Comparative study of ProTaper gold, reciproc, and ProTaper universal for root canal preparation in severely curved root canals.

AIM: The aim of this study is to evaluate the root canal transportation, centering ability, and instrumentation times with the ProTaper Gold (Dentsply Tulsa Dental, Tulsa, OK, USA), Reciproc (VDW, Munich, Germany), and ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland) using cone-beam computed tomography (CBCT).
MATERIALS AND METHODS: Thirty mesial root canals of mandibular first molars with curvature angles of 35°-70° and radii of 2-6 mm were included in the study. Root canal instrumentation was performed up to F2 or R25. The instrumentation times were recorded. CBCT scanning was performed both pre- and post-instrumentation. Root canal transportation and the centering ratio were calculated for groups, and the data were analyzed using a one-way ANOVA and least significant difference post hoc tests for the instrumentation time, root canal transportation, and centering ratio at the 95% confidence level (P = 0.05).
RESULTS: At 3, 5, and 7 mm levels, there was no significant difference in the root canal transportation and centering ratio among the groups (P > 0.05). There were significant differences between the Reciproc and ProTaper Universal groups in the instrumentation times (P < 0.05).
CONCLUSION: Root canal transportation and the centering ratio with the ProTaper Gold were similar to those obtained with the ProTaper Universal and Reciproc.

INTRODUCTION

Root canal transportation can occur as a result of root canal instrumentation in curved root canals.[1] Inside the curved root canal, the instrument has a tendency to recover its original shape.[2] Several studies demonstrated that flexible nickel-titanium (NiTi) instruments resulted in a more centered root canal instrumentation than nonflexible stainless steel hand files.[34] Recently, a more flexible NiTi instrument, ProTaper Gold (Dentsply Tulsa Dental, Tulsa, OK, USA) has been introduced. According to the manufacturer, ProTaper Gold instruments have the same geometry as that of ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland) but offer increased flexibility. The manufacturer claims that the ProTaper Gold instruments have resistance to cyclic fatigue and maintain canal centering, especially when preparing curved canals.[5] To the best of our knowledge, there is no root canal transportation study comparing ProTaper Gold and Universal.

A new concept in NiTi files has been introduced, with different working motions and root canal shaping finished with only a single file. One of these single file systems is Reciproc® (VDW, Munich, Germany), which is used in a reciprocating motion and is made from M-Wire technology. The aim of the present study was to evaluate the root canal transportation, centering ability, and instrumentation times with the ProTaper Gold, Reciproc, and ProTaper Universal using cone-beam computed tomography (CBCT). The null hypothesis was that there would be no significant difference between the groups.

MATERIALS AND METHODS

Mandibular first molars were selected from a collection of teeth that had been extracted for reasons unrelated to this study. The teeth were stored in distilled water until use. The initial inclusion criterion was a tooth having visible curvature in the mesial root. The teeth were decoronated, and the distal root was separated. The teeth were then fixed in a silicone impression material and numbered. The mesial roots were scanned with a CBCT scanner (NewTom FP QR-DVT 9000 Verona, Italy), and the images obtained were analyzed using image analyzing software (ImageJ; http://imagej.nih.gov/ij/) to determine the curvature and the radius. Straight lines, with the same lengths, beginning from the apical and coronal regions were drawn. The midpoints of the lines were marked, and a circle was drawn over the midpoints. The radii were measured, and the angle between the lines was recorded as the curvature angle.

Roots with curvature angles of 35°–70° and radii of 2–6 mm were included in the study. According to these criteria, 30 specimens were selected for the study and assigned according to the curvature and radius to three root canal shaping procedures (n = 10). According to a one-way ANOVA, there was no significant between-group difference in the canal curvatures and radii (P > 0.05).

The working length of the canals was determined by inserting a #10 K-file (Dentsply Maillefer) into the root canal terminus and subtracting 1 mm from this measurement. Each instrument was used in four root canals. Root canal instrumentation was performed up to F2 according to the manufacturer's instructions in the ProTaper Universal (Dentsply Maillefer), ProTaper Gold (Dentsply Tulsa), and Reciproc groups. The instrumentation times for the groups were also recorded. The instruments were used according to the manufacturers' instructions.

After completion of the root canal instrumentation, the roots were placed in a silicone impression material using the same setup as that used in the preinstrumentation. Scanning was performed, with images obtained at 3, 5, and 7 mm from the apical terminus of the root for both pre- and post-instrumentation. Root canal transportation was calculated was calculated for each level using the following formula, as described by Gambill, Alder[6]: (x1−x2)-(y1−y2). x1 and x2 represent the shortest mesial distances from the outside of the curved root to the periphery of the uninstrumented and instrumented canal, respectively, and y1 and y2 represent the shortest distal distances from the outside of the curved root to the periphery of the uninstrumented and instrumented canal, respectively. The canal centering ratio at each level was calculated using the following formula[6]: (x1−x2)/(y−y2) or (y1−y2)/(x1−x2) [Figure 1].

Figure 1

Measurement of root canal transportation (a) before, and (b) after instrumentation

Data were analyzed using a one-way ANOVA and least significant difference post hoc tests (P = 0.05) for the instrumentation time, root canal transportation, and centering ratio. The statistical analyses were performed using IBM® SPSS® Statistics 20 software (IBM SPSS Inc., Chicago, USA) at the 95% confidence level (P = 0.05).

RESULTS

Table 1 shows the root canal transportation and centering ratio values at the 3, 5, and 7 mm levels for the groups. At these three levels, there was no significant difference in the root canal transportation and centering ratio among the groups (P > 0.05).

Table 1

Mean Root Canal Transportation (mm) and Centering Ratio Values of the Tested Groups. There were no significant differences among the groups in the transportation and canal centering values at any level (P>0.05)

No instrument fracture occurred during instrumentation in any of the groups. The mean and standard deviation for the instrumentation times were 1.05 ± 0.43 s for Reciproc, 0.78 ± 0.34 s for ProTaper Gold, and 0.63 ± 0.35 s for ProTaper Universal. There were significant differences in the instrumentation times between the Reciproc and ProTaper Universal groups (P < 0.05). However, the instrumentation times of the ProTaper Gold and ProTaper Universal were similar (P > 0.05).

DISCUSSION

The present study evaluated the root canal transportation, centering ability, and instrumentation times with the ProTaper Gold, Reciproc, and ProTaper Universal using CBCT. According to the results of the present study, there were significant between-group differences in the root canal transportation and centering ratio. Thus, the null hypothesis was rejected.

The ProTaper Gold has a convex triangular cross-section and a progressive taper. It also has a noncutting tip design, allowing the instrument to follow the original shape of the root canal. The ProTaper Universal has the same features. One important difference between these systems is that the ProTaper Gold has been metallurgically enhanced through heat-treatment technology.[5] According to the results of the present study, there were no significant differences in the root canal transportation and centering ratio between the ProTaper Gold and Universal. In the current literature, there are no studies comparing the ProTaper Gold with other instruments. However, the ProTaper Universal and Reciproc have been compared previously. Arslan et al.[7] compared the effects of six different rotary systems on the root canal transportation and the centering ratio and found that Reciproc and ProTaper Universal produced similar root canal transportation in the preparation of mesial canals of mandibular molars. This finding is in agreement with our results.

CBCT is a noninvasive and reliable method for evaluating root canal geometry.[8] Previous studies confirmed that CBCT was useful to assess the effectiveness of rotary systems with regard to root canal geometry.[910]

CONCLUSION

The root canal transportation and centering ration of the ProTaper Gold were similar to that produced with the ProTaper Universal and Reciproc.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.