Aim: To evaluate the microcrack propagation after root canal instrumentation using instruments operating in rotary, reciprocating, translinear, and centrifugal motions.
Materials and methods: An estimated 80 mandibular molars were divided into three experimental groups (n = 20). Group I—rotary motion (ProTaper Universal Dentsply, Maillefer, Ballaigues, Switzerland, and F2 file). Group II—reciprocating motion (WaveOne Dentsply, Maillefer, Ballaigues, Switzerland, Primary Files ISO 25, and 8% taper). Group III—translinear motion (Self-Adjusting File, ReDent Nova, Ra\'anana, Israel). Standard access cavities were prepared and the canals were manually prepared up to a 15-K file to establish patency. Shaping and cleaning was performed according to manufacturer\'s instructions for each group, keeping the irrigation protocol constant. The samples were then scanned in a four-dimensional X-ray microscopy machine (ZEISS Xradia 510 Versa) and were virtually sectioned. The Z test was applied for statistical analysis.
Results: No significant difference was found between rotary (ProTaper Universal) and reciprocating groups (WaveOne) (p = 0.3112). Translinear motion (Self-Adjusting File) showed statistically significant least microcracks (p = 0.000).
Conclusion: (1) Self-adjusting file proved to be the most minimally invasive file system. (2) Reciprocation showed lesser samples with cracks than rotary motion. (3) Apical sections showed significantly higher cracks than the other sections. (4) Four-dimensional X-ray microscopy could be a promising tool for dental imaging.
Clinical significance: The stress induced by aggressive preparation procedures of certain file systems have led to microcrack propagation, reduction in the resistance form, and subsequently failure of endodontic therapy owing to vertical root fracture. Literature suggests that kinematics of the file influences crack propagation in a radicular dentin. Hence, this study has been undertaken to compare and evaluate the effect of four different kinematics of nickel–titanium file systems on microcrack propagation in a radicular dentin.
Rosen H. Operative procedures on mutilated endodontically treated teeth. J Prosthet Dent 1961;11:972–986. DOI: 10.1016/0022-3913(61)90158-5.
Helfer AR, Melnick S, et al. Determination of the moisture content of vital and pulpless teeth. Oral Surg Oral Med Oral Pathol 1972;34: 661–670. DOI: 10.1016/0030-4220(72)90351-9.
Bier CAS, Shemesh H, et al. The ability of different nickel–titanium rotary instruments to induce dentinal damage during canal preparation. J Endod 2009;35:236–238. DOI: 10.1016/j.joen.2008.10.021.
Shemesh H, Bier CAS, et al. The effects of canal preparation and filling on the incidence of dentinal defects. Int Endod J 2009;42:208–213. DOI: 10.1111/j.1365-2591.2008.01502.x.
Versiani A, Souza E, et al. Critical appraisal of studies on dentinal radicular microcracks in endodontics: methodological issues, contemporary concepts, and future perspectives. Endodontic Topics 2015 Nov;33(1):87–156. DOI: 10.1111/etp.12091.
Kim HC, Lee MH, et al. Potential relationship between design of nickel-titanium rotary instruments and vertical root fracture. J Endod 2010 Jul 1;36(7):1195–1199. DOI: 10.1016/j.joen.2010.02.010.
Schilder H. Cleaning and shaping the root canal. Dent Clin North Am 1974 Apr;18(2):269–296.
Kim HC, Sung SY, et al. Stress generation during self-adjusting file movement: minimally invasive instrumentation. J Endodo 2013 Dec 1;39(12):1572–1575. DOI: 10.1016/j.joen.2013.07.021.
Ashwinkumar V, Krithikadatta J, et al. Effect of reciprocating file motion on microcrack formation in root canals: an SEM study. Inter Endodo J 2014 Jul;47(7):622–627. DOI: 10.1111/iej.12197.
Berutti E, Chiandussi G, et al. Canal shaping with WaveOne Primary reciprocating files and ProTaper system: a comparative study. J Endod 2012b;38:505–509. DOI: 10.1016/j.joen.2011.12.040.
Haapasalo M, Shen Y. Evolution of nickel-titanium instruments: from past to future. Endod Top 2013 Sept;17(1):3–17. DOI: 10.1111/etp.12049.
Franco V, Fabiani C, et al. Investigation on the shaping ability of nickel-titanium files when used with a reciprocating motion. J Endod 2011;37:1398–1401. DOI: 10.1016/j.joen.2011.06.030.
Yared G. Canal preparation using only one Ni-Ti rotary instrument: preliminary observations. Int Endod J 2008;41:339–344. DOI: 10.1111/j.1365-2591.2007.01351.x.
Bürklein S, Hinschitza K, et al. Shaping ability and cleaning effectiveness of two single file systems in severely curved root canals of extracted teeth: reciproc and wave one versus Mtwo and ProTaper. Int Endod J 2012;45:449–461. DOI: 10.1111/j.1365-2591.2011.01996.x.
Metzger Z, Teperovich E, et al. The self-adjusting file (SAF). Part 1: Respecting the root canal anatomy – A new concept of endodontic files and its implementation. J Endod 2010;36:679–690. DOI: 10.1016/j.joen.2009.12.036.
Hof R, Perevalov V, et al. The self-adjusting file (SAF). Part 2: Mechanical analysis. J Endod 2010;36:691–696. DOI: 10.1016/j.joen.2009. 12.028.
Hin ES, Wu MK, et al. Effects of self-adjusting file, Mtwo, and ProTaper on the root canal wall. J Endod 2013;39:262–264. DOI: 10.1016/j.joen.2012.10.020.
Yoldas O, Yilmaz S, et al. Dentinal microcrack formation during root canal preparations by different NiTi rotary instruments and the self-adjusting file. J Endod 2012;38:232–235. DOI: 10.1016/j.joen.2011.10.011.
Liu R, Hou BX, et al. The incidence of root microcracks caused by 3 different single-file systems versus the ProTaper system. J Endod 2013;39:1054–1056. DOI: 10.1016/j.joen.2013.04.013.
Metzger Z. The self-adjusting file (SAF) system: an evidence-based update. J Conserv Dent 2014;17:401–419. DOI: 10.4103/0972-0707.139820.
Adorno CG, Yoshioka T, et al. The effect of root preparation technique and instrumentation length on the development of apical root cracks. J Endod 2009;35:389–392. DOI: 10.1016/j.joen.2008.12.008.
Adorno CG, Yoshioka T, et al. The effect of working length and root canal preparation technique on crack development in the apical root canal wall. Int Endod J 2010;43:321–327. DOI: 10.1111/j.1365-2591.2010.01684.x.
Adorno CG, Yoshioka T, et al. Crack initiation on the apical root surface caused by three different nickel–titanium rotary files at different working lengths. J Endod 2011;37:522–525. DOI: 10.1016/j.joen.2010.12.002.