Reamer with alternating cuttingedges concept and clinicalapplicationMICHAEL A. BAUMANN
Background
Within the last decade numerous NickelTitanium
(NiTi) instruments have been designed and dentists,
physicists, chemists and manufacturer have worked
hard to optimize instrument geometry and their
surfaces in order to maximise their potential in every
day practice. The reamer with alternating cutting edges
(RaCe) instrument system is unique and this article
summarizes its design, outlines its clinical application
and describes the various scientific reports that have
been published.
Instrument design
In 1999, 10 years after the first NiTi instruments were
introduced, the RaCe system (Table 1) became
available; it had a number of new features:
A RaCe with twisted areas similar to conventionalfiles alternating with straight areas, to giving a larger
space for debris and to reduce the tendency to
thread (Fig. 1).
Sharp cutting edges resulting from a square cross-sectional shape in the small instruments (15/0.02
and 20/0.02) and a convex triangle (similar to
ProTaper (Dentsply Maillefer, Ballaigues, Switzer-
land) or FlexMaster (VDW, Munchen, Germany))
in the remaining RaCe instruments.
Reduced active cutting regions on some instru-ments (916mm).
The two largest instruments (35/0.08 and 40/0.10) are available in NiTi and stainless steel, the
latter being more efficient.
The NiTi surface is treated chemically resulting in anobviously smoother surface than other instruments
(Fig. 1).
As a consequence of this design the manufacturer has
recommended that a dedicated endodontic motor is
not essential. This is only a claim and has not been
investigated independently. Daily practice and personal
experience shows that the tendency for threading into
the canal is less with RaCe than with other NiTi
systems, however, this finding is only empirical and
scientific evidence is lacking.
Scientific evidence
Within the last 15 years a considerable amount of
research has been carried out on NiTi instruments. In
common with most NiTi instruments the RaCe system
allows a well-centered canal shape to be prepared, often
within a shorter time than hand instrumentation.
Ledges and zipping occur rarely and the cleaning
ability in terms of debris and smear layer removal is
equal or better than with hand techniques.
In 2002 the first description of the RaCe system
appeared in the German journal Endodontie giving
detailed information on the design, the sequences and
a comparison with other NiTi products on the market
together with case reports (Baumann, 2002). An
expanded version of the article in English followed in
Endodontic Practice (Baumann, 2003).
In 2002 the first scientific results were published as
abstracts at the Chicago meeting of the American
Association of Endodontists (AAE) comparing the
centering ability of ProTaper and RaCe using the Endo
Cube. At 3 mm from the apex RaCe showed the least
176
Endodontic Topics 2005, 10, 176178All rights reserved
Copyright r Blackwell Munksgaard
ENDODONTIC TOPICS 20051601-1538
amount of deviation form the canal centre . . . and . . . the
greatest amount at the level of maximum canal curvature.
In the following AAE meeting in Tampa the cleaning
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
of the root canal than by hand and smear layer removal
after irrigation superior to hand instrumentation.
At the AAE meeting in Anaheim in 2004 two
additional abstracts on RaCe were presented. Cyclic
fatigue of ProFile, K3 and RaCe was compared in a
special setting. The first study by Elasaad et al. (2004)
demonstrated that overall, K3 25/0.04 files were
Tab
le1.A
vailab
lese
tsan
dto
tally
avai
lable
inst
rum
ents
of
RaC
e.
Set
sC
od
eIS
OT
aper
Mat
eria
l
Ste
pb
ack
0.0
6/
0.0
201
.72
0.2
5.S
25
30
/2
5/
30
/3
5/
40
0.0
6/
4
0.0
2N
ickel
Tit
aniu
m(N
iTi)
Ste
pb
ack
0.0
6/
0.0
401
.72
1.2
5.S
25
30
/4
0/
25
/3
0/
35
06
/0
.06
/3
0.0
4N
iTi
Cro
wn
do
wn
0.1
00
.02
01
.72
2.2
5.S
40
40
/3
5/
30
/2
5/
25
10
/0
.08
/0.0
6/
0.0
4/
0.0
20
.10
and
0.0
8:st
ainle
ssst
eel(
SS)
or
NiT
i
Files
avai
lable
Tap
erG
round
sect
ion
Tota
lle
ngth
/cu
ttin
gpar
tM
ater
ial
40
0.1
0}
19
/9
SS
or
NiT
i
35
0.0
8}
19
/9
SS
or
NiT
i
30
/4
00.0
6}
19
/1
0N
iTi
25
/3
0/
35
0.0
4}
25
/1
6N
iTi
15
/2
00.0
2&
25
/1
6N
iTi
25
/3
0/
35
/4
0/
50/
60
0.0
2}
25
/1
6N
i/T
i
Fig. 1. Design of the reamer with alternating cuttingedges file (SEM): twisted areas alternate with straightparts. The surface is very smooth because of a specialchemical treatment.
Fig. 2. Upper left second premolar after treatment withreamer with alternating cutting edges files and filling withResilon/Epiphany and glass fiber postinsertion.
RaCe
177
significantly more resistant to cyclic fatigue compared
with the other instruments in this study. The second
study focused on the torsional testing of ProFile, K3
and RaCe in the sizes #25 with 0.02, 0.04 and 0.06
taper and #40 in all three tapers of K3 and ProFile
(Fessenden et al., 2004). In this study the RaCe file
series exhibited lower values for maximum torque and
rotations to fracture. The authors speculated that a
smaller diameter at 3 mm could be a possible reason for
the lower resistance to torque of RaCe.
At this time only a small number of peer-reviewed
articles on RaCe is available. Two recently published
articles compare ProTaper with RaCe regarding their
ability to shape canals in resin blocks or extracted teeth.
In plastic blocks, RaCe was superior to ProTaper
regarding shaping ability and comparable in opera-
tional safety. These findings were confirmed in ex-
tracted teeth (Schafer & Vlassis, 2004b).
Summarizing the research on RaCe, it shows lower
resistance to cyclic fatigue and seems to have some
advantageous properties compared with other well-known
systems regarding maintenance of the canal curvature or
cleaning ability. Cases treated (Fig. 2) and daily use of RaCe
instruments confirm they are efficient and a rapid method
to achieve predictably good results in root canal treatment.
Further reading
1. Baumann MA. Maschinelle Wurzelkanalaufbereitungmit dem RaCe-system. Endodontie 2002: 11: 239249.
2. Baumann MA. The RaCe system. Endodontic Practice2003: 6: 513.
3. Baumann MA Nickeltitanium options and chal-lenges. Dent Clin North Am 2004: 48: 5567.
4. Baumann MA, Leinbrock O, Hellmich M, Baumann-Giedziella UA. Effectiveness of root canal instrumenta-tion with RaCe: an SEM study. J Endod 2003: 29: 286(abstract OR8).
5. Elasaad MG, Isler AE, McDonald NJ. An evaluation ofthe root canal centering abilities of ProTaper and RaCeNiTi rotary files and flexofiles. J Endod 2002: 28: 247(abstract OR50).
6. Fessenden SD, Byrne BE, Carter JM. Torsionaltesting of RaCe, K3 and ProFile nickel titaniumendodontic files. J Endod 2004: 30: 275 (abstractPR10).
7. Glosson CR, Haller RH, Brent Dove S, del Rio CE.Comparison of root canal preparations using NiTi-hand, NiTi engine-driven, and K-Flex endodonticinstruments. J Endod 1995: 21: 146151.
8. Hulsmann M. Wurzelkanalaufbereitung mit NickelTitan-Instrumenten. Ein Handbuch. Berlin: Quintes-senz, 2002.
9. Schafer E, Vlassis M. Comparative investigation of tworotary nickeltitanium instruments: ProTaper versusRaCe. Part 1. Shaping ability in simulated curvedcanals. Int Endod J 2004a: 37: 229238.
10. Schafer E, Vlassis M. Comparative investigation of tworotary nickeltitanium instruments: ProTaper versusRaCe. Part 2. Cleaning effectiveness and shaping abilityin severely curved root canals of extracted teeth. IntEndod J 2004b: 37: 239248.
Baumann
178
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