Effect of Reciprocating Systems and Working Lengths on Apical Microcrack Development: a micro-CT Study

Abstract

The objective of this study was to evaluate the effect of root canal preparation with single-file reciprocating systems at different working lengths on the development of apical microcracks using micro-computed tomographic (micro-CT) imaging. Forty extracted human mandibular incisors were randomly assigned to 4 groups (n=10) according to the systems and working length used to prepare the root canals: Group A - WaveOne Gold at apical foramen (AF), Group B - WaveOne Gold 1 mm short of the AF (AF-1 mm), Group C - Unicone (AF) and Group D - Unicone (AF-1 mm). Micro-CT scanning was performed before and after root canal preparation at an isotropic resolution of 14 µm. Then, three examiners assessed the cross-sectional images generated to detect microcracks in the apical portion of the roots. Apical microcracks were visualized in 3, 1, 1, and 3 specimens in groups A, B, C, and D, respectively. All these microcracks observed after root canal preparation already existed prior to instrumentation, and no new apical microcrack was detected. For all groups, the number of slices presenting microcracks after root canal preparation was the same as before canal preparation. Root canal preparation with WaveOne Gold and Unicone, regardless of the working length, was not associated with apical microcrack formation.

Micro‐computed tomographic assessment of dentinal microcrack formation in straight and curved root canals in extracted teeth prepared with hand, rotary and reciprocating instruments

“…Under this micro-CT technology, the current study revealed that no microcrack could be attributed to root canal instrumentation with either the ProTaper Universal for Hand Use, the HyFlex EDM or the Reciproc Blue. This result agrees with previous investigations (de Oliveira et al 2017a, b, PradeepKumar et al 2019, R€ odig et al 2019) that also showed a lack of relationship between microcrack formation and biomechanical preparation with hand, rotary or reciprocating instruments by using micro-CT analysis.…”

“…These conflicting findings reported in micro-CT studies can be related to different methodological approaches used. Some of these are as follows: scanning and reconstruction parameters, interpretation of defects and digital artefacts, number of cross-sectional images assessed and, mainly, the conditions of samples storage (Versiani et al 2015, de Oliveira et al 2017a, R€ odig et al 2019. Concern has been raised that dehydration of extracted teeth may induce spontaneous cracking or may affect the biomechanical response of root dentine to instrumentation, and so, decrease teeth resistance to the fracture (Versiani et al 2015).…”

“…This result agrees with previous investigations (de Oliveira et al . 2017a, b, PradeepKumar et al . 2019, Rödig et al .…”

“…Various studies have investigated the effect of root canal shaping on the induction of dentinal defects (Versiani et al 2015), as they are likely to act as a starting point for vertical root fractures and, ultimately, tooth loss (Tour e et al 2011). However, reports from research data have been inconsistent concerning the incidence of dentinal cracks after shaping of straight and curved root canals (Adorno et al 2013, Ceyhanli et al 2016, Bayram et al 2017, de Oliveira et al 2017a) with either hand, rotary and reciprocating instruments (B€ urklein et al 2013, Abou El Nasr & Abd El Kader 2014, De-Deus et al 2014, de Oliveira et al 2017b, often generating confusion and uncertainty on the part of practitioners who are seeking the safest technique.…”

“…2017, de Oliveira et al . 2017a) with either hand, rotary and reciprocating instruments (Bürklein et al . 2013, Abou El Nasr & Abd El Kader 2014, De‐Deus et al .…”