Flow characteristics of positive and negative pressure irrigation in an immature tooth - A computational fluid dynamics study.

Aim: This study aims to investigate the irrigation dynamics in an immature tooth during positive and negative pressure irrigation using a computational fluid dynamics (CFDs) model. Materials and Methods: Cone-beam computed tomography scan of the maxillary central incisor with Cvek's stage III root development was used for the reconstruction of the root canal geometry. The computer-aided design models of open (front vent and notched) and closed (side vent [SV]) needles were positioned inside the root canal at two penetration depths, i.e., 3 mm and 1 mm short of apex. The negative pressure microcannula (MiC) was positioned at the level of the root apex. A prevalidated CFD model was used to simulate endodontic irrigation. Results: The irrigant velocity in the apical root canal beyond the needle tip exceeded 0.1 m/s. As the needles were positioned closer to the apex, the wall shear stress (WSS) increased for the open-ended needles and decreased for the SV needle. MiC produced the lowest WSS. The mean apical pressure produced by the SV needle and MiC were below the critical threshold for periapical extrusion. Conclusions: The SV needle inserted within 1-3 mm of root apex during endodontic irrigation in an immature tooth allows adequate irrigant exchange with minimal risk of periapical extrusion.