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

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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

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