|Year : 2015 | Volume
| Issue : 1 | Page : 21-25
Radicular dentinal defects incidence after using EDTA gel with different root canal instrumentation techniques
Mohamed Abdel Aziz Mohamed El Sayed1, Maryam Omar Al amoud2, Malak Rashid M'gharfaoui2
1 Department of Conservative Dentistry, Mansoura University, Mansoura, Egypt; Department of Restorative Dentistry, Faculty of Dentistry, Ajman University, Ajman, United Arab Emirates
2 Department of Restorative Dentistry, Faculty of Dentistry, Ajman University, Ajman, United Arab Emirates
|Date of Web Publication||27-Jan-2015|
Mohamed Abdel Aziz Mohamed El Sayed
Department of Conservative Dentistry, Faculty of Dentistry, Mansoura University, Mansoura, Egypt
Source of Support: None, Conflict of Interest: None
Objectives: The purpose of this study was to compare the incidence of dentinal defect formation after using EDTA gel during root canal preparations by three different instrumentation techniques. Materials and Methods: One hundred and forty maxillary central incisors were decoronated and roots were embedded in resin blocks. Twenty samples were left unprepared (Control group), and the remaining 120 samples were divided into three groups. Each group was divided equally into two subgroups according to the use of EDTA gel during root canal instrumentation. Roots were prepared with hand file (Group 1), ProTaper Universal (Group 2) and WaveOne (Group 3). Roots were sectioned 3, 6, and 9 mm from the apex, and the cut surface was observed microscopically and the presence of dentinal defects was checked. The differences between groups were analyzed using Fisher's exact test. Results: Unprepared roots did not show any dentinal defects. Dentinal defects were observed in all prepared roots. The difference between experimental groups and subgroups regarding the incidence of dentinal defects was not statistically significant. Conclusion: Canal preparation using hand or rotary files created radicular dentinal defects. The use of EDTA gel during root canal preparation did not reduce the incidence of dentinal defects.
Keywords: Canal preparation, dentinal defects, ProTaper, WaveOne
|How to cite this article:|
El Sayed MA, Al amoud MO, M'gharfaoui MR. Radicular dentinal defects incidence after using EDTA gel with different root canal instrumentation techniques. J Res Dent 2015;3:21-5
|How to cite this URL:|
El Sayed MA, Al amoud MO, M'gharfaoui MR. Radicular dentinal defects incidence after using EDTA gel with different root canal instrumentation techniques. J Res Dent [serial online] 2015 [cited 2019 Dec 7];3:21-5. Available from: http://www.jresdent.org/text.asp?2015/3/1/21/150027
| Introduction|| |
Chemo-mechanical preparation is a critical step to achieve a successful root canal treatment. Perforation, canal transportation, ledge or zip formation, and fracture of files are some of the complications that may occur during the root canal preparation. ,, Furthermore, instrumentation procedures can also cause localized dentinal defects such as craze lines or incomplete cracks with subsequent root fracture when the tooth is subjected to repeated stress by occlusal forces. ,
Recently, many nickel-titanium (NiTi) rotary systems have been introduced and despite of their various clinical advantages over hand instrumentation such as saving the time and better cutting efficiency, they can generate higher stresses within the root canal. ,, ProTaper Universal NiTi rotary system (Dentsply, Maillefer, Ballaigues, Switzerland) is a modification of the original ProTaper system. It includes five finishing files with more rounded and safe tip than those of the original ProTaper system, which may improve the working and shaping ability.  However, the large apical tapers produced by this system can theoretically cause more dentinal cracks, especially in small weak roots. 
WaveOne (Dentsply Maillefer) is a new reciprocating single-file system, which is able to prepare canals with only one file, thereby requiring less working time.  WaveOne files are made of a special NiTi alloy called M-wire, which increases flexibility and resistance to cyclic fatigue.  At present, this system is composed of three files; 21/0.06, 25/0.08 and 40/0.08. It might be assumed that when using only one file for complete preparation more stress will be generated during mechanical instrumentation, which may increase the incidence of dentinal defects. Currently, insufficient data are available to prove or disprove this assumption.
A lubricant material such as Ethylenediaminetetraacetic acid (EDTA) gel can be used during rotary canal instrumentation to reduce the incidence of file separation and facilitate the instrumentation procedures.  Meanwhile, using EDTA gel reduces the microhardness of radicular dentin and this may contribute in the dentin defect formation.  The effect of using EDTA gel with hand or rotary instruments on the incidence of dentinal defect formation was not previously studied. Therefore, the purpose of the current study was to compare the incidence of dentinal defects while using hand files, reciprocating (WaveOne), and full sequence rotary files (ProTaper Universal) with EDTA gel.
| Materials and methods|| |
One hundred and forty freshly maxillary central incisors with nearly similar root length and radicular dentin thickness were selected after radiographic examination and stored in distilled water. Crowns were cut at cemento-enamel junction using a low-speed diamond disc under copious water cooling, leaving roots approximately 12 1 mm in length. Exact length of each root was measured and 1 mm was subtracted from this length and recorded as the working length (WL). All roots were examined microscopically under 12Χ magnification and cracked roots were excluded and replaced by new sound ones. Size of the initial file for all samples was not larger than size 25 K-file.
A standard model for periodontal ligament (PDL) simulation was used for all groups.  Roots were placed in melted wax up to 1 mm below the coronal end of the root. After cooling, the roots were embedded in 2 Χ 2 Χ 2 cm blocks filled with a clear acrylic resin. After setting, the roots were removed and the wax was cleaned from the root surface and sockets using warm water. Sockets were then filled with a silicone impression material (Affinis Precious; Colten Whaledent AG, Switzerland) and the roots were reinserted into the respective sockets. The excess impression material was removed with a scalpel.
Twenty samples were left unprepared and considered as a control group. Remaining samples were divided according to the instrumentation techniques into three experimental groups of 40 samples each. Each experimental group was further divided into two subgroups of 20 samples each according to the use of EDTA gel (Diaprep; Diadent, Seoul, Korea) as a lubricant agent during canal instrumentation. In Subgroup A, EDTA gel was not used while in Subgroup B EDTA gel was used.
In Group 1, the canals were prepared with a stainless steel K-file (Dentsply Maillefer, Ballaigues, Switzerland) to a master apical file # 40 with 1 mm increments step-back up to K-file files # 70. Each file was used to prepare 5 canals.
In Group 2, ProTaper Universal rotary files (Dentsply Maillefer) were used in a modified crown-down manner by using a gentle in-and-out motion. Instrumentation sequence was SX instrument at two-thirds of WL, S1 and S2 at WL minus 1 mm and then F1 (20/. 07), F2 (25/08), F3 (30/.09), and F4 (40/.06) at full WL.
In Group 3, WaveOne file size 40/0.08 was used without creation of a glide path in a reciprocating, slow in-and-out pecking motion according to the manufacturer's instructions. Each rotary file was used to prepare four canals.
Each canal was irrigated with 2 mL of 3% NaOCl after each file using a Max-i-Probe 27-gauge irrigating needle (Dentsply, Maillefer). Each canal was then irrigated with 0.5 mL of 17% EDTA solution for 30 sec and finally rinsed with 5 mL distilled water. All root canal preparations and the following root sectioning procedure were completed by one operator.
Root sectioning and microscopic examination
All roots were sectioned horizontally at 3, 6, and 9 mm from the apex using Isomet 1000 Precision Saw (Buehler, an ITW Company, Illinois, USA) under water cooling. A total of 60 sections in the control group and 120 slices in the experimental groups were viewed by two other examiners who were blinded with respect to all experimental groups using a digital stereomicroscope (Leica EZ4HD; Leica microsystem, Wetzlar, Germany) at 25Χ magnification. The appearance of dentinal defects was inspected and pictures were captured and stored in the computer. In cases of discrepancy in the observations of the examiners, the slices were re-evaluated and discussed until an agreement was reached.
Definitions of the dentinal defects
Dentinal defects [Figure 1] were classified according to Wilcox et al.  "No defect" was defined as root dentin devoid of any cracks. "Defect" was defined as fracture lines (Type I defect), craze lines or partial cracks (Type II defect). Craze line is a line extending from the outer root surface into dentin but without reaching the canal lumen. Partial crack is a line extending from the canal wall into the dentin without reaching the outer root surface. Roots were classified as defected if at least one of three sections showed a craze line, partial crack or a fracture.
|Figure 1: Different dentinal defects: (a) No defects, (b) Complete fracture, (c) Craze line, (d) Partial crack (black arrow pointing dentin defects)|
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Results were expressed as the number and percentage of roots showing dentinal defects in each subgroup. Type of dentinal defects in each section was also recorded regardless the number of these defects. Fisher's exact test was performed to compare the incidence of different dentinal defects between the experimental groups and subgroups using the SPSS version 20.0 computer program (SPSS, Chicago, IL, USA). The level of significance was set at P < 0.05.
| Results|| |
The unprepared samples showed no defected roots. Dentinal defects were found in all experimental groups. In Groups 1 and 3, the percentage of overall defected roots [Figure 2] regardless of the type of these defects was higher in Subgroup B (with EDTA gel) than in Subgroup A (without EDTA gel). The difference between the experimental groups in the appearance of the dentinal defects was not significant. When considering the defected root slices [Figure 3], instrumentation techniques with EDTA gel demonstrated more defects than those without EDTA gel at all cross-section levels except the apical sections of Groups 2 and 3 that showed less dentinal defects. But the difference between groups and subgroups was not statistically significant. [Table 1] and [Table 2] presented number and percentage of root sections showing different types of dentinal defects in different subgroups. Statistically, there was no significant difference between groups and subgroups regarding the type of dentinal defects.
|Figure 2: The percentage and number of roots, presenting a detinal defect as a result of root canal instrumentation in all groups. Groups and subgroups with the same letter denote no statistical significant difference between them (P > 0.05)|
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|Figure 3: Number of root sections having dentinal defects in all subgroups and groups. Groups and subgroups with the same letter denote no statistical significant difference between them (P > 0.05)|
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|Table 1: Number and percentage of root sections presenting different types of dentinal defects in Subgroup A (No EDTA gel) of all groups as a result of root canal instrumentation|
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|Table 2: Number and percentage of root sections presenting different types of dentinal defects in Subgroup B (EDTA gel) of all groups as a result of root canal instrumentation|
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| Discussion|| |
Currently, the reciprocating single-file systems and new types of full sequence rotary files are available and could facilitate the instrumentation procedures. Until now, most of the research has focused on the effect of stress on the instrument, little effort has been put into the effect of the same stress on the root dentine.  Some authors , concluded that rotary files can produce various degrees of radicular dentinal defects. The extent and percentage of such a defect formation may be related to the file movement, tip design, cross-section geometry, constant or progressive taper type, constant or variable pitch, and flute form. 
The use of a lubricant material such as EDTA gel during rotary canal instrumentation is known to reduce the incidence of file separation and facilitate the instrumentation procedures. Moreover, this lubricant material can reduce rotational and frictional force on the radicular dentinal wall and may theoretically reduce the incidence of dentinal defects. Nevertheless, the use of EDTA gel reduces the microhardness of radicular dentin,  which may contribute in dentin defect formation. So the aim of the present study was to study and compare the effect of using EDTA gel during root canal instrumentation using hand files, ProTaper Universal and WaveOne reciprocating single-file systems on the incidence of radicular dentinal damage in the form of microcracks in root dentin.
In the present study, maxillary central incisors of nearly similar root size were selected to minimize anatomical variations. Similar studies ,,, have used mandibular premolars, lower central incisors and distal roots of mandibular first molars. The root surfaces were coated with a layer of silicone impression material before placing within the acrylic blocks to simulate periodontal ligaments (PDL) and distribute stresses during root canal preparation. 
The forces of extraction and sectioning procedures may contribute to the observation of incomplete fractures. But the samples in the control group did not show any defects, so it may be concluded that the dentinal defects seen were a result of different preparation procedures. The sectioning method used in the present study allowed the evaluation of the effect of root canal preparation procedures on the root dentin by direct inspection of three root sections and is in agreement with the methodology described by Shemesh et al. 
The results of the present study showed that all canal instrumentation techniques produced dentinal defects without a significant difference between them. This result is consistent with previous studies that demonstrated increased crack formation and fracture susceptibility of teeth as a result of instrumentation.  However, this seems in contrast to the study of Bier et al.,  which showed no influence of hand technique on crack formation. They used a balanced force technique in their study, while a step back technique was used in the current study. ProTaper and WaveOne are characterized by a triangular or modified triangular cross-section that results in a lower cutting efficiency and less chip space.  Rotational forces associated with ProTaper files and the large apical tapers produced by this system  may contribute in crack formation. ,, Reciprocal motion seems to enhance debris transportation toward the apex and may increase torsional forces.  The overall dentinal defects occurred in between 35% and 55% of the roots. Many in vitro studies , showed a lesser incidence of dentinal defects. However, our study is in accordance with the studies of Shemesh et al.  and Wilcox et al. 
The number of root sections showing communicating cracks (fracture lines) was less than other defects (craze lines or partial cracks) regardless of the instrumentation technique, which is in agreement with previous studies. , In our study, few internal craze lines were observed and most of the defects were external cracks. These results are consistent with the results of a study by Shemesh et al.  and Milani et al.  This may be due to the stress generated by instrumentation within the canal, which is transmitted to the outer surface of the tooth where it overcomes the bonds holding the dentin together. 
The use of EDTA gel insignificantly increased the percentage of dentinal defects in all experimental groups. This may be explained by the gel form of EDTA, which may collect more debris in the cutting flutes of the files decreasing the cutting efficiency of the file and indirectly increasing the stress on the dentinal wall and enhancing dentinal crack formation. ,
It may be concluded that, based on the current observations, the use of hand files and rotary NiTi instruments either with full or reciprocal rotation could induce different types of dentinal defects. The use of EDTA gel did not significantly affect the incidence of radicular dentinal defects.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]