ROTARY ENDODONTIC INSTRUMENTS

INTRODUCTION NICKEL TITANIUM 1988---Walia et al Shaping and cleaning:----- -type of instrument used -material -techniques Operator skill -- Rc instruments Limitations of cs &ss NICKEL TITANIUM 1988---Walia et al Stainless steel Carbon steel

Disadvantages of stainless steel instrumentation Too many instruments and steps Increase time of canal prep Each resultant shape will be different Obturation difficult Canal transportation Coronal enlargement burs cause excessive dentin removal

Advantages of nickel titanium rotary : 2-3 times more elastic flexibility than s.s [walia et al 1988,JOE] Superior resistance to fracture in clockwise and counter clockwise torsion owing to ductility {Walia et al 1988,JOE} NiTi undergoes large amount of elastic deformation when compared to stainless steel [S.A Thompson IEJ 2000]

OPERATORS achieved better canal preparations with rotary instruments than with manual files. No difference in fracture rate was recorded between the two systems. D. Sonntag et al , IEJ;2003

Disadvantages of NiTi Cutting efficiency is 60% than the corresponding ss. It does not give any indication before it fractures High torque motors used ,created continuous cycle of tensile and compressive forces on the instruments producing a very destructive form of loading

Principles of NiTi Rotary Instrumentation CROWN DOWN PREPARATION not designed for pathfinding,negotiating small calcified canals or curved canals, or bypassing ledges Use ss for w/l as more radio opaque Hand piece head aligned with the long axis of each canal Must always be used in a lubricated canal system

Avoid using in abrupt curvatures , s shaped canal system –may break Once stressed, inst. Should be discarded NEVER force a rotary instrument

Use only light pressure (similar to writing) Use intermittent tapping motion Listen to hand piece, reduce pressure if it slows down Always use a torque-reverse hand piece

Do not use rotaries in severely curved canals The curvature of root canals seem to be the most important factor that increases the risk of instrument breakage Gabriela Zeleda et al, JOE ,July 2002

Rotary Instrument features

TAPER

Rake angle Cutting efficiency depends on rake angle Negative – Scraping of dentin rather than cutting it.

Too much positive – Blade engages into the surface and binds without forming chips. Slightly positive – Effective cutting action

Radial land Surface that projects axially from the central axis, between flutes Full land  keeps the file centered  More friction Recessed land  less friction Combination of broad and recessed land BEST

Pitch Number of spirals or threads / unit length. Constant Pitch  “sucking down into” the canal  Crack formation Variable pitch is preferred.

Tip Design Non – cutting tip (Pilot tip) Minimize procedural errors ledging, transportation apical perforation etc. Severe curvature Delicate apical region

Helical Flute Angle : Angle that the cutting edge makes with the long axis of the file. File with constant helical flute angle  Debris accumulation.  Screwing down effect. Variable helical angle preferred

Movements of Rotary instruments Reciprocal rotational movement (Giromatic) Lifting combined with quarter turn rotation (Kerr endo lift) Pure rotational (Endocursor) Oscillating ( Ex-calibur)

Reciprocating Hand piece -Available since 1964 Consist of right angled hand piece which accepts specially designed instruments Continuous rotation of the hand piece is transformed into an alternating quarter turn movement

Two types 1)Giromatic 2)Endocursor Giromatic - accepts only latch type instruments - quarter turn motion is delivered 3000/min - produced wider apical deviations in canals with sharp apical curves

Vertical Stroke Hand piece Endocursor Introduced by Levy Driven either by air or electrically Delivers vertical stroke ranging from 0.3 – 1 mm Also has a quarter turn reciprocating motion that kicks along with the vertical stroke when canal is under bind

Ultrasonic Handpiece Based on the system in which sound as an energy source Richman 1957 Marketed in 1976 Martin & Cunnimgham Cavi Endo System Debriding actions -acoustic streaming -cavitation -Implosion

Sonic Hand piece Attaches to the regular airline at a pressure of 0.4Mpa Air pressure may be varied with an adjustable ring to give an oscillatory range of 1500 – 3000cycles/sec Water irrigant /coolant Micro mega1500/sonic air endo system

ROTARY INSTRUMENT SYSTEMS

Profile Series Introduced by Schilder in 1992 Based on constant percent change of dimension D1 Shows a constant percentage increment of 29% at D1 between successive instruments Numbered 1-11 1 corresponds to ISO 10 8 instruments instead of 11

Profile size ISO 1 10 2 12.9 3 16.7 4 21.6 5 29.9 6 36 7 26.5 8 60 9 77.5 100

Profile 0.04/0.06 Introduced in 1994 Non cutting tip Flexible Niti fabrication Shorter working blade Radial lands –centered preparation Greater taper 0.04 to 0.06 mm/mm

• Better elimination of debris • The passive tip functions as a guide allowing penetration with a minimum pressure •Non cutting tip- Risk of deviation is minimized

• taper 5 to 8 % – number 1 to 6 (20 to 80) ProFile® O.S. (Orifice Shapers) ProFile®.06 ProFile®.04 ProFile®.02 • used for preparing the coronal section • taper 5 to 8 % – number 1 to 6 (20 to 80) • ProFiles O.S. carry 3 colored rings • used for preparing the median canal zone • taper 6% – number 15 to 40 • .06 ProFiles carry 2 colored rings • Used for preparing the terminal part of the canal • taper 4% – number 15 to 90 • .04 ProFiles carry 1 colored ring • used for preparing curved terminal • taper 2% – number 15 to 40 • .02 ProFiles carry 1 colored ring

Flexibility of profile nickel-titanium Gambarini ,J of Evolutionary Dentistry Mechanical properties of the instruments were evaluated according to test procedures described by ANSI/ADA Specification no.28 Comparison of the results with the above mentioned Specification showed that both series of instruments satisfied and far exceeded the standard values.

Yared, G.M.,et al, Influence of rotational speed, torque and operator's proficiency on ProFile failures. Int Endod J, 2001. 34(1): p. 47-53. Preclinical training in the use of the PRI technique with crown-down at 150 rpm were crucial in avoiding instrument separation and reducing the incidence of instrument locking and deformation.

Yared, G.M et al ,Failure of ProFile instruments used with high and low torque motors. Int Endod J, 2001. 34(6): p. 471-5. The results indicated no difference between the three motors with respect to the incidence of instrument failure. The results suggest that the use of PRI in a crown-down manner with air control motors was safe.

GT Range of Instruments All have gold plated shanks Consist of 3 types of instruments which are identified by colored rings on the shank

Type 1 Rotary Files - taper 6 – 12% -length- 21 & 25mm -size :all have ISO tip , Type 2 Rotary files -taper 4% -no:20 to 35 sizes -length 21,25& 31 mm -Used for the prep of the terminal part of the root canal - identified by one ring on the shank

Accessory Files - taper 12% - Diameter 35,50 & 70 - Length: 21 & 25 mm - may be used in the final phases of the preparation to obtain more tapered preparation Operational Sequence Crown down w/l determination Apical preparation Final shaping

Protaper Rotary Instruments Specially designed to instrument difficult ,highly calcified, and severely curved canals Progressive taper Advanced flute design flexible

Triangular Cross Section • High cutting efficiency • Dentine – instrument contact is reduced to prevent screwing Variable Helix Angle and Guiding Tip • No screwing effect • Better elimination of debris Multiple and Variable Taper • Deep shape that facilitates cleaning, obturation and makes it safer • File stress is minimized • Fewer instruments needed for shaping

used to prepare the coronal third of the canal ProTaper S1 used to prepare the coronal third of the canal S1 ProTaper S2 used to shape the middle part of the canal S2 ProTaper F1, F2 & F3 used to prepare the apical part of the canal. F2 and F3 are used for large canals, otherwise use F1 only F1 F2 F3 If necessary, use ProTaper SX with a brushing action to move the coronal aspect of the canal away from the furcation or to create more coronal shape SX

Light Speed Instrument System Consist of 17 GG like reamers Size 0.2mm to 1 mm including 9 half sizes 0.225- 0.65mm. Blade design changed from U-style to spade style Eliminates flutes that fill with debris and lose cutting efficiency world's first NiTi rotary instrument that does not require grinding

Flat radial land with neutral rake angle Allow tactile control with apical enlargement Design reduces stress on the instrument and root canal wall thereby reducing the incidence of separation

Hand piece Speed – faster is better Hand piece Speed – faster is better. Speeds below 2000 rpm are not recommended. 2500 to 3000 rpm works well. Hand piece Torque – higher torque is better. Helps instrument cut through dentin more easily.

ISO Color and Size Identifier Handle ISO Color and Size Identifier Shank -- Depth rings @ 19, 20, 22, 24 mm Shaft / Shank Junction @ 18 mm Shaft Flexible and Noncutting Cutting Blade Spade Type Available in 21, 25, 31 and 50 mm lengths

Very short cutting surface for great cutting efficiency and less “binding” Non cutting Tip Plenty of space for cut debris Has no flutes that can fill with debris. Therefore it maintains excellent cutting efficiency Noncutting Tip

Shaft Twist-Up Shaft Pulls Loose from the Handle Excessive forces cause instrument to pull loose from the handle or twist-up. This makes retrieval from canal easier.

Technique Determine the Apical Determine the Light Speed Preparation Size Determine the Light Speed Size to Begin Mechanical Instrumentation Complete Apical Instrumentation

Versümer, M et al ,International Endodontic Journal  - January 2002  A comparative study of root canal preparation using ProFile .04 and Lightspeed rotary Ni–Ti instruments. Conclusion: Both systems under investigation respected original root canal curvature and were safe to use. Both systems can be recommended for clinical use

K3 Designed by Dr. John McSpadden – 2002. K3 – third generation- triple fluted – asymmetric endodontic file system Designed to cut efficiently, quickly and safely with unparalleled debris removal. Enables clinicians to create uniformly tapered preparation even in anatomically difficult canal.

Rake Angle K3 features a slightly positive rake angle Optimum cutting efficiency

K3 possess three lands Radial land Pitch Two broad and recessed land and a narrow full land. Pitch K3 – Variable pitch

Tip Design K3 - Non – cutting tip (Pilot tip) Minimize procedural errors ledging, transportation apical perforation etc. Severe curvature Delicate apical region Helical Flute Angle : K3 Variable helical flute angle. i.e., Degree of taper increases from the tip to the handle. Debris removal efficiently.

Simplified Color Coding 0.04 – Green 0.06 – Orange Two color bands on the handle Top band – Taper Bottom band – Standard ISO sizing

Advantages By Design Access Handle Variable Core Diameter Improved access to the posterior region Variable Core Diameter Increases flexibility Variable Helical flute angle Less chances of compaction of debris Safe Ended Tip Less chances of procedural errors

K3 – Clinical Guidelines Instruments K3 system include Three orifice openers 0.08 Taper 0.10 “ 0.12 “ b) A full set of ISO-sized NiTi rotary files 0.02 Taper  Tip Size 15 – 45 0.04 “  Tip Size 15 – 60 0.06 “  Tip Size 15 - 60 Tip Size No. 25 Length – 17, 21, 25 Length – 21, 25, 30mm

The EndoSequence System The first 4th Generation endodontic file. Constant .06 tapered preparation .04 available for small canals. A simple, sequence for every canal size.

EndoWave NiTi-Files Advantages of EndoWave Five files for preparation   Five files for preparation No step formation in narrow and curved canals The tips follow the canal contour perfectly and prevent canal straightening Risk of instrument fracture minimized Quick, safe preparation with higher rpm

Anti-screwing design ensures that the files do not screw into or jam in the root canal. prevents the files being automatically drawn into the root canal, so preparation is much safer. greatly reduces the amount of force the operator has to apply. Minimizing File Fracture The triangular cross-section of the files minimizes the risk of fracture in the root canal.

Extremely smooth surface texture Unique safety tip have a rounded tip that ensures maximum safety even when preparing in the apex of the root. smoothly follows the contour of the canal, ensuring perfect preparation. Extremely smooth surface texture

RaCe system : Reamer with Alternating cutting edges prevent the threading on/blocking effect have the advantage of an extremely low operating torque; Sharp cutting edges for improved efficiency with fewer instruments;

Safety MemoDisc® for controlling NiTi fatigue; Electro-chemical treatment: better resistance to torsion and metal fatigue

Alternating triangular and square cross sections

Quantec Rotary NiTi Consists of graduating taper ranging from 0.02 – 0.12 Computer generated design Cutting angle is slightly positive Helical angle ideally channel debris out of the canal Recommended rotation speed is 340rpm Recessed radial lands – rotational friction is greatly reduced

25/.12 FILE NO25/.06 FILE #20 HAND FILE

25/.05 FILE 25.08 FILE 25/.04 FILE 25/.03 FILE

HERO 642 PACKET OF 9 INSTRUMENTS 6% - n° 20-25-30 - Length 21 mm - 25 mm 4% - n° 20-25-30 – Length 21 mm - 25 mm – 29mm 2% - n° 20-25-30-35-40-45 Length 21 mm - 25 mm - 29mm

advantages of the HERO 642 Three cutting edges for a positive cutting in a curette effect. bigger inner core for a stronger instrument and a better resistance to breakage. progressive pitch/fluting reducing the screwing-in effect.

3)Three variable tapers which peel the canal wall on small contact points (less risk of stalling and fracture). 4) tip which stays centered in the canal and hardly ever makes contact with the canal walls. 5) No packing of the smear layer into the tubuli because of cutting edge contact.

HERO 642

M. Hülsmann, et al International Endodontic Journal October 2001Volume 34 Issue 7   A comparative study of root canal preparation with HERO 642 and Quantec SC rotary Ni–Ti instruments Both systems respected original root canal curvature well and showed good cleaning ability; Quantec SC showed deficiencies in terms of safety.

WHAT CAUSES BREAKAGE? WHAT IS TORSION? Breakage is directly related to excessive stresses of torsion and fatigue. Torsion is the axial force of being twisted that results when one part of a file rotates at a different rate than another part. Any distortion of a file that results from twisting, such as unwinding, is caused by stress of torsion. However, as torque is essentially impossible to sense during automated instrumentation, understanding the factors of file breakage is the most important aspect for learning this modality for canal preparation.

Discarded rotary NiTi showing visible defects without fracture All files show unwinding, indicating torsional defects

Sotokawa’s classification Type 1 ---bent instrument Type 2 ---straightening of twist contour Type 3---peeling of metal at blade edges Type 4---partial clockwise twist Type 5 – cracking along axis Type 6 —full fracture

WHAT IS FATIGUE? File fatigue is the result of repetitive stress predominantly during flexion while rotating around a canal curvature. A file can withstand more stress during a single rotation around a curvature than it can after numerous rotations. Metal fatigue usually begins at the surface where minute defects act as points where stresses become concentrated.

A fatigue failure is particularly insidious because it can occur without any obvious warning Knowledge of the relationships of file sizes and canal anatomy is especially important when dealing with the combined stresses of torque and fatigue.

least resistant to breakage are the NiTi files, especially the rotary files.  NiTi begins to micro fracture as soon as it is used in the root. No matter how light your touch, the NiTi micro fractures.  It is just a matter of time before the instrument fractures all the way. 

the combination of compressive and tensile stress causes the file to break even sooner. The faster you rotate the file and the more you bend the rotary instrument, the quicker it fractures. Unfortunately, NiTi instruments tend to fracture with no visible warning.  The instrument may look perfectly normal, yet fracture in the tooth. 

We can do two things to help reduce the risk of NiTi fracture: Examine the file for deformations every time before placing it into the patient’s mouth. Bend the file to at least an 80-degree angle, every time before placing it into the root, to see if it will fracture.

The most important relationships of the components of NiTi ground files designs and canal anatomies that enable us to improve our technique include: – A file with a more efficient cutting design requires less torque and/or pressure to accomplish the same degree of root canal enlargement. – In a straight canal, the ability of a file to withstand torque varies directly with the square of its diameter. – In a curved canal, the ability of a file to resist fatigue varies inversely with the square of its diameter.

– The torque required to rotate a file varies directly with the surface area of the file’s engagement in the canal. – Fatigue of a file increases with the number of rotations of the file in the canal. – Fatigue of a file increases with the degree of curvature of the canal. – To improve efficiency, the smaller the surface area of a file engaged in the canal, the greater the rotation speed should be.

more spirals a flute has per unit length the greater the torque is required to rotate a file more stress concentration points there are for potential failure, more flexible it is. fewer spirals a flute has per unit length, the more it resists deformation, but the more rigid it is.

–– The sharper the cutting blade of a file, the fewer spirals per unit length the file should have. -The greater the number of flutes with similar helix angles, the greater tendency a file has to screw into the canal and become bound. – Maximum engagement of a file occurs when it progresses into the canal at a rate that is equal to its feed rate.

A cleaning protocol for rotary nickel-titanium endodontic instruments Step Method 10 vigorous strokes in a scouring sponge soaked in 0.2% chlorhexidine solution 30 minute pre-soaking in an enzymatic cleaning solution 15 minute ultrasonication in an enzymatic cleaning solution 20 second rinse in running tap water P Parashos,* P Linsuwanont,* HH Messer* Australian Dental Journal 2004;49:(1):20-27

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