doi:10.1111/iej.12570
Letter to the Editor
Critical appraisal of some methodological aspects of using micro-CT technology in the study of dentinal microcracks in endodontics Dear Editor We would like to take this opportunity to comment on the recently accepted paper entitled ‘Comparison of ProTaper, RaCe, and Safesider instruments in the induction of dentinal microcracks: A micro-CT study’ (Ceyhanhi et al. 2015). The authors evaluated the incidence of dentinal microcracks after root canal preparation with three instrumentation systems using micro-computed tomography (micro-CT). Firstly, it would be worth stressing the positive aspects of using this highly accurate contemporary non-destructive methodology to enhance the overall understanding of the relationship between intracanal procedures and the development of dentinal defects: • It allows the assessment of the specimens before the experimental procedures; thus, pre-existing cracks can be detected (Fig. 1); • Three-dimensional (3D) spatial location of dentinal cracks is possible with or without the use of contrast agents; • The same specimen can be evaluated at different stages of the root canal treatment and serve as its own control; • The presence of dentinal defects can be correlated with other outcomes of mechanical instrumentation (Fig. 2) (De-Deus et al. 2014, 2015). Nevertheless, as with any other methodological approach, micro-CT technology has also limitations: • Scanning and reconstruction procedures take a considerable time; • The technique is not suitable for clinical use; • The equipment is expensive and; • The complexity of the technical procedures requires a steep learning curve and an in-depth knowledge of dedicated software. Recently, several authors have raised important concerns regarding the development of dentinal defects due to motor-driven rotary nickel-titanium instrumentation; however, the literature reveals that there is a lack of consensus on microcrack formation after canal preparation with rotary or reciprocating
216
International Endodontic Journal, 49, 216–219, 2016
Figure 1 Random cross-sections of three different teeth acquired from a micro-CT imaging system showing the presence of preexisting cracks.
instruments, with the reported incidence of cracks varying from 0% to 80%. This wide range variation may be explained by differences in the methodological procedures, the experience of the operator, and the output quality of the observational tool. The latter is of critical relevance as it must allow reliable visualization of the dentinal defects and, consequently, it has a major impact on the accuracy of the results. When using micro-CT technology, the output quality of the acquired images is directly related to the high spatial and temporal resolution of the micro-CT scanner, as well as, the adoption of adequate input parameters for the scanning and reconstruction procedures. These
© 2016 International Endodontic Journal. Published by John Wiley & Sons Ltd
Letter to the Editor
Figure 2 Micro-crack tracking in sequential cross-section images after root canal preparation in a given mesial root.
factors make reliable dentinal surface examination challenging but, in the end, they lead to the expected and required overall trustworthiness of the study. Based on the aforementioned considerations, we would like to point out some aspects of the abovementioned study that might impact on its conclusions: 1. According to the authors, the root canals ‘were instrumented up to size 30 for all systems’; however, in the Safesider group, previous preparation of the root canal was performed to the working length with manual files from size 08 to 35; 2. Despite the use of a 3D technology, the methodology surprisingly followed the conventional sectioning approach. For instance, 700–900 CT
© 2016 International Endodontic Journal. Published by John Wiley & Sons Ltd
slices [. . .] were obtained per root”, but only 10 sections were evaluated in each specimen, which represent
Letter to the Editor
Critical appraisal of some methodological aspects of using micro-CT technology in the study of dentinal microcracks in endodontics Dear Editor We would like to take this opportunity to comment on the recently accepted paper entitled ‘Comparison of ProTaper, RaCe, and Safesider instruments in the induction of dentinal microcracks: A micro-CT study’ (Ceyhanhi et al. 2015). The authors evaluated the incidence of dentinal microcracks after root canal preparation with three instrumentation systems using micro-computed tomography (micro-CT). Firstly, it would be worth stressing the positive aspects of using this highly accurate contemporary non-destructive methodology to enhance the overall understanding of the relationship between intracanal procedures and the development of dentinal defects: • It allows the assessment of the specimens before the experimental procedures; thus, pre-existing cracks can be detected (Fig. 1); • Three-dimensional (3D) spatial location of dentinal cracks is possible with or without the use of contrast agents; • The same specimen can be evaluated at different stages of the root canal treatment and serve as its own control; • The presence of dentinal defects can be correlated with other outcomes of mechanical instrumentation (Fig. 2) (De-Deus et al. 2014, 2015). Nevertheless, as with any other methodological approach, micro-CT technology has also limitations: • Scanning and reconstruction procedures take a considerable time; • The technique is not suitable for clinical use; • The equipment is expensive and; • The complexity of the technical procedures requires a steep learning curve and an in-depth knowledge of dedicated software. Recently, several authors have raised important concerns regarding the development of dentinal defects due to motor-driven rotary nickel-titanium instrumentation; however, the literature reveals that there is a lack of consensus on microcrack formation after canal preparation with rotary or reciprocating
216
International Endodontic Journal, 49, 216–219, 2016
Figure 1 Random cross-sections of three different teeth acquired from a micro-CT imaging system showing the presence of preexisting cracks.
instruments, with the reported incidence of cracks varying from 0% to 80%. This wide range variation may be explained by differences in the methodological procedures, the experience of the operator, and the output quality of the observational tool. The latter is of critical relevance as it must allow reliable visualization of the dentinal defects and, consequently, it has a major impact on the accuracy of the results. When using micro-CT technology, the output quality of the acquired images is directly related to the high spatial and temporal resolution of the micro-CT scanner, as well as, the adoption of adequate input parameters for the scanning and reconstruction procedures. These
© 2016 International Endodontic Journal. Published by John Wiley & Sons Ltd
Letter to the Editor
Figure 2 Micro-crack tracking in sequential cross-section images after root canal preparation in a given mesial root.
factors make reliable dentinal surface examination challenging but, in the end, they lead to the expected and required overall trustworthiness of the study. Based on the aforementioned considerations, we would like to point out some aspects of the abovementioned study that might impact on its conclusions: 1. According to the authors, the root canals ‘were instrumented up to size 30 for all systems’; however, in the Safesider group, previous preparation of the root canal was performed to the working length with manual files from size 08 to 35; 2. Despite the use of a 3D technology, the methodology surprisingly followed the conventional sectioning approach. For instance, 700–900 CT
© 2016 International Endodontic Journal. Published by John Wiley & Sons Ltd
slices [. . .] were obtained per root”, but only 10 sections were evaluated in each specimen, which represent
