An Arithmetic Crown-down Dynamic Tactile Instrumentation Technique: A Case Report of an S-shaped Root Canal

The preparation of severely curved S-shaped double-curved root canals can be technically challenging. A novel root canal instrumentation technique is proposed, which modifies 2 techniques: the McSpadden crown-down technique and the tactile controlled activation technique. In the McSpadden crown-down technique, the root canal is divided into 2 portions: the coronal zone and the apical zone. However, rather than focusing on the length of file engagement, a formula is proposed to calculate the maximum insertion depths of higher tapered instruments to prevent overflaring of the canal and preserve pericervical dentin. Tactile-controlled activation involves activating martensitic nickel-titanium rotary files upon engagement and then immediately withdrawing the files. The proposed technique recommends 3 apical strokes after the initial engagement before withdrawal to minimize instrumentation time. This novel technique is described in a case report involving the management of an S-shaped double-curved maxillary lateral incisor. The technique presents a new method of crown-down instrumentation that prevents overflaring and avoids instrument separation. (J Endod 2021;47:836?843.) Preparation of the root canal system is recognized as an essential stage of nonsurgical endodontics1. Instrumentation serves to mechanically debride the root canal, create a space for penetration of irrigation, enable the delivery of a medicament, and create an optimized canal geometry for adequate obturation2. The mechanical preparation of the root canal is inevitably impacted by the variations in root canal anatomy, such as the angle of the canal curvature, the radius of curvature, and the location of the curvature3,4. Preparation of curved canals may alter the original canal anatomy, which can affect the outcome of endodontic treatment and retreatment if it prevents complete instrumentation to the apical constriction5,6. Since the introduction of nickel-titanium (NiTi) instruments to the armamentarium for root canal preparation, NiTi has been increasingly used by general dentists and endodontic specialists to facilitate

Automated summary

The preparation of severely curved S-shaped double-curved root canals can be technically challenging. A novel root canal instrumentation technique is proposed, which modifies 2 techniques: the McSpadden crown-down technique and the tactile controlled activation technique. The proposed technique recommends 3 apical strokes after the initial engagement before withdrawal to minimize instrumentation time. This technique presents a new method of crown-down instrumentation that prevents overflaring and avoids instrument separation.