Journal of Pharmacy And Bioallied Sciences

: 2021  |  Volume : 13  |  Issue : 6  |  Page : 1700--1704

Evaluation of crack propagation after root canal preparation with continuous and reciprocating files and final finishing with XP Endo Finisher – An In vitro study

R Hariprasad1, VN Anoop2, P Rajesh Raj3, Vishnu Teja Obulareddy4, Renju M Kunjumon5, Kiran Kumar Sadula6,  
1 Specialist in Endodontics, Department of Dentistry, Employees State Insurance Corporation Hospital, Ezhukone, Kollam, Kerala, India
2 Senior Lecturer, Department of Conservative Dentistry and Endodontics, Noorul Islam College of Dental Sciences, Aralumoodu, Kerala, India
3 Consultant in Oral Medicine Diagnosis and Radiology, Karunya Dental Clinics, Pulincunnu, Kavalam, Thuruthy, Kottayam district, Kerala, India
4 Associate Dentist, Private Practice, SV Dental Clinic and Implant Center, Malkajgiri, Hyderabad, Telangana, India
5 Senior Lecturer, Department of Oral Medicine and Radiology, Annoor Dental College, Kerala, India
6 Junior Consultant, Private Practice, Hyderabad, Telangana, India

Correspondence Address:
R Hariprasad
Full time specialist in Endodontics, Department of Dentistry, Employees state insurance corporation hospital, Ezhukone, Kollam, kerala


Introduction: One of the disadvantages of stainless steel instruments used for root canal preparation is the lack of flexibility and shape memory. The invention of rotary instruments has been successful in overcoming these problems to a greater extent; however, some drawbacks still remain, one of which is vertical root fracture and the cause for it is microcracks formation in dentin, which in turn causes vertical root fracture. There are enough studies for microcracks using different rotary systems and this study compared microcracks with single as well as reciprocating files followed by final finishing with XP endo finisher. Apart from other studies, we used conefocal laser scanning microscope to assess microcrack propagation before and after instrumentation with each rotary system. Aim: To evaluate microcrack propagation in mandibular molars after root canal preparation with continuous and reciprocating file systems followed by final finishing with XP Endo finisher. Materials and Methods: Thirty mandibular molars indicated for the extraction due to periodontal causes were selected for this study. They were divided into three groups based on rotary systems used: Group A: ProTaper universal; Group B: ProTaper gold; and Group C: Waveone gold. All specimens were subjected to scanning before instrumentation to assess the presence of any existing cracks. Cone focal laser microscopic scanning is again repeated for each specimen after instrumentation with each rotary system and also after final finishing with XP Endo finisher. Statistical Analysis: One-way ANOVA is used. Results: Crack propagation is the highest with ProTaper universal and least with waveone gold. After final finishing of canals with XP Endo finisher, crack propagation observed was negligible. Conclusion: The success of root canal treatment depends on effective disinfection of root canal system. XP Endo finisher can be used as a final finishing file by considering its advantageous properties, moreover crack propagation with XP Endo finisher in an previously instrumented canal is negligible.

How to cite this article:
Hariprasad R, Anoop V N, Raj P R, Obulareddy VT, Kunjumon RM, Sadula KK. Evaluation of crack propagation after root canal preparation with continuous and reciprocating files and final finishing with XP Endo Finisher – An In vitro study.J Pharm Bioall Sci 2021;13:1700-1704

How to cite this URL:
Hariprasad R, Anoop V N, Raj P R, Obulareddy VT, Kunjumon RM, Sadula KK. Evaluation of crack propagation after root canal preparation with continuous and reciprocating files and final finishing with XP Endo Finisher – An In vitro study. J Pharm Bioall Sci [serial online] 2021 [cited 2022 Dec 7 ];13:1700-1704
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Stainless steel hand files were used for root canal preparation since long. Procedural errors are more common with stainless steel files and evolution of rotary systems created a revolutionary change in Endodontics. Stainless steel files were replaced by rotary NiTi files and its only disadvantage is that it fractures without showing any symptoms. Once it fractures retrieval becomes more challenging. Kinematics of engine driven NiTi instruments have been divided into rotary motion, reciprocating motion, vertical vibration (SAF) based on in and out motion to remove dentine.[1] It has been observed in many studies that mechanical instrumentation could be a reason for additional removal of dentine structure and may induce micro crack formation in dentine.[2] During masticatory function, microcracks induced by different root canal preparation would eventually compromise tooth mechanical performance.[3] Higher frequency of defects in dentin exponentially increases the risk of stress concentration during mechanical loading and potentially impairs the mechanical performance of the restorative assembly. It in turn lead to catastrophic fracture under lower loads than the conventional masticatory loads.[4] To assess the presence of microcracks on tooth structure, two major methodologies are used. First, the destructive test method in which teeth are visually inspected for external surface defects and instrumented when there is no dentinal defects, slices are made, and each slice is separately analyzed considering the presence or absence of defects.[5] The second, nondestructive techniques, normally employing micro-computed tomography analysis. Here, the teeth are initially scanned for microcracks and are rescanned after instrumentation, and then, the images superposed. This method has contributed in higher accuracy, more reliable, and precise data.[6],[7],[8],[9],[10] This study has extensively used cone focal laser scanning microscope to determine microcrack propagation.


To evaluate microcrack propagation in mandibular molars after root canal preparation with continuous and reciprocating file systems followed by the final finishing with XP Endo finisher.

 Materials and Methods

Mandibular molars were selected based on certain inclusion criteria. Periodontally compromised teeth indicated for extractions were included in the study. Confocal laser microscopic scanning is done for all teeth to exclude those teeth with dentinal cracks or surface defects. Mandibular molars were divided into three groups depending on the rotary system used.

Group A: ProTaper universalGroup B: ProTaper goldGroup C: Waveone gold.

Modern endodontic access cavities were prepared on all teeth under operating microscope. 10K size file is introduced into the canal to check the patency of the canal and working length of mesiobuccal and mesiolingual was determined by passing 10k file beyond apex and reducing 0.5–1 mm from the exposed file. Distal canal was left uninstrumented. Canals were enlarged to 15K file and rotary systems were introduced. For ProTaper universal and ProTaper gold, the filing sequence follows the order Sx, S1, S2 and F1. Single file used in this study was waveone gold. Finally, mesiolingual canal of all teeth was obturated leaving mesiobuccal canal. All teeth were sectioned at furcation area to separate distal canal. All tooth specimens were again subjected to microscopic examination for the determination of micro cracks. XP Endo finisher is introduced into mesiobuccal canal of tooth in all groups and tooth surfaces were examined again to determine whether is there any crack propagation of existing cracks while final finishing with XP Endo finisher.

Statistical analysis

The data were processed using the SPSS software and study consisted of 30 samples in total with 10 belonging to each groups, namely ProTaper universal, ProTaper gold, and waveone gold. Level of significance is set as P < 0.05 there by accepting null hypothesis.


ProTaper universal showed greater amount of microcracks and waveone gold showed the least [Figure 1]. All specimens were scanned after instrumentation using cone focal laser scanning microscope. Three-dimensional image of microcrack propagation is recorded [Figure 2]. Fluorescent method of scanning is done and microcracks were measured. XP Endo finisher is introduced as final finishing file and specimens were again subjected to cone focal microscopic scanning [Figure 3]. Study results showed that crack propagation is more with universal ProTaper and less with waveone gold [Figure 4]. Furthermore, there is no significant crack propagation is noticed after final finishing with XP Endo finisher [Figure 5].{Figure 1}{Figure 2}{Figure 3}{Figure 4}{Figure 5}


Since extraction forces itself induce microcracks on dentine surface, those periodontally compromised tooth indicated for extractions were used in this study and specimens were stored in normal saline to prevent desiccation of dentine.[11] Distal root of all mandibular molars was left untouched, and chemomechanical preparation was completed in mesiobuccal and mesiolingual root of all molars and mesiolingual roots were obturated with their corresponding gutta-percha cones, distal root is sectioned at the level of furcation. The above procedure is done to reduce bias that may happen during cone focal laser scanning. De-Deus et al. reported that root sectioning to assess microcrack propagation itself induces dentinal microcracks and allows analysis of only few slices per sample. By using nondestructive methods such as micro CT, highly accurate results can be obtained since it is possible to evaluate hundreds of slices in a single tooth.[6],[7],[11] In this study, mesiobuccal root of mandibular molars was selected since curvature is more common in mesiobuccal root, and hence, the instrument strain during rotary motion. Fröner et al.,[12] Pécora et al.,[13] and Peter's,[14] observed that apical anatomy of medial roots presents with complex morphology related to shape and variation of root canals. They also mentioned that curvatures resulted in asymmetric removal of dentine during cleaning and shaping and chance for apical transportation are higher.

Instrument used for root canal preparation induces strains in the root canal which in turn creates microcracks and finally vertical root fracture. Microcracks were observed in buccolingual directions. Kim et al. stated that tensile stress during canal shaping is concentrated on buccal and lingual surfaces; moreover, the tensile strength of buccal and lingual root structures is less than the mesial and distal ones.[15] There are many studies which used confocal laser scanning microscope to study crack propagation in bones. Dentinal crack propagation using confocal microscope was first reported by Felipe et al. Confocal scanning micro-scopes, and there is sufficient literature focusing on their ability to exclude out-of-focus information.[16],[17] It has also been demonstrated that confocal scanning can improve the resolution in stereoscopic imaging of object surfaces. PHOIBOS is a confocal microscope scanner developed at the Royal Institute of Technology, Stockholm.[18] It scans specimens by using incident-light illumination and detecting the fluorescent or reflected light from the specimen. In the present study, only the fluorescent light was detected. The confocal scanning method permits accurate photometric point measurements in a raster format. Furthermore, fluorescein fading is kept at a minimum because of the point illumination. Here the specimen remains stationary during scanning, and the focused laser beam is moved in two perpendicular directions by means of rotating mirrors.

Most common complication with crack propagation is vertical root fracture. Mesiobuccal root of mandibular molars was selected since curvature is more in it and chances for strip perforation are more common in the mesial root of mandibular molars since dentine thickness is less. Among the three different rotary systems used, if one system demonstrates less crack in mesiobuccal root it means would imply that chances of that rotary system in inducing cracks in other tooth are unlikely. More crack propagation was observed with PTU. Several strategies have been implicated to improve mechanical properties of Ni-Ti endodontic instruments that include electropolishing, surface coatings, and heat treatment.[19] Ni-Ti alloys which are rich in Ni demonstrate one stage transformation, i.e., from Austinite to martensite. These Ni-Ti files are stiffer and have shape memory. Stiffer files generate higher stress concentration in apical root dentine, responsible for greater crack propagation with PTU. PTG, the heat treated file has transformation from Austinite to matrensitic and Austentic-R-Martensitic followed by additional heat treatment which leads to finely spread Ni-Ti particles in matrix.[20] During manufacturing of this file, it passes through intermediate R phase; moreover, Ni content is reduced that is responsible for its super elasticity. This property explains about less crack propagation with PTG. WaveOne Gold single file system is a newer version of WaveOne, here the kinematics of the system remain unchanged but the flexibility is enhanced by their modification in cross-section, size and geometry. Moreover, the change in thermomechanical property from M wire to newer Gold (G) wire is the reason for their higher flexibility[21] and increased cyclic fatigue resistance than its predecessor.[22] It has a reverse helix, semi-active modified guiding tip with an offset parallelogram-shaped cross-section,[23] responsible for less crack propagation with waveone gold. Till date, there are only few studies which evaluated the incidence of dentinal microcrack formation from the use of these single file systems in rotary and reciprocating motion.{Table 1}

Most of the studies on XP Endo finisher had evaluated intra canal medicaments removal, sealer removal from the root canal. In this study, XP Endo finisher was used as a final finishing file and crack propagation is evaluated after final finishing with XP Endo finisher, since manufacturers claim that it has the property to adapt to canal morphology and its expansion capacity is 100x to its core size and if it happens, it could exert some force in dentinal wall and which in turn cause existing cracks to propagate. All specimens were subjected to cone focal laser microscope scanning and it is noticed that there is no crack propagation is seen after final finishing with XP Endo finisher.


This study, given the limitations would conclude, that reciprocating files produces less microcracks than any other rotary systems. Here, XP Endo finisher was used as finishing file. Although there are enough studies with XP Endo finisher relating to sealer removal, intracranial medicaments removal., etc., this is the first study to evaluate microcrack propagation with XP Endo finisher as finishing file to suggest that crack propagation is negligible.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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