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Article

The Influence of Root Canal Preparation with ProTaper Next, WaveOne Gold, and Twisted Files on Dentine Crack Formation

1
Department of Conservative Dentistry and Endodontics, Poznan University of Medical Sciences, 60-812 Poznan, Poland
2
Department of Biomaterials and Experimental Dentistry, Poznan University of Medical Sciences, 60-812 Poznan, Poland
*
Author to whom correspondence should be addressed.
Machines 2021, 9(12), 332; https://doi.org/10.3390/machines9120332
Received: 2 November 2021 / Revised: 24 November 2021 / Accepted: 1 December 2021 / Published: 3 December 2021

Abstract

:
(1) Background: Root canal preparation constitutes an important factor for success in endodontics. However, various complications may occur during this stage. The aim of this study was to compare the incidence of cracks within radicular dentin after instrumentation with ProTaper Next (PTN), WaveOne Gold (WOG), and Twisted Files (TF), which utilize different kinematics. (2) Methods: Eighty single-rooted teeth were classified into four groups (n = 20). Three groups were instrumented using PTN (X1, X2), WOG (Primary), and TF (SM1–3). The non-instrumented group constituted the control group. Post-preparation, the roots were sectioned 3, 6, and 9 mm from the apex using a low-speed saw (Southbay Technology Inc., San Clemente, CA, USA). The specimens were viewed through a microscope at x25 magnification (Leica M320, Wetzlar, Germany), and their surface was assessed tactilely to determine the presence of the crack. (3) Results: Partial cracks within radicular dentine were observed in all study groups (PTN: n = 4/20%, WOG: n = 3/15%, TF: n = 4/20%); no cracks were observed in the control group. No significant differences were observed among experimental groups. OR values for the incidence of cracks were: OR = 11.182 for PTN, OR = 8.2 for WOG, and OR = 8.2 for TF. (4) Conclusions: Instrumentation with PTN, WOG, and TF may result in dentinal cracks formation.

1. Introduction

The removal of organic debris and appropriate dentin cutting during root canal preparation constitutes a key factor for success in the modern concept of endodontic treatment [1]. However, this stage of the procedure may be associated with a number of complications, including the change in the original pathway of the root canal (transportation), perforation or formation of other obstacles that can impede appropriate outcome, instrument fracture, and eventually, tooth crack and fracture [2]. The latter complication may potentially be the most hazardous one, as cracks are difficult to diagnose, weaken tooth fracture, and also constitute a pathway for bacteria between the endo- and periodontium [3]. As forces exerted by the endodontic file inside the root canal system have been hypothesized to cause cracks within radicular dentin, several research studies addressed this issue in order to try to determine the association between these two factors, i.e., instrument movement parameters, such as kinematics, torque, speed, etc., and dentinal crack formation [4].
Research studies performed by various groups worldwide have shown, beyond doubt, different endodontic instrumentation systems cause damage to radicular dentine to a different extent. However, there are vast differences between files available for use, including their shapes, metallurgy, master apical file size and taper, and also movement kinematics [5]. When it comes to instrument movement kinematics, the instruments can be classified into three main groups, i.e., those that employ rotary movement, reciprocal movement, and “adaptive motion”, i.e., rotary or reciprocal, depending on the conditions within the root canal system [6]. Rotary endodontic instruments move using the same motion e.g., a dental drill, when placed in the handpiece. However, in order to be able to use them effectively, the clinician needs to be able to control their speed of rotation and torque. Nevertheless, the shape of the root canal and the environment inside it, also when it comes to the physical environment, is different, as any endodontic file has limited space for movement and there is less room for debris in its lumen, all of which make the file more likely to break. A solution to this problem has been proposed, namely the use of reciprocating motion, i.e., repeated movement in the clockwise and anti-clockwise direction [7]. The extent of movement (the angles) in each direction varies for different systems, and the two most widespread systems worldwide, Reciproc (VDW, Munich, Germany) and WaveOne Gold (Dentsply Sirona, Charlotte, NC, USA) move 150 degrees in the counterclockwise direction (CCW) and 30 degrees in the clockwise direction (CW). This type of movement seems particularly effective in cases of small root canals, obstructions in the root canal lumen, and retreatment [7]. The fact that the file engages and disengages with root canal dentine is believed to be the factor responsible for their lower likelihood of separation, but they remove less debris in the coronal direction [8]. In order to combine the advantages of both types of movement, the concept of adaptive motion has been introduced to the market, i.e., a special endodontic engine was developed that propels the instrument in such a way that they rotate if the stress exerted on the instrument is low (they rotate in 600-degree cycles), and as the situation in the root canal lumen becomes more difficult (obliteration, obstruction, curvature), the engine changes its operation mode to reciprocation within the limits of 370 degrees CW and 50 degrees CCW) [8]. Therefore, it could be hypothesized that these differences in movement may be related to complications such as crack formation, and the question whether the movement kinematics influences the incidence of crack formation has been a topic of research for a significant period of time, as dental equipment manufacturers come up with new systems and improvements, and each of them needs clinical assessment. When we take a closer look at the results of published studies, no consensus has been reached. Chronologically, as reciprocal instruments were introduced to the market, some research groups suggested their use may be more detrimental to root canal dentine than rotary files [9,10]. However, observations made later did not confirm this phenomenon, and the issue seems unresolved, as the values achieved by different, unrelated teams seem to be similar [11,12].
As it seems worthwhile to assess each clinical instrument that is made available for sale and use, the aim of our study was to check whether root canal instrumentation performed with instruments using different movement kinematics and are made of different types of NiTi alloy—ProTaper Next (Dentsply Sirona, Charlotte, NC, USA), WaveOne Gold (Dentsply Sirona, Charlotte, NC, USA), and Twisted Files (Kerr Endodontics, Orange, USA)—produces cracks within radicular dentine, and whether the differences are statistically significant. The underlying factor for clinical relevance was the observation that such cracks may be recolonized by biofilm and contribute to treatment failure, as well as such defects having a negative impact on the physical properties of the treated tooth. The reason these systems were chosen was the fact that the majority of published studies focus on the conventional WaveOne instrument, which is being discontinued, and was replaced worldwide by the thermomechanically treated WaveOne Gold instrument. The null hypothesis was that there would be no differences in crack formation among the groups.

2. Materials and Methods

Eighty freshly extracted single rooted premolar teeth with one root canal and mature apices were chosen for the study. G*Power (Dusseldorf University, Dusseldorf, Germany) software was used to calculate the power. With the set degree of freedom for our chi-square calculations, the calculated power for the test was 0.81. Ethical review and approval were waived for this study, due to the decision of the Bioethics Committee at the Poznan University of Medical Sciences (28 February 2017). Before conducting the proper study, a pilot study was conducted in order to determine the ability to discriminate the cracks in the specimens, in which several root fragment specimens were assessed 3 times by Operator 1 and Operator 2 (both endodontists) and intra-rater agreement was evaluated, as were the possible miscomprehensions, and in order to adjust the environment (microscope, lighting, environment). The teeth were extracted due to universally accepted indications for extraction, i.e., non-restorability, periodontal disease, orthodontic indications. Inclusion criteria included age (only teeth from patients aged 20–40 were chosen for the study), the possibility of atraumatic extraction, and the absence of symptoms of parafunctions. Exclusion criteria included root caries and pathological resorption. Criteria were assessed using the medical history form and visual inspection with the use of a microscope (Leica M320, Leica Optics, Wetzlar, Germany). The teeth were stored in a 100% humidity environment at 37 degrees in distilled water. The teeth were divided into 4 groups (for each group n = 20) and were randomly classified into one of the groups using www.random.org software [13] by Operator 2. Operator 2 distributed the specimens in a random way to Operator 1, without disclosing the number of the specimen, and Operator 1 performed the preparation process. After the access cavity was prepared, the working length was established by inserting a stainless-steel (SS) K-file (ISO 10, 2%) in the root canal, until its tip was visible at the apex, which was confirmed using a dental operating microscope (Leica M320, Leica). One millimeter was subtracted from this length, in order to set the working length (WL) at the physiological constriction. The crowns were evened out to ensure a working length of 16 mm. The glidepath was then prepared manually up to a size of 20/2%. Afterwards, the canals were prepared with the instruments, according to the manufacturers’ instructions:
Group 1: ProTaper Next (PTN)—X-Smart endomotor (Dentsply Sirona, Charlotte, NC, USA), 300 rpm, torque 2,0 Ncm; size X1 (17, 4%) and X2 (25, 6%).
Group 2: WaveOne Gold (WOG)—X-Smart endomotor (Denstply Sirona, Charlotte, NC, USA)—WOG reciprocating mode; size: WOG Primary (25, 7%).
Group 3: TF Adaptive (TF)—Elements Motor endomotor (Kerr Endodontics, Orange, USA)—Adaptive Motion; size SM1 (20; 4%), SM2 (25; 6%), SM3 (35; 4%).
Group 4 was left non-instrumented, as it constituted the control group. It underwent further processing stages for the purpose of crack evaluation in the same way as the experimental groups.
Between each instrument insertion, the root canal was rinsed with 1 mL of 0.9% NaCl.
All the roots were then embedded in acrylic blocks by Operator 2 (Duracryl Plus, Spofadental, Jičín, Czech Republic) and sectioned horizontally 3, 6, and 9 mm from the apex with a low-speed saw under water cooling (Southbay Technology Inc., San Clemente, CA, USA). The slices were then viewed through a stereomicroscope at ×25 magnification. The samples were inspected visually and in a tactile manner 3 times with the dental probe in order to determine the presence of dentinal cracks by Operator 1. A crack was defined as any lines, microcracks, or fractures in root dentin. No crack was defined as root dentin devoid of craze lines, microcracks at the external surface of the root, and microcracks at the internal surface of the root canal wall. A second rater was called for cross-reference if a doubt appeared. An χ2 test was used for statistical analysis of differences in the incidence of cracks between the experimental groups (PQStat Software, Poznan, Poland). Kruskal–Wallis ANOVA (Past 4.03, Oslo, Norway) was used to compare the differences in the number of cracks between all groups. The level of significance was set at 0.05. The odds ratio was calculated for all teeth (Past4.03, Oslo, Norway) using the Haldane–Anscombe correction.

3. Results

Partial cracks within radicular dentine were observed in roots using all instruments. No cracks were observed in the control group. Chi-squared analysis showed that the difference between PTN and the control group and the difference between TF and the control group was significant (p = 0.0350), whereas the difference between WOG and the control group was insignificant (p = 0.0717). The difference between PTN and WOG was also not significant (p = 0.6773). The number of cracked specimens was the same for PTN and TF (p = 1). Examples of cracked specimens are shown in Figure 1, and non-cracked specimens are shown in Figure 2.
The highest number of cracks was observed in the apical portion of the root canal for PTN and WOG instruments, and in the middle portion of the root canal for TF. No cracks were observed in the control group. The absolute number of cracks and the differences in the number of cracked specimens are shown in Table 1.
For all instruments, OR (odds ratio) was calculated in order to determine the difference in the risk of crack formation. The values calculated were as follows: For PTN instruments, OR = 11.182 (95% CI = 0.567…223; p = 0.11385); for WOG instruments, OR = 8.2 (95% CI = 0.39567…169.9; p = 0.17364); for TF, OR = 11.182 (95% CI = 0.567…223; p = 0.11385.
For PTN instruments, cracks were observed in four teeth: In two teeth at 3 and 6 mm from the apex, in one tooth at 3 mm from the apex, and one tooth at 6 and 9 mm from the apex. For WOG instruments, cracks were observed in three teeth at 3 mm from the apex, in one tooth at 3 and 6 mm from the apex, and in one tooth at 3, 6, and 9 mm from the apex, respectively. For TF instruments, the cracks were observed in four teeth—in one tooth within 3 mm and 6 mm from the apex, in one tooth within 6 and 9 mm from the apex, and in one tooth at 3 mm, 6 mm, and 9 mm from the apex, in one tooth at 3 mm from the apex, and in one tooth at 6 and 9 mm from the apex. The numbers of cracks in all groups and all levels are shown in Table 2. There was no significant difference between the experimental groups (Kruskal–Wallis ANOVA p = 0.865).
Friedman ANOVA was used to determine whether there was any statistically significant difference between all levels in specimens prepared with the same files. The analysis showed that there were no statistically significant differences between all segments in each group (p-value for Friedman ANOVA: PTN: p = 0.4398, WOG: p = 0.3123, TF: p = 0.1853).

4. Discussion

The relationship between root canal instrumentation and damage to radicular dentine has been shown in several research studies [11,14,15,16,17]. As engine-driven endodontic instruments became an inevitable part of modern endodontic care, all instruments introduced to the clinical practice have been the topic of research papers whose aim was to determine the possible relationship between the instrument size, taper, cross-section, tooth anatomy, etc., and complications related to radicular dentine, such as improper disinfection or crack formation [7]. Among these factors, movement kinematics has been a topic of research since reciprocal and adaptive motion instruments were introduced to the market [18,19]. Therefore, our study aimed to determine whether instruments of similar sizes and shapes may influence dentin crack formation. We chose those specific systems for the study on the basis of their clinical applicability. Even though they may differ in size or shape, we chose the most similar instruments in terms of the sequence used in order to reflect the clinical situation that is possible to be purchased commercially and used in clinical situations. Choosing only one group of instruments in different motion patterns would also be impossible—this would make no sense, as TF cuts when moving clockwise while WOG cuts when moving in the counter-clockwise direction, therefore, using one endomotor would be impossible. Another thing they have in common is that they are in line with the modern concept of minimally invasive dentistry, i.e., they tend not to remove excessive dentine in the cervical area [20]. The reason SM3 was also included in the protocol was because the aim of the study was to reflect the clinical reality and use the protocol for preparation which was suggested by the manufacturer and researchers who are responsible for its development. When it comes to irrigant choice, we decided to use NaCl as a neutral irrigant, in order to focus on the physical aspect of instrument movement. Even though sodium hypochlorite is the main irrigant used nowadays, other fluids, such as EDTA, citric acid, chlorhexidine, or mixed fluids such as MTAD, QMix, etc., are available for use and indicated in certain circumstances [21]. Therefore, examination of their influence on dentin properties is best performed using different models, e.g., by examining changes in dentin properties (microhardness, surface structure, collagen loss, etc.) rather than in studies involving instrumentation [22].
When it comes to methodology, the protocol we employed in the study was similar to the majority of ex vivo experiments whose aim was to assess the incidence of cracks after root canal preparation, i.e., the specimens were cut using a low-speed saw into three fragments: 3, 6, and 9 mm from the apex, and viewed using a microscope [23]. Similarly, our study did not show statistically significant differences between all systems. The percentages and numbers of cracks are similar, as they oscillate between 10 and 50% of all specimens. Furthermore, no cracks were observed in the control group, which is also in agreement with other studies [10,16,24,25]. This approach provides excellent visualization of the root surface. Nevertheless, the samples cannot be viewed before instrumentations, and are destroyed post-operatively—therefore, the comparison before and after preparation cannot be performed. That is why the possibility of atraumatic extraction constituted an inclusion criterion for the study. In order to overcome the issue of potential induction of damage during surgical procedures, micro-computed tomography (micro-CT) has been gaining popularity recently, as it provides the possibility of examining the specimens before and after intervention [26]. However, exposure to high doses of radiation and placement in the scanner cause an increase in temperature and dehydration of the specimens, which in turn may also be related to dentinal defects. Moreover, it is much more expensive and requires editing software in order to assess the images. Therefore, none of these methods are viewed as the gold standard. Additionally, conventional CT and cone-beam CT (CBCT) have not been proven to be fully reliable for diagnosing fractures within the root, both in in vivo and ex vivo conditions; nevertheless, CBCT remains the modality of choice in difficult clinical cases in patients and is superior for clinical diagnostics [24,25]. Moreover, the majority of papers on the topic utilize the same ex vivo model, in which the teeth are placed in gauze, silicon impression material, or floral foam. However, such specimens do not replicate the actual situation within the oral cavity. The tooth undergoing endodontic treatment should have appropriate periodontal support [27]. Therefore, periodontal collagen fibers take over the forces generated by the instrument in the operator’s hand, and transfer them to the bone [28]. That is why results acquired by e.g., Liu et al. [29], who concluded that apical detachment may be a serious endodontic complication, may have to be reviewed with caution. All this can also explain why research studies conducted on human cadavers or animal specimens, in which the teeth were fixed in the bone, showed different results. Several research groups [30,31,32] observed that the cracks present after preparation had already been present before the preparation and could have been attributed to a variety of other factors, e.g., extraction [33]. This may also be related to the issue of torque and rotation speed, as greater force allowed and expressed by the instrument has been linked to a higher incidence of cracks, but this, again, was observed in an ex vivo environment [34].
Another point that may seem necessary to discuss, regarding study methodology, is the choice of the material, i.e., single rooted premolar teeth. As root canal anatomy shows some degree of variability, there are two possible ways of overcoming potential bias when it comes to the influence of root canal morphology on the final outcome—either choosing one particular group of teeth or establishing appropriate inclusion and exclusion criteria that ensure that the original shape of the root canal influences the shaping process to a minimum extent. We decided to follow the suggestions, as variability within one particular group of teeth may depend on other factors, as e.g., gender or age, which has been shown by Monsarrat et al. [35] The inclusion criteria accepted for the purposes of the study included age, the possibility of atraumatic extraction, and the absence of symptoms of parafunctions. Exclusion criteria included root caries and pathological resorption. This is related to the second factor that should be discussed, i.e., the degree of preliminary preparation of the root canal. Even though the minimum recommended size of the initial negotiation of the root is size ISO 15, systems of small-size files for glidepath preparation were available only for rotary instruments (Proglider, Dentsply Sirona, Charlotte, NC, USA) and reciprocal instruments (WaveOne Gold Glider, Dentsply Sirona, Charlotte, NC, USA). There is no file designed for use in adaptive motion for initial recognition of the root canal. This, however, may not be of clinical significance, as the original size of the apical constriction, according to morphological studies, constitutes on average 0.2–0.3 mm, which corresponds to an ISO size of 20 [36,37,38]. Even though the results were published earlier, their original aim was to present root canal anatomy and not endodontic instruments. Furthermore, hand instrumentation of up to size 20 has not been shown to induce root canal damage when performed to the correct working length [29]. Furthermore, while the issue of root canal cleanliness and its relationship with the movement of the instrument in limited space may seem important, it is crucial to note the morphology of the root canal, i.e., its working length, along with the original shape of the root canal, determine the volume of free space available for the instrument to rotate. As each tooth differs, the working length is always determined individually for each case according to the accepted endodontic treatment guidelines [27]. In order to overcome this problem, inclusion criteria, mentioned before, were implemented, so that cases of dubious architecture and morphology were excluded, while negotiation performed by an endodontist also provided information regarding the inside of the root canal system. Moreover, as it is widely known that the walls of the root canal remain untouched [26,39], the instruments should be moved in such a manner that they touch all walls of the root canal, so that the risk of debris accumulation is minimized; therefore, following appropriate techniques recommended by the manufacturer was ensured during the study [40,41,42].
When discussing the results of the study, our observations showed that the use of all chosen systems resulted in the formation of cracks in radicular dentine in ex vivo conditions. This finding is similar to what was concluded in other studies that utilized similar designs, as all of them showed virtually all instrument types may induce cracks and fractures [15,43,44,45,46]. However, it has to be taken into account that, even though no ultimate agreement has been reached, it seems that manual preparation may be the least destructive, as it has been related to the lowest incidence of dentinal defects. Moreover, studies conducted in different centers on the same instruments did not confirm this phenomenon—reciprocal instrumentation has been shown to be similar to other instrumentation methods. Furthermore, the results were not the same for files that utilize the same movement pattern, e.g., ProTaper Next and ProTaper Universal, as Karatas et al. observed significant differences between the systems [15]. In addition, files that were designed in such a way in order not to be destructive, e.g., the Self-Adjusting File, have been shown by some authors to induce a certain number of dentine defects [43]. Additionally, Twisted Files have shown different results, as Kesim et al. concluded they caused fewer cracks than reciprocating instruments, whereas Gergi et al. achieved completely different results [47,48]. Some explanations for these observations were proposed by Kwak et al. [49] and Jamleh and Alfouzan [50], as they concluded that peak torque values observed while the adaptive motion was used were lower, which could translate to less stress being exerted on dentine. However, there may be a reason for the lower number of cracks induced by reciprocal instruments in our study and those used in other cases. WaveOne Gold files undergo thermomechanical treatment, during which they become more elastic and more resistant to fracture [51]. They adapt better to the walls of the root canal, and their memory-shape effect is less pronounced. Other research groups observed the same situation, e.g., Pedulla et al. saw that files after thermomechanical treatment—HyFlex EDM, WaveOne Gold—induced much fewer cracks than instruments produced of the conventional NiTi alloy [46]. This may constitute an interesting point for other studies.
As the ultimate goal of studies related to the clinical performance of endodontic instruments, at this point, it would be worth discussing the reliability of the investigations and possibility of their translation in the clinical practice [52]. Evaluating this issue in in vivo conditions presents a huge problem, as, first of all, if a clinically significant crack is present, the tooth needs to be extracted, and secondly, the possibilities of diagnostic imaging in very high resolution are related to the use of very high doses of radiation that would be unacceptable and dangerous to the patient. Regarding the first issue, if cracks influenced the longevity of the tooth in the oral cavity, the values observed in other studies would seem slightly overestimated, as endodontic treatment success rates are higher, and in the longer term, more than 50% of teeth are retained [53]. Furthermore, it is generally agreed that dentine cutting may weaken the tooth structure and contribute to treatment failure; however, in further studies, the relationship between cracks and bacterial invasion should be investigated, as it is the microbiological cause that may contribute to the development of clinical symptoms and failure. When it comes to imaging modalities that would enable us to diagnose cracks and fractures with the highest level of sensitivity and specificity, it is also generally agreed that, as has been stated earlier, CBCT may not be the most reliable tool for their diagnostics, and the aforementioned methods, i.e., micro-CT, use radiation doses that are unacceptable from the point of view of radiation safety. Therefore, they can be used in cadaver studies only [54].
Apart from the observation that all root canal preparation methods are related to an increased risk of dentine cracks, the final outcome and conclusions regarding the influence of movement kinematics cannot be drawn unequivocally on the basis of the literature. There are several reasons for this issue, namely the variety of statistical methods used for comparison and the methodology used. An example of the difficulty with statistical comparisons is the case of the studies conducted by Burklein et al. [9] who concluded that reciprocating motion causes the highest number of cracks. However, apart from the presence of the crack, they attempted to compare the number of cracks in all specimens and compare it with the number of specimens. From a clinical point of view, though, it is the mere presence of the crack that constitutes a bad or unsatisfactory outcome. As the incidence of fracture can be viewed as a nominal category of data (it is present or absent), we decided to follow the approach suggested by Bier et al. [55] to use chi-squared statistics and compare the mere fact of whether the crack was present or absent, which enables us to show the only significant difference between instrumented and non-instrumented groups was seen for PTN and TF, and not for WOG. The question of whether the specimen is cracked more or less does not in fact influence the clinical diagnosis; nevertheless, we attempted to check whether the differences regarding this aspect are significant, and our calculations disproved that. Having discussed and taken into account all these issues, it can be concluded that the issue of dentin crack formation constitutes a multi-faceted issue that requires further investigations.

5. Conclusions

Under the study conditions and within the limitations of this study, it can be concluded that instrumentation with the use of ProTaper Next, WaveOne Gold, and TF Adaptive files can result in dentinal cracks; however, the tendency to induce cracks does not differ significantly between these groups. The comparison with the control group allows us to conclude that instrumentation with WOG is, however, less detrimental, than the other two methods.

Author Contributions

Conceptualization, W.E., B.C. and A.S.; methodology, W.E., B.C. and A.S.; software, W.E.; validation, W.E., B.C. and A.S.; formal analysis W.E.; investigation, W.E.; resources, W.E., B.C. and A.S.; data curation, B.C. and A.S.; writing—original draft preparation, W.E.; writing—review and editing, W.E., B.C. and A.S.; visualization, W.E., B.C. and A.S.; supervision, B.C. and A.S.; project administration, W.E.; funding acquisition, W.E., B.C. and A.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Ethical review and approval were waived for this study, due to the decision of the Bioethics Committee at the Poznan University of Medical Sciences (28 February 2017).

Informed Consent Statement

Not applicable.

Data Availability Statement

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. A cross-section of cracked specimen (a) and (b) (red arrow).
Figure 1. A cross-section of cracked specimen (a) and (b) (red arrow).
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Figure 2. A cross-section of non-cracked specimen after preparation (a) and control group (b).
Figure 2. A cross-section of non-cracked specimen after preparation (a) and control group (b).
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Table 1. Absolute number of cracked specimens in all experimental groups.
Table 1. Absolute number of cracked specimens in all experimental groups.
Instrument SystemsOverall No. of Cracked TeethNo. of Cracked Specimens at 3 mmNo. of Cracked Specimens at 6 mmNo. of Cracked Specimens at 9 mm
PTN4331
WOG3321
TF4342
Table 2. Absolute number of cracks in all experimental groups.
Table 2. Absolute number of cracks in all experimental groups.
Instrument SystemsAbsolute No. of CracksAbsolute No. of Cracks at 3 mmAbsolute No. of Cracks at 6 mmAbsolute No. of Cracks at 9 mm
PTN9351
WOG6321
TF12363
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Eliasz, W.; Czarnecka, B.; Surdacka, A. The Influence of Root Canal Preparation with ProTaper Next, WaveOne Gold, and Twisted Files on Dentine Crack Formation. Machines 2021, 9, 332. https://doi.org/10.3390/machines9120332

AMA Style

Eliasz W, Czarnecka B, Surdacka A. The Influence of Root Canal Preparation with ProTaper Next, WaveOne Gold, and Twisted Files on Dentine Crack Formation. Machines. 2021; 9(12):332. https://doi.org/10.3390/machines9120332

Chicago/Turabian Style

Eliasz, Wojciech, Beata Czarnecka, and Anna Surdacka. 2021. "The Influence of Root Canal Preparation with ProTaper Next, WaveOne Gold, and Twisted Files on Dentine Crack Formation" Machines 9, no. 12: 332. https://doi.org/10.3390/machines9120332

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