Cone-Beam Computed Tomography Assessment of Canal-Centering Ability for Traditionally Used Nickel Titanium and Nickel Titanium Files with Reciprocating Hand Piece and Wave-One Files.

AIM OF THE STUDY: Need for our study was to evaluate a comparison between canal preparation ability of nickel-titanium (NiTi) hand files with step-back manual technique, of NiTi files installed on a reciprocating hand piece and of Wave-One files utilizing noninvasive cone-beam computed tomography (CBCT) technique.
MATERIALS AND METHODS: Thirty extracted intact single-rooted human mandibular premolars were used in the study, segregated in three sets of 10 specimens each, where canal instrumentation was done by different methods using NiTi in step-back technique, using reciprocating hand piece with NiTi files and using primary file with the use of Wave-One reciprocating system. Later, evaluation of centering ability was conducted using the references through CBCT images.
RESULTS: Hand NiTi files showed even less canal centering ability as compared to other two sets. Mesiodistal diameter at 9 mm length of the prepared canal was 1.06 and later was 0.98, which shows excessive preparation in case of Set I versus Set II. In case of comparison between Set III and Set I, mesiodistal diameter at 9 mm length of the prepared canal was 0.99, and later was 1.06, depicting better canal shaping ability with Wave-One file.
CONCLUSION: The use of hand NiTi files installed on a reciprocating hand piece would be economically beneficial producing the similar results as that of wave one without any deviation from the original canal anatomy. Copyright:

INTRODUCTION

It is imperative that effective biomechanical preparation is required adhering to tooth anatomy, for proper endodontic therapy.[1] Studies have shown that ideal shaping and biomechanical preparation of root canal are directly dependent upon few factors like alloy with which file is manufactured, geometrical angle of cutting edge of file, manufacturing with heat, motion changes.[2] Nickel–titanium (NiTi) files still suffer from some disadvantages such as fatigue fracture and failure due to torsional forces. Consequently, advancements in NiTi files technology were introduced.[3] NiTi has made huge progress as there has been the development of instruments like protaper next, Revo-S, which are leads to asymmetric off centered crosssections in biomechanical preparation.[4] This particular reciprocating movement comprises of rotations back and forth around to complete 360° rotation which is a balanced force technique.[5] Apical transportation is caused when there is excessive instrumentation in a different path than desired, resulting in an area apically which is of tear drop shape and causes canal zipping also. This phenomenon also compromises for compaction of gutta percha properly and also results in over-extension of obturation filling.[6] One of the endodontic challenges is the mesial canal of mandibular molars where due to its often-aberrant curvatures and variations in its anatomy, selection of appropriate files is extremely important to attain an ideal tapered biomechanical preparation of its canals.[7]

Aim of the study

Need for our research was to assess the comparison between canal preparation ability of NiTi hand files with step-back manual technique, of NiTi files installed on a reciprocating hand piece and of Wave-One files utilizing noninvasive cone-beam computed tomography technique.

MATERIALS AND METHODS

Thirty extracted intact single-rooted human mandibular premolars were selected for the present study based on the inclusion and exclusion criterion, which were then stored in 0.1% thymol solution for 24 h. These teeth were segregated into three sets each of ten specimens. The teeth were mounted in a wax block with ten specimens of each set where canal curvatures were determined using the Schneider method [Figures 1 and 2]. Access cavity preparation was accomplished using diamond burs in all the specimens, and apical patency was tested with the help of 15# k file. Later-on, further instrumentation was done according to the required sets. Set I-10 teeth are prepared using hand NiTi files in a conventional step back technique. Set II-10 teeth are prepared using hand NiTi files mounted on a reciprocating hand piece. Set III-10 teeth are prepared using Wave-One reciprocating system, Wave-One Primary file in X-Smart Plus motor in “Wave-One” mode. The ratio of mean centering capability of the instrument denoting its capacity to remain in the center of the canal, which can be calculated by the following formula: buccolingually, D1 = (x − x')/(x1 − x1') and mesiodistally, D2 = (z − z')/(z1 − z1') Various tests were utilized such as mean analysis, standard deviation, ANOVA (utilized for various set contrasts of canal transportation as well as centering capability) followed by post hoc Tukey honestly significant difference for set wise comparison.

Figure 1

(a) Thirty extracted intact single-rooted human mandibular premolars. (b) Teeth mounted in three wax blocks with 10 specimens each

Figure 2

Pre- and Post-operative cone-beam computed tomography images at 3 mm (a), 6 mm (b) and 9 mm (c): (a) Showing cone-beam computed tomography image of Hand used NiTi files for canal shaping, (b) cone-beam computed tomography image of nickel titanium files on reciprocating hand piece, (c) cone-beam computed tomography image of Wave-One system primary file for canal instrumentation

RESULTS

The results show that when comparing Set I (hand held NiTi files) with Set II (NiTi files mounted on reciprocating hand piece), mesiodistal diameter at 9 mm length of the prepared canal was 1.06 and later was 0.98, [Table 1] which shows excessive preparation in case of Set I. Buccolingually diameter was 1.17 for Set I and 1.01 for Set II, which clearly shows that hand held NiTi files caused excessive preparation, which in turn decreases the canal centering ability as well as weakens the root canal system [Table 2]. In case of comparison between Set III (Wave-One file system) and Set I, mesiodistal diameter at 9 mm length of the prepared canal was 0.99 and later was 1.06, [Table 3] depicting better canal shaping ability with Wave-One with less of compromised dentinal structure. Similar result was evident in case of buccolingual diameter, which was 1.17 in Set I and 0.99 in Set III. This shows that Set III had statistically significant result of far more precise canal centering capability. While comparing Set II and III, there was negligible difference statistically in the diameter of prepared canal, showing both NiTi on reciprocating hand piece as well as Wave-One had similar canal centering capability.

Table 1

Inter-set comparison of mean and standard deviation between Set I and II

Direction	Distance (mm)	Set I		Set II		P
		Mean	SD	Mean	SD
Mesiodistal	3	0.66	0.03	0.72	0.16	0.025 (S)
	6	0.71	0.05	0.81	0.13	0.008 (S)
	9	1.06	0.14	0.98	0.15	0.038 (S)
Buccolingual	3	0.61	0.15	0.51	0.12	0.018 (S)
	6	0.59	0.09	0.70	0.15	0.002 (S)
	9	1.17	0.11	1.01	0.11	0.014 (S)

SD: Standard deviation, S: Significant

Table 2

Inter-set comparison of mean and standard deviation between Set II and III

Direction	Distance (mm)	Set II		Set III		P
		Mean	SD	Mean	SD
Mesiodistal	3	0.72	0.16	0.69	0.09	0.692 (NS)
	6	0.81	0.13	0.77	0.12	0.590 (NS)
	9	0.98	0.15	0.99	0.12	0.763 (NS)
Buccolingual	3	0.51	0.12	0.49	0.13	0.551 (NS)
	6	0.70	0.15	0.66	0.16	0.053 (NS)
	9	1.01	0.11	0.99	0.09	0.415 (NS)

SD: Standard deviation, NS: Not significant

Table 3

Inter-set comparison of mean and standard deviation between Set I and III

Direction	Distance (mm)	Set I		Set III		P
		Mean	SD	Mean	SD
Mesiodistal	3	0.66	0.03	0.69	0.09	0.019 (S)
	6	0.71	0.05	0.77	0.12	0.000 (S)
	9	1.06	0.14	0.99	0.12	0.003 (S)
Buccolingual	3	0.61	0.15	0.49	0.13	0.040 (S)
	6	0.59	0.09	0.66	0.16	0.037 (S)
	9	1.17	0.11	0.99	0.09	0.024 (S)

SD: Standard deviation, S: Significant

DISCUSSION

Saber et al. conducted a study where he determined that out of Wave-One, Reciproc, and One shape instrumentation systems, one shape files did not have a proper centering ability as compared to other two systems. Wave-One proved to have a better performance at cervical as well as apical thirds statistically also with showing negligible difference in shaping ability of middle third of root canal as compared to other two systems.[8] According to Kandaswamy & Estrela[910] law of equal and opposite action and reaction is evident during root canal shaping while reciprocating motion is under play which in turn reduces the stress implicated by torsion and decreases the risk of separation of Wave-One file.[9] Some studies have shown that certain instruments which have high degree of flexibility and increased resistance to torsional stress, can have larger cross-section also.[10] No statistically noteworthy variation was noted in the study, between the canal preparation capability of Wave-One as well as NiTi files mounted on reciprocating hand piece. Considering the available literature on Wave-One files, it decreases canal length in canals with excessive curvature considerably[11] and is not economical as well even though it does have some advantages. Therefore, NiTi files mounted on reciprocating hand piece is a better choice in a clinical setting for canal shaping and maintaining original anatomy of the root canal.

CONCLUSION

Use of hand NiTi files installed on a reciprocating hand piece would be economically beneficial producing the similar results as that of Wave-One without any deviation from the original canal anatomy. However, as observed in our study, both Wave-One and NiTi files on reciprocating hand piece are equally effective in shaping the canal in a proper way without causing endodontic mishaps as iatrogenic problems will be minimized.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.