Surface Characteristics of Reciprocating Instruments Before and After Use - A SEM Analysis

Abstract

The presence of debris, defects and deformations of endodontic reciprocating instruments before and after chemical-mechanical preparation (MCP) was analyzed using scanning electron microscopy (SEM). The following 26 instruments were divided into 2 groups: Waveone (n=13) and Reciproc (n=13) and examined by SEM (150 x magnification) prior to canal preparation at 2 and 4 mm from the tip. The instruments were used in the preparation of mesial root canals of 26 extracted human permanent mandibular molars. The instruments were then washed in ultrasonic bath and subjected to new microscopic analysis of debris and deformation by a score that used the presence or absence of irregular edges, grooves, microcavities and burrs as criteria. After the SEM analysis and with the scores of the examiners, the collected data were subjected to descriptive statistical analysis using the Kruskall-Walis and Mann Whitney test at a 5% significance level. All instruments examined presented debris before and after use. A statistically significant difference was found for defects and deformation between the groups (p<0.05). The presence of defects and deformities was higher in the WaveOne instruments, and Reciproc instruments presented a lower rate.

Topographic and Chemical Analysis of Reciprocating and Rotary Instruments Surface after Continuous Use

“…As they are manufactured of M-Wire alloy, the clinical reuse of these instruments must be avoided, thereby, diminishing deterioration of the metal alloy, and consequently, the risk of an unexpected fracture of the instrument during use (3,7,9).…”

“…The following features on the active part of each instrument were considered in the analysis: irregular edges, grooves, microcavities and burrs (3). A scoring system similar to that used by Troian et al (8) was adopted to classify the topographic changes in the instruments: 1 -long axis of the instrument without any defect or deformation on the examined surface; 2 -long axis of the instrument with approximately one to three areas with defects or deformations on the examined surface; 3 -long axis of the instrument with approximately four to five areas with defects or deformations on the examined surface; 4 -long axis of the instrument with over 5 areas with defects or deformations on the examined surface.…”

“…Among the characteristics of these instruments, flexibility, cyclic fatigue and torsional resistance are the most important, as they allow safer biomechanical preparation of canals with accentuated curvature (2,3). However, different manufacturing strategies have been proposed even now to improve mechanical properties, by reducing risks of fracture and increasing the useful life of NiTi instruments (4).…”

“…However, manufacturers have recommended their use to a maximum of three or four canals in the same patient. Constant reuse of instruments manufactured in M-Wire leads to wear and deformation, increasing the risk of fracture during preparation (3,7).…”

“…There are few studies that evaluated the topographic and chemical changes that occur on these instrument's surface after their repeated use (3,7). Therefore, the aim of this study was to evaluate the changes in surface characteristics and chemical composition of NiTi alloy of reciprocating and rotary instruments before and after continuous use.…”