Influence of needle working length and root canal curvature on irrigation: a computational fluid dynamics analysis based on a real tooth

Abstract

Backgrounds To compare the irrigation efficiency with different needle working length and different root canal curvature based on a real unshaped root canal using computational fluid dynamics (CFD) method. Methods Images of the root canal of the maxillary first molar after being prepared to .04/15 were scanned using micro-CT, and then imported into the software for three-dimensional reconstruction. A palatal root canal with a curvature of 23.4° was selected as the experiment canal. The needle working length of the 30-G flat needle was 4.75 mm, 5 mm, 5.25 mm and 5.5 mm short of apical foramen respectively, the flow pattern, irrigation velocity, shear stress were compared. The modified curved canals with a curvature of 0°, 5°, 10°, 20° and 30°were reconstructed via software. The flat needle was replaced at the optical inserted depth, and key parameters of irrigation efficiency were analyzed. Results Decreased needle working length had a positive impact on irrigation efficiency. With the optimal needle working length, the replacement of the apical irrigation fluid, the effective velocity, and wall shear stress were significantly improved in more severely curved root canals. With the same needle working depth and analogous canal curvature, irrigation efficiency is higher in real canal than that of modified canal. Conclusions Short needle working depth, large curvature and the anomalous inner wall of canals help to improve irrigation efficiency.

Influence of needle design and irrigation depth in the presence of vapor lock: A computational fluid dynamics analysis in human oval roots with apical ramification

“…The design of the MiC was based in previous studies 27 . Different geometries were created with each positive pressure needle (SV1, SV3, FV1, FV3, N1, N3); two different irrigation positions, 1 and 3 mm from WL, were chosen for each of them due to the influence of needle working length on irrigation results 32 ; and the MiC placed at WL following manufacturer's direction for use.…”

“…Computational fluid dynamic (CFD) is a non‐invasive validated method to observe the behavior of irrigants and irrigation key magnitudes (wall shear stress ( τ w ), flow velocity, irrigant replacement and P a ) in the root canal system 30–32 . It allows the standardization of samples and reduce human errors.…”

“…Computational fluid dynamic (CFD) is a non-invasive validated method to observe the behavior of irrigants and irrigation key magnitudes (wall shear stress (τ w ), flow velocity, irrigant replacement and P a ) in the root canal system. [30][31][32] It allows the standardization of samples and reduce human errors. Thus, the aim of this study was to analyze the influence of needle design and irrigation depth in the removal of a simulated vapor lock and to assess CFD key irrigation magnitudes during syringe and MiC irrigation in the apical ramification of an oval distal root of a human mandibular molar when a vapor lock is present.…”

Computational fluid dynamics in root canal irrigation

“…It has been proved that the wall shear stress distribution and the irrigant replacement in the root canal could be improved by locating the irrigation needles at the resorption level. Zhou et al 14 simulated the palatal roots of maxillary first molars with different root canal curvatures and found that the root canal with large curvatures was conducive to improving irrigation efficiency. Therefore, the use of simplified geometric shapes rather than a simulation of actual root canal anatomy may facilitate the analysis of irrigation efficiency, but it is not possible to obtain conclusions that can directly translate to clinical situations.…”

“…Specifically, it can reach those minute regions in the root canal system so as to prevent microbial residue effectively, further improving the success rate of root canal treatment. In recent years, a large number of studies have found that many factors can affect root canal irrigation efficiency, such as the methods of root canal irrigation, 8 the types of root canal irrigation needles, 9 the depth of irrigation needle insertion, 10 the movement of irrigation needle, 11 the composition of irrigants, 12 the size of root canal preparation, 13 the curvature of the root canal, 14 and so on.…”