|Year : 2022 | Volume
| Issue : 1 | Page : 1-8
The effects of different root canal instrumentation techniques on dentinal microcracks formation: A narrative review
Faisal T Alghamdi1, Adel S Alqahtani2, Othman M Baradwan3, Fahad O Almolla3, Omar R Alkhattab4, Khalid A Merdad4
1 Department of Oral Biology, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia
2 Department of General Dentistry, Primary Health Care Center, Ministry of Health, Tabuk, Saudi Arabia
3 Department of Conservative Dentistry, College of Dentistry, AL-Jouf University, AL-Jouf, Saudi Arabia
4 Department of Endodontics, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia
|Date of Submission||31-Mar-2021|
|Date of Decision||19-Apr-2021|
|Date of Acceptance||02-Jun-2021|
|Date of Web Publication||8-Jan-2022|
Faisal T Alghamdi
Department of Oral Biology, Faculty of Dentistry, King Abdulaziz University, P. O. Box 80209 Jeddah 21589
Source of Support: None, Conflict of Interest: None
Introduction: The influence of intracanal instrumentation technique on microcrack formation is a debatable subject. This review aimed to review the effect of different root canal instrumentation techniques (hand, continuous rotary, reciprocal rotary, adaptive, and self-adjusting file techniques) on microcracks formation and evaluate whether the incidence of cracks formation differs between destructive and nondestructive evaluation methods.
Materials and Methods: All in vitro studies comparing the influence of at least two different instrumentation techniques were searched for this narrative review in PubMed, Scopus, and Google Scholar databases. The search included articles that were published from 2016 to 2020. The search was carried out by six independent reviewers in this review.
Results: A total of twenty-five (n = 25) articles met the eligibility criteria. Only six studies showed the absence of new cracks development in 320 human teeth according to the instrumentation technique while the majority of the studies (n = 19) illustrated the presence of new cracks development in 1696 teeth. The results of this review showed that nondestructive methods may be less likely to cause microcracks than destructive methods.
Conclusions: The number of dentinal microcracks varies depending on the type of instrumentation techniques and evaluation methods used. Therefore, in destructive evaluation methods, root canal instrumentation with hand, reciprocating, rotary, adaptive, and self-adjusting systems resulted in the development of more new dentinal microcracks than nondestructive methods.
Keywords: Dentinal microcracks, microcomputed tomography analysis, root canal instrumentation, stereomicroscope analysis
|How to cite this article:|
Alghamdi FT, Alqahtani AS, Baradwan OM, Almolla FO, Alkhattab OR, Merdad KA. The effects of different root canal instrumentation techniques on dentinal microcracks formation: A narrative review. Saudi Endod J 2022;12:1-8
|How to cite this URL:|
Alghamdi FT, Alqahtani AS, Baradwan OM, Almolla FO, Alkhattab OR, Merdad KA. The effects of different root canal instrumentation techniques on dentinal microcracks formation: A narrative review. Saudi Endod J [serial online] 2022 [cited 2022 May 23];12:1-8. Available from: https://www.saudiendodj.com/text.asp?2022/12/1/1/335245
| Introduction|| |
The purpose of root canal instrumentation is mainly to lower microbial count by removing pulp tissue remnants. However, microcracks, craze lines, and vertical root fractures (VRFs) could cause root canal wall damage.,, The most unwanted complication of endodontic treatment is VRF which eventually leads to tooth loss.
The variety in design of nickel-titanium (NiTi) instruments presents several advantages compared to conventional files, such as decreased working time and increased flexibility. On the other hand, NiTi instruments are still associated with an inherent risk of instrument fracture and incidence of dentinal cracks., Root canal walls can be damaged by different NiTi shaping systems with various angle degrees., Kinematics of engine-driven NiTi instruments may be divided into rotary motion, rotational reciprocating motion, vertical vibration and rotary motion plus rotational reciprocating motion (adaptive motion). The efficacy of these endodontic file systems on canal preparation and their significance on the outcome of endodontically treated teeth are potentially influenced and moderated by variant kinematics and parameters of uses.
Different studies proposed that mechanized instruments may induce tooth structure elimination and stimulate dentinal microcracks development, thereby presenting an increased biological cost.,, Even with lower loads than traditional nominal resistance, the massive increase in stress concentration during mechanical loading caused by an elemental defect in the material would impair mechanical efficiency and prematurely lead to three catastrophic fractures and that dentinal microcracks induced by different root canal instrumentation techniques could compromise tooth mechanical performance during masticatory function. In contrast, some studies disprove any correlations between instrumentation technique and microcracks formation.,,,
Assessing the formed microcracks on tooth structure can be evaluated by two main fundamental tests. The first approach is based on destructive tests, whereby teeth are first inspected visually for any external surface and dentinal defects. After canal instrumentation, the teeth are split, and each cut is investigated individually to consider either the presence or absence of defects.,, Some investigations employing this test usually use noninstrumented teeth as a control group for the baseline comparison condition, and it is possible that such a processing technique could induce microcracks., The second approach utilizes nondestructive tests, which are highly accurate, precise, and reliable. The teeth are scanned for any microcracks initially and then rescanned after instrumentation is performed using microcomputed tomography (μCT).,,,,
Limited systematic reviews have been conducted to evaluate the role of endodontic files in microcracks formation during the root canal preparation. A systematic review was conducted in 2016; which showed controversial outcomes regarding the dentinal defects in reciprocating motion of NiTi instruments compared to continuous rotation. Therefore, the aims of this review article were to (1) review the effect of different root canal instrumentation techniques (hand, continuous rotary, reciprocal rotary, adaptive, and self-adjusting file [SAF] techniques) on microcracks formation; (2) evaluate whether the incidence of cracks formation differs between destructive and nondestructive evaluation methods.
| Materials and Methods|| |
Literature search strategy
An electronic search for articles in the English language was performed using PubMed, Scopus, and Google Scholar from 2016 to 2020 due to lack of updated and limited published reviews cover this research area in endodontics. The literature search strategy was carried out in February 2020 and then updated in December 2020. The search for this narrative review was done using the following electronic databases: Public Medline (PubMed), Scopus, and Google Scholar digital data basis. Communication with the authors of the studies included, for additional data or clarification was done. The search was conducted using the following combination of keywords and Boolean operators (“AND,” “OR”): ([Dentinal cracks] OR [dentinal microcracks] OR [dentinal defect] OR [dentinal damage]) AND ([Root Canal Instrumentation] OR [Root Canal Preparation] OR [Canal Preparations] OR [Canal Instrumentations]).
- Studies were included if they followed the applied criteria:
- Published in vitro studies that compare at least two different root canal instrumentation techniques (adaptive, hand, reciprocating, rotary, and SAF) on the dentinal microcracks formation, and evaluate the presence or absence of microcracks
- Published in vitro studies that implement microcrack evaluation techniques (destructive or nondestructive)
- Scientific papers published between 2016 and 2020
- Scientific papers published in the English language
- Studies conducted on extracted human teeth only.
Studies were excluded if they met any of the following applied criteria:
- Narrative/critical or systematic reviews
- In vivo, ex vivo and in situ studies
- Editorial or personal opinion articles
- Papers that illustrated clinical trials about dentinal microcrack formation
- Papers that discussed the role of root canal instrumentation techniques with different endodontic file systems on microcrack formation by percentages and samples taken from nonhuman sources.
The five reviewers were independently read the full articles and considered the following variables: Title, abstract, material and methods, and main results. The data were then verified for completeness and accuracy and were harvested into a standardized Microsoft Office Excel worksheet.
Data were gathered and organized into columns with the following information: study (author and year), sample (tooth type, number), the methodology used to evaluate microcracks (i.e., destructive versus nondestructive method), instrumentation technique, cracks at baseline, and important findings.
| Results|| |
A total of 1207 articles were initially obtained through the keywords using the databases. Of those 873 articles were deleted because they displayed either duplicity or unrelated topics and 61 articles based on abstract and title. Only 273 full-text articles were carefully assessed for eligibility. Out of that, 248 studies were excluded from this extensive review due to following reasons:
- Narrative/critical or systematic reviews (n = 19)
- In vivo, ex vivo and in situ studies (n = 34)
- Editorial or personal opinion articles (n = 3)
- Clinical trials (n = 19)
- Considers only one instrument technique (n = 98)
- Considers endodontic retreatment technique (n = 12)
- Considers accuracy of crack detection (n = 21)
- Mimic para-endodontic surgery instrumentation and induction of defects (n = 17)
- Considers different outcomes: Defect on the instrument or its resistance (n = 8); shaping ability of instrument (n = 13); studies of finite element analysis (n = 4).
Lastly, 25 papers were selected to be included in this review. The literature search strategy for this review is summarized in [Table 1].
This review included 25 studies with a total sample size of 2016 human teeth. Ten studies compared rotary and reciprocating instruments,,,,,,,,,,,,, four studies compared hand, rotary, and reciprocating techniques,,,, four studies tested hand and rotary techniques,,,, and seven studies compared SAF/twisted file adaptive with different endodontic file techniques.,,,,,, Mandibular incisors were used in 8 studies,,,,,,,, mandibular premolars in 7 studies,,,,,,, and mandibular molars in 9 studies.,,,,,,,, Only one study was not determined by the type of human teeth. The irrigating solution most frequently used in all the selected studies was sodium hypochlorite (NaOCl) in different percentages of solution ranging from 1% to 5.25%. The majority of investigated studies (n = 16) used destructive techniques for microcracks assessment [Table 2]. Four-teen studies evaluated the microcracks using a stereomicroscope,,,,,,,,,,,,,, two studies used dental operating microscope (DOM),, eight studies used the μCT,,,,,,,, and one study used the scanning electron microscope (SEM) as shown in [Table 2] and [Table 3].
|Table 2: Summary of studies that used destructive evaluation methods (n=16)|
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|Table 3: Summary of studies that used nondestructive evaluation methods (n=9)|
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Dentinal microcracks formation
Among the 25 included studies, only six studies revealed no new microcracks formation according to the used instrumentation technique during root canal preparation.,,,,, On the other hand, nineteen studies showed new microcracks formation as shown in [Table 2] and [Table 3]. Among the 2016 teeth in the included studies, 1696 teeth (1466 teeth using destructive evaluation methods, 230 teeth using nondestructive evaluation methods) demonstrated new microcracks formation, while 320 teeth (240 teeth using μCT, 80 teeth using DOM) were with no new microcracks formation as shown in [Table 2] and [Table 3].
[Table 2] illustrates the outcomes of studies using destructive methods to evaluate the microcracks initiation (n = 16).,,,,,,,,,,,,,,, Overall, most of these studies were induced microcracks (n = 15) except one study by Coelho et al. not accepted the microcracks initiation hypothesis through root canal instrumentation. It is important to highlight this study because they did not observe any microcrack formation following instrumentation independent of kinematics (Profile on rotary motion, TRUShape on rotary motion, and WaveOne Gold on reciprocating motion). Among the studies that partially support the influence of instrumentation technique, hand,, and SAF kinematics were used when no microcracks were noticed.
Selected studies' outcomes that assessed microcracks using nondestructive methods are illustrated in [Table 3]. Five studies revealed no formation of new microcracks after root canal preparation,,,,, whereas three studies illustrated new microcracks formation following root canal instrumentation: Ceyhanli et al. found the NiTi rotary system (Protaper Universal) to be the highest in generating microcracks formation compared to RaCe system and reciprocating Safesider system. Furthermore, all the three systems increased the number of microcracks. Li et al. found that the OneSahpe rotary system increased the microcracks, and Mandava et al. showed that the HyFlex Edm and Vortex Blue rotary systems exhibited a statistically significant increase in microcracks formation compared to the hand Ni-Ti Flex files. However, one in vitro study assessed the external apex region of teeth with various applied kinematics. A comparison was done between hand and rotary instrumentation Overall, this study illustrated a direct relationship between the instrumentation method and the introduction of defects (independent from the applied kinematics), which facilitated microcrack development. On the other hand, there was an important factor considered in this study. It was the working length (WL) for canal preparation. When the WL was equal to or greater than the total root canal length (RCL), the risk of microcracks initiation was gradually increased. Conversely, a WL at least 1 mm less than the RCL corresponded to a decreased risk of microcracks initiation. Furthermore, it was observed that when the WL is set at either RCL or RCL-1 mm, there was similar microcrack development using hand instruments. However, when applying other considered systems (e.g., Race and K3 rotary instruments), there was a significant decrease in microcrack development.
| Discussion|| |
The purpose of this review was to collect all recent in vitro studies within the last 5 years assessing microcrack formation of endodontically treated teeth by various instrumentation techniques. This review included 25 studies with different root canal instrumentation techniques. The dentinal microcracks development was assessed using different dentinal microcrack detection methods (destructive and nondestructive methods).
The lack of unanimity about the influence of the root canal instrumentation on microcracks formation was induced mainly by the confounding effect of different evaluation methods. Stereomicroscope and other destructive methodologies coincided with formation of microcracks not present before the canal instrumentation.,,,,,,,,,,, On the other hand, studies that used reliable and accurate methods such as μCT analysis revealed no new formation of microcracks after root canal instrumentation.,,,,
Wei et al. measured microcrack development using destructive tests. They compared the incidence of dentinal microcracks when using reciprocating versus rotary systems. They found that the risk of dentinal microcracks was higher in the rotary system (ProTaper system) compared to other systems. Other studies, which measured microcrack development using nondestructive tests, showed that no new cracks formed after root canal instrumentation regardless of kinematics. One problem with measurements using destructive tests is that prospected injuries, which may cause different sources of stress in various treatment stages of root canal dentin, were not considered. Additionally, several issues related to the procedure that was not considered including NaOCl irrigation, mechanical instrumentation, slice sectioning technique, dehydration when not maintaining a suitable condition during the duration of the lengthy procedure, and alcohol evaporation before SEM analysis. Moreover, destructive methods cannot evaluate the entire length of the root canal.
Microcomputed tomography analysis evaluates the entire RCL, allowing one to locate dentinal microcracks with higher accuracy. Furthermore, this three-dimensional reconstruction can be evaluated in multiple levels of endodontic treatment, including during the preintervention stage, since it is a nondestructive method., Due to the effect of dehydration on the measurement of microcracks, Shemesh et al. indicated that even studies using μCT analysis are liable to bias. However, each study included in this review adopted all necessary precautions to preserve teeth hydration.
Three studies using μCT,, illustrated an increase in the number of microcracks by their instrumentation file systems. There was an alteration in the outcomes of these studies oriented by some factors such as method perspectives which included: Features of the used instrument and the sense of use for the operator with hand techniques. For illustration, De-Deus et al. indicated several factors that could interfere with the findings of Ceyhanli et al.: Namely, the whole RCL. It was not evaluated since each specimen had only 10 sections assessed (<1.5% of the scanned image). The chosen method did not adequately distinguish between microcracks and artifact/noise, leading potentially to a false-positive finding; and unreported details about scanning and reconstruction prevent reproducibility of the study.
The effect of the WL set for root canal preparation is a very important factor. Various studies agree that, across all instrumentation techniques, the WL should be 1 mm less than the RCL to prevent any microcrack initiation at the apical region of the tooth. However, one study in this review reported that microcrack formation was still found in the apex region. They concluded that, when rotary files were used, the WL of canal preparation had a significant impact on microcracks development.
The included studies in this review showed large heterogeneity in the used instrumentation technique, evaluation method, and type of evaluated teeth. However, more studies are needed to investigate different instruments and their relation with microcrack formation during the root canal preparation. In addition, the μCT method can be considered an accurate and reliable detection tool for dentinal microcracks formation.
Strengths and limitations
The strength of our review includes a thorough comparison of all peer-reviewed studies published during the past 5 years in line with our exclusion and inclusion criteria. This review presents comprehensive knowledge of dentinal microcracks formation and the evaluation methods which are essential for the clinician to detect the proper instruments during root canal preparation for the purpose of decreasing the dentinal root surface damage. To our knowledge, this is the only review that covered the topic using the PubMed, Scopus, and Google Scholar as search engines. One advantage of using Google Scholar is to prevent missing any appreciated research published in journals that are still not cited in PubMed and Scopus. The majority of studies included in this review had a low risk of bias. The scoring of low risk of bias was given to different studies due to these studies show enough information in all the different domains to make a clear judgment, and results are considered valid. Only one study gives a high risk of bias in one of the domains (a measurement of the outcome) because of knowledge of the allocated interventions by outcome assessors. On the other hand, although the studies were randomly selected in this review, the included studies compared different instrumentation techniques and used different evaluation methods and this is the main reason why systematic review or meta-analysis cannot be done. Even though it appears to be certain that the root canal instrumentation method is likely not identified with microcrack progression, the effect of different restorative procedures after endodontic treatment on the development of microcracks stays to a great extent obscure.
| Conclusions|| |
It can be concluded that the number of dentinal microcracks after root canal instrumentation varies depending on the type of instrumentation techniques and evaluation methods used. Therefore, the root canal preparation with hand, reciprocating, rotary, adaptive, and self-adjusting systems in destructive evaluation methods induced more new dentinal microcracks development than nondestructive methods.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]