ORIGINAL RESEARCH PAPER COMPARATIVE EVALUATION OF FRACTURE RESISTANCE OF ENDODONTICALLY TREATED TEETH IRRIGATED WITH FOUR DIFFERENT IRRIGATING SOLUTIONS: AN IN-VITRO STUDY Dr. Vaibhav Kelkar Final year PG Student, Department of Conservative Dentistry and Endodontics, Inderprastha Dental College and Hospital, Sahibabad-201010. Dr. Anika Mittal Ex Professor and Head, Department of Conservative Dentistry and Endodontics, Inderprastha Dental College and Hospital, Sahibabad-201010. Dr. Sarita Singh Professor, Department of Conservative Dentistry and Endodontics, Inderprastha Dental College and Hospital, Sahibabad-201010. Dr. Dakshita Joy Sinha* Professor and Head, Department of Conservative Dentistry and Endodontics, Inderprastha Dental College and Hospital, Sahibabad-201010. *Corresponding Author Dr. Nidhi Sharma Senior lecturer, Department of Conservative Dentistry and Endodontics, Inderprastha Dental College and Hospital, Sahibabad-201010. Dr. Vipul Goel Reader, Department of Conservative Dentistry and Endodontics, Inderprastha Dental College and Hospital, Sahibabad-201010. INTRODUCTION: The success of endodontic treatment depends on three main steps: efcient access cavity preparation and caries removal, followed by thorough chemo-mechanical preparation and lastly proper obturation [1] that provide a complete sealing of the root canal systems. Among these, the chemo-mechanical preparation is a vital step as it results in the elimination of microorganisms by using various irrigating solutions and intracanal medicaments. Ideally, an irrigating solution should promote debridement, lubrication, dissolve organic tissue and eradicate the microorganisms [2-3] from the root canal system. Sodium Hypochlorite (NaOCl) is one of the traditional irrigants which is used most commonly. It was rst produced in 1789 in Javelle, France, by passing chlorine gas through a solution of sodium carbonate. The resulting liquid was known as “Eau de Javelle” or [4] “Javelle water”. Coolidgelater introduced NaOCl to endodontics. It is an excellent antibacterial agent, capable of dissolving necrotic tissue, vital pulp tissue, and the organic components of dentin and [5] biolms. NaOCl possesses a broadspectrum antimicrobial activity against endodontic microorganisms and biolms, including microbiota difcult to eradicate from root canals, such as [6] Enterococcus, Actinomyces, and Candida species. During endodontic therapy, NaOCl solutions are used at concentrations ranging from 0.5% to 6%. However, the most commonly used concentrations are 2.5% and 5.2%. Even though NaOCl is the most widely used irrigant, studies have related sodium hypochlorite irrigation with dentin microhardness [7] reduction. Furthermore, nal irrigation with NaOCl negatively affects various physical properties of root canal dentin including [8] elasticity and exural strength. Hence, fracture resistance of the teeth may be affected by the use of sodium hypochlorite as an irrigating solution. Keeping in mind these possible adverse effects of sodium hypochlorite, there has been constant advancement and discovery of new irrigating solutions that might have lesser adverse effects than sodium hypochlorite. ASEP-RC is a new irrigating material that was introduced in 2015 which consists of 2% Chlorhexidine as its constituent. Chlorhexidine (CHX) is a chemical that was developed more than 50 years ago at Imperial Chemical Industries in England and rst marketed in the United Kingdom in 1953 as an antiseptic [9] cream. Since 1957, it has been used for general disinfection purposes and the treatment of skin, eye, and throat infections in both humans and [9] animals. Subsequently, CHX began to be used as an endodontic irrigant as well as an intracanal medicament. The action of CHX is due to the fact that it is a wide-spectrum antimicrobial agent, active against gram-positive and gram-negative [10] bacteria as well as yeasts. Owing to its cationic nature, CHX is capable of electrostatically binding to the negatively charged surfaces of bacteria,damaging the outer layers of the cell wall and rendering it [11-12] permeable. Depending on its concentration, CHX can have both bacteriostatic and bactericidal effects. At high concentrations, by damaging the cell membrane, it causes precipitation of the cytoplasm and thereby exerts INTERNATIONAL JOURNAL OF SCIENTIFIC RESEARCH Endodontics International Journal of Scientific Research 25 Volume - 10 | Issue - 06 | June - 2021 | PRINT ISSN No. 2277 - 8179 | DOI : 10.36106/ijsr ABSTRACT Introduction:Various solutions have been used for chemo mechanical preparation during endodontic treatment. However there have been reports suggesting that there might be some detrimental effects of these irrigants on the fracture resistance of root canal treated dentin. The aim of this study was to comparatively evaluate the effects of different irrigants, on the fracture resistance of endodontically treated teeth. Methods:Eighty freshly extracted, single rooted human mandibular premolars were selected. Access cavities were prepared, working lengths were measured and root canals were prepared till #45 K-le (MANI, INC., Japan). 5ml Normal Saline was used for irrigation during preparation. After preparation, they were divided into following groups: Group I-Normal Saline, Group II- ASEP-RC (Anabond Stedman pvt. ltd. Chennai, India), Group III-2.5% NaOCl (Sodium Hypochlorite, PRIME Dental Products, Maharashtra) Group IV- Q Mix 2-in-1 (® Dentsply, Tulsa Dental Specialities) Obturation was done using Gutta Percha with cold lateral compaction. Teeth were incubated at 37°C and 100% humidity for a week. Fracture resistance was tested for the teeth under a Universal Testing Machine (UTM). One-way ANOVA and one-way Tukey HSD test were used for the comparative analysis of the groups and signicance level was set at 0.001. Results: Group IV (QMix 2-in-1) showed signicantly higher values of fracture resistance compared to other groups. Conclusion: Roots that were irrigated using QMix 2-in-1 demonstrated higher fracture resistance compared to the other groups. KEYWORDS ASEP-RC, Endodontics, Final Irrigation, Fracture resistance, Irrigants, NaOCl, Qmix 2-in-1.