DOI: https://doi.org/10.53350/pjmhs221651421 ORIGINAL ARTICLE P J M H S Vol. 16, No. 05, May 2022 1421 Compare of the Frequency of Instrument Fracture of Endodontic File Using Rotary Pro Tapers and HY Flex Series AOSAF ANWAR 1 , FEROZE ALI KALHORO 2 , MOWAFFAQ ABDULLMOMEN AL ABSI 3 , FOZIA RAJPUT 4 , OSAMA SHAIKH 5 , BATOOL BIBI 6 1 Assistant Professor, Department of Operative Dentistry, Bhittai Dental and Medical College, Mirpurkhas 2 Professor, Department of Operative Dentistry, Liaquat University of Medical and Health Sciences, Jamshoro 3 Associate Professor, Department of Operative Dentistry, Isra Dental College, Isra University, Hyderabad 4 Associate Professor, Department of Operative Dentistry, Liaquat University of Medical and Health Sciences, Jamshoro 5 Lecturer, Department of Prosthodontics, Liaquat University of Medical and Health Sciences, Jamshoro 6 Assistant Professor, Department of Periodontology, Dr Ishrat Ul Ebad Khan Institute of Oral Health Sciences, Dow University of Health Sciences, Karachi. Correspondence to: Aosaf Anwar, Email: aosafanwar88@hotmail.com, Cell: 0333-2684206 ABSTRACT Objective: To compare the frequency of instrument fracture of endodontic file using Rotary Pro Tapers and EDM Hy Flex series. Study Design & Setting: This experimental in vitro study was conducted at Institute of Dentistry Liaquat University of Medical and Health Sciences Jamshoro. Subjects and Methods: Data was prospectively collected from extracted human teeth. A total of 66 canals were included. Simple descriptive statistics were used to present demographic data, along with frequency and percentages to present qualitative variables. It was decided to perform a post-stratification chi square test taking a p-value of less than 0.05 as significant. Results: A total of 66 canals (33 each endodontic file using Rotary Pro Tapers and EDM Hy Flex series) were included. Mean endodontic file in group A and B was 1.28±0.14 mm and 0.58±0.08 mm. Comparison of instrument separation in endodontic file using Rotary Pro Tapers and Hy Flex series showed separation of 09 (27.3%) and 02 (6.1%) respectively. Conclusion: Based on the results of this study, Protaper files generated much more stress than EDM Hy Flex files, but comparisons of instrument separation between the two instruments showed that the latter performed better overall. Keywords: Root canal treatment, Endodontic file, Rotary Pro Tapers and Rotary EDM Hy Flex. INTRODUCTION Root canal treatment involves the treatment of vital or necrotic teeth in order to relieve the pain and retain natural teeth with function and esthetics. 1 Root canal treatment can be unsuccessful due to variety of iatrogenic errors ranging from poor access cavity design , untreated infected canals , mishandling of endodontic instruments that could lead to ledges, perforations, instrument breakage/fracture and over and under obturation of root canals, these must be carefully evaluated and examined. 2 This includes appropriate dental and medical history , detailed clinical examination and radiograph for detecting the reason for failure and formulate treatment plan whether to go for nonsurgical endodontic treatment, surgical endodontic procedure or extraction. 3 By easing the operator's job in preparation of root canals without changing their centricity, curve or length, nickel titanium NiTi rotary instruments have revolutionized root canal treatment. 4 The increased used to nickel titanium rotary endodontic instruments allowed the manufacturers to produce various designs and systems of endodontic file system. 5 The main disadvantage of these instruments is accidental fracture/instrument separation which may block narrow, curved canals and does not allow proper cleaning and shaping of canal. 6,7 According to previous studies on the mechanism of instrument fractures/separations, the most important factor is the operator's clinical skills and conscious decision to use the instrument for a specified time period. 8-11 Fractures are also significantly reduced when the angle of curvature of the canal is decreased. 12 There are, however, very few studies on rotary NiTi instrument fractures and the different techniques used to treat them. 13-14 One of the study conducted on Rotary ProTaper concluded that incidence of instrument fracture is 22% using rotary protapera and also more crack formation at dentinal surface. 9,15 Whereas another study on the Hyflex endodontic files system concluded that there is no evidence of instrument separation when Hyflex file was used in three canals. 16 Other study on Hyflex endodontic system concluded that Hyflex system files are more bendable and flexible compared to other endodontic file system. 17 And are more fatigue resistant. 18 The Hyflex endodontic system offers minimum amount of significant errors in canal preparation. 19 To the best of knowledge, there is limited available data on frequency of instrument separation of Rotary NiTi Hy Flex which claims to be less liable to fracture. This study will compare the frequency of instrument separation of rotary Pro Taper and Hy Flex series and its clinical implications and will eventually help to plan the management strategies to minimize the risk of instrument fracture leading to poor prognosis of tooth. MATERIAL AND METHODS This experimental in vitro study with non-probability consecutive sampling was carried out from January to October 2019. The sample size was calculated by using the WHO software with Power of test=90%. The calculated sample size was 33 in each group and total 66.  Inclusion Criteria:  Extracted human maxillary and mandibular molars molar with completed root formation.  Exclusion Criteria:  Non-consenting.  Previously Endodontic treated tooth.  Teeth external and internal root resorption or open apices.  Teeth with sclerosed or calcified canals. Data Collection Procedure: We obtained approval for this study from the College of Physicians and Surgeons Pakistan. A collection of extracted maxillary and mandibular molars from Liaquat University of Medical and Health Sciences' Department of Oral and Maxillofacial Surgery in Jamshoro was used in this study. A cylindrical diamond bur was used to prepare straight line access for each canal after the teeth were mounted in wax blocks. A stainless steel K File (Mani, Utsunomiya Tochigi, Japan) size 6-20 was used to negotiate the canal orifices with the DG 16. A reference point was taken at the cusp tip of the adjacent cusp tip to determine how far from the apical foramen to establish the working length. Following the digital periapical radiograph, the canal curvature was measured using the Schneider method using 15 ISO file. In this stage, each canal was assigned to one of two random groups.