Comparing the Impact of Different Motion Modes on Dentin Cracking: A Meta-Analysis

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Comparing the Impact of Different Motion Modes on Dentin Cracking: A Meta-Analysis

https://doi.org/10.21203/rs.3.rs-4710237/v1

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Objective: We aim to compare the effects of different exercise modes of single file on dentin cracks.

Methods: A literature search was conducted in PubMed and other databases to conduct meta-analysis on randomized controlled trials published before March 22, 2024, and subgroup analysis was performed on WaveOne and Reciproc single file. After preparing the root canal of a single file with reciprocating and rotational motion, the dentin cracks were evaluated under a stereomicroscope on the 3mm, 6mm, and 9mm sections of the root apex.

Results: A literature search yielded 264 records, and 8 randomized clinical trials were finally included in this study. We found that both reciprocating and rotating single files may cause dentin cracks, but there was no significant difference in the incidence of dentin cracks (RR=1.03; 95% CL, 0.89-1.18; P=0.72).

Health sciences/Health care

Health sciences/Medical research

rotational motion

Reciprocating motion

Single file

dentin crack.

The success of endodontic treatment depends on debridement, thorough disinfection, and closure. Root canal instruments are designed to eliminate pulp tissue and microorganisms, etc., and to create sufficient space for rinsing agents, room seals, and root canal filling⁽¹⁾. In recent years, mechanical nickel-titanium instruments have improved the efficiency of root canal therapy⁽²⁾. Chemomechanical preparation (CMP) plays an important role in achieving the success of endodental treatment as it removes bacteria, debris and enlarges the diameter of the root canal for closure. During root canal preparation, the contact between endoplastic instruments and the dentin wall of the root produces transient conditions during biomechanical preparation, and the concentration of dentin stress may lead to dentin defects and crack lines. Long-term propagation of dentin cracks may lead to vertical root fracture (VRF)⁽³⁾. Vertical root fractures are responsible for 10.9-31% of tooth extractions⁽⁴⁾. Even without VRF, the presence of microcracks can affect the outcome of endodontic treatment⁽⁵⁾. Researchers evaluated the effect of dentin microcracks on periapical surgery outcomes. They found that the cure rate for teeth with microcracks (noted during surgery) was 31.8 percent at a 3-year follow-up after surgery, compared to 91.7 percent for teeth with no visible microcracks. VRF may develop dental cleft during treatment or after prolonged functional stress such as chewing⁽⁶⁾.

In recent years, endodontic instruments have undergone a series of changes and introduced kinematic changes to improve efficiency. It has been suggested that if a single file rather than multiple files is used to prepare the root canal, the generation of microcracks may be influenced by different kinematics^(7-11). Using a single file to prepare the shaped root canal reduces the number of root canal contacts and can show equal or better root canal cleaning results. There was a significant association between the number of times the instrument touched the tube wall and microcrack formation(3). Reciprocating motion can reduce cyclic fatigue and torsional stress on the instrument^{(12, 13)}. Is it as good as ever at reducing dentin cracks? It has been known that different motion modes of single or multiple file and NiTi system are associated with different number of dentin microcracks^(14-16). However, there are few systematic studies in the literature on the incidence of dentin cracks in rotary and reciprocating motion using single file, so this study is for the purpose of this study.

The current system evaluation is based on the preferred reporting item (PRISMA) for system evaluation and meta-analysis, which states whether a single reciprocating instrument (I) has fewer dentin crack results (O) in extracted human teeth (P) compared to a single rotating instrument (C) when evaluated in vitro studies using a stereomicroscope.

Inclusion and exclusion criteria

The inclusion criteria for this system evaluation include:

1.Randomized controlled trials;

2.A study comparing the apical crack situation of single file with reciprocating motion (R) and continuous rotational motion (CR) in root canal preparation;

3.Evaluate the incidence and/or results of dentin cracks using a three-dimensional microscope after using 3mm, 6mm, and 9mm apical sections;

4.Research conducted using human teeth in vitro;

5.Research published in both English.

Exclusion criteria include the use of motion systems other than reciprocating and rotational motion, such as adaptive motion.

Search strategies

We combined theme words such as "dentinal cracks", "single file", "reciproc", "rotation", and their synonyms to search English databases such as PubMed, Cochrane Library, EMBASE, Wiley, and Web of Knowledge. Collect randomized controlled studies on the effects of reciprocating and rotating single file motions on dentin cracks published both domestically and internationally. The search deadline is from the establishment of each database to March 22, 2024. The article was re searched before submission to ensure no omissions. After importing all records into EndNote X8 (Clarivate Analytics, Philadelphia, Pennsylvania), remove duplicates, titles, and abstracts.

Based on the combination of the following keywords and topic words (1 and 2 and 3 and 4):

1.cracks in the root dentin OR dentinal microcracks OR root fracture OR dentinal damage OR Dentinal cracks OR;dentinal defect.

2.single-file OR single-file systems OR single-instrument OR single file endodontic.

3.reciprocating OR reciprocating file OR reciprocation systems OR Reciproc.

4.continuously rotating OR sequence rotary OR Rotary file OR rotary instrument OR rotary nickel titanium OR rotary niti OR niti rotary instrument OR endodontic rotary file OR continuous movement OR continuous rotation OR nickel-titanium rotary OR rotary OR rotating .

Data extraction

Three independent reviewers (SD,DS and WC) independently screened to determine the study based on inclusion criteria. The content of creating a data extraction table is as follows: first author and country of first author, publication year, sample size, research type,Storage conditions，Simulate periodontal ligame,sample type, tube curvature, stereo microscope magnification, type and concentration of flushing agent, experimental instruments, exercise method, and results.

Quality assessment

The above three independent reviewers evaluated the quality of the included studies based on the revised Cochrane bias risk tool, which is applicable to the nature of in vitro studies. Each criterion is divided into "high", "low", or "unclear" bias risks. Five main areas (randomization,allocation concealment, subject and professional blindness in the study, blind outcome evaluation, and other biases) were considered for evaluating the quality of the study. In the evaluation of in vitro randomization processes, allocation concealment is not considered a qualified parameter due to the difficulty in masking the instrument techniques used for comparison. In addition, as objective evaluation can be made through a stereomicroscope, it is impossible for bias to occur due to the blinding effect of the results. This study has been registered on the PROSPERO website (registration number: CRD42023476068).

Literature search

The PRISMA flowchart in Figure 1 provides information about the literature search performed. The initial search resulted in 264 studies. Repeated identification resulted in the exclusion of 85 studies. The selection of titles and abstracts for other studies resulted in further exclusion of 139 studies based on selection criteria. The full texts of the remaining 8 studies were retrieved and met the eligibility criteria. Finally, 8 studies were selected and included in quantitative synthesis (Table 1). Table 1 shows the characteristics of 8 studies, including the magnification of the stereo microscope used (ranging from 2.5X to 40X). These studies were conducted on central incisors, single root canals of premolars, single root canals of molars, and single root canals of maxillary premolars. The sample size in the study was 20 to 72 root canals per group, with root canal curvature ranging from 0 to 30 degrees. The quality evaluations included in the study are listed in Figure 2.

Study characteristics

There are a total of 8 articles included in this study, including 6 articles on the incidence of cracks in single file sections 3mm, 6mm, and 9mm from the root apex after root canal preparation (See Table 1 for details) Among them, 2 articles are binary data, and 6 articles are hierarchical data. Among the 8 articles included, the reciprocating single file system includes WaveOne, WaveOne Gold, Reciproc, and Reciproc Blue; The rotary motion single file system includes Proteper-F2, OneShape, F360, F6 SkyTape, HyFlex EDM, Neolix, and One curve. Due to the fact that the literature has multiple data groups for comparison, the literature will be grouped for data comparison. For example, the literature of Hend Mahmoud 2013 was divided into two groups, Priya NT 2014 was divided into four groups, Eugenio Pedulla 2016 was divided into nine groups, and E Ozlek 2021 was divided into two groups, all of which were grouped for comparison. Import the inclusion of literature into Review Manager 5.3 software for operation. Perform sensitivity analysis on those with high heterogeneity in the results (I²>50%). Subgroup analysis and sensitivity analysis were conducted on the dentin crack situation after root canal preparation using Reciproc, WaveOne single file, and rotary motion single file.

Meta-analysis

In the first part of the included research, there were 8 articles and 21 sets of data (See Figure 3 for details), comparing the incidence of dentin cracks after root canal preparation with reciprocating motion and rotary motion single file. There was mild to moderate heterogeneity among the studies (P=0.04,I ²=39%),so a fixed effects model was chosen to calculate the combined statistics. The results showed that there was no statistically significant difference between the fracture rate of reciprocating single file and the fracture rate of rotary single file after root canal preparation in the overall dentin crack incidence (RR=1.03; 95% CL, 0.89-1.18; P=0.72). Subgroup analysis was conducted, and the incidence rates of dentin cracks in 3mm, 6mm, and 9mm after root canal preparation using reciprocating and rotary motion single file were I²=53% and P=0.58, respectively, for all cross-sections; I²=32%, P=0.16; I²=15%, P=0.51.

The second part was included in the study (See Figure 4 for details), which consisted of 5 articles and 8 sets of data. The study compared the dentin cracks in all cross-sections after root canal preparation between Reciproc single file and rotary motion single file. There was mild to moderate heterogeneity among the studies (P=0.02, I²=41%), so a fixed effects model was chosen to calculate the combined statistics. The results showed that there was a statistically significant difference in dentin cracking between the Reciproc single file and the rotary motion single file after root canal preparation[RR=1.20; 95% CI (1.02, 1.41); P=0.03]. Subgroup analysis was conducted, and after root canal preparation with Reciproc single file and rotary motion single file at 3mm, 6mm, and 9mm, the sum of dentin cracks in all cross-sections was I²=59%, P=0.22, respectively; I²=45%, P=0.02;I²=37%, P=1.00; I²=42%, P=0.38.For the 3mm subgroup, each group was removed one by one, and the removal of the Eugenio Pedulla 2016-8 group was not statistically significant[I²=0%, P=1.00].For the 6mm subgroup, each group was removed one by one, and the Elham Khoshbin 2018 group was not statistically significant [I²=8%, P=0.41].

The third part was included in the study, which consisted of 3 articles and 5 sets of data (See Figure 5 for details). The study compared the dentin cracks in all cross-sections after root canal preparation between WaveOne single file and rotary motion single file. There was heterogeneity among the studies (P=0.009, I²=50%), so a random effects model was chosen to calculate the combined statistics. The results showed that there was a statistically significant difference in the incidence of dentin cracks between WaveOne single file and rotary motion single file after root canal preparation surgery [RR=1.22;95% CI (1.00, 1.48); P=0.05]. Subgroup analysis was conducted, and the root canal preparation of WaveOne single file and rotary motion single file resulted in a total of I²=80% and P=0.24 for dentin cracks at 3mm, 6mm, and 9mm cross-sections, respectively; I²=13%, P=0.63; I²=0%, P=0.09;I²=73%, P=0.68.For the 3mm subgroup, each group was removed one by one, and the removal of the Eugenio Pedulla 2016-7 group was not statistically significant[I²=2%, P=0.5].For the aggregated subgroups, each group was removed one by one, and the removal of the Hend Mahmoud 2013-1 group was not statistically significant [I²=24%, P=0.06].

Research has shown that as a key step in root canal treatment, root canal cleaning and shaping can increase the likelihood of dentin microcracks and have adverse effects on prognosis^{(17, 18)}. The literature on the kinematics of instruments for the formation of dentin cracks reports contradictory results. Some people believe that reciprocating motion reduces the formation of dentin cracks because it minimizes torsional and bending stresses to the greatest extent possible. However, B ü rklein et al.⁽⁷⁾ reported that the risk of dentin crack formation increases due to the increased torsional force caused by the combination of reciprocating systems and cutting edges. The study^(19-21) showed no correlation between the kinematics of the display mechanism and the formation of dentin microcracks, and no new cracks were formed after instrument preparation.However, a study reported that the length of dentin microcracks was less in reciprocating motion compared to rotating instruments. After root canal preparation, the incidence of dentin microcracks is high^(22-25). However, there is controversy or no consensus on the reported data on the formation of dentin cracks after the use of rotary and reciprocating single file preparations^(26-28). All dentin cracks inherent in detached teeth were excluded before the experiment, and excluding dentin slices would not cause any microcracks⁽²⁹⁾. In this study, we evaluated and compared the situation of dentin cracks after using these systems, and the results showed that dentin cracks occurred at distances of 3mm, 6mm, and 9mm from the root apex after root canal preparation. In this study, there was no statistically significant difference in the incidence of dentin cracks at distances of 3mm, 6mm, and 9mm from the root apex after root canal preparation between reciprocating and rotating single file movements ((Figure 3), indicating that there was no significant difference in the incidence of dentin cracks between the two types of single file movements.

All included literature indicates that all experiments were stored in distilled water or saline solution to prevent experimental effects caused by dehydration; Almost all studies have simulated periodontal ligament, and it is known that periodontal ligament plays a crucial role in buffering pressure.

The nickel titanium file system may produce varying degrees of microcracks in dentin due to differences in material, tip design, cross-sectional shape, taper type, etc. WaveOne, Reciproc are the most commonly used commercial representative files for single reciprocating files.Figure 4 and Figures 5 show that these two types of reciprocating files have statistical differences compared to other rotating files. It was unexpectedly discovered that HyFlex EDM and Neolix can significantly reduce the incidence of dentin cracks. In terms of dentin cracks, HyFlex EDM is superior to Reciproc and WaveOne; Neolix is superior to Reciproc. HyFlex EDM and Neolix are both manufactured using electrical discharge machining. Electrical discharge machining can be used for high-precision manufacturing of conductive materials with various hardness. The sparks generated during this process melt and vaporize the material of the workpiece on its top layer. This innovative manufacturing process is a non-contact machining process that produces excellent fracture resistance and improved cutting efficiency. Perhaps it is precisely this manufacturing process that sets it apart, giving it controllable memory effects and high microhardness. These two types of files also have rectangular cross-sections and non cutting tips. Electrical discharge machining creates a rough and hard surface, combined with rectangular cross-sections and cutting blades to produce high cutting efficiency, which can improve the cutting efficiency of these files⁽³⁰⁾. Can effectively clean root canals with anatomical variations and enable single file to better adapt to root canal walls⁽³¹⁾. During the preparation of the rotary file root canal, the stress applied to the dentin wall is relatively small; Therefore, the risk of microcrack formation is reduced^{(32, 33)}. The fewer cracks formed by Neolix and HyFlex EDM files may be attributed to their overall design and unique alloy composition⁽³⁴⁾.

To our knowledge, this is the first meta-analysis on the occurrence of dentin cracks in a single file that integrates different motion modes. One of the advantages of this review is conducting subgroup analysis using two types of files as representatives. Most of the articles included in this article provide a detailed introduction to laboratory research. Therefore, the results of this meta-analysis are reliable and can provide some guidance for clinical dentists. This study also has certain limitations. The included studies are limited to English, and the number of included studies is relatively small, which may lead to research bias.

In this study, it was shown that using a stereomicroscope to observe single file sections 3mm, 6mm, and 9mm away from the root tip, reciprocating and rotating motions had a good effect on the generation of dentin cracks, and there was no significant difference.

Disclosure Statement

The authors declare no potential conflicts of interest with regard to the authorship and / or publication of this article.

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Table 1 is available in the Supplementary Files section

No competing interests reported.

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Comparing the Impact of Different Motion Modes on Dentin Cracking: A Meta-Analysis

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