Endodontic Topics 2005, 10, 176–178 Copyright r Blackwell Munksgaard
All rights reserved ENDODONTIC TOPICS 2005
1601-1538
Reamer with alternating cutting
edges – concept and clinical
application
MICHAEL A. BAUMANN
Background The NiTi surface is treated chemically resulting in an
obviously smoother surface than other instruments
Within the last decade numerous Nickel–Titanium (Fig. 1).
(NiTi) instruments have been designed and dentists, As a consequence of this design the manufacturer has
physicists, chemists and manufacturer have worked recommended that a dedicated endodontic motor is
hard to optimize instrument geometry and their not essential. This is only a claim and has not been
surfaces in order to maximise their potential in every investigated independently. Daily practice and personal
day practice. The reamer with alternating cutting edges experience shows that the tendency for threading into
(RaCe) instrument system is unique and this article the canal is less with RaCe than with other NiTi
summarizes its design, outlines its clinical application systems, however, this finding is only empirical and
and describes the various scientific reports that have scientific evidence is lacking.
been published.
Scientific evidence
Instrument design Within the last 15 years a considerable amount of
research has been carried out on NiTi instruments. In
In 1999, 10 years after the first NiTi instruments were
common with most NiTi instruments the RaCe system
introduced, the RaCe system (Table 1) became
allows a well-centered canal shape to be prepared, often
available; it had a number of new features:
within a shorter time than hand instrumentation.
A RaCe with twisted areas similar to conventional Ledges and zipping occur rarely and the cleaning
files alternating with straight areas, to giving a larger ability in terms of debris and smear layer removal is
space for debris and to reduce the tendency to equal or better than with hand techniques.
thread (Fig. 1). In 2002 the first description of the RaCe system
Sharp cutting edges resulting from a square cross- appeared in the German journal ‘Endodontie’ giving
sectional shape in the small instruments (15/0.02 detailed information on the design, the sequences and
and 20/0.02) and a convex triangle (similar to a comparison with other NiTi products on the market
ProTaper (Dentsply Maillefer, Ballaigues, Switzer- together with case reports (Baumann, 2002). An
land) or FlexMaster (VDW, München, Germany)) expanded version of the article in English followed in
in the remaining RaCe instruments. Endodontic Practice (Baumann, 2003).
Reduced active cutting regions on some instru- In 2002 the first scientific results were published as
ments (9–16mm). abstracts at the Chicago meeting of the American
The two largest instruments (35/0.08 and 40/ Association of Endodontists (AAE) comparing the
0.10) are available in NiTi and stainless steel, the centering ability of ProTaper and RaCe using the Endo
latter being more efficient. Cube. At 3 mm from the apex RaCe showed ‘the least
176
RaCe
0.10 and 0.08: stainless steel (SS) or NiTi
Nickel–Titanium (NiTi)
SS or NiTi
SS or NiTi
Material
Material
Ni/Ti
NiTi
NiTi
NiTi
NiTi
Fig. 1. Design of the reamer with alternating cutting
10/0.08/0.06/0.04/0.02
edges file (SEM): twisted areas alternate with straight
Total length/cutting part
parts. The surface is very smooth because of a special
chemical treatment.
06/0.06/3 0.04
0.06/4 0.02
19/10
25/16
25/16
25/16
Taper
19/9
19/9
30/25/30/35/40
30/40/25/30/35
40/35/30/25/25
Ground section
Table 1. Available sets and totally available instruments of RaCe.
ISO
&
}
Fig. 2. Upper left second premolar after treatment with
reamer with alternating cutting edges files and filling with
Resilon/Epiphany and glass fiber postinsertion.
01.720.25.S25
01.721.25.S25
01.722.25.S40
amount of deviation form the canal centre’ . . . and ‘. . . the
greatest amount at the level of maximum canal curvature’.
Taper
Code
In the following AAE meeting in Tampa the cleaning
0.10
0.08
0.06
0.04
0.02
0.02
effectiveness and shaping ability was investigated in an
SEM study (Baumann et al., 2003): It was shown that
RaCe enabled an obviously better canal form at all levels
Crown down 0.10–0.02
25/30/35/40/50/60
of the root canal than by hand and smear layer removal
Step back 0.06/0.02
Step back 0.06/0.04
– after irrigation – superior to hand instrumentation.
At the AAE meeting in Anaheim in 2004 two
Files available
additional abstracts on RaCe were presented. Cyclic
25/30/35
fatigue of ProFile, K3 and RaCe was compared in a
30/40
15/20
special setting. The first study by Elasaad et al. (2004)
Sets
40
35
demonstrated that overall, K3 25/0.04 files were
177
Baumann
significantly more resistant to cyclic fatigue compared 2. Baumann MA. The RaCe system. Endodontic Practice
with the other instruments in this study. The second 2003: 6: 5–13.
3. Baumann MA Nickel–titanium – options and chal-
study focused on the torsional testing of ProFile, K3
lenges. Dent Clin North Am 2004: 48: 55–67.
and RaCe in the sizes #25 with 0.02, 0.04 and 0.06 4. Baumann MA, Leinbrock O, Hellmich M, Baumann-
taper and #40 in all three tapers of K3 and ProFile Giedziella UA. Effectiveness of root canal instrumenta-
(Fessenden et al., 2004). In this study the RaCe file tion with RaCe: an SEM study. J Endod 2003: 29: 286
series exhibited lower values for maximum torque and (abstract OR8).
5. Elasaad MG, Isler AE, McDonald NJ. An evaluation of
rotations to fracture. The authors speculated that a the root canal centering abilities of ProTaper and RaCe
smaller diameter at 3 mm could be a possible reason for Ni–Ti rotary files and flexofiles. J Endod 2002: 28: 247
the lower resistance to torque of RaCe. (abstract OR50).
At this time only a small number of peer-reviewed 6. Fessenden SD, Byrne BE, Carter JM. Torsional
testing of RaCe, K3 and ProFile nickel titanium
articles on RaCe is available. Two recently published
endodontic files. J Endod 2004: 30: 275 (abstract
articles compare ProTaper with RaCe regarding their PR10).
ability to shape canals in resin blocks or extracted teeth. 7. Glosson CR, Haller RH, Brent Dove S, del Rio CE.
In plastic blocks, RaCe was superior to ProTaper Comparison of root canal preparations using NiTi-
hand, NiTi engine-driven, and K-Flex endodontic
regarding shaping ability and comparable in opera-
instruments. J Endod 1995: 21: 146–151.
tional safety. These findings were confirmed in ex- 8. Hülsmann M. Wurzelkanalaufbereitung mit Nickel–
tracted teeth (Schäfer & Vlassis, 2004b). Titan-Instrumenten. Ein Handbuch. Berlin: Quintes-
Summarizing the research on RaCe, it shows lower senz, 2002.
resistance to cyclic fatigue and seems to have some 9. Schäfer E, Vlassis M. Comparative investigation of two
rotary nickel–titanium instruments: ProTaper versus
advantageous properties compared with other well-known RaCe. Part 1. Shaping ability in simulated curved
systems regarding maintenance of the canal curvature or canals. Int Endod J 2004a: 37: 229–238.
cleaning ability. Cases treated (Fig. 2) and daily use of RaCe 10. Schäfer E, Vlassis M. Comparative investigation of two
instruments confirm they are efficient and a rapid method rotary nickel–titanium instruments: ProTaper versus
RaCe. Part 2. Cleaning effectiveness and shaping ability
to achieve predictably good results in root canal treatment.
in severely curved root canals of extracted teeth. Int
Endod J 2004b: 37: 239–248.
Further reading
1. Baumann MA. Maschinelle Wurzelkanalaufbereitung
mit dem RaCe-system. Endodontie 2002: 11: 239–249.
178
