RECENT ADVANCES IN ENDODONTIC INSTRUMENTS

Introduction

Endodontic treatment is based on the principles of – Debridement,

Sterilization and obturation of the root canal system.

Careful cavity preparation, can preparation and canal obturation are

the keystones to successful root canal therapy which are dependent

on complete removal of

- Pulp tissues

- Pulp remnants

- Bacteria

- Bacterial components from pulp space.

The factors which defect these are –

- Type of instrument used

- Material

- Techniques

- Operators skill

History:

Before 1958, endodontic instruments were manufactured without

benefit of any established criteria. There was little uniformity in

quality control of manufacturer.

Earlier for the manufacturer of root canal instruments, the primary

forms was mainly on 2 materials

1. Carbon Steel.

2. Stainless steel.

Carbon Steel – instrument was usually produced by grinding

graduated sizes of round piano wire into square or triangular

configuration. It was a very hard material.

Stainless steel instrument was resilient and ductile than carbon steel.

These wires are ground along its long axis into a 4 sided (square

cross section) or 3 sided (Triangular cross section) tapered shaft that

is twisted into each blade of a similar sized instrument determines

whether that instrument is a reamer having less flutes or a file having

more flutes. The cutting efficiency of these material is more as

compared to other materials. But it also has limitations like – distorts

faster, Fractures, problems with precurving in highly curved canals.

Due to these drawbacks or limitations Titanium was introduced.

Titanium is a flexible material with favourable properties for an ideal

instrument design.

Titanium along with Nickel forms a still better material than others.

Titanium with Fluminium is also introduced which I would be

discussing later in recent advances.

Classification of Instruments

I. All to Grossman

a) Exploring instruments

i.e. to locate the canal orifice and determine its patency.

Endodontic explorers

Smooth broaches

b) Debriding instruments

i.e. intirpate the pulp and remove any foreign debris.

- Barbed broaches

c) Shaping instruments

i.e. the shape the root canal laterally and apically.

- Reamers

- Files

d) Obturating instruments

i.e. to cement and park gutta-percha into the root canal

- Spreaders

- Pluggers

- Lentuth – spirals

AUTOMATED ROOT CANAL PREPARATION DEVICES

If used in collaboration with hand instruments most of the devices

can same as useful adjustments in root canal preparation. Danger

zones, apical preparation and narrow curved canals are difficult to be

treated by engine driven root canal instruments.

Advantages

- It is easy to use.

- Saves time.

- Ideal preparation of RC

- Reduction in fatigue (overall strain becomes less and fatigue is

led).

- Reduction is treatment time which depends on the tooth to be

treated to be treated and expertise of clinicians.

Limitations:

- They can be used only after manual early phase of treatment

carried out.

- These can be used only after the completion of preparation of

canals using ISO size no. 15.

- There is lack of tactile sensation.

They can be generally classified as

1) Reciprocal

2) Rotary

3) Ultrasonic

4) Sonics.

ISO Groups II and III:

Engine driven instruments can be used in 3 types of contrangled

handpieces:

- Full 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

instruments is stressed.

Au to Stock:

- They can be classified au to the type of movement imported 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:

1) To develop coronal access to canal orifice do not bend.

2) To wider as much as 2/3 r d or canals.

3) To prepare post channels for final restorations.

As these instruments do not bend they should be used in slow

speed handpieces.

Example:

- Medidenta gear reduction handpiece

- Sensomatic handpiece.

Where, the torque is controlled and speed is reduced to as much as

10 RMP.

The most popular engine – driven instruments are:

- Gates – Glidden

- Reso reamers

- Nitimac

- Orifice opener

- Canal master U

- McSpadden Engine file

Gates – Glidden Drills:

- Made of hardened carbon steel.

- It has a long, thin shaft ending in a flame shaped head with a

safe tip to guard against perforations

Uses:

For initial opening of canal orifice.

For deepest penetration in both straight and curved

canals.

To remove the lingual shoulder in anterior teeth.

- The flame shaped head cuts laterally and is used with gentle,

apically directed pressure.

- They are inflexible therefore the instrument was designed to

have a weak spot in the part of the shaft closest to the

handpiece, so that if the instrument separates the separated part

can be easily removed.

- They come in sizes 1-6 which are ISO standard.

GGD 0.5, 0.7, 0.9, 1.10; 1.30, 1.50

Dia-in mm 1 2 3 4 5 6

Peeso Reamers:

- Made of hardened carbon steel.

- These have long sharp flutes.

- These are also flame shaped.

- Sharper cutting edge, cuts laterally.

- More efficient.

Uses:

1) Used in preparing coronal part of root canal for post and core.

2) To remove gutta-percha.

Sizes 1-6

Diameters in mm 0.7, 0.9, 1.10, 1.30, 1.50, 1.70

1 2 3 4 5 6

Disadvantage:

- These instruments corrode easily.

- Inflexible.

McSpadden Engine File:

- Designed to be used in rotary instrument.

- NiTiMAC – a new gear reduction handpiece (NT company

USA) is used which runs at 300rpm.

- Also Sensomatic Handpiece can be used.

- 2 different types of NiTi files have been designed.

Sensory files NiTixl files

- Redesigned H-type instrument - U-type configuration made

from Ni-Ti. - Now called NT-power

files. - Are the finishing files.

Advantages

Flexible

Resistance to fracture

- These files are manufactured with a affective tip that facilitates

negotiating around curvatures and ledges.

Orifice Opener:

- Martin has developed an orifice opener used to flare and

prepare the cervical and middle portions of the canal.

- Used in slow speed latch type handpiece.

- Comes in sizes 25-70.

- This M series of openers are more flexible than GGD.

Canal Master System

- Introduced by Widley and Senia.

- As discussed before in hand instruments these are K-style

modifications with a engine driven system.

These are same with a latch type to be used in engine.

II. RECIPROCAL

- This uses a special handpiece which contra-rotates the

instrument, through 90° 3000 times / min (quarter-turn

motion).

- These were introduced in 1899 by Rollins.

- These may be classified depending on the direction of

movement that they import.

Rotary Vertical (Push-pull)

- Giromatic- Kerr M4- Endo cursor

- Canal finder system- Intra endo 3LDSV- Endolift

Giromatic:

- Introduced in 1964

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

Giro pointer (orifice opener 16mm)

Giro broach

Giro file (H-file configuration)

Giro reamer

Heligirofile (3 cutting blades in C-S)

Au to Weine:

Giromatic produced wider apical deviations (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 endo

instrument.

- Used at 1500 rpm.

- Safely H-files are used with this handpiece.

Disadvantages

1) Causes frequent breakage of instrument.

2) Creates hour-glass preparation, ledges zips, and strip

perforations.

Canal Finder System

- It was developed in France.

- It is a specialized handpiece with a vertical movement of 0.3 to

1mm + a free rotation a movement (1/4 turn)

If there is no resistance in the canal the instrument

moves upto 1mm.

In cases of minimal resistance it moves 0.3mm.

In severe resistance it stops.

Increasing the vertical pressure will stop the

vertical movement.

- The free rotational movement allows the tip of the instrument

to more away from an obstruction in the root canal wall.

- A file / K-files either made of stainless steel / Ni-Ti can be

used.

- The cutting instruments are specially designed as they have 40°

helical angle more pronounced cutting and better debridement

as discussed earlier.

- The clinical research associates described it as “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 :

- Shaping the canal.

- Retreatment of root canals containing gutta-percha.

Canal Leader:

- Is a modified speed reducing handpiece

- Has a vertical movement and of 0.4 – 0.8mm and contra-

rotational movement which is restricted to 30°.

- Three cutting instruments are available:

K-file with safe ended tip for narrow C.

More aggressive H-file.

A universal file which is flexible H-file with safe

ended tip.

Intra Endo 3-LDSV:

- It is a easier – type handpiece.

- Is a look-alike of the canal finder system.

- Apart from up and down movement, it can import full turn

movement when axial pressure is applied.

- The vertical movement is in range of 0.4mm.

- It can make use of conventional reamer and H-file.

Endo Lift (Kerr):

- Is also a look-alike of canal finder system.

Excalibur

- Produces a random lateral vibratory motion.

- It vibrates only laterally and is derived of vertical movement.

- The amplitude of movement is 1.5 – 2mm.

- K-files are used at 20,000 – 25000 rpm.

- This device may be classified as a subsonic instrument

(oscillates at 1000-2000 frequency/sec).

Disadvantages:

- Due to its effective cutting ability it may remove excessive

dentin.

- Tends to straighten the canals or causes strip perforations.

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.

- It imports sinusoidal vibrations of high intensity to root canal

instrumentation in the range which is above that of audible

perception.

- The main debriding action was thought to be by cavitation.

Originally introduced to endodontics by Richman in 1957, it was

further developed by Howard, Martin and Walter Cunningham in

1976.

Intereslingly, ultrasonics was intended by them to be used as a root

canal sterilizing device.

There are 2 methods of generating ultrasoncis oscillations in the file

shank.

Magnetostrictive Peizo-electric

- Requires water cooling i.e.

if NaOCl is used as an

irrigant, the water must be

led away from the stack via

additional tubing. This

makes the handpiece both

clumsy and expensive

- More powerful.

- Does not require water-

cooling.

Disadvantages: Apical widening

ledges in curved canals.

Eg. : ENAC, Neosonic Miniendo

(30,000 – 35000 KHz)

- Produces tapered canal eg:

Cavi Endo (25,000 Hertz)

2 types of files are used:

1) Both use K-file

2) Diamond impregnated file for the straight part of the canal.

Advantages;

1) Cleaning of root canal due to aroustic streaming (turbulence

along the shank of the file when immersed in a fluid).

2) Causes less extrusion of root canal debris into periapex.

10-15 number files should be used as they are most flexible and

therefore causes less ledges.

Uses:

a) As a root canal shaping device.

b) As a debriding device by cavitation process i.e. a process

by which bubbles formed from action of file become

unstable, collapse and cause a vacuum like ‘implosion’.

c) To remove posts or fracture instruments.

d) To coat the canal wall with sealer.

IV. SONICS

- The principal sonic endodontic handpiece available today is the

Micro mega 1500 (MM1500).

Sonic Air Endo System.

- These use compressed air at a pressure of 0.4MPa.

- They impart vibration in the frequency of 1500-3000 Hz.

- A vibrational wave form is imported to the file shank.

- 3 choices of files that can be used with sonic handpieces are:

Rispi sonic

Shaper sonic

Trio sonic

- All these instruments have a safe ended non-cutting tip of 1.5 –

2.0mm in length.

- The ISO size range from 15-40.

Rispi Shaper Trio- Dev by Dr.

Retano Spina in Italy

- by Dr. L.M. Laurichesse in France.

- also known as heliosonic or triosonic.

- Resembles rat tail file

-

- Resembles hirsky barbed broach.

- Resembles a reamer or tipple helire H-file

- Used in coronal 2/3 r d of root canal

- Used in apical third (1/3 r d)

- for coating sealers and placing Ca(OH) 2 paste.

- 8 cutting blades-

- 16 cutting blades

- Produces undulating / rippled canal wall

- most effective in widening than canals (than respisonic)

- least effective

Micromega Retroprep :

- Tips are designed for periapical surgeries, these are available in

3 standardized members (#35, #45, #55) and in 3 lengths (2mm,

3mm) but these can only by used where there is an existing hole

in the tooth in which it insert.

- When lateral movement is stopped in the canal a vertical movement of approx

100ml is evident. The movement of the file shank creates a form of acoustic

microstreaming with 2 areas of turbulence – one around the midshank; other cut

the tip.

Ultrasonics Sonics

Permits use of either an inert,

sterile or chemically active

irrigant selected by clinician

(NaOCl).

Irrigation in limited to filtered

H2O as delivered through the

dental unit cooling system.

Oscillations are transverse It is elliptical

It requires a setting up or special

connection as it involves only a

handpiece.

Circumferential filing Circumferential filing

Frequency 20,000-25000/sec 1500-6500 cycles/min.

LASERS

- The use of lasers is still to be approved by the US food and

drug administration. Nonetheless the method appears

promising.

- Wachman was the first be suggest lasers.

- Levy made use of Nd:YAG laser mounted with fibre-optic to

clean and shape the canal.

- Wavelengths of 1.06m was used.

- The laser beam is carried through a silica fibre accompanied by

a cooling system that delivers a spray of air and water.

- Leavy compared the laser preparation. Using SEM evaluation

he concluded that preparation with a laser beam is opossible

with an improvement in the cleanliness of canal walls when

compared to conventional techniques.

MCXIM Series (Mity files) (IEJ, 2000)

- Are a series of Ni-Ti rotary instruments available in 5 different

tapers and 4 designs.

Tapers 0.03, 0.04, 0.045, 0.5 and 0.055 all with identical tip

size 25.

- Have flattened radial land a non-cutting tips.

- 4 different blade design.

a) U type

b) H with progressive radial with dissimilar helical L’s to

permit widening at the apex and preferential side cutting.

c) 0.02 tapers with equal radial lands utmost their lengths.

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 GP 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 lacking the

instrument in the closed position. This mechanism allows easier

transfer of and instrument and material from assistant to

operator during treatment.

(ii) Endodontic condenses (pluggers) and spreaders

- Are smooth 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 techniques.

Spreaders Pluggers

Have more tapered and pointed

tips for lateral packing of the

material

Have slunt or flat ended tips for

compression

According to the ISO/ADA in 1990, these instruments are modeled as

No. 15-45 for spreaders

No. 15-140 for pluggers

This new attempt to bring order out of chaos would abondon 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 operative head at various Ls to the shaft.

- M-series plugger, spreader are double-ended long-handled

instruments that correspond to the standard sizing and taper of

K-type files and reamers.

- The handles are color coded.

- A specification for spreaders and plugger is currently

developed by the ANSI standard.

5 digit no. the first 2 digits represent the diameter of the

instruments at the tip.

remaining 3 digits designate the taper in hundredths of mm.