ROTARY ENDODONTIC INSTRUMENTS

BASICS AND DEVICES

PRESENTED BY:

TIRTHANKAR BHAUMIK1st year PG student

Dept. of Conservative Dentistry and Endodontics

GNIDSR

CONTENTS• 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

INSTRUMENTS

INTRODUCTION

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

WHAT?

INSTRUMENTS WHICH ARE USED WITHIN THE ROOT CANALS AND

FOLLOW THE DYNAMICS OF ROTATIONAL MOTION

ROTARY ENDODONTIC INSTRUMENTS

WHY?

• 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.

CLASSIFICATION

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

CLASSIFICATION

Rotary HandpieceThey are 3 types-

• a) Micromotor handpiece

• b) Reduction gear handpiece

• c) Vertical Stroke handpiece

CLASSIFICATION OF ROTARY INSTRUMENTS

• Low-Speed Rotary Instruments

Gates-Glidden burs

Peeso instruments

• Rotary Instruments for Canal Preparation

HISTORY• The first description of the use of rotary devices seems to have been by

Oltramare.In 1889

• 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 waslimited 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)

in 1964.

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

files.

Why Nickel-Titanium

• 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 deformation

Advances in Nickel-Titanium Metallurgy1)M-wire NiTi - Developed by Dentsply Tulsa Dental Specialties (Tulsa, OK, USA)

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

files.

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.

Angular velocity=theta/time.

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 motor.

LATEST DEVELOPMENT

• 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 NiTisystems because they ensure a constant rpm level however, they alsodeliver 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 suggestedthat torque control motors may be helpful mainly to inexperiencedclinicians. These motors probably do not reduce the risk of fracturecaused by cyclic fatigue; also, even if the torque is below the fractureload at D3, a fracture at the smaller diameter (D2) is still possible.

First-generation motor without torque control

Fully electronically controlled second-generation motor with sensitive torque limiter.

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 other uses.

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,andsupports 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 use water.

A rotary endodontic system incorporates three key

elements into its operation:

• 1) torque-sensing, which monitors how much twisting force the file is encountering

• 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 recommend.

• 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

wireless controller.

SPECIFICATION: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 the patient!

3) The eStylus controller displays actual bur speed, the gear ratio of the attachment in use and, when in the “endo” mode, the torque-limit setting.

• The eStylus ENDO mode offers 4 preset torque-limit settings allowing clinicians to tailor the torque sensing. When the torque limit is reached, eStylusautomatically reverses the file.

Research possibilities for Future developments ofrotary 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.

REFERENCE: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, YaShen, DDS, PhD,* Hui-min Zhou, DDS, PhD,† Yu-feng Zheng, PhD,‡ Bin Peng, DDS, PhD, and Markus Haapasalo, DDS, PhD

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

Thank you for your attention