Longitudinal craze line propagation in human root dentin after instrumentation with NiTi rotary files of different instrument tapers after long-term chewing simulation

• Published in: Clinical oral investigations 2022-03, Vol.26 (3), p.2671-2679
• Main Authors: Heberer, Marie-Therese, Roggendorf, Hubert C., Faber, Franz-Josef, Lawrenz, Nicolai-Alexander, Frankenberger, Roland, Roggendorf, Matthias J.
• Format: Article
• Language: English
• Subjects: Dental Pulp Cavity - surgery; Dentin; Dentistry; Humans; Mastication; Medicine; Original; Original Article; Root Canal Preparation; Root Canal Therapy; Tooth Root
• ISSN: 1432-6981; 1436-3771
• DOI: 10.1007/s00784-021-04238-3

Objectives The aim of this study was to investigate whether file design and taper significantly influence microcrack initiation during machine preparation. Materials and methods Sixty extracted teeth with straight single canals were selected. The teeth were randomly assigned to four groups based on their root canal anatomy and the corresponding NiTi rotary file system (I, Mtwo ; II, ProTaper Universal ; III, F6 SkyTaper ; control, no preparation and filling). The root canals of the experimental groups were filled using the single-cone technique. The tested teeth were all subjected to a mechanical chewing simulation with flat lead loading over a period of 3 years (corresponding to 150,000 cycles). The teeth were checked for dentinal defects (accumulative crack growth in length) under the digital microscope ( Keyence VHX-5000 ) at time 0 (baseline prior to chewing simulation) and after 3, 6, 12, 24, and 36 months of loading. The cumulative crack increase was statistically analyzed using the Kruskal–Wallis test, Jonckheere–Terpstra test, and the Wilcoxon rank-sum test. The significance was set at p