Endodontic instruments / dental implant courses by Indian dental academy by indiandentalacademy

ENDODONTIC INSTRUMENTS Introduction and History Endodontic treatment is based on the principles of debridement, sterilization, and obturation of the root canal system. However, successful treatment is dependent on the complete removal of pulp tissue and pulp remnants, bacteria and bacterial components from the pulp space. Cleaning and shaping of the root canal in turn depends on various factors like: -

Type of instrument used.

Material.

Techniques.

Operatorâ&#x20AC;&#x2122;s skill Earlier, for the manufacture of root canal instruments, the

primary focus was mainly on 2 materials i.e. -

Carbon steel (i.e. a round, tapered piano wire was used)

Stainless steel. The stainless steel wire is ground along its long arms into a 4-

sided (square cross-section) or 3 sided (angular cross-section) tapered 1

shaft that is twisted into flutes. The number of flutes twisted into each blade of a similar sized-instrument determines whether that instrument is a reamer (less flutes) or a file (more flutes). Before 1958, endodontic instruments were manufactured without benefit of any established criteria. There was little uniformity in quality control or manufacture, no uniformity existed in progression from one instrument to the next, and there was no co-relation of instruments and filling materials in terms of size and shape. In 1959, a new line of standardized instruments and filling material was introduced by Ingle and Levine. i)

Instruments shall be numbered from 10 to 100, the numbers to advance by 5 units to size 60, then by 10 units to size 100.

ii)

Each number shall be representative of the diameter of the instrument in hundredths of a mm at the tip. e.g. No. 10 is 10/100 or 0.1mm at the tip.

iii)

The working blade (flutes) shall begin at the tip, designated site D1, and shall extend exactly 16mm up the shaft, terminating at designated site D2. The diameter of D2 shall be 32/100 or 0.32mm > than that of D1 , 2

for e.g. No. 20 reamer 0.2 at D1 0.2+ 0.32 = 0.52mm at D2 This sizing ensures a constant increase in taper of 0.02mm per mm for every instrument regardless of the size. In addition, instruments handles have been colour coded for easier recognition. The 1S0 slightly modified Ingle’s original standarization. i)

Addition of D3  3mm from D1

ii)

Specifications for shapes of the tip  75° tip ±15° Instrument sizes should increase by 0.05mm at D 1 between

No.10-60 e.g. No. 10,15 and 20 and by 0.1 from 60-150. In January 1976, the American Standards Institute granted approval of “ADA specification No. 28” for endodontic files and reamers. ADA spec. No. 28 (JADA, 1989, 118; 239) stated (finally revised in March 81). a) Instrument sizes 06 and 08 and 110 to 150 were added to the original standardization.

b) D1 and D2 were changed to D0 and D16 respectively, to clarify in terms of mm from the tip. D0  at the point of the tip. D16  measured 16mm from the tip. Instruments are available in lengths of: 21mm 25mm 28mm 30mm Reamers are also available in 40 mm length for use in preparing root canals for endodontic implants. SCAN FIGURE

Classification of Instruments I According to Grossman a) Exploring instruments – i.e. to locate the canal orifice and determine its patency

Endodontic explores Smooth broaches

b) Debriding instruments 4

i.e. to extirpate the pulp and remove any foreign debris

Barbed broach

c) Shaping instruments i.e. to shape the root canal laterally and apically

Reamers Files

d) Obturating instruments i.e. to cement and pack gutta-percha into the root canal

Spreaders Pluggers Lentulo-spirals

II. International standards organization (ISO) has grouped root canal instruments according to their use Group I ď&#x192; Hand use only

Files

K-type (Kerr) H-type (Hedstroem)

Reamers â&#x20AC;&#x201C; K-type Broaches Pluggers Spreaders

Group II : Engine driven latch-type. Same design as Group I but made to be attached to a handpiece (includes paste fillers also). Group III: Engine driven latch-type – Drills / Reamers Crates-Glidden

Peeso

A, D, O, K, O, T

(G-type)

(P-type)

(M-type reamers)

Group IV: Root canal points

Gutta percha Silver Paper

III. According to Stock Instruments can be classified as: Twisted

Machined

K-files

- H-file

K-reamer

- Flex-R

K-flex

- Heliapical

Flexo

- Canal Master

Zipper Flexicut

- Flexogates - McSpadden Engine file

K-type instrument, Reamer/Files – OHP  First designed by Kerr manufacturing Co. in 1915. 6

 These are the most widely copied and extensively manufactured endodontic instrument, world-wide.  Now made of stainless steel.  Are produced by grinding graduated sizes of rounded “Piano” wire into either a square or triangular configuration.  Cutting edges on spirals are then given where the instrument is grasped by a machine and twisted counter-clockwise. Files

Reamers

Given tighter flutes

Loose spirals

(1.93-0.88 mm)

(0.80-0.28mm)

Square blank -

Are generally used for smaller, fragile instruments.

Resists # better -

Triangular blank -

Used for larger instruments.

Cutting efficiency is 2-5 times > square blank

The cutting edges are known as “Rakes” of the blade

Triangular design is brittle and the cutting efficiency is less

the more acute this rake, the sharper the blade

 There are approximately twice the number of spirals on a file as on a reamer of corresponding size. 7

(K-type) Reamers  Are used for drilling.  They cut by being tightly inserted into the canal, twisted clockwise  one ¼ to ½ turn to engage the blades into the dentin and then withdrawn. Penetration  rotation  Retraction and the cut is made during retraction.  Reaming is the only method that produces a round, tapered, preparation  possible only in straight canals Reamers, in such cases they are rotated ½ turn. In slightly curved canals  reamers should be rotated only ¼ turn as more stress will cause breakage.  Files as well as reamers can be used for reaming but conversely, reamers do not work well as files – their flutes are too widespread to rasp. Files  Achieves its principal cutting action on “withdrawl”.  But it cuts on push motion as well.

 The withdrawal cutting action can be effected in both filing and reaming motion.

Filing action (Rasping) Instrument is placed in the canal at the desired length, pressure is exerted against the canal wall and while this pressure is maintained, the instruments is withdrawn, without turning. Reaming action (Drilling) : same as for reamers. ↓ Penetration  rotation  retraction  Files tend to set in the dentin more readily than reamer must be treated more carefully. ↓ Withdrawing will cut away this engaged dentin.

Efficacy of K-type Instrument Tri-angular Reamers

Square Reamers

• Cut with greater cutting efficiency. • Lose their sharpness more rapidly. • # easily.

 Wear does not appear to be factor in instrument function but rather instruments fail because of deformation or fracture of the blades. Sotokawa studied discarded instruments and indicated metal fatigue as the culprit in breakage and distortion. First, a starting point crack develops on the file’s edge and then “metal fatigue fans out from that point, spreading towards the file’s axial centre”. Classification of instrument damage Type I

Bent instrument.

Type II

Stretching / straightening of twist contour.

Type III :

Peeling off metal at blade edges.

Type IV :

Partial clockwise turn.

Type V

Cracking along axis.

Type VI :

Full fracture.

In order to overcome these problem, Ni-Ti has been substituted for stainless steel – NITINOL K-STYLE MODIFICATIONS -

After having dominated the market for 65 years, K-style endodontic instruments came into a series of modifications beginning in the 1980’s. 10

A] K-flex file  In 1982 Kerr manufacturing co introduced a new instrument termed K-flex file.  Cross section is rhombus / diamond shaped.  It

viewed

the

fore-runner

the

so-called

hybrid instrument designs ↓ those designs that attempt to integrate the strength and versatility of K-type files with the aggressive cutting properties of H-type instruments.  When twisted to produce spiral/flutes, it results in alternating high flutes and low flutes.  The cutting edges of the high flutes are formed by the 2 acute <s of the rhombus. ↓ Increase the sharpness and cutting efficiency.  The alternating low flutes are formed by the obtuse <les of the rhombus. ↓ these provide more area for debris removal

 The decreased contact by the instrument with the canal walls provides a space reservoir, which with proper irrigation further reduces the danger of compacting dentinal filing in the canal.

 Another advantage  increased flexibility. FLEX-R-FILE  Developed by the union Broach company is one of the variations in the design of the top.  ADA specifications No.28 and No.58 state that the design of the tip of K-file is optional.  This instrument was designed to be used in the top balanced force technique.  The tip <le is reduced, so the file stays untired within the original canal and cuts all sides more evenly.  The fluted edges are milled rather than twisted. This allows better control of instrument flexibility and cutting efficiency and influences torsional strength.  Anti-clockwise rotary motion is used.  An important feature of this instrument is its modified safeended/ non-cutting. 12

 Weine, suggested trimming 1mm from the tip of the file and rounding off sharp edges on a diamond nail file. In this way, files sizes 10, 15, 20, 25 may be converted to 12, 17, 22 and 27.  The disadvantages of this technique are that the files are made disposable and the edges may be difficult to smooth, which therefore creates ledges during filing. A recent innovation by Maillefer overcomes these problems using the intermediate files “Golden Mediums”. Zipper Flexicut  Produced by twisting a triangular shank made from SCS spacecraft steel.  It is a high vacuum-fired chrome nickel steel. Advantages: -

Flexibility.

Non-aggressive tip.

 Other companies have introduced such instruments as control safe files, the anti-ledging tip <, safety H-file.

Flexo-File  This is a flexible instrument twisted from a stainless steel blank of angular cross-section.  With 1.81 flutes/mm length.  Tip is modified to be non-cutting.  A recent addition “Golden Medium” is of parallel design but provides a range of intermediate sizes (12, 17, 22, 27, and 32). Zipper Flexicut HEDSTROEM (H) – FILES  Machined from a blank of circular cross-section.  The flutes are produced by machining a single helix into the metal, producing a series of intersecting curves which increase in size from the tip to the handle.  The strength and flexibility of the instrument is determined by the depth of the flute or the residual bulk of metal in the central portion of the file.  The blades thus formed are virtually at rt. <s to the dentin surface (+ve rake <).

Helical < of K and H type Greater cutting efficiency is achieved in filing motion as the helical < approaches 90° to the dentin surface. Advantages:  H-files cut in one direction  retraction.  The most efficient cutting motion is a pulling motion.  It was found to be 3 times more effective on than K-files, also did not tend to pack debris at the apex. Disadvantages:  They are fragile, hence are not used in torquing action. ADA specification No. 58 was applied to H-files. It stated:  Included requirements for sterilization of handles.  Adds requirements that physical properties of the files remain unchanged after cycling through a stenm autoclave and dry heat sterilization sequence. Modifications of the H-files  Mc Spadden was the first to modify the traditional H-file. E.g., Burns unifile, Dynatrak.



These files were designed with 2 spirals for cutting blades – a double helix design.



In cross section, the blades present as ‘S’ shape rather than the single helix tear-drop cross-sectional shape of the H-file.



Mc Spadden claimed that unifile cuts more efficiently than the standard H-file but it generally failed the torque twisting test.



Authors found that it should not be twisted more than ¼ turn. Dynatrak file also developed by McSpadden was the first

instrument

designed

for

use

the

reciprocating

handpieces

(Crinomatic). This variation of the unifile had a non-cutting pilot tip and an altered helical pitch angle to prevent the instrument from binding, when in use. “S” File  Is a variation of the unifile in its double helix configuration as well as variations in flute depth.

 It differs from the unifile since the angle of the flutes remains uniform through the length of the instrument and the depth of the flutes increases from tip to handle.  Cutting by reaming is also possible due to its flute design.

Buchanan has further modified the H-type file as the safety Hedstroem ↓ has a non-cutting side to prevent ledging in curved canals. NT-SENSOR FILES  Another variation by Mac Spadden.  These instruments have 3 flutes, the third flute set as half the < of the other two S-shaped flutes. ↓ MAC FILE  Newest version.  Produced in nickel-titanium, which gives the instrument superelasticity. A-FILE  Modified by levy to function better with the automated canal finder system. 17

 Also available as a hand file. Unique features of A-File  Steep depth of the flutes.  40° helical angle of the cutting blades (these cut more efficiently than standard 60°/70° helical <). Advantages:  Can be used in a curved canal (the steep blades on the inner wall collapse and lose their cutting ability. It is more aggressive on the external wall. Non-cutting tip follows lumen without ledging. On withdrawl, H-file represents +ve cutting action on internal wall (arrow) where stripping perforation frequently occurs, and sharpened tip tends to ledge into external wall. “U-file”  Developed by Heath.  Marketed as the canal Master ‘u’ files.  Triangular cross-section with two 90° cutting edges at each point of the triangular blade.  Adapts well to the curved canal.

 Non-cutting pilot tip ensures that the file remains in the lumen of the canal, thus avoiding ‘zipping’ and transportation at the apex.  These files are used in both a push-pull and rotary motion.

APICAL PREPARATION TYPE HAND INSTRUMENTS I] Canal Master Instruments

Hand Engine driven

Developed by Wildey and Senia.

3 major feature

 a 1.0mm non-cutting pilot tip.

 a small size-cutting head (3mm; since reduced to 1-2mm)  a non-cutting shaft with increased flexibility.  To overcome problems (rapid wear and breakage) with the canal master, a new design of the cutting blades ensued  canal master ‘u’.  Here the blades are the ‘u’ design developed by Heath.  Hand instruments come in sizes (20-80) with a number of half sizes in between 22.5 32.5 42.5 etc  Engine driven instruments are in 150 sizes 50 – 100.  Originally it was recommended that these instruments be used in a reaming action  i.e. 90° turn to the right and 90° turn to the left.

 However, with the new u design, continuous rapid clockwise, yet gentle “drilling action” is recommended. Advantages:  It reduces the incidence of transportation within the canal. Disadvantages:  Instrument breakage. ↓ to overcome this problem, the canal master ‘u’ is made from Nickel-Titanium – Ni-Ti canal Master ‘u’ (CMU). Advantages: -

Less tendency for transportation, ledging and zipping.

Less breakage.

Less debris being forced through the apical foramen.

FLEXOGATES (Gates – Glidden Modification) (a.k.a. Handygates) -

Is a hand instrument also designed for apical preparation.

Is a safe-tipped variation of the traditional G.G. Drill.

It consists of a smooth, flexible shank which is circular and small in cross section.

The non-cutting tip is followed by approximately one spiral/fluting on an extended head carried on a shank.

As in G.G.D., the flexogates is made deliberately weak at the handle end of the thin shank to ensure access for removal of broken instruments.

 BRISENO has compared flexogates and canal master in vitro and found flexogates less likely to cause apical transportation. HELIAPICAL  This instrument resembles a conventional file in the apical 45mm, the remainder being a narrow blank shank. Care is needed in its use; small sizes may # if a continuous rotational motion is used. ‘BROACHES’  Are of 2 type

Barbed Smooth

 Rasps are also included in this category.  ADA specification No. 63 seperates broaches and rasps.  The major difference between broaches and rasps lies in the depth and < of cut in the wire shaft (core) which results in barbs of different height and shapes.

Mc Spadden Engine File  Designed to be used in a rotary instrument slow speeds (300rpm).  Constructed from a superelastic Ni-Ti alloy. These instruments are designed to avoid binding into canal walls by  a) 15-35 sizes – flat areas are substituted for blades and cutting is achieved by a planning action.; b) in sizes 40-60, the same is achieved using 2 or more spiraled blades.  The most unique feature of this instrument is that it “pulls” the canal systems contents out rather than forcing them apically. Rasp

Barbed Broaches

 Barbs are equal to 1/3rd the diameter of the tip.

 Barb height should be ½ the core diameter.

 Taper is 0.015 mm/mm

 Taper of broaches is 0.007mm/mm (less than half that of rasps).

 Similar in design to barbed broaches, but having shallower and more rounded Uses: barbs produce more rough a. Are used primarily for the walled canal preparation. removal of intact pulp tissue. b.

To loosen the debris in the necrotic canals.

To remove paper points or cotton pellets from within the canal.

 Available in different sizes XXXF to XC  Break very easily.

Smooth Broaches  There is a smooth broach, which is sometimes used as a Pathfinder. ↓  Pathfinder CS, made of carbon steel, is less likely to collapse when forced down a fine canal.  Manufactured (developed) by Kerr.  Is similar in appearance to the K-type file but possesses a narrower taper to uniformly distribute the axial stress along the instrument shaft, thus reducing the tendency to bend at the tip.  These instruments come in pre-sterilized single-unit packages and are available in 19-21 and 25mm lengths and 2 sizes

K1 K2

 The carbon steel shaft is reported to provide greater sharpness and strength for penetrating calcified root canals. AUTOMATED ROOT CANAL PREPARATION DEVICES If used in collaberation with hand instruments, most of the devices can serve as useful adjuvants in root canal preparation. ‘Danger zones’, apical part of root canals, and narrow, curved canals are the area suggested to be treated by hand instruments as it 24

generally is difficult to control the preparation of these areas using engine driven root canal instruments. Advantages: -

Easy to use.

Saves time.

Renders ideal preparation of root canal.

 Reduction in fatigue The overall strain becomes less and fatigue is decreased. Moreover, procedural time may also be less compared to hand instrumentation.

 Reduction in treatment time But several factors are involved like: -

Not all the devices reduce the treatment time.

It depends on the type of tooth being treated.

Expertise of the clinician.

Limitations:  They do not simplify the entire root-canal treatment procedure as they have no role in the early phase of the treatment. Correct diagnosis, proper access cavity, locating the orifices, debriding the canals and determining the root canal length, have to be done manually using one’s intelligence, knowledge and clinical experience. Moreover, most of 25

these devices can be used in the root canals only after the completion of preparation of canals using 150 size No. 15.  Lack of tactile sensation This is an advantage with hand instruments such registration with instruments (apical stop) alerts the clinician to be cautious and greatly aids in avoiding procedural mishaps. Continuous use of automated handpiece against resistance may lead on to either # of the RC instrument or cause mishaps. Newer models such as canal finder system are designed to stop functioning on countering resistance in the root canal. The problem of lack of tactile sensation can be overcome to a great extent three proper and sequential use of automated root canal instruments and expertise. Classification. A. Reciprocal  (impact specially designed short reciprocal most to the cutting instrument). B. Rotary. C. Ultrasonic. D. Sonic. A. Handpieces that work on the principle of offering ‘alternating’ movement to RC instruments are termed ‘reciprocal handpieces’.

First engine driven rotary reciprocal RC shaping instrument was introduced in 1899 by Rellins. AUTOMATED ROOT CANAL INSTRUMENTS ISO Groups II and III (According to Ingle): Engine driven instruments can be used in 3 types of contra<handpieces:  Fully rotary (latch / friction grip).  Reciprocal quarter-turn.  Special handpiece that imparts a vertical stroke but with an added reciprocating quarter turn that “cuts-in” when the instrument is stressed. According to Stock  They can be classified according to the type of movement imparted to the cutting instrument. -

Rotary

Reciprocal.

Vertical.

Random.

I] ROTARY  Instrumentation with a full rotary handpiece is by straight line drilling or side-cutting. Uses: 27

These are used primarily to develop coronal access to canal orifices.

They are used in perfectly straight canals (since they do not bend).

To prepare post channels for final restoration.

To widen as much as two-thirds of the canal. To overcome this problem (they do not bend), they should be

used in slower handpieces. e.g,

- Medidenta reduction Gear handpiece. - Sensomatic handpiece. Where the torque is controlled and speed is reduced to as much as

10RPM. “NITIMAC”  is a new gear reduction handpiece (NT Company, USA). -

runs at 300 rpm

2 different types of Ni-Ti files have been designed by Mac Spadden.

Sensor files -

Nitixl files

Redesigned hedstroem type

instruments

Made from Nickel-titanium (u-style configuration).

Advantages:

Now called NT-power files

Flexibility.

Are the finishing files

Resistance to #

of these files allow preparation of severely curved root canals

These files are manufactured with an off-centre tip that facilitated negotiating around curvatures and ledges. The two most popular engine-driven instruments are: -

Gates Glidden drills

Peeso reamers (drills)

GGD â&#x20AC;&#x201C; has a long, thin shaft ending in a flame-shaped head with a safetip to guard against perforation. Uses: -

For initial opening of the canal-orifices.

Deeper penetration in both straight and curved canals.

To remove the lingual shoulder in anterior teeth. The flame head cuts laterally and is used with gentle, apically directed pressure. Both are made of hardened carbon steel and corrode easily. Both

are inflexible. 29

This instrument was designed to have a weak spot in the part of the shaft closest to the handpieces, so that, if the instrument separates, the separated part can be easily removed from the canal.

Working head is small.

They comes in sizes / through 6

These sizes have been now converted to the 150 instrument sizes and colours. Both are flame shaped Has long sharp flutes

Sharper cutting edges.

More efficient.

Peeso Reamer -

Is most often used in preparing the coronal part of the root canal for a post and core.

It cuts laterally â&#x20AC;&#x201C; sizes and dimensions of GGD and Peeso Reamers

Peeso Reamer No.

GGD (diameter mm)

0.7

0.5

0.9

0.7

1.10

0.9

1.30

1.10

1.50

1.30

1.70

1.50

Orifice Opener -

Martin has developed an “Orifice Opener” used to flare and prepare the cervical and middle portions of the canal.

Used in a slow speed latch-type handpiece.

Come in sizes 25-70.

This ‘M’ series orifice opener is more flexible than GGD.

But still recommended only for straight parts of the canal.

Canal Master System (introduced by Wildey and Senia) -

Are a k-style modification.

Cutting head is shortened to only 3-4mm above the non-cutting pilot tip.

They are now made in Nickel-titanium (CM ‘U’).

The recent advancement in this is the light speed system.

II] RECIPROCAL  This uses a special handpiece which contra-rotates the instrument, through 90°  3000 times / minute (quarter-turn motion). -

These were first introduced in 1899 by Rellins.

They may be classified depending on the direction of movement that they impart. Rotatory

Vertical (push-pull)

Giromatic

Canal Finder system

Kerr M4

Intra-Endo 3- LDSY

Endo-Cursor

Endo Lift

Giromatic Introduced in 1964 A variety of canal instruments can be used with the Giromatic. -

Giro pointer – orifice opener (16mm).

Giro broach.

Giro-file – a hedstroem configuration

Giro reamer

Heli-Girofile (3 cutting blades in cross-section).

According to Weine -

Giromatic produced wider apical derivations (“Zip”) in canals with sharp apical curvature. Later instruments like “Triocut” were designed for Giromatic.

Kerr M4 -

It is so named because it utilizes 4:1 gear reduction handpiece.

It imparts a reciprocal “watch-winding” 30° motion to the endodontic instrument.

It is devoid of any vertical movement.

Safety Hedstroem files are used with this type of instrument.

Disadvantages: -

Causes frequent breakage of instrument in the canals.

Creates hour-glass preparations, ledges, zips.

Creates strip perforations.

Canal Finder System -

Developed in France

Is a specialized handpiece with a vertical movement of 0.3 to 1.0mm + a free rotational movement (1/4 turn).

(If there is no resistance in the canal, the instrument moves upto 1mm; in case of minimal resistance, it move 0-3mm. In several resistance in stops). Increasing the vertical pressure will stop the vertical movement. -

The free-rotational movement allows the tip of the instrument to move away from an obstruction in the root canal wall.

Master, Hedstroem A-file /K-files either made of stainless steel / nickel titanium can be used.

The cutting instruments are specially designed. The files have increased cutting efficiency as it has 40Â° helical angle, and the flute depth is also more pronounced for better debridement.

The files tip are rounded and negative cutting angle is given for the first flute. This avoids procedural errors.

The clinical Research Associates described it as â&#x20AC;&#x153;simple, easy, predictable, automated instrument that compares favourably to or exceeds, hand instrumentation and especially well suited for narrow or highly curved canals.

Disadvantages: -

Causes zipping / transportation.

Uses: -

It can also be used in retreatment of root canals containing guttapercha.

Canal header  Is a modified speed reducing handpiece.  Has a vertical movement and of 4 – 8mm and a contra-rotational movement which is restricted to 30°. Three cutting instruments are available. -

K-file with a safe-ended tip for narrow canals.

A more aggressive H-file.

A universal file which is a flexible H-file with a safe-ended tip.

Intra-Endo 3-LDSY  is a racer-type handpiece.  is a “look-alike” of the canal finder system.  apart from up and down movement, it can impart also full turn movement; the latter occurring when axial pressure is applied.  the vertical movement is in the range of 0.4mm.  it canal also make use of conventional reamers and H-files. Another type of “look-alike” of the canal finder system is the Endo-lift (Kerr).

EXCALIBUR  produces a random lateral vibratory motion.  it vibrates only laterally and is devoid of any vertical movement.  the amplitude of movement is 1.5-2mm.  K-files are used at 20,000-25,000 rpm.  this devices may be classified as a subsonic instrument (oscillates at 1000-2000 frequency per sec.). Disadvantages:  due to its effective cutting ability, it may remove dentin excessively.  tends to straighten the canals or causes strip perforation. III] ULTRASONICS – is based on a system in which sound as energy source activates a file. This results in a 3-D activation of the file. The main debriding action was though be by”cavitation”. -

It denotes a device which imparts sinusoidal vibration of high intensity to root canal instrumentation, in the range which is above that of audible perception.

Originally introduced to endodontics by Richman in 1957, it was further developed and promoted through extensive research by Howard Martin and Walter Cunningham in 1976). 36

Interestingly, ultrasonics was originally intended by them to be used as a root canal sterilizing device. -

There are 2 methods of generating ultrasonic oscillations in the file shank.

Magnetostrictive -

Peizo-electric

Requires water-cooling i.e.

More powerful.

if NaOCl is used as an

Does not require water-

irrigant, the water must be

cooling.

led away from the stack via additional

tubing.

Disadvantages:

This

makes the headpiece both clumsy and expensive.

apical widening.

Ledges in curved canals.

e.g. Cavi Endo (25,000 k hertz) e.g. ENAC, Neosonic, MiniEndo by Martin and Cunningham (30-35,000 K hertz). followed by ENAC unit. 2 types of files -

Both these handpieces use K-file.

Diamond-impregnated file for the straight part of the canal.

Can produce a tapered canal shape as the tip is constrained by pressing against the canal wall.

Advantages: -

Cleaning of the root canal due to acoustic streaming (turoulence along the shank of the file when immersed in a fluid).

Causes less extrusion of root canal debris into the periapex.

10-15 No. files should be used as there are most flexible and less likely to cause ledges.

Uses: a) as a root canal shaping device. b) As a debriding device. -

Acoustic streaming caused by high vibration of the file is the main mechanism. The main action of ultrasonics was initially thought to be by cavitation, a process by which bubbles formed from the action of the file, become unstable, collapse, and cause a vacuum like â&#x20AC;&#x2DC;implosionâ&#x20AC;&#x2122;.

The instrument including the tip should be freely movable in the canal to maintain optimum efficacy. c) for the removal of posts, fractured instruments. d) Coating the canal walls with sealer before filling.

SONICS ď&#x192; The principal sonic endodontic handpiece available today is the o Micro Mega 1500 (MM 1500) o Sonic Air Endo System -

These use compressed air at a pressure of 0.4MPa.

Impart vibrations in the frequency of between 1500 and 3000Hz.

A vibrational wave form is imparted to the file shank.

ď&#x192;¨ 3 choices of files that can be used with sonic handpieces. -

Rispi Sonic.

Shaper Sonic.

Trio sonic. Rispi

Shaper

Developed

Dr.

L.M.

Dr. Retano Spina

Lawrichesse

in Italy.

France.

Resemble rat-tail

Used

the

husky

the root canal.

broach.

blades.

cutting

Heliosonic

the

Resembles

reamer. a

barbed

Useful

for

coating the canal wall with sealers and

cutting

placing

Ca(OH)2 pastes.

blades. -

Also known as Triosonic files.

Resembles

coronal 2/3rd of

Has

apical 1/3rd.

file. -

Trio

Resembles

Disadvantages: -

Produces undulating rippled

/ canal

Most effective in

triple-helix

widening

Hedstroem file.

canal

the (than

Least effective

Rispisonic)

walls.

 All these instruments have a safe-ended non-cutting tip of 1.5-2.0mm in length.  the 150 sizes range from 15-40.  Micro-mega retropreparation tips are designed for periapical surgeries. These are available in 3 standardized lengths (#35, #45, #55) and in 2 lengths (2mm, 3mm) but these can only be used where there is an existing hole in the tooth in which to insert.  when lateral movement is stopped in the canal, a vertical movement of approx. 100µm is evident. The movement of the file shank creates a form of acoustic microstreaming with 2 areas of turbulence. One around the mid shank

other at the tip

LASERS  The use of laser is still to be approved by the U.S. food and Drug Administration. Nonetheless, the method appears promising.  Wachman was the first to suggest lasers.

Levy made use of Nd-YAG laser mounted with a fibre-optic to clean and shape the canal (Neodynium, Yttrium aluminium garnet laser)  Wavelength of 1.06µm.  The laser beam is carried through a silica fibre accompanied by a cooling system that delivers a spray of air and water.  Levy compared the laser technique with the conventional stop back procedure. Using SEM evaluation he concluded that preparation with a laser beam is possible, with an improvement in the cleanliness of the canal walls when compared to conventional techniques. Ultrasonics

Sonics

 Permit the use of either an inert  Irrigation is limited to filtered sterile or chemically active irrigant H2O as delivered through the selected by the clinician.

dental unit cooling system.

 Oscillation is transverse.

 It largely elliptical.

 Both use circumferential filing  are affordably priced. method.

 It does require setting up or special connections as it involves only a handpiece.  Chances of transportation of the canals is less. 41

INSTRUMENTS FOR SEALING THE ROOT CANAL A. Hand and Finger Held instruments i)

Several varieties of specialized endodontic pliers and forceps are available for placement of silver point and G.P. cones. The pliers generally have a tapered groove along the beak for

firmly grasping the ridged silver cone, whereas the forceps may have either grooved or serrated beaks for holding G.P. cones. Endodontic forceps differ from

common college or cotton

forceps in that they have a latch mechanism for locking the instrument in the closed position. This mechanism allows easier transfer of instrument and material from assistant to operator during treatment. ii)

Endodontic condense (pluggers) and Spreaders Are smooth tapered metal instruments used to compress and

compact the G.P. material either laterally or vertically within the prepared root canal space according to either the lateral or vertical condensation of G.P. filling technique. Spreaders

Pluggers

Have more tapered and pointed Have slunt or flat-ended tips for tips for lateral packing of the compression material

According to 150/ADA in 1990, these instruments are modeled as: No.: 15-45 for spreaders. No. 15-40 for pluggers. This new attempt to bring order out of chaos would abondan the old confusing numbering systems (1-10, D-11, D-11T, ABCD, XF, FF, F, M, FM etc.). -

Long handled spreaders / pluggers are formed of chrome-plated or stainless steel with the operative head at various angles to the shaft.

M-series plugger, spreaders are double-ended long-handled instruments that correspond to the standard sizing and taper of Ktype files and reamers.

The handles are color-coded.

A specification for spreaders and plugger is currently developed by the ANSI standard. â&#x2020;&#x201C; 5 digit no.

ď&#x192;°

The first 2 digits represent the diameter of the instrument at the tip.

ď&#x192;°

Remaining 3 digits designate the taper in hundredths of mm.

RECENT ADVANCES IN ENDODONTIC INSTRUMENTS Titanium-Based instruments Recently new alloys characterized by lower elastic modulus have developed for root canal instruments in order to overcome undesirable shaping effects especially in narrow-curved or severely curved canals. Some of these instruments use titanium and a distinction has to be made between Ni-Ti alloys and Ti-Al alloys. Ti-Al Most recently microtitane marketed by Micro-Mega have been introduced (to improve the cutting efficiency of Ni-Ti). These are titanium-based instruments and consist of about: 90% Ti. 5% Al by wt. They are available as reamers, K-files and H-files for manual use. -

The fracture resistance of Ti-Al is same as flex S.S..

Increased flexibility.

Unlike Ni-Ti â&#x20AC;&#x201C; no superelastic property.

Cutting efficiency is less than flex S.S. as they cut more on the outer surface of the canals in curved canals.

Ni-Ti History In the early 1960’s, a Ni-Ti alloy was developed by W.F. Buchler, a metallurgist investigating non-magnetic, salt-resisting, water proof alloys for the space programme at Naval Ordinance Lab, USA. The term ‘NITINOL’, an acronym suggests the elements from which the material is composed. Ni-NICKEL Ti-TITANIUM Nol –NAVAL ORDINANCE LABORATORY In dentistry, Andersen and Hilleman (1971) were first to introduce it in the field of orthodontics. Walia et al in 1988 inspired its introduction in endodontics. Advantages over S.S. -

Nitinol files have 2-3 times more elastic flexibility.

Superior # resistance in clockwise and counter clockwise torsion owing to the ductility.

Ni-Ti files can retain the shape of the curved canal and do not straighten like stainless steel.

Ni-Ti undergoes large amounts of elastic deformation when compared to S.S.

Disadvantages over S.S. -

Cutting efficiency of Nitinol is only 60% than that of matching S.S. file.

Does not give any indication of #.

Properties of Ni-Ti The alloys contain: 54% - Ni. 44% - Ti 2% or less cobalt. These alloys undergo superelastic deformation and undergo a stress inducted Martenisitic phase (close packed hexagonal phaseweaker phase) transformation from a parent structure that is Austenite (body-centred cubic lattice) â&#x20AC;&#x201C; stronger and stable phase.

On release of stress, the structure reverts back to Austenite. Austenite â&#x20AC;&#x201C; Martensitic --> Austenite.

Features of Ni-Ti a) Shape memory -

The ability of the material to revert back to its original shape.

The transition temperature is lowered by adding Co and increasing the content of Ni.

The application of shape memory in endodontology is to remove any deformations within the Ni-Ti instruments by heating them above 125째C.

b) Super/Pseudo elasticity -

When stresses are induced on Ni-Ti, there is a stress-induced formation of martensitic phase. This reverts immediately to austenitic as soon as the stresses are removed. This process elicits a springy (rubber-like) elastic property to the material --> Pseudoelasticity.

Ni-Ti files are machined rather than twisted. It is known that grinding of Ni-based alloys difficult. This leads

to structural defects especially at the cutting edges of Ni-Ti. Some authors have found that the cutting edges of Ni-Ti show irregularities, structural defects or metal flast due to the manufacturing grinding

process. This was thought to be responsible for their relatively low cutting efficiency. Recently Maillefer Co. introduced the Nitiflex-K-file. -

Union Broach.

Onyx-R-file. These 2 instruments have proved to be superior to other Ni-Ti

instruments. Topic of controversy -

Schafer has demonstrated that one cycle of steam sterilization or autoclave is enough to produce a significant decrease in the cutting efficiency of Ni-Ti K-files.

On the other hand, neither 10 cycles of autoclaving nor steam sterilization causes a reduction in the cutting efficiency of S.S. instruments.

Ideal Requirements and Features of Ni-Ti Instruments a) Cutting angle -

If slightly +ve, results in an effective cutting action.

If too much +ve, the blade becomes engaged into the surface excessively and binds without forming chips.

A â&#x20AC;&#x201C;ve angle will scrape the dentin rather than cutting it.

b) Flute design -

A progressively larger flute space, distance to the blade is preferred so as to avoid any compaction of debris and also provides an effective channel for its removal.

c) Radial land -

Gives more mass to the cutting edge thus preventing crack formation and helps in deflecting the instrument around the curvature.

d) Frictional Resistance -

A small marginal land area is required and the remaining radial land is recessed thus decreasing the peripheral surface.

A wide land can result in frictional resistance.

e) Notch -

If the notch is too close to the cutting edge, stresses will tend to concentrate on the notch e.g. is H-file that will lead to crack formation to ideally it should be away from the cutting edge.

f) Working surface/taper (Santa Claus principle) -

We decrease the surface of the instrument coming to contact with the canal by giving greater taper and as a result, all the forces get concentrated in a smaller area leading to better cutting. 49

g) Non-cutting tip (Pilot tip) -

In cases of canals of severe curvature.

Ni-Ti Rotary Instruments -

Profile series 29 followed by profile with ISO series.

Quantec 2000 followed by Quantec LX, SC tips and Q Flare series.

HERO 642.

Light speed.

Profile Family I] 29 series a) Hand instruments â&#x20AC;&#x201C; 0.02 taper. b) Rotary instruments â&#x20AC;&#x201C; 0.04, 0.06 taper II] ISO series a) 0.04 and 0.06 ISO rotary instruments (also available as hand instruments). III] Profile Orifice shaper 0.05-0.08 taper IV] Profile GT rotary instruments (also available as hand files) I a) Profile 29 series with 0.02 taper -

Introduced by Stephen Buchanan.

Available in both S.S. and Ni-Ti instruments. 50

Resemble the original engine driven Ni-Ti, â&#x20AC;&#x2DC;Uâ&#x20AC;&#x2122; files.

Have a constitution 29% increase in tip diameter.

All of them have a narrow 0.2% taper.

Advantages: 1) 8 files replace the 11 files of the traditional ISO sizes 1060. 2) These instruments are spread with more instruments at smaller sizes and less instruments at the larger sizes. 3) Transition between sizes is enhanced due to greater and gradual increase in diameter. 4) Come in total of 13 instruments instead of ISO 21 instruments. b) Profile series 29 with 0.04 and 0.06 Rotary Type: -

These instruments were manufactured in order to have an added advantage of greater taper.

Have an increase of 29% in the tip diameter to make instrumentation easier.

Prevent procedural errors. (The standard ISO are manufacture with a constituent

0.05/0.1mm of the width at the tip between each instrument e.g. the 51

difference in the area of cross-section of ISO size 10 and 15 is 50% whereas between 55 and 60-9% only. That is why instrumentation with the change over of instruments between 15 and 20 or 20 and 25 is generally difficult but is easier between 35-40 or instruments higher in size). Disadvantages: -

Fewer instruments as the size increases thus causing more deformations.

c) Profile 0.04 and 0.06 of variable Taper Rotary Instruments -

Have radial land which has a â&#x20AC;&#x2DC;Uâ&#x20AC;&#x2122; shaped flute and helps in lifting the debris coronally.

Has a safety tip design with minimum transitional angle to prevent ledging and transporting.

Can be used more efficiently around curved canals allowing the creation of a tapered preparation.

0.06 Taper -

Taper is 6%

Length 0.21 and 25mm

No. available : 15 to 40.

Use: -

For preparing the middle portion of the canal.

Carries 2 coloured rings on the shank (identification).

McXIM Series (Mity files) (IEJ, 2000) -

are a series of Ni-Ti rotary instruments available in 5 different tapers and 4 designs.

Tapers --> 0.3, 0.4, 0.045, 0.05 and 0.055 all with identical tip size 25. -

have flattened radial land and non-cutting tips.

4 different blade designs.

a) u-type. b) Hedstroem with progressive radial lands. c) 0.02 tapers with equal radial lands throughout their lengths. d) With dissimilar helical angles to permit widening at the apex and preferential side cutting. 0.04 Taper -

Taper is i) 4%

Length ii) 21, 25 and 31mm

No.â&#x20AC;&#x2122;s available â&#x20AC;&#x201C; 15-90 (15, 20, 25, 30, 35, 40, 45, 60, 90).

Also available as hand instruments.

Carries a single coloured ring on the shank.

Use: -

For preparing the terminal part of the canal.

Advantages: This instrument is much wider at D3 (end of the cutting part of the instrument towards the handle). Therefore gives the necessary coronal flare to the root canal automatically. -

the tip is bullet-nosed.

Used in a 6:1 gear-reduction hand-piece at an rpm of 150-350.

Prepares the root canal with a 3-D effect.

d) Profile O.S. Use: -

are used for preparing the coronal section of the canal and also for removing G.P. and sealer before inserting the post.

RCT of milk teeth.

Identification: 3 coloured rings on the shank. -

These instruments replaced the G.G.D. They shown to be more effective in preparing the coronal portion when compared with GGD, as the non-cutting tip of the instrument opens the coronal area with more control than GGD. 54

They operate at very slow speed of 350 rpm thus assuring safe handling.

The u-file radial landed flute design keeps the instrument centred.

e) New profile greater taper rotary instrument (GT) New generation of endodontic instruments. -

Lets negotiation even in the most severely curved canals with less risk of apical transporting, ledging or perforating.

Variable pitched flutes provide reamer like efficiency.

f) GT Range -

All have gold plated shanks.

Have flat outer edges with a patented 16-section designed to prevent screwing of the instrument in the canal.

3 types identifiable by coloured rings on the shanks.

Are said to impart predetermined shapes to the root canal preparation.

GT Rotary

GT Rotary 0.04 File

GT Accessory files

Taper is 6-12%

Taper is 4%

Taper is 12%.

Length: 21 and

21, 25 and 31

21 & 25mm

diameter 35, 50

25mm -

4 in no. all have

ISO size at the tip

i.e.

sizes. -

and 70mm -

Used

for

used in the final phases

preparation

The

sleepest

the terminal part

obtain a more

taper is used first

of the root canal.

tapered

Identified by one

portion.

technique.

ring

0.06 --> narrow

shank.

curved canals. -

20-35

D1=0.2mm

for crown down

No.â&#x20AC;&#x2122;s

0.08

smaller

most roots

like mesial roots of

mandibular

molars.

the

Used canals.

coronal

large

II] Quantec 2000 Series -

Introduced by McSpadden.

The original Quantec 2000 series had a 90°-tip. This sharp tip appears to predispose to problems like zips, elbows and perforations. So, they were replaced. 

QLX Non-cutting.



QSE safe-cutting tip with (60°).

Quantec Endodontic File Flute Design -

Have a +ve cutting blade angle, as a result the dentin is cut rather than scraped.

Ideal helical angle.

Channels debris out of the canal quickly and efficiently.

Peripheral structure was increased along with its cone structure.

Radial lands adds support and also prevents stress cracks in the flutes cutting edges.

Available in graduating tapers from 0.02-0.06.

Tip Design

SC-safe cutting. LX-non-cutting

SC -

Cuts as it moves apically.

Ideal for: -

Small tight canals.

Narrow curvatures in tight spaces.

Calcified canals.

Constricted / obliterated canals.

LX -

Non-cutting tip, which maintains a central-axis.

Deflects around severe curvatures.

Ideal for: -

Severe curvatures.

Enlargement of mid-root and coronal aspect.

Delicate apical regions.

Advances in Micromotor a) Quantec ETM (Electric Torque Control Motor) -

Helps to provide a smooth feel and tactile response, i.e. essential for success.

b) Quantec E (Irrigation System) -

Helps to provide a constant irrigation flow directly over the rotating file.

Speed in 340 rpm.

III] HERO 642 -

Introduced by Daryl Green

Is a micromega instrument which is made from Ni-Ti alloy.

HERO 642 means. H

– High.

– Elasticity.

– Rotation.

642 – available in tapers of 0.06, 0.04 and 0.02. -

Used in a special contra angled handpieces at 300-600 rpm.

Are modified Micromega Helifiles.

3 tapers 6% - Sizes 20, 25, 30 opening.

- Used for the initial orifice

Length 21 and 25mm 4%

Orifice opening

- Sizes 20, 25 and 30

- Used 2mm short of the W.L.

Length 21, 25 and 29mm 2%

the W.L.

- Sizes 20, 25, 30, 35, 40 & 45

- Used till the full W.L.

Length 21, 25 and 29mm

And additional 0.02 tapers in sizes 35 and 40.

These instruments have a Triple Helix Geometry -

3 cutting edges for cutting in curette effect.

No radial land so no packing of smear layer.

An inactive tip.

Progressive pitch.

Disadvantages: -

Lacks adequate taper of the canal.

IV] LIGHT SPEED -

Is an engine driven version of the Ni-Ti can Master â&#x20AC;&#x2DC;Uâ&#x20AC;&#x2122;.

Resembles the GGD and are used in low speed handpieces 13002000 rpm (10:1 gear reduction).

Flexible non-cutting shaft with length markings on the instrument. The no.s indicate the length of the instrument from the tip 21, 25 and 31 mm in length.

Non-cutting pilot tip. This helps to keep the instrument within the canal and avoid ledging.

The instrument is also available in half-sizes, which is identified by a double ring on the handle or a dot on the end of the handle.

Available in sizes from 20-100 with intermediate sizes present in between 20-60. 60

Cutting tips vary in length from 0.25mm for size 20 to 1.75mm for size 100 [ 20, 22.5, 25, 27.5, 30, 32.5, 35, 37.5, 40, 42.5, 45, 47.5, 50, 52.5, 55, 57.5, 60, 65, 70, 80, 90, 100].

MAR -

Master apical rotary.

Is the smallest light speed used for instrumentation in the apical part of the canal.

Points to be kept in mind using Ni-Ti -

Always irrigate (as smear layer is accentuated with use of Ni-Ti).

(each Ni-Ti) - Used approx. for 700 rotations or 6-10 RCT’s. - 5% NaOcl cause corrosion. - Fracture resistance of Ni-Ti is unaffected by prolonged exposure to NaOcl. Disadvantages of Ni-Ti Rotary  Apical zip/tear drop transportations. -

Defined as an irregular widened area created by the master apical file near the end point of the preparation.

 Elbows -

Occurred with apical zip and formed a narrower region more coronally. 61

 Ledges -

Are irregular areas created by more removal of the dentin from the outer aspect of the curved portion.

Narrower region coronally.

 Perforations -

Occurs as separate and distinct false canals not continuous with the original canal.

 Danger zones -

Is the area coronal to the elbow where excess dentin has been removed from the inner aspect of the curve.

Transportation External -

Caused by failing to precurve instruments while using larger instruments.

Apical foramen is torn and given an hour glass shape.

2nd type is worn and also gives an hour-glass shape.

Usually begins as a ledge

Internal

- Occurs when the portal of exit is moved internal to its external position by blocking position by blocking the canal with dentin mud. This results in a new false path.

Conclusion -

The evolution of endodontic instrumentation is an ongoing process in which the benefits are continuously being refined.

A successful clinician must have the tools of understanding consistency and accuracy can also be attained three practices and observation.