Computational fluid dynamics study on mesial roots of mandibular molars

Abstract

Objectives: To evaluate the fluid dynamics of syringe irrigation in mesial root canals of mandibular molars. Material and methods: A computational fluid dynamics (CFD) model was experimentally validated using micro-particle image velocimetry (micro-PIV) measurements and subsequently employed to evaluate fluid dynamics in confluent canals acquired by micro-computed tomography (micro-CT) of natural teeth sequentially after mechanical preparation with three different instrument sizes. In addition to root canal enlargement, the influence of the type and depth of needle placement and the presence of anatomical features on the flow pattern, irrigant renewal and penetration, wall shear stress, and apical pressure generated during syringe irrigation were also evaluated. The same methodology and numerical model were applied to independent canals in order to compare the differences in fluid dynamics between the two canal configurations. Results: Root canal configuration and needle type had the greatest effect on the flow pattern, with the other variables having less influence. Irrigation velocity was limited within the isthmuses and accessory canals studied. Apical renewal and penetration of the irrigant were also mainly influenced by root canal configuration. In confluent canals, the depth of confluence relative to the working length (WL) had a direct proportional effect on irrigant penetration and apical renewal. Needle type mostly affected apical penetration in the merged portion of confluent canals, with the open-ended needle always allowing more apical penetration than the side-vented needle, as in independent canals. Although root canal enlargement improved apical renewal and penetration of the irrigant, it had a smaller effect than the previous ones. The depth of needle placement improved apical penetration, except for the side-vented needle in confluent canals, where the results depended on its position relative to the confluence zone. Apical pressure decreased with root canal enlargement, with needle placement further from the WL and with the sidevented needle. Conclusions: The type of root canal configuration affects the irrigant fluid dynamics during syringe irrigation. Confluent canals have a greater influence on irrigant velocity, apical renewal, and penetration compared to independent canals. These factors are mostly improved up to the confluence region. The results imply that when the confluence is closer to the WL, the irrigant's apical renewal and penetration increase during syringe irrigation.