Glide Path Enlargement of Curved Molar Canals Using HyFlex EDM Glide Path File versus PathFile: A Comparative Study of Preparation Times and Postoperative Pain

doi:10.21203/rs.3.rs-28602/v1

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Glide Path Enlargement of Curved Molar Canals Using HyFlex EDM Glide Path File versus PathFile: A Comparative Study of Preparation Times and Postoperative Pain

https://doi.org/10.21203/rs.3.rs-28602/v1

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published 23 Mar, 2021

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Background

This randomized clinical trial aimed to compare the preparation times and severity of postoperative pain between the HyFlex EDM Glide Path File and PathFile.

Methods

Eighty patients who were treated by the same specialist were enrolled. After access cavity preparation, the patients were randomly assigned to receive glide path enlargement with either HyFlex EDM GPF or PathFile. ProTaper Next X1 and X2 files were used to prepare the canals. The time of preparation was assessed and the severity of postoperative pain over the next 7 days was recorded.

Results

Preparation time and postoperative pain severity were significantly lower in the HyFlex EDM GPF group compared to that in the PathFile group ( P < 0.05 for both).

Conclusion

Postoperative pain and glide path preparation time could be reduced by using the HyFlex EDM GPF system.

Head & Neck Surgery

Dentistry

Glide path

postoperative pain

HyFlex EDM Glide Path File

Endodontic postoperative pain is a sensation of discomfort experienced by 25–40% of patients after root canal treatment [1, 2]. Post-endodontic pain usually occurs during the first two days after treatment and generally diminishes within a few hours. However, in some cases, the pain may persist for several days. Multiple factors contribute to the pain sensation and severity. Clinical investigation of the postoperative pain is challenging [3]. Mechanical, chemical, and microbiological injuries to periapical tissues are regarded as the main causes of acute periapical inflammation [4]. Irritants such as infected debris extruded into the periradicular tissues during root canal preparation may induce the acute-inflammatory response. Extruded debris can also cause different levels of postoperative pain, and to date, all root canal preparation instruments and techniques have been associated with some degree of debris extrusion. Procedural steps such as glide path preparation and the establishment of apical patency as well as the root canal instrumentation technique are important factors that influence and reduce the post-treatment pain incidence [3, 5, 6].

The endodontic glide path is the smooth tunnel created from the orifice of the root canal to the physiological terminus of the root apex, which facilitates cleaning and shaping during root canal treatment.⁷ Preliminary canal enlargement is also considered an important step as it can reduce torsional stress, and further, increase the life span of the shaping instruments. This also reduces the risk of procedural errors such as ledge formation, canal transportation, and perforations [8, 9]. Glide path enlargement can be performed with precurved stainless steel K-files or nickel–titanium (NiTi) glide path files (GPFs). In 2017, Alovisi et al and Paleker et al demonstrated that NiTi rotary instruments enable faster and safer preparation of a glide path that respects the original canal anatomy [10, 11].

The HyFlex EDM (Coltene/Whaledent, Altstätten, Switzerland) NiTi GPF was the first file system produced using an innovative manufacturing process called Electrical Discharge Machine with a controlled memory (CM) wire. In EDM, instead of conventional grinding, electric discharges are used to shape the file via melting and vaporization of the material [12]. This method creates a cratered surface, which further increases the file’s cyclic fatigue resistance and the shelf life [13]. The HyFlex EDM GPF consists of a single file with a tip size of 10 and a 5% taper. The cross-section of the HyFlex EDM GPF varies along its length, being quadratic at the tip, trapezoidal in the middle, and triangular at the shaft.

The PathFile (Dentsply Sirona, Ballaigues, Switzerland) NiTi rotary GPF system consists of three file systems, which are made of conventional NiTi alloy with different tip sizes such as 13#, 16#, and 19#. The files have square cross-sections, with four cutting edges and a 2% taper.

The aim of this study was to compare the preparation times and severity of postoperative pain with two glide path preparation systems—HyFlex EDM GPF versus PathFile.

The study was approved by the local university clinical research ethics committee with vide letter no. PKUSSIRB-201735063. Informed consent was obtained from the patients before enrolling in the study.

The sample consisted of 80 patients who were treated at the Second Dental Center of Peking University School of Stomatology between June 2018 and February 2019. All participants were informed about the study and had provided written informed consent prior to treatment. The following inclusion criteria had to be fulfilled by the patients to be enrolled in the study: 1) No previous history of systemic diseases. 2) Selected for root canal treatment for asymptomatic or symptomatic irreversible pulpitis in the maxillary or mandibular molars with at least one severely curved canal (> 25°). The exclusion criteria were 1) pulp necrosis, with or without apical periodontitis. 2) Acute or chronic apical abscess. 3) Signs of systemic infection. 4) Allergic to local anesthetic agents. 5) Progressive periodontal disease at any stage.

Before the procedure, pulpal and periradicular status was evaluated by means of vitality tests such as thermal and electric pulp tests (Diagnostic, SybronEndo, USA), palpation, and percussion. Periodontal probing was processed and charting recorded. The periodontal indices were also recorded. After the administration of local anesthesia with 4% mepivacaine with adrenaline 1:100,000 and isolation of the tooth with a rubber dam, a standard access cavity was prepared using diamond burs. At this stage, a sealed envelope containing the randomization code was opened and the patient was assigned to receive glide path enlargement with either the HyFlex EDM GPF or PathFile, with 40 patients in each group. Patients were blinded regarding the file system utilized. All the patients were treated by a single dentist.

HyFlex EDM GPF Group

The working length (WL) was determined using the Root ZX apex locator (SM-DP-ZX, Morita, China) by inserting a size 10 K-file into the root canal up to the apical foramen. The WL was confirmed radio-graphically and was also repeatedly checked during the treatment procedure. The HyFlex EDM GPF (size 10/0.05) was operated with an endomotor (X-SMART; Dentsply Maillefer, Switzerland) in continuous rotation at a speed of 300 rpm and 1.8 Ncm of torque, according to the manufacturer’s instructions. Irrigation with 5.25% NaOCl and 17% EDTA was carried out during the glide path enlargement and the preparation time was recorded from the insertion of the glide path file till the completion of the enlargement, including irrigation time during the enlargement. After instrument use, the root canal was irrigated with 5 mL of 5.25% NaOCl and 5 mL of 17% EDTA.

PathFile group

The WL was determined as described above in the HyFlex EDM GPF group. The PathFile (size 13/0.02 and 16/0.02) instruments were operated using the same endomotor (X-SMART) at a speed of 300 rpm and 5 Ncm of torque. Irrigation with 5.25% NaOCl and 17% EDTA was carried out during the glide path enlargement and the preparation time was recorded from the insertion of the PathFile 13/0.02 till the completion of the PathFile 16/0.02 enlargement, including the irrigation time during the enlargement and the time required to change files. After enlargement, the root canal was irrigated with 5 mL of 5.25% NaOCl and 5 mL of 17% EDTA.

After glide path creation, subsequent endodontic procedures were standardized as per the protocol. The root canals were then prepared with X1 and X2 instruments by using the ProTaper Next (Dentsply Maillefer, Switzerland) rotary instrumentation system and then irrigated with 5.25% NaOCl and 17% EDTA recurrently.

Preparation times for the GPFs and ProTaper Next were recorded. Only the times used for active instrumentation such as checking the WL, cleaning the flutes of the instruments, and irrigation were included. The time taken to change files was not considered.

Finally, the prepared root canals were irrigated again with 10 mL of 5.25% NaOCl with a 30-gauge needle syringe and then dried with sterile paper points. Calcium hydroxide [Ca(OH)₂] was placed in the canals, temporary filling was performed, and an appointment was scheduled to complete the subsequent root canal procedure.

All patients were instructed to record postoperative pain intensity twice daily (morning and evening) for 1 week using a visual analog scale (VAS). The pain score was recorded on a scale of 0 to 10. Pain intensity was categorized as no pain (0), mild pain (1–3), moderate pain (4–6), and severe pain (7–10).

Statistical analysis

SPSS version 20.0 (IBM Corp., Armonk, NY, USA) was used for statistical analysis. The distributions of age, sex, the tooth treated, and the angle of root canal curvature in the two treatment groups were compared by using the chi-square test. The preparation time and the postoperative pain scores were compared using one-way analysis of variance (ANOVA). Statistical significance was recognized at P ≤ 0.05 (two-sided).c

The total sample of 80 patients was divided equally into two groups, i.e. 40 patients in each group. The age of the patients in the Hyflex EDM GPF group was 48.1 ± 14.1 (12 men and 28 women) compared to 45.5 ± 14.4 (11 men and 29 women) in the PathFile group. Regarding the tooth type, 19 first molars and 21 second molars were included in each group. The angle of the root canal was 28.8° ± 6.8° in the Hyflex EDM GPF group and 26.5° ± 8.3° in the PathFile group. Demographic variables such as age and sex and clinical variables such as the tooth type and the angle of the root canal curvature were similarly distributed in the two treatment groups (all P > 0.05; Table 1).

Table 1

Characteristics of the two groups
Demographic data	HyFlex EDM GPF group	PathFile group	P value^*
Age, years	48.1 ± 14.1	45.5 ± 14.4	P > 0.05
Male	12	11
Female	28	29
First molar	19	19
Second molar	21	21
Angle of root canal	28.8° ± 6.8°	26.5° ± 8.3°
Data are mean ± standard deviation or number.
*P > 0.05, statistically not significant.

Table 2 presents the mean total times for glide path preparation using both methods. Glide path enlargement was significantly shorter with HyFlex EDM GPF (27.828 ± 2.345 s) than with PathFile (48.942 ± 2.864 s) (ANOVA, P < 0.001). The preparation time with ProTaper Next in the HyFlex EDM GPF group was 69.432 ± 3.964 s, which was significantly faster than that in the PathFile group (73.889 ± 4.476 s).

Table 2

Preparation times (in seconds) in the two groups
Group	n	Time for glide path preparation	Time for ProTaper Next preparation	Total time
HyFlex EDM GPF group	40	27.8 ± 2.3	69.4 ± 4.0	97.3 ± 6.0
PathFile group	40	48.9 ± 2.9	73.9 ± 4.5	122.8 ± 6.5
F statistic		1559.66	6.75	333.80
P		< 0.001	0.011	< 0.001
Values are means ± standard deviations

Figure 1 presents the mean preoperative and postoperative VAS scores. HyFlex EDM GPF group patients reported significantly less postoperative pain than PathFile group patients overall, with a significant P value of less than 0.05.

This randomized clinical trial aimed to compare the HyFlex EDM GPF versus PathFile with regard to the glide path preparation times and postoperative pain. The mean preparation time was significantly shorter with HyFlex EDM GPF than with PathFile. This shorter time can be explained by the fact that multiple instruments are used in the PathFile system, whereas only a single instrument is used in the HyFlex EDM GPF system. A recent study by Kirchhoff et al. that compared glide path preparation with both systems that require single (ProGlider; Dentsply Sirona, Ballaigues, Switzerland) and multiple instruments (PathFile) in curved mandibular canals also reported that faster glide path preparation was achieved with the single instrument system [9]. Another study also compared the glide path preparation times with the ProGlider file, PathFile, X-Plorer Canal Navigation NiTi file, and stainless-steel K-file [14]. They also reported that there was a significantly shorter preparation time with the ProGlider file compared to the preparation times with the other systems. The ProGlider is a single-instrument system, whereas the PathFile and X-Plorer Canal Navigation NiTi file systems are multiple file systems.

Interestingly, the present study found that the time for ProTaper Next preparation was also significantly shorter in the HyFlex EDM GPF group than in the PathFile group as the preliminary enlargement of the root canal at the coronal and middle portions reduced torsional stress during subsequent root canal preparation, and therefore the WL could be achieved more easily with the ProTaper Next. It should also be noted that the larger taper (up to 5%) of the HyFlex EDM GPF creates a larger canal at the coronal and middle portions.

Postoperative pain is considered to have a significant impact on quality of life, thus proper management of the pain is very important. Although postoperative pain is multifactorial, the instrumentation technique is considered to play a major role in the pain [15, 16]. During chemomechanical preparation, infected debris and extruded bacteria may be transported to periapical tissues, where they can induce an acute inflammatory response in the periapical region [17]. Glide path preparation minimizes the debris and/or bacterial extrusion into the periapical region, which further reduces the postoperative pain regardless of the instrument types used for canal shaping [16, 18]. A study by Ha et al. indicated the progressive taper design of ProGlider, the off-center cross-section of One G, and the alternative-pitch design of ScoutRace are intended to increase the efficiency of debris removal and minimize extrusion during glide path preparation. Debris extrusion is reported to be lower with the ProGlider system than with the PathFile and One G systems [18]. In the present study, postoperative pain was significantly lower in the HyFlex EDM GPF group compared with that in the PathFile group. The larger taper (up to 5%) of the HyFlex EDM GPF is intended to remove cervical interference from the root canal entrance, providing free access for endodontic instruments and irrigants to the periapical region, which further helps in reducing the extrusion of debris.

Glide path preparation prior to mechanical enlargement helps in reducing procedural errors during subsequent root canal procedures. Apical transportation and foramen widening may result in the loss of the apical stop, which further causes more postoperative discomfort [19]. Glide path preparation using instruments with large taper designs could produce enlargement in the coronal and middle third of the root canal, which will allow subsequently used instruments to more consistently reach the apical foramen and also helps in improving the precision of electronic apex locators for determining the WL.

The HyFlex EDM GPF has significantly greater cyclic fatigue resistance and flexibility than PathFile [12]. A study demonstrated that the porous cratered surface of the EDM files was maintained with no change to the cutting blades even after being used in curved root canals [12]. Another study compared the cyclic fatigue resistances amongst different file systems in artificial canals created with HyFlex GPF (Coltene-Whaledent), G Files (Micro-Mega, Besançon, France), ProGlider (Dentsply Sirona), PathFile, and ScoutRaCe (FKG Dentaire, La Chaux-de-Fonds, Switzerland) NiTi rotary GPFs. The authors found that the greatest cyclic fatigue resistance was in HyFlex GPF made of CM alloy [20]. The cyclic fatigue resistance for HyFlex EDM was 700% greater than that for HyFlex CM files made of the same alloy.

Glide path preparation time is faster and postoperative pain severity is lower with the HyFlex EDM GPF than with PathFile. Glide path preparation with HyFlex EDM GPF is advantageous to the subsequent NiTi instruments and can reduce postoperative pain.

glide path files (GPFs), controlled memory (CM).

Ethics approval and consent to participate

Ethical approval was obtained from Biomedical ethics committee of Stomatological Hospital of Peking University. The committee’s reference number is PKUSSIRB-201735063. The informed consent obtained from study participants was written.

Consent for publication

Not Applicable

Availability of data and material

The datasets used and analyzed during the current study available from the

corresponding author on reasonable request.

Competing interests

The authors declare that they have no competing interests.

Funding

This work was supported by the National Natural Science Foundation of China (81200826) . The funder is the corresponding author of this article.

Authors' contributions

Guided the study: Xiao-Mei Hou. Wrote the manuscript: Yi Han, Xiao-Mei Hou. Performed the experiment: Yi Han. Collected and analyzed the data: Yi Han. Designed the experiment: Yi Han, Xiao-Mei Hou. All authors have read and approved the final manuscript.

Acknowledgements

Not Applicable

Authors' Information

The Second Dental Center of Peking University School of Stomatology, No. 66 Anli Road, Chaoyang District, Beijing, 100101, China.

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Glide Path Enlargement of Curved Molar Canals Using HyFlex EDM Glide Path File versus PathFile: A Comparative Study of Preparation Times and Postoperative Pain

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Abstract

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Background

Methods

HyFlex EDM GPF Group

PathFile group

Statistical analysis

Results

Discussion

Conclusions

Abbreviations

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