Scanning Electron Microscopic Evaluation of Debris and Smear Layer after Use of Revo-S and CMA Instruments in Straight Root Canals

Biomechanical preparation, disinfection and obturation all together constitute equally important phases of the endodontic treatment [1].Root canal treatment is based on cleaning, shaping and sealing the root canal system.Its main objectives are the elimination of residual pulp tissue, infected dentine and debris and the reduction of the number of microorganism from root canal system [2,3].Many nickel-titanium (NiTi) rotary instruments have been introduced in the last years.All these endodontic files produce dentine debris and a smear layer as a consequence of their action on root canal walls [4].Debris contains vital and/or necrotic pulp tissue and dentinal chips that loosely attach to the root canal walls; it is usually infected [2].The smear layer consists of dentine particles, remnants of vital or necrotic pulp tissues, bacterial components, and retained irrigants [5].The smear layer is reported to prevent the penetration of irrigating solutions, medications and filling materials into dentinal tubules and many researchers believe that it is detrimental [6].The design features of the cutting blade of endodontic instruments are important and may affect the cleansing efficiency of the instruments: as a rotary reamer works in a canal, the dentinal debris needs to be removed quickly and effectively [7].Irrigation plays a key role in successful debridement and removing smear layer during preparation.Sodium hypochlorite (NaOCl) is an irrigant solution widely used in root canal treatment because of its antibacterial properties and ability to dissolve organic tissue.However, it's not effective in removing the inorganic smear layer.Ethylenediaminetetraacetic acid (EDTA) as a chelating agent can remove the smear layer [8].Thus, a combination of NaOCl and EDTA has been reported to be suitable for removing both the organic tissue and the inorganic smear layer [9,10].EDTA acts upon the inorganic components of the smear layer and decalcifies the peri-and intertubular dentine and leaves the collagen exposed.Subsequently, the use of NaOCl dissolves the collagen, cleaning the dentinal walls [9].