Canal Wall Thickness After Preparation With NiTi Rotary Files TATJANA BRKANIC ´ , 1 * IVANA STOJS ˇ IN, 1 SLAVOLJUB Z ˇ IVKOVIC ´ , 2 AND KAROLINA VUKOJE 1 1 Dental Clinic, Medical Faculty, Novi Sad, Serbia 2 Dental Faculty, Belgrade, Serbia KEY WORDS residual dentin thickness; canal diameter; nickel-titanium; polarized light microscopy ABSTRACT Root canal preparation is the most important phase of endodontic procedure and it consists of adequate canal space cleaning and shaping. In recent years, rotary instruments and techniques have gained importance because of the great efficacy, speed, and safety of the prepara- tion procedure. AIM: The aim of this research was to investigate measurement of maximal and minimal residual dentine thickness (RDT) and canal diameter after the canal preparation with dif- ferent NiTi rotary files. METHODS: The research has been conducted on extracted human teeth in vitro conditions. The teeth have been divided in seven groups (20 teeth per group) depending on the kind of instruments used for root canal preparation: ProTaper, GT, ProFile, K-3, FlexMaster, hand ProTaper, and hand GT. The canals have been shaped in a crown-down manner and irrigated with 5.25% sodium hypochlorite. The roots of the teeth have been cut 1 and 3 mm from the apex. Apical preparation quality has been assessed under the polarized light microscope. RESULTS: The maximal residual dentine thickness at distance 1 mm from apex, ranged from 1.16 to 1.45 mm, and at distance 3 mm from apex, from 1.44 to 1.84 mm. The minimal dentine thickness at distance 1 mm from apex ranged from 0.52 to 0.73 mm, and at distance 3 mm from apex, from 0.66 to 0.83 mm. The canal diameters after preparation at distance 1 mm from apex ranged from 0.42 to 0.49 mm, and at distance 3 mm from apex, from 0.53 to 0.63 mm. CONCLUSIONS: There was no signif- icant difference neither in maximal and minimal RDT, nor in canal diameters shaped with differ- ent NiTi instruments tested. All tested NiTi files have accomplished good quality preparation of apical root canal parts. Microsc. Res. Tech. 00:000–000, 2011. V V C 2011 Wiley Periodicals, Inc. INTRODUCTION The primary aim of all endodontic procedures is to remove canal contents, specifically infected microor- ganisms. Root canal preparation is the most impor- tant phase of endodontic procedure and it consists of adequate canal space cleaning and shaping. Thor- ough instrumentation of the apical region has long been considered to be an essential component in cleaning and shaping process. One of the controver- sies that surrounds the cleaning and shaping process is how large the apical preparation should be and what are the correct diameter, length, and taper. A canal should have a larger diameter at the coronal orifice with a gradual decreasing taper toward the apical constriction that has the smallest diameter. Preparation of the apical third to the proper size for bacteria and necrotic tissue removal could reduce the residual dentin thickness (RDT) to critically low val- ues, weaken the tooth at this level, and increase the probability of vertical root fractures (Baugh and Wallace, 2005; Sauaia et al., 2010; Siqueira, 2001; Souza et al., 2008). In recent years, rotary instruments and techniques have gained importance because of the great efficacy, speed, and safety of the preparation procedure. They are popular because of their apparent ease of use and reduced number of instruments (Brkanic ´, 2005; Brkanic ´ et al., 2004, 2005). Manufacturers of these instruments claim that it is possible to shape a canal with minimal number of instruments, but some authors noted that the strong emphasis on reducing the number of instruments and limiting apical prepa- ration to small sizes does not produce clean apical prep- aration of diseased teeth. The aim of this research was to investigate the maxi- mal and minimal residual dentine thickness and canal diameter after canal preparation with different NiTi rotary files. MATERIALS AND METHODS The research has been conducted on extracted untreated human teeth with fully formed apexes and no root resorption in vitro conditions. The sample consisted of 140 single root teeth from various morpho- logical groups. The teeth have been cleaned after extraction and stored until used in saline solution under the temperature of 48C. Access openings were made with a high-speed handpiece and a round dia- mond bur. Working length was set by subtracting 1 mm from the length of the size 010 K file when its tip was just visible at the apical foramen. Apex has been sealed with blue wax to prevent flow of the irrigant *Correspondence to: Tatjana Brkanic ´, Hajduk Veljkova 12, 21,000 Novi Sad, Serbia. E-mail: tanjahom@gmail.com Received 12 April 2011; accepted in revised form 22 May 2011 DOI 10.1002/jemt.21049 Published online in Wiley Online Library (wileyonlinelibrary.com). V V C 2011 WILEY PERIODICALS, INC. MICROSCOPY RESEARCH AND TECHNIQUE 00:000–000 (2011)