Rotary Canal Preparation

Dr. Ebtissam Al-Madi

1Al-Madi, 491 Den

Outline• Objectives of Cleaning & Shaping

– Biological

– Clinical

– Mechanical

• Instrumentation Techniques– Stepback technique

– Crowndown technique

– Rotary Instrumentation

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• Biological Objectives – Removal of all tissue, bacteria and bacterial

products and substrates from the root canal system

• Mechanical– Shaping of the root canal system to

facilitate placement of a root canal filling

• Clinical– Eliminate apical periodontitis and return

tooth to normal function3Al-Madi, 491 Den

Cleaning

Shaping Filling

Endodontic

Triad

Shaping to facilitate cleaning and Filling

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Access

Preparation

Cleaning & Shaping

of the canal

Obturation

Restoration

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Stepback

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Stepback Technique (1960’s)

• The most widely used preparation technique

• Replaced Non-tapering Preparation technique

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Stepback Technique• Apical Preparation:

1. Establish access (straight line)

2. Establish working length

3. File Instrument (watch-winding, file, ream, etc)

4. Place next larger file, instrument, and repeat till you reach file 3-4 sizes larger (MAF)

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Stepback Technique

• Step back:1. Place next larger file to a

length 1 mm shorter of working length, file, irrigate and recapitulate

2. Repeat process with successively larger files at 1 mm increments shorter than preceding file.

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Stepback Technique• Variations to the classic stepback

technique– Initially enlarge coronal aspect with GG

burs

– Complete coronal preparation with GG burs

– Use of small GG burs in mid-root level

– Use of Hedstrom files to flare the preparation

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Stepback technique• Advantages

– Minimize procedural errors (transportation, ledging, apical perforation)

• Disadvantages– Significant apical

extrusion of debris (post-operative pain)

– Apical blockage

– Canal deviation

– Alteration of working length

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Crown down

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Crowndown Technique

• More recent technique

• Produce similar result to step-back

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Crowndown technique• Development of straight-line access• Eliminate pulp chamber obstructions

and check patency• GG enlargement with size 4-3-2,

irrigate• Coronal to mid root enlargement with

instruments from large to small, irrigate

• Establish working length, irrigate• Introduce progressively smaller files

deeper into the canal until resistance is encountered

• Establish apical preparation size• Complete preparation 14Al-Madi, 491 Den

Crowndown technique• Variations to the classic crowndown

technique– Crown-down pressure-less technique

– Roane technique

– Double flare technique

– Modified double flare technique

– Rotary Instrumentation

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Crowndown technique• Advantages

– Reduce apical extrusion (reduce pain)

– Elimination coronal interferences

– Improved irrigation to apical part of canal

– Facilitate working length determination

• Disadvantages– Early blockage of

canal

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Instruments

Hand Instruments

Rotary Instruments

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Hand instruments• Been in use for over 100

years

• Still integral part of cleaning & shaping

• Better tactile sensation

• ISO standardization

• Broaches, k-files, Flex-R files, NiTi files, H-files

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Hand engine driven• Properties of NiTi Alloy

– Superelasticity

– High resistance to cyclic fatigue

• Series 29

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Rotary Files• Advantages

– Less transportation and ledging

– Shape canal uniformly

– Reduced operator fatigue

– Improved efficiency

• Disadvantages– Cannot be used in

some cases– Buildup of debris– Cannot use beyond

apical foramen– Fracture can occur

suddenly– Initial cost– Loss of tactile

sensation

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Rotary Instruments• Lightspeed

• Profile

• Hero

• Quantec

• K3

• Flexmaster

• GT

• Protaper

• Sequence

• RaCe

• V-taper

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Design characteristics• Non-cutting vs cutting

tip

• Tip size

• Taper

• Cross section

• Rake angle

• Helix angle

• Pitch

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• Tip could be

non-cutting,

cutting

Tip shape

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Tip Size

• Can be the same as ISO hand tips sizes- color coded accordingly

• Can be half sizes (12.5, 17.5, etc) as in Light Speed.

• Can skip sizes ( only 20,30, 40) as in GT rotary

• Can be nonspecific sizes (according to percentages ex. 18.5, 20..) as in ProTaper.

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Taper ranges from 0.02 to 0.12

Tip Taper

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• Constant taper- Variable tip

– Hand files (0.02)

– Profile 0.04

• Graduating taper- constant tip size

– GT series

– Quantec

• Varying taper- different tip sizes– ProTaper

Tip Taper

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Cross section- Radial Lands

A radial land is a surface that projects axially from the central axis, between flutes, as far as the cutting edge

Non-cutting tips and radial lands keeps a file centered in the canal.

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Increased radial land

increases peripheral

strength behind the

cutting blade

Smaller radial land

equals decreased

strength for blade

support

Cross section- Radial Lands

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Rake Angle

The rake angle is the angle formed by the cutting edge and a cross section taken perpendicular to the long axis of the instrument

Rake angles affect the cutting efficiency and the aggressiveness of the file

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Overly Positive Rake Angle

Positive Rake Angle

Neutral Rake Angle

Negative Rake Angle

Rake Angle

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• As the flute angle is increased more debris can be carried away from canal.

Helical flute angles

The helical angle is the angle that the cutting edge makes with the long axis of the file

• Constant helical flute angles allow debris to accumulate and are more susceptible to the effect of “screwing in” forces.

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Pitch

Pitch is the number of spirals or threads per unit length.

Constant pitch and constant helical angles produce a “pulling” or “sucking down into” the canal.

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Lightspeed (Senia & Wildey 1990’s)

• Long, thin non-cutting shaft

• U shape design

• Most flexible RI

• Low incidence of transportation, preparation errors, and loss of working length

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Profile (Ben Johnson 1994)

• Increased taper

• Began as series 29 #0.02 taper, then #0.04 and 0.06 tapers

• Profile (maillefer-Europe) manufactured tips similar to ISO

• Negative rake angle

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• Coronally pre-enlarge

• Use of Orifice shapers

• Alternative use of #.04 and #.06 tapers as well as alternate tip sizes

• Same basic technique for similarly designed files

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Profile41Al-Madi, 491 Den

Profile

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K3 (McSpadden)

• Predecessors:

Quantec

• Unique cross sectional design with +ve rake angle, 3 wide radial lands, peripheral blade relief

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ProTaper(Cliff Ruddle, John West, Pierre Matchou)

• Only 6 instruments

• Modified k file with no radial lands

• Varying taper that increase coronally in shaping files and opposite in finishing files

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ProTaper52Al-Madi, 491 Den

Hybrid technique• Instruments can be used in a manner that

promotes their individual strengths and avoids their weaknesses

• Hand instruments secure a patent glide path

• Tapered rotary instruments efficiently enlarge coronal canal areas

• Less tapered instruments allow additional apical enlargement

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Newer Rotary Instruments?

• Light Speed

• Hero 642

• GT files

• Quantec

• Flexmaster

• RaCe

• V-Taper

• Endo Sequence

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More information• Pathways of the Pulp 9th e-edition• Endodontics- Ingle 5th CD editon• Advanced Endodontics- Rhodes• Endodontics- Stock• JOE• IEJ• Company brochures & Videos• Internet

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How & Where to learn?• Read & understand the brochure-

Don't be fooled!• Read the literature in textbooks and

journals- Be an informed consumer.• Try on extracted teeth till you

master the technique- try before you buy.

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