BASICS AND DEVICES
1st year PG student
Dept. of Conservative Dentistry and Endodontics
• 1) INTRODUCTION
• 2) ROTARY ENDODONTIC INSTRUMENTS-WHAT?
• 3) ROTARY ENDODONTIC INSTRUMENTS- WHY?
• 4) CLASSIFICATION
• 5) HISTORY
• 6) COMPOSITION OF ROTARY ENDODONTIC INSTRUMENTS
• 7) WHY NICKEL-TITANIUM
• 8) COMPARATIVE STUDY OF METALS
• 9) COMPONENTS OF THE FILE
• 10) DYNAMICS OF ROTATIONAL MOTION
• 11)IMPORTANCE OF SPEED,IMPORTANCE OF TORQUE
• 12) ROLE OF HANDPIECE,ROLL OF MOTOR
• 13) NEW ADVANCEMENT OF DEVICES
• 14) RESEARCH POSSIBILITIES FOR FUTURE DEVELOPMENT OF ROTARY ENDODONTIC
The technical demands and level of precision required for successful
performance of endodontic procedures have traditionally been
achieved by careful manipulation of hand instruments within the root
canal space and by strict adherence to the biologic and surgical
principles, essential for disinfection and healing. To improve the speed
and efficiency of the treatment, recently there has been a resurgence
of mechanized or automated system for both preparation and sealing
of root canal system.
ROTARY ENDODONTIC INSTRUMENTS
INSTRUMENTS WHICH ARE USED WITHIN THE ROOT CANALS AND
FOLLOW THE DYNAMICS OF ROTATIONAL MOTION
• ROTARY SHAPING INSTRUMENTS ARE REPLACING THE
CONVENTIONAL HAND FILE SYSTEMS TO ENHANCE SHAPING ABILITY
OF THE CANAL,REDUCE CLINICAL MISHAPS LIKE
BLOCKS,LEDGES,TRANSPORTATION AND PERRFORATION.
• WHEN THE CLINICIAN MASTERS THE METHOD OF USE PRODUCTS OF
ROTARY SHAPING INSTRUMENTS, UNPREDICTABLE FILE
BREAKAGE,METAL FATIGUE,LOSS OF CUTTING EFFICIENCY, VARIATION
IN LENGTH, DIAMETER AND CURVATURE OF THE CANAL CAN BE
AVOIDED AND BETTER SHAPING OF THE CANALS WITH DISERVED
TAPER WILL BE ACHIEVED.
GENERATIONS OF MOTORS
• a) First generation motor without torque control.
• b) Second generation motor with torque limiter.
• c) Third generation motor with simple torque control.
• d) Forth generation motor with apex locator and torque control
They are 3 types-
• a) Micromotor handpiece
• b) Reduction gear handpiece
• c) Vertical Stroke handpiece
CLASSIFICATION OF ROTARY INSTRUMENTS
• Low-Speed Rotary Instruments
• Rotary Instruments for Canal Preparation
• The first description of the use of rotary devices seems to have been by
• William H. Rollins developed the first endodontic handpiece for automated
root canal preparation. He used specially designed needles, which were
mounted into a dental handpiece with a 360 degree rotation.
To avoid instrument fractures rotational speed was
limited to 100 r.p.m.
• In 1928 the ‘Cursor filing contra-angle’ was developed by the Austrian
company W&H (Bu¨rmoos,Austria).
This handpiece created a combined rotational
and vertical motion of the file.
Finally,endodontic handpieces became
popular in Europe with the marketing of the
Racer-handpiece (W&H) in 1958 and
the Giromatic (MicroMega, Besanc¸on,France)
Ni-Ti rotary instruments introduced later use a 360 degree
rotation at low speed and thus utilize methods and
mechanical principles described more than 100 years ago
by Rollins. While hand instruments continue to be used,
Ni-Ti rotary instruments and advanced preparation
techniques offer new perspectives for root canal
preparation that have the potential to avoid some of the
major drawbacks of traditional instruments and devices.
COMPOSITION OF ROTARY ENDODONTIC INSTRUMENTS
• Historically, carbon steel and stainless steel instruments were used for
root canal instrumentation. In 1988, Walia and colleagues introduced
nickel-titanium (NiTi) files to endodontic. Since then, many NiTi file
systems have been developed. Rotary NiTi instruments have become
popular as they can clean and shape root canals with fewer
procedural errors and more predictability than stainless steel hand
• reversible rearrangement of the nickel and titanium atoms at the
molecular level. A new endodontic file is composed of nickel and
titanium atoms arranged in a body-centered cubic lattice structure
NiTi alloys are unique in that applied stress (i.e. bending) causes a
called the austenite phase. When this file is placed in a curved canal,
the atoms rearrange into a closely-packed hexagonal array and the
alloy is transformed into the more flexible martensitic crystal
structure. This molecular transition enables these files to bend easily
and around severe curves without permanent deformation.
COMPARATIVE STUDY OF METALS
Nickel titanium Stainless steel
Excellent flexibility Less flexible
Conforms to canal Straightens and
curvature transports canal
Plastic deformation Permanent
Advances in Nickel-Titanium Metallurgy
1)M-wire NiTi - Developed by Dentsply Tulsa Dental Specialties (Tulsa, OK,
Advantage: This material has greater flexibility and an increased
resistance to cyclic fatigue when compared to
traditional NiTi alloys
2) R-phase NiTi – Developed by SybronEndo (Orange, CA, USA)
Advantage: Files have reduced stiffness and more fracture
resistance compared to standard NiTi files.
3) Controlled-Memory (CM) NiTi
Advantage: Files have superior cyclic fatigue resistance and
increased torque strength over traditional NiTi
Components of a File
• 1) Taper
• 2) Flute
• 3) Land
• 4) Helix angle
• 5) Rake angle
• 6) Pitch
• 7) Cutting edge
DYNAMICS OF ROTATIONAL MOTION
DEFINITION: WHEN A PARTICLE OR PARTICLES OF A RIGID BODY MOVE IN CONCENTRIC
CIRCLE ROUND A COMMON CENTRE,THE MOTION IS CALLED ROTATIONAL MOTION.
OF ROTATIONAL MOTION,CDYNAMICS ontd.
• RADIAN: IT IS DEFINED AS THE ANGLE SUBTENDED AT THE CENTRE OF
A CIRCLE BY AN ARC EQUAL IN LENGTH TO RADIOUS OF THE CIRCLE.
i.e. theta in the diagram.
WHAT IS ANGULAR VELOCITY?
The angular velocity of a rotating particle is defined as the time rate
change of angular displacement.
WHAT IS ANGULAR ACCELARATION?
Angular acceleration of a rotating body is defined as the time rate
change of angular velocity.
Angular acceleration=angular velocity/time.
WHAT IS r.p.m.?
• THE ROTATIONAL SPEED IS EXPRESSED IN REVOLUTION PER MINUTE,
ABBREVIATED AS r.p.m.
If N be the r.p.m. then in 1minute there is N complete revolution.
So ,for one complete rotation it takes=60/N second.
RELATION BETWEEN TORQUE AND ANGULAR ACCELARATION
• ROTATION OF A RIGID BODY?
A rigid body means a body in which the distance between each
pair of particles remain invariant.
• WHAT IS TORQUE?
It is the sum of moments of the
force acting on the particles.
Torque act in a rotational manner.
Importance of Speed
Speed refers not only to revolutions per minute but also to the surface
feet per unit that the tool has with the work to be cut.
In endodontics, speed varies from 150-40,000 rpm Greater the speed,
more the cutting efficiency.
But at higher speed, there are more disadvantages such as :
1) loss of tactile sensation
2) breakage of instruments preceded by flute distortion
3) change in anatomical curvature of canal
4) loss of control
Importance of Torque
• According to Marzouk, torque is the ability of the handpiece to
withstand lateral pressure on the revolving tool without decreasing
its speed or reducing its cutting efficiency
Torque is dependent upon the type of bearing used and the amount
of energy supplied to the handpiece.
Torque is another parameter that might influence the incidence of
instrument locking, deformation, and separation. Theoretically, an
instrument used with a high torque is very active and the incidence
of instrument locking and consequently deformation and separation
would tend to increase, whereas a low torque would reduce the
cutting efficiency of the instrument, and instrument progression in
the canal would be difficult.
Conventional endodontic motors to recent motors use a wide range of
speed of 150 rpm - 40,00Orpm, which are either controlled by
electrical or air-driven instructions handpieces.
Role of Handpiece
• A handpiece is a device for holding rotating instrument, transmitting
power to them and for positioning them intra orally.
Both speed and torque in a handpiece can be modified by the
incorporation of gear systems. A common method of gearing a
handpiece is the use of an epicyclic ball-race gear system. This is
usually located in the shank of the handpiece. The basic design is a
modification of a ball-race bearing.
ROLE OF MOTOR
• Torque control motors allow the setting of torque generated by the
motor. In low torque control motors, torque values set on the motor
are supposed to be less than the value of torque at deformation and
at separation of the rotary instruments. Where as in high torque
control motors, the torque values are relatively high compared to the
torque at deformation and at separation of the rotary instruments.
REVERSE - ROTATION
• During root canal preparation all the instruments are subjected to
different levels of torque. If the level of the torque is equal or greater
than the torque at deformation or at separation, the instrument will
either deform or separate.
• With low torque control motors, the motor will stop rotating and can
even reverse the direction of rotation when the instrument is
subjected to torque levels equal to the torque values set on the
• The latest development with regard to torque control is the
incorporation of gear systems within the handpiece that regulates
torque depending on the size of the rotary instrument. (Endoflash-
Kavo, Anthogy Ni-Ti control- Dentsply). This obviates the need for
torque control motors.
Motors and Devices
• Newer motors have been developed for rotary instruments since the
simple electric motors of the first generation in the early 1990s.
• Electric motors with gear reduction are more suitable for rotary NiTi
systems because they ensure a constant rpm level however, they also
deliver torques much higher than those required to break tips.
• Torque-controlled motors which have been used for several years,
increase operational safety. However, some authors have suggested
that torque control motors may be helpful mainly to inexperienced
clinicians. These motors probably do not reduce the risk of fracture
caused by cyclic fatigue; also, even if the torque is below the fracture
load at D3, a fracture at the smaller diameter (D2) is still possible.
Fully electronically controlled second-generation motor with sensitive
Third-generation simple torque-controlled motor
• Forth-generation motor with built-in apex locator and torque control
NEW ADVANCEMENT OF DEVICES
• The Midwest eStylus electric
handpiece system includes a
motor,tubing, and remote
controller. Available attachments
include a red 1:5 attachment for
high-speed work, a Blue 1:1
attachment for low-speed work,
a Green 10:1 attachment for
rotary endodontics, and a
straight 1:1 attachment for
trimming, adjusting, prophy, and
The Red 1:5 eStylus attachment accepts friction
grip burs and supports high-speed operations
up to 200,000 rpm.it provides brilliant optics
and a 4-port water spray.
The Blue 1:1 eStylus attachment accepts latch burs
and supports low-speed operations from 40,000
RPM to 1500 rpm.It provides brilliant optics and a
4-port water spray.
• The Green 10:1 eStylus attachment
accepts latch burs and files,and
supports lows-peed operations,
including rotary endodontics, from
4000 rpm to 150 rpm. It provides
brilliant optics, but omits water
spray since endo procedures do not
A rotary endodontic system incorporates three key
elements into its operation:
• 1) torque-sensing, which monitors how much twisting force the file is
• 2) auto-reversing, which will reverse the rotation of the file if the file
exceeds the torque limit
• 3) constant file rotational speed, which many file manufacturers
• All these features help to reduce the chance of files breaking in the
canal. Torque limits and speed control allow the dentist to adjust the
unit’s feel and develop the appropriate degree of finesse during
rotary endodontic procedures.
• One electric system available today, the Midwest eStylus from
Dentsply Professional, incorporates all of these features into its
1) Three handpieces in one—a
high-speed, low-speed, and true
rotary endodontic system.
2) eStylus involves its signal to its
auto-reverse mode. Instead of an
audible beep, the eStylus flashes
the optics on the attachment on
and off during the auto-reverse
cycle. This provides a clear, silent
signal to the clinician—but not
3) The eStylus controller displays
actual bur speed, the gear ratio
of the attachment in use and,
when in the “endo” mode, the
• The eStylus ENDO mode offers 4
preset torque-limit settings
allowing clinicians to tailor the
torque sensing. When the torque
limit is reached, eStylus
automatically reverses the file.
Research possibilities for Future developments of
rotary endodontic instruments
• 1) Use of ion implantation and thermal nitridation to provide harder
and wear resistant cutting edges in the file.
• 2) Investigation of failure models in Ni-Ti files ’to develop
mathematical models to accurately predict the life expectancy of
these files during use.
• 3) Optimization of flexibility, bending and torsional strength of files
without sacrificing cutting ability, by using modern mechanics and
analysis methods: for example, finite element analysis.
1)Cohen’s PATHWAYS of the PULP
2)Grossman’s Endodontic Practice,12th edition
3)A Text book of PHYSICS, Chittaranjan Dasgupta
4) 21ST-CENTURY ENDODONTICS GERALD N. GLICKMAN, D.D.S., M.S., M.B.A.; KENNETH A. KOCH, D.M.D.
5) New Developments in Rotary Nickel-Titanium Instruments, Lieutenant Commander Evan Whitbeck, DC, USN
and Colonel Kathleen McNally, DC, USA
6)Current Challenges and Concepts of the Thermomechanical Treatment of Nickel-Titanium Instruments, Ya
Shen, DDS, PhD,* Hui-min Zhou, DDS, PhD,† Yu-feng Zheng, PhD,‡ Bin Peng, DDS, PhD, and Markus Haapasalo,
7)NEW DIRECTIONS IN ENDODONTICS, Exclusive Interview with Clifford J. Ruddle, DDS
8) Revolutions in Endodontic instruments- A review ‘Revathi M “Rao CVN and “*‘Lakshminarayanan L
9)Current developments in rotary root canal instrument technology and clinical use: A review
Ove A. Peters, DMD, MS, PhD1/Frank Paqué, Dr Med Dent2
10)Mechanical preparation of root canals: shaping goals, techniques and means
MICHAEL HU¨ LSMANN, OVE A. PETERS & PAUL M.H. DUMMER