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ONE SINGLE INSTRUMENT FOR A SAFE ROOT CANAL PREPARATION | ONE SHAPE - Micro-Mega
endodontic treatments, Nickel-Titanium instruments in continuous rotation (1) optimize root canal shaping. Generally, rectilinear
and barely curved root canals with a round or oval section does not cause
difficulties and can be prepared by using all standard techniques.
particularly thin and moderately or strongly curved canals with a laminar
section are more difficult to shape and involve a considerable risk of failure.
super elastic qualities, Nickel-Titanium alloy has one important inconvenience,
namely its low resistance in case of repeated use which results in instrument separation.
can occur either through material fatigue caused by a significant number of
compression-tension cycles or through torsion due to obstruction of the
instrument’s tip in the canal (2) (4).
A certain number
of factors such as the pressure exercised on the contra-angle head (5), the speed of rotation and the number of clinical
applications favour the occurrence of instrument separation.
to these procedural mistakes, instrument diameter, taper, profile (6) (7) and machining as well as canal curvature are
crucial for the occurrence (or not) of instrument fracture (8).
Continuous rotation versus reciprocating technique
In recent years, we have seen several
alternating movement systems (clockwise – counter-clockwise rotation) come forward,
destined to limit instrument separation, for example M4® (Sybron
Endo), Endo-Eze AET® (Ultradent), EndoExpress® (Essential
Dental System), WaveOne®
(Dentsply) and Reciproc® (VDW).
The alternative movement technique
varies between 30° and 90°, being thus either symmetric or asymmetric,
depending on the manufacturer. The kinetics of reciprocation reproduces the
manual movement of the intra-canal file, restricts the risk of instrument
fracture and facilitates the penetration into calcified canals (9).
The systems with a 90° alternative
and symmetric movement require a large instrumental sequence whereas the
systems limited to a 30° movement have a restricted cutting capacity and a
tendency to extrude dentine and pulp debris towards the periapex (10).
The latest generation systems with
an asymmetric range do not require any pressure being exercised on the
Although an evolution of the
GIROMATIC® technology seemed to be possible, the new One Shape®
instrument is used in continuous rotation. The acknowledged benefits of this
rotational dynamic are an excellent tactile sensation and a remarkable cutting
The difficulty in the instrument’s
development lies in its profile which is specifically dedicated to root canal
shaping with only one single instrument in continuous rotation.
instrument’s variable cross-section with a diameter of 25/100 mm and a .06
taper constitutes the innovation of One Shape® (fig.1).
resistance of a NiTi instrument to separation as a result of torsion and bending
depends on its diameter and cross-section (11) (12).
2 cutting edges provide an outstanding resistance to bending whereas a triple
helical pitch better withstands torsion (13).
presents 3 different cross-section zones along its length to ensure greater
flexibility and limit aspiration.
The 16 mm
cutting zone consists of:
first zone with a length of 2 mm presenting a variable 3-cutting-edge design to
ensure a centred progression of the file towards the apex. At the same time the
file respects the initial canal path and curvatures, due to the guidance of its
non-working tip (fig.2).
second transitional zone with a length of 7.5 mm which progressively changes
from 3 to 2 cutting edges.
third coronal zone with a length of 6.5 mm provided with 2 symmetric and
positive cutting edges for an efficient upward debris removal.
innovative concept of an instrument with variable cross-sections (fig.3)
facilitates the downward movement in the root canal, guarantees greater
flexibility and respects the original canal path, thanks to a centred
progression and the continuous rotation technique.
A single use instrument
One Shape® is a single
use instrument. However, it can be used for the endodontic treatment of teeth
with one or more roots. Above all, the single instrument concept implies a
considerable simplification of the application protocol and thus ensures safe
and efficient root canal shaping, whereas the single use concept avoids a systematic
control of the tip or the file for unwinding signs.
The single use concept – One Shape®
is supplied in sterile blister packaging (14) –
which also prevents cross-contamination as a consequence of insufficient
the single use concept evades the weakening of NiTi instruments due to their contact
with sodium hypochlorite irrigating solution and autoclaving (15) (16).
The use of
One Shape® requires an endodontic contra-angle connected to a
“traditional” motor with a rotational speed of 400 rpm. The instrument
gradually descends into the root canal by simultaneously brushing the canal
walls in a range of 1 to 2 mm without pressure on the contra-angle head. This
brushing process eliminates dentine overhangs and constraints (17).
shapes the root canal and limits obstructions towards the apex. Once the
working length is reached, a wide range brushing movement with pressure exercised
on the canal walls is recommended in order to verify the free space of the One
Shape® instrument in the canal and eliminate the pulp parenchyma.
mechanical preparation process with a wide taper ensures extensive irrigation
and efficient cleaning of the root canal system (19).
the anatomy and the constriction of the apical zone is essential for the
success of each endodontic treatment. An over instrumentation beyond the apical
limit with wide tapered NiTi files always results in apical zipping (20), over obturation with apical transgression and a defect
in the three-dimensional sealing (21).
of complication during the operation often leads to the failure of the
endodontic treatment, particularly in case of a preoperative, periapical
differ considerably concerning the perfect diameter and taper for the
preparation of the last apical third.
preparation of the constriction or an apical limit prepared with a diameter of
40/100 mm and a .06 taper is not “cleaner” than a preparation with a diameter
of 20/100 mm and a .08 taper (23).
the precise determination of the apical limit and its verification during the operation
are vital for a successful endodontic treatment (25).
length actually evolves during the root canal preparation due to the
instrument’s linear action (24).
Shape® method helps to carry out a safe root canal preparation
provided that the simple protocol is applied. As for all the root canal
preparation methods the pulp chamber opening has to be sufficient for a direct
access to the canal system. Dentin overhangs have to be eliminated. The real
challenge in endodontics is to locate the canal path, make it permeable and secure
it down to the working length (26).
exploration of the root canal is accomplished by using either a MMC 15 type
manual file or mechanized instruments such as G-Files® 12/100 mm
or/and 17/100 mm. In the case of a strongly curved canal path, the coronal part
of the canal has to be widened and straightened by using EndoFlare®.
This procedure also restricts the bending stress on the instrument during the preparation
of the canal's most apical portion (28). After
validation of the exploration process, the pulp chamber has to be thoroughly
irrigated using sodium hypochlorite (3 % to 5.25 %).
of the One Shape® instrument starts with a downward movement of a
few millimetres into the canal at a rotational speed of 400 rpm. As soon as a
resistance is encountered, a low range up and down movement has to be carried
out. This brushing movement on the canal walls facilitates the access to the
accurately measure working length and achieve apical patency, a thin diameter
file connected to an electronic apex locater will guarantee maximum precision. This
determination method of the apical limit after enlargement of the coronal 2/3
yields reliable and reproducible results, particularly in long and curved
canals (29). As a matter of fact, the working
length varies significantly during root canal shaping.
A MMC 15
file retraces the canal path, frees the foramen from any obstruction and
activates the irrigation solution (30). This verification
of the apical anatomy is particularly important when using a single instrument
method, since over instrumentation leads to significant post-operative
The use of
an electronic apex locator is highly recommended (32),
especially regarding their current precision after elimination of constraints
in the coronal third (33).
– the single file system for root canal shaping – is a solution destined to
practitioners who face the following difficulties:
to adopt new techniques
and inadequate root canal preparation
instrument One Shape® is an innovative concept for root canal
shaping. Thanks to its diameter of 25/100 mm and its .06 taper, this instrument
with a simple and rapid protocol allows even the shaping of thin and curved
root canals. The instrument design combined with a continuous rotation movement
guarantees a reliable efficacy all the way down to the apex without stress on
1. Peters OA. Current challenges and concepts in the preparation ofroot canal systems: a review. J Endod 2004;30:559–67.
2. Alapati SB, Brantley WA, Svec TA, Powers JM, Nusstein JM, Daehn GS. SEM observations ofnickel-titaniumrotary endodontic instruments that fractured during clinical use. J Endod 2005;31:40–3.
3. Berutti E, Chiandussi G, Gaviglio I, Ibba A. Comparative analysis oftorsional and bending stresses in two mathematical models ofnickel-titaniumrotary instruments: ProTaperversus ProFile. J Endod 2003;29:15–9.
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8. Yared GM, Bou DagherFE, Machtou P. Influence ofrotational speed, torque and operator’s proficiency on ProFile failure. Int Endod J 2001;34:47–53.
9. Ann R Australas Coll Dent Surg. 1991 Oct;11:82-95. Anatomical barriers in endodontics. Martin AP
10.Reddy SA, Hicks ML: Apical extrusion ofdebris using two hand and two rotary instrumentation techniques, J Endod 24:3, pp. 180-183, 1998.
11. Guilford WL, Lemons JE, EleazerPD. Acomparison oftorque required to fracture rotary files with tips bound in simulated curved canal. J Endod 2005;31:468 –70.
12. Turpin YL, Chagneau F, Vulcain JM. Impact oftwo theoretical cross-sections on torsional and bending stresses ofnickel-titaniumroot canal instrument models. J Endod 2000;26:414 –7.
13. Berutti E, Chiandussi G, Gaviglio I, Ibba A. Comparative analysis oftorsional and bending stresses in two mathematical models ofnickel-titaniumrotary models: ProTaperversus ProFile. J Endod 2003;29:15–9
14. Letters S, Smith AJ, McHugh S, Bagg J: Astudy ofvisual and blood contamination on repro- cessed endodontic files fromgeneral dental practice, BrDent J 199:8, pp. 522-525, 2005.
15. Serene TP, Adams JD, Saxena A. Nickel-titaniuminstruments. Applications in endodontics. St. Louis, MO: Ishiyaku EuroAmerica, Inc., 1995.
16. Chaves Craveiro de Melo M, Guiomarde Azevedo Bahia M, Buono V. Fatigue resistance ofengine-driven rotary nickel-titaniumendodontic instruments. J Endod 2002;28:765–9.
17. Li UM, Lee BS, Shih CT, Lan WH, Lin CP. Cyclic fatigue ofendodontic nickel-titaniumrotary instruments: static and dynamic tests. J Endod 2002;28:448 –51.
18. Yared GM, Bou DagherFE, Machtou P. Cyclic fatigue ofProFile rotary instruments afterclini- cal use. Int Endod J 2000;33:204 –7.
19. Ruddle CJ: Endodontic disinfection: tsunami irrigation, Endodontic Practice 11:1, pp. 7-15, 2008.
20. Iqbal MK, Firic S, Tulcan J, KarabucakB, KimS. Comparison ofapical transportation between ProFile and ProTaperNiTi rotary instruments. Int Endod J 2004;37:359–64.
21. Yared GM, Bou DagherFE. Apical enlargement: influence on overextensions during in vitro vertical compaction. J Endod 1994;20:269–71.
22. de Chevigny C, Dao TT, Basrani BR, et al. Treatment outcome in endodontics: the Toronto study— phase 4: initial treatment. J Endod 2008;34:258–63.
23. Albrecht LJ, BaumgartnerJC, Marshall JG: Evaluation ofapical debris removal using various sizes and tapers ofProFile GTfiles, J Endod 30:6, pp. 425-428, 2004.
24. Davis RD, Marshall JG, BaumgartnerJC. Effect ofearly coronal flaring on working length change in curved canals using rotary nickel-titaniumversus stainless steel instruments. J Endod 2002;28:438– 42.
25. Weine FS, Kelly RF, Lio PJ. The effect ofpreparation procedures on original canal shape and on apical foramen shape. J Endod 1975;1:255–62.
26. West, JD: The endodontic glidepath: secret to rotary safety, Dentistry Today 29:9, pp. 86-93, 2010.
27. LeebJ. Canal orifice enlargement as related to biomechanical preparation. J Endod1983;9:463–70. 28. Sattapan B, Nervo GJ, Palamara JE, MesserHH. Defects in rotary nickel-titaniumfiles afterclinical use. J Endod 2000;26:161–5.
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30. Berutti E, Cantatore G, Castellucci A, et al. Use ofnickel-titaniumrotary PathFile to create the glide path: comparison with manual preflaring in simulated root canals.
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31. PakJG, White SN. Pain prevalence and severity before, during, and afterroot canal treatment: a sys- tematic review. J Endod 2011;37:429–38.
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Dr Mayada Jemâa( email@example.com )- Assistant Professor, Department of Dental Medicine, Military Principal Hospital of Instruction, Tunis, Tunisia
Dr H. Jegham - Assistant Professor, Department of Dental Medicine, Military Principal Hospital of Instruction, Tunis, Tunisia Dr H. Ouertani - Assistant Professor, Department of Dental Medicine, Military Principal Hospital of Instruction, Tunis, Tunisia Pr S. Marouane - Professor, Department of Dental Medicine, Military Principal Hospital of Instruction, Tunis, Tunisia Pr L. Bhouri - Professor, Department of Restorative Dentistry and Endodontics, Dental Clinic, Monastir, Tunisia Pr MB. Khattech - Professor, Department of Dental Medicine, Military Principal Hospital of Instruction, Tunis, Tunisia
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The main goal in comprehensive orthodontic treatment is to obtain an optimal functional occlusion, overbite and overjet. Tooth size discrepancies of the maxillary and the mandibular arches are an important factor for achieving this goal. Inadequate relationships between the maxillary and the mandibular teeth can pose problems in achieving the ideal occlusion. Early treatment planning and proper diagnosis of tooth size discrepancy minimizes problems attained at finishing stage. Bolton’s ratios set an ideal relationship of maxillary tooth width to mandibular tooth width. This article shows the significance, validity as a diagnostic tool and the methods of measuring tooth size discrepancy.
By Dr. Sawsan Nasreddine,Dr. Fida Sayah, Dr. Fady Kassir, and Pr. Mounir Doumit, of the Lebanese University, School of Dentistry
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