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ORIGINAL ARTICLE
Year : 2018  |  Volume : 8  |  Issue : 3  |  Page : 202-207

Shaping ability of ProTaper gold and WaveOne gold nickel-titanium rotary file in different canal configurations


1 Department of Endodontics, Riyadh Elm University, Riyadh, Kingdom of Saudi Arabia
2 Department of Restorative Dentistry, Riyadh Elm University, Riyadh, Kingdom of Saudi Arabia
3 Department of Preventive Dentistry, Riyadh Elm University, Riyadh, Kingdom of Saudi Arabia

Date of Web Publication25-Jul-2018

Correspondence Address:
Dr. Abdulrahman Abdullah Al-Dhbaan
Department of Endodontics, Riyadh Elm University, Riyadh
Kingdom of Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sej.sej_98_17

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  Abstract 

Objective: This study compared the shaping ability of the ProTaper Gold (PTG) and WaveOne Gold (WOG) systems in simulated L-and S-shaped root canals.
Materials and Methods: Forty L-and S-shaped root canals in resin blocks were randomly divided into four groups (n = 10). Each canal was prepared to the standard working length (16 mm) and enlarged to an apical size 25 using PTG set of files in the sequence S1, S2, F1, and F2 at a speed of 300 rpm and a torque of 2.5 N cm until each file reached the working length. For WOG, primary file was used in a reciprocating motion until the working length was achieved. The canals were photographed before and after instrumentation using different colors. The two images were superimposed, five points were selected, and canal widths were measured with image analysis software. The preparation time, instrument failure, and presence of aberrations were noted and compared between systems.
Results: Findings revealed a highly significant difference (P < 0.001) in preparation time between instruments. A total of nine aberrations in the danger zones of PTG/L-shaped (1), PTG/S-shaped (4), WOG/L-shaped (1), and WOG/S-shaped (3), canals were noted. WOG/L-shaped canals were wider at the canal orifice than PTG/L-shaped canals (P < 0.05), but PTG use resulted in a greater width at the halfway point of the straight section and the beginning of the curve than WOG (P < 0.05). PTG/S-shaped root canals were wider at the beginning of the first curve of the prepared canal (P < 0.05).
Conclusions: The WOG system demonstrated better shaping ability, fewer canal aberrations, and more rapid preparation than the PTG system. All files straightened the curvature of multicurved canals in the apical region.

Keywords: Canal shape, nickel-titanium, root canal preparation, rotary instruments, simulated canals


How to cite this article:
Al-Dhbaan AA, Al-Omari MA, Mathew ST, Baseer MA. Shaping ability of ProTaper gold and WaveOne gold nickel-titanium rotary file in different canal configurations. Saudi Endod J 2018;8:202-7

How to cite this URL:
Al-Dhbaan AA, Al-Omari MA, Mathew ST, Baseer MA. Shaping ability of ProTaper gold and WaveOne gold nickel-titanium rotary file in different canal configurations. Saudi Endod J [serial online] 2018 [cited 2018 Dec 14];8:202-7. Available from: http://www.saudiendodj.com/text.asp?2018/8/3/202/237567


  Introduction Top


Root canal preparation constitutes a vital step in endodontic treatment. Main objectives of root canal preparation are to eliminate infected and necrosed pulp tissue from the canals, smoothen the dentinal walls to ease irrigation and obturation, maintain the anatomy of the root apex, and keep sound dentin for prolonged period.[1],[2] However, the complex canal anatomy causes instrumentation challenges, which may prevent adequate disinfection of the root canal system or cause procedural errors such as instrument separation, transportation, ledges, or perforations.[3]

Today, there are several nickel-titanium (NiTi) file systems are used within the field of dentistry. NiTi rotary file system of good flexibility has reduced the incidence of iatrogenic errors of ledge, danger zone, perforation and transportation of canals. Thus contributing to the better efficiency and safety of the root canal preparation.[3],[4] Several approaches have been developed by the manufacturer to improve the flexibility and resistance to fracture of NiTi rotary endodontic instruments.[5],[6],[7] These approaches include changing the taper over the length of the cutting blade, modifying the instrument's cross-sectional design, and enhancement of the manufacturing process or the use of new alloys that provide improved mechanical properties.[5],[8]

ProTaper Gold (PTG) and WaveOne Gold (WOG) are relatively new canal preparation files resulting from advancement in NiTi systems. PTG files were developed with proprietary advanced metallurgy and have a progressively tapered design that is claimed by the manufacturer to enhance cutting efficiency and safety. PTG files have a convex triangular cross-section and progressive taper. This navigates challenging curves in the apical region of the canal. The file also has a feature of shorter 11mL handle for improved accessibility to the teeth.

WOG reciprocating single-file instrument system has a distinctive gold appearance. It has a unique parallelogram shaped cross-sectional design with one or two cutting edges depending on the location along the file. These edges significantly reduces torque, minimizes screwing effect on the cutting efficiency, and allowing better removal of debris.

The distinctive gold appearance of the PTG and WOG files is the result of a unique heat treatment process applied after manufacture. The raw metal is repeatedly heated and cooled, giving it not only its gold color, but also considerably improved strength and flexibility.[9] Most studies that evaluated the shaping ability of NiTi files have been conducted in vitro using several procedures. Resin blocks with simulated root canals are generally accepted as effective study models to get rid of the canal variations of natural teeth.[10] In addition, simulated root canals can be produced by standardized working length, taper, curvature, and uniform hardness in three dimensions.[3] Therefore, this study evaluated the shaping ability of the PTG system and compared it with the WOG system in simulated L-and S-shaped root canals by analyzing the preparation time, instrument failure, root canal aberrations, and canal widths.


  Materials and Methods Top


Study sample

A total of 40-simulated root canals in clear resin blocks (Dentsply Maillefer, Ballaigues, Switzerland) were used in this study. Two types of canals were used: L-shaped and S-shaped canals. L-shaped canals have a standard length of 16 mm; the curvature length to the apical end is 8 mm. S-shaped canals are 16 mm long and have two curves, a 30°coronal curvature and a 20°apical curvature. The blocks were randomly divided into four equal experimental groups (n = 10) according to the canal shape and NiTi rotary file system used for instrumentation.

Preparation of simulated canals

Root canal instrumentation was performed in accordance with the manufacturer's recommendations for each system using an X-Smart™ Plus motor (Dentsply Maillefer). The order of preparation of the groups of resin blocks was randomized and the canals prepared by a single experienced endodontic resident. Each canal was prepared to the standard working length (16 mm), and the final apical preparation of each group was set to size 25. A glide path was created using PathFile (Dentsply Maillefer) instruments 1, 2, and 3 at the full working length; Glyde (Dentsply Maillefer) was used as the lubricating agent. Between each file size, the root canal was irrigated with 2 mL of distilled water using a 30G needle (Henry Schein Inc., Melville, NY, USA); patency was maintained using a size #10 K-file (Dentsply Maillefer, Tulsa, OK, USA). Each instrument was discarded after use in five canals. The preparation sequence varied according to the shape of the canal and the system used, as follows; for the PTG file system (Dentsply, Tulsa Dental Specialties, Tulsa, OK, USA), a set of files in the sequence S1, S2, F1, and F2 was used at a speed of 300 rpm and a torque of 2.5 N·cm until each file reached the working length. For WOG (Dentsply, Tulsa Dental Specialties, Tulsa, OK, USA), primary file was used in a reciprocating, slow in-and-out pecking motion according to the manufacturer's instructions until the working length was achieved.

Assessment of canal preparation

Before instrumentation, each block was coded by a number and four vertical orientation grooves. All specimens were then filled with blue India ink (Higgins, Leeds, MA, USA) to create a clear image of the canal, and were photographed using a digital camera (Canon 70D, Canon Inc., Tokyo, Japan) mounted on a modified microscope stage at a constant distance. After instrumentation, each canal was filled with red India ink (Higgins) and a postinstrumentation photograph was taken using the same technique. For each sample, block before and after instrumentation images were overlaid and standardized to create a composite image using Adobe Photoshop CS6 Extended (Adobe Systems Inc., San Jose, CA, USA). The following observations were made for each composite image.

Root canal aberrations

Several types of canal aberrations, including zipping, elbow, ledges, perforations, danger zone, and outer widening were assessed and recorded as described by Al-Omari.[4]

Preparation time

The canal preparation time was recorded to the nearest second. It included the total active instrumentation time, instrument changes within the sequence, cleaning of the instrument flutes, and irrigation.

Instrument failure

Instruments were visually examined after every use for any fractures or defects such as bending and unwinding.

Width measurements

The amount of resin removed during canal preparation was assessed at five points along the canal length using the method described by al-Omari et al.[4] and image analysis software ImageJ (https://imagej. nih. gov/ij/).

Positions in L-shaped canals

  • O: Canal orifice
  • HO: Halfway point of the straight section of the canal
  • BC: Beginning of the curve
  • AC: Apex of the curve
  • EP: End-point of preparation.


Positions in S-shaped canals:

  • HO: Halfway point of the straight section of the canal
  • BC1: Beginning of the first curve
  • AC1: Apex of the first curve
  • AC2: Apex of the second curve
  • EP: Endpoint of preparation.


Data recording, storage, and analysis

Data were collected and analyzed using SPSS version 21 (SPSS Inc., Chicago, IL, USA) software. Statistical analyses between the different groups were performed using one-way ANOVA and Scheff's post hoc tests. In all analysis, the level of statistical significance was set at (P< 0.05).


  Results Top


Root canal aberrations

A total of nine aberrations in the danger zones were noted: 1 in the PTG/L-shaped canals, 4 in the PTG/S-shaped canals, 1 in the WOG/L-shaped canals, and 3 in the WOG/S-shaped canals [Figure 1]. However, no other incidences of canal aberrations, including zip or elbow, ledge, perforation, outer widening, or instrument failure, were observed.
Figure 1: Photograph showing a resin block prepared by WaveOne gold with root canal aberrations (D = danger zone)

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Preparation time

[Table 1] shows the mean canal preparation time by canal type and instrument type. In each type of canal, the use of the WOG system resulted in a significantly faster preparation time than the PTG system (P< 0.001).
Table 1: Comparison of mean canal preparation time (min) between groups

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Total mean canal width between prepared by PTG-and WOG-at the first three points showed significant difference. However, a comparison between the total mean canal widths at the apex of the curve and the end-point of the preparation did not reveal any significant difference between the PTG-and WOG-prepared canals [Figure 2]. These comparisons are summarized in [Table 2].
Figure 2: Mean and standard deviation values of canal preparation time in various groups

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Table 2: Total mean canal width (mm) of L-shaped canals

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[Table 3] shows the comparisons between the total mean canal widths of S-shaped canals prepared using PTG or WOG instrumentation. The only significant difference in width was observed at the beginning of the first curve.
Table 3: Total mean canal width (mm) of S-shaped canals

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  Discussion Top


One of the primary goals during root canal instrumentation is to achieve a shape that tapers in the apical to coronal direction and maintains the original root canal anatomy.[1] Therefore, it is important to evaluate the efficiency of instruments designed for root canal preparation. The present study compared the shaping abilities of the PTG and WOG systems in simulated L-shaped and S-shaped root canals.

One of the important contributing factors for the good canal shaping is the capability of root canal instrument to remain within the center of root canal space without causing iatrogenic mistakes.[4] Various methods have been utilized to assess the shaping ability of an endodontic instrument. This study considered resin blocks to evaluate instrument shaping capabilities due to the fact that resin blocks can be easily standardized for many root canal parameters such as; canal curvature, taper, length and hardness. On the contrary, these parameters cannot be standardized in extracted teeth.[11] While inferring instrumentation studies using these models few factors needs to be considered. Foremost, assessment of canal preparation is restricted to the longitudinal plane of the canal representing two dimensions instead, instrumentation prepare canal in three dimensions. Second, the resin blocks do not match with the physical features of human dentin, especially with regard to microhardness. Hardness of the resin block is half of that observed in the dentin in natural teeth. Hence, any root canal instrumentation studies that utilized the resin blocks more likely to show increased deviation or canal transportation than natural teeth canal preparations. Finally, resin blocks exhibit completely different thermal properties compared to human dentin.[12] While canal instrumentation with endodontic rotary instruments produces large amount of frictional heat, in some instances it melts the resin.[13] This condition is totally different from the clinical use of endodontic instruments as it is not found in human teeth.

The preparation time of a root canal is a primary factor in the assessment of endodontic instrument efficacy. It depends on the experience of the person using the instruments, the number of instruments in use, and the type of instrument and technique used.[14] The experience of the operator plays an important role in determining the time necessary for canal preparation.[15] In this study, the canal preparation time was recorded; it included the total active instrumentation time, instrument changes within the sequence, cleaning the flutes of the instruments, and irrigation. All of these features are helpful in determining the accurate time and for performing a proper comparison of the results derived from earlier experiments under the same conditions.[16],[17],[18] In the present study, the time required for canal preparation was significant in all groups; it demonstrated that the WOG NiTi rotary file system prepared both L-shaped and S-shaped canals faster than the ProTaper NiTi rotary file system. No previous study has compared the preparation times when using these systems. Bane et al.[19] compared the single-file WaveOne system with the multi-file ProTaper Universal system and found the average time to shape a canal using a single-file system was much lower compared to the ProTaper system. Another study showed that reciprocating file systems can complete canal preparation more quickly than continuous rotary file systems.[20]

The fracture of NiTi rotary instruments occurs due to cyclic flexural fatigue or torsional failure.[21] However, in our study, there was no deformation or fracture of the files used in canal instrumentation. This is due to improvements in the metallurgy of the G-wire, which not only provides the gold color, but also considerably improves the flexibility.[9] The cyclic fatigue resistance of the WOG Primary system improved by more than 50% compared to the WaveOne Primary system.[22] However, the PTG system has a three-fold increase in fracture resistance compared to the ProTaper Universal system, and it is also reported to have excellent cyclic fatigue resistance and elasticity.[23],[24]

Previous studies have reported that maintaining the original canal shape with a less invasive method decreased the possibility of canal transportation, with a subsequently lower incidence of canal curvature straightening, ledge formation, and irregular apical enlargement.[25],[26],[27] However, procedural errors such as canal transportation can occur when shaping curved root canals.[28] In this study, WOG and PTG NiTi rotary files showed the same number of aberrations during the preparation of L-shaped canals. However, the WOG system showed fewer aberrations than the PTG system in S-shaped canals. A study by Takeshi et al., compared between WaveOne gold and other WaveOne systems and found that the WaveOne gold produced only few canal aberrations and better performance. However, until now, no study has compared the incidence of aberrations between these systems.

Many studies have shown that more flexible instruments produce more centered root canal preparations.[4],[29] The PTG system presented more centralization in the curved portion compared to the ProTaper Universal system.[23],[30] The manufacturing processes, which affect stress-strain distribution patterns and bending behaviors, making PTG files more flexible and decrease their tendency to straighten in curved canals.[31] Our study did not show any significant difference in the widths of S-shaped canals or in the curved portions of L-shaped canals prepared by the WOG and PTG systems. However, in a comparison of the total mean canal widths of the PTG and WOG systems in both L-shaped and S-shaped canals, canals prepared using PTG had increased widths. In the present study, the final taper was 0.08 at the apical 3 mm for PTG and 0.07 for WOG. The shaping ability of root canal instruments with different tapers have been compared in many studies, which have proved that the final taper might influence the removal of material from the walls of the canals.[32],[33] Comparison of shaping ability of four single file systems with different tapers showed that the resin removal is higher in case of more tapered instruments, and it is the predetermining factor for the shaping ability of the tested instrument.[34] One of the limitations of the study was to identify the exact factors attributable for better canal preparation by WOG than PTG.


  Conclusions Top


Within the limitations, it can be concluded that both WOG and PTG NiTi instruments prepared severely curved and multicurve simulated canals efficiently without instrument failure. The WOG instruments prepared all types of canals significantly faster than the PTG instruments.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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[PUBMED]  [Full text]  
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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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