Effect of Different Instrumentation Motions on the Canal Cleanliness and File Surface Topography : In-Vitro Study /

Abstract

Root canal treatment procedure aims to clean and shape the root canal system achieving a complete seal of the 3D space and its accessory canals. However, the thorough mechanical and chemo-mechanical treatments have shown to produce an environment of less bacterial count, but not bacterial free.(1) Cutting dentin with either hand or rotary instruments results in shattering of the mineralized tissues, producing a considerable amount of debris. These of collagen matrixes small size are spread all over the surface forming what is known as the smear layer.(2) This layer of amorphous structure is of 1-2 um and may contain bacteria and their by-products. It compromises the penetration of irrigants, intra canal medicaments, and the adaptation of the root filling materials into dentinal walls. Thus, compromising the seal with obturating material resulting in percolation of fluids from the inflamed periapical tissues, causing failure of the treatment.(3) This problem necessitates a thorough chemical debridement; but unfortunately, no irrigating solution has the power of acting simultaneously on both the organic and inorganic elements of the smear layer. Over the past few decades, changes in the understanding of the concepts of cleaning and shaping the root canal systems led to the evolution from the use of manual hand files to the use of rotary nickel titanium files, making them part of the new era in endodontics as it is generally believed that engine-driven or manually used nickel-titanium (NiTi) instruments produce better-prepared root canals than their stainless steel counterparts. These different Rotary methods of canal preparation rapidly transformed the shaping process in comparison with the traditional hand files. The concept of automated reciprocation was then re-introduced in 2008 after it has been discarded in 1964 as the resulted in a greater number of procedural errors. This time the reciprocation was commenced using single NITi file ProTaper (F2) to completely shape the root canal. This was shown to be effective at cleaning the canal as the full ProTaper system and extrude similar amount of apical debris.(5) However, no file or type of motion have been identified as the ideal, and that is due to the inherent properties of the NiTi alloy and the different changes they undergo following the mechanical preparation.