de debris gerados após a instrumentação endodôntica.

The present study evaluated the effect of the insertion of the irrigation needle (max-i-probe, Smith and Nephew MPL, Franklin Park, IL) at two different depths on the removal of hard tissue debris. Mandibular molarswith isthmuses in the mesial root canalsystem weremicro-CT scanned at an isotropic resolution of 14.16 µm. Each tooth was randomly assigned to 2 experimental groups (n = 10) according to the depth of needle insertion during irrigation of the root canal system: 5 or 1 mm short of working length. All teeth were instrumented with the Reciproc system (VDW, Munich, Germany) and the very same irrigation protocol was used, differing only by the depth of needle insertion. Second micro-CT scans were performed after cleaning and shaping procedures and after that, the matched images, before and after preparation, were examined from the furcation level to the apex to volumetrically identify, measure and map the amount of accumulated hard-tissue debris. Mann-Whitney test was used to statistically compare the percentage volume of accumulated hard tissue debris between the irrigation groups. The result showed a significant influence of the depth of needle insertion on removal of debris (P < .05). A significant reduction in the percentage of hard tissue debris was observed when the needle was inserted up to 1 mm from the apex (P < .05). The depth of needle insertion has a significant influence on the final amount of the accumulated hard-tissue debris. It is fair to conclude that the nearest to the apex the irrigation needle is, the less is the final amount of hard-tissue debris generated.