Article Options
Categories


Search


Advanced Search



This service is provided on D[e]nt Publishing standard Terms and Conditions. Please read our Privacy Policy. To enquire about a licence to reproduce material from endodonticsjournal.com and/or JofER, click here.
This website is published by D[e]nt Publishing Ltd, Phoenix AZ, US.
D[e]nt Publishing is part of the specialist publishing group Oral Science & Business Media Inc.

Creative Commons License


Recent Articles RSS:
Subscribe to recent articles RSS
or Subscribe to Email.

Blog RSS:
Subscribe to blog RSS
or Subscribe to Email.


Azerbaycan Saytlari

 »  Home  »  Endodontic Articles 6  »  Efficiency of rotary nickel-titanium FlexMaster instruments compared with stainless steel hand K-Flexofile - PART 1
Efficiency of rotary nickel-titanium FlexMaster instruments compared with stainless steel hand K-Flexofile - PART 1
Shaping ability in simulated curved canals



E. Schafer & D. Lohmann
Department of Operative Dentistry, University of Munster, Munster, Germany.

Introduction.
The unique metallurgical properties of nickel-titanium have made it possible to develop relatively safe rotary instruments. All the new systems incorporate instruments with a taper greater than the ISO standard 0.02 design; indeed rotary nickel-titanium instruments are available with tapers ranging from 0.04 to 0.12 (Thompson & Dummer 1997a). These greater taper instruments have been introduced to improve the relatively low cutting efficiency (Tepel et al. 1995) of nickel-titanium instruments, to reduce the incidence of instrument failures and to enhance canal shape.
Recently, there have been many reports on the effectiveness of rotary nickel-titanium instruments while shaping either simulated root canals in resin blocks (Tepel1997,Thompson & Dummer1997a,b, Baumann & Roth 1999, Schafer & Fritzenschaft 1999, Kum et al. 2000,Thompson&Dummer 2000a) or extracted human teeth with curved root canals (Kosa et al. 1999, Jardine & Gulabivala 2000).These studies corroborate the ability of rotary nickel-titanium instruments to maintain the shape of even severely-curved canals. Furthermore, in most of these studies, it has been pointed out that canal enlargement was significantly faster with rotary nickel-titanium instruments compared to the hand preparation. However, other aspects of the root-canal preparation with rotary nickel-titanium instruments, such as their increased cost and their susceptibility to corrosion under clinical conditions (Thompson 2000) are controversial (Schafer1998,Thompson 2000).
To date, little information on the mechanical properties and shaping ability of nickel-titanium FlexMaster instruments is available. The FlexMaster instruments are made of 55-nitinol (Lohmann in press), with cutting edges machined in to a round blank, resulting in a convex cross-section that is characterized by three equally spaced cutting edges, which are very similar to K-type blades (Fig.1).The instrument does not have radial lands or U-shaped blades. The FlexMaster instruments have £attened, non-cutting tips and a rounded transitional angle (Fig. 2). Thirteen FlexMaster instruments are available: sizes 20, 25 and 30 have three different tapers (0.02, 0.04 and 0.06), size 35 has two different tapers (0.02 and 0.06) and sizes 40 and 45 have only a 0.02 taper. The manufacturer recommends that root canals be enlarged with these instruments using the crown-down technique. Depending on the clinical situation, all instruments are not needed for canal enlargement and the instrumentation sequence can be modified according to the degree of curvature and the diameter of the root canal to be prepared. In curved and/or narrow canals, the instruments with greater tapers are designed to initially enlarge the coronal and middle portion of the canal, whilst the 0.02-tapered instruments are used to ¢finish the apical area and to merge the apical and coronal preparations.

Figure 1. Scanning electron microscope image of the cross-section of a FlexMaster instrument (0.06 taper size 30; original magnification 80x) showing three equally spaced K-type cutting edges. The cross-section of a K-type ?le is indicated by dotted lines.

Scanning electron microscope image of the cross-section of a FlexMaster instrument

Figure 2. Scanning electron microscope images of the tip region of FlexMaster instruments showing a non-cutting, flattened tip with rounded transitional angles (0.06 taper size 20; original magnification 320x).

Scanning electron microscope images of the tip region of FlexMaster instruments showing a non-cutting, flattened tip with rounded transitional angles

The purpose of this study was to compare automated FlexMaster rotary nickel-titanium instruments with stainless steel hand K-Flexofiles (Dentsply Maillefer, Ballaigues, Switzerland) used in a reaming motion during the shaping of simulated curved root canals in resin blocks.