Virginia Technique

Endodontic Instrumentation Endodontic Instrumentation Endodontic Instrumentation Endodontic Instrumentation With the Virginia TechniqueWith the Virginia TechniqueWith the Virginia TechniqueWith the Virginia Technique

Frederick R. Liewehr, DDS, MS

Root Canal Instrumentation

Aim

After instrumentation the root canal space should be free of bacteria.

This should be achieved without excessively weakening the root or affecting the ability to adequately

restore the tooth.

Early endodontic access preparation

(No longer practiced at VCU)

Goerig "Step-down" technique

• Flaring the coronal portion of canal before instrumenting to apex

• Allows deeper penetration of the irrigant

• Eliminates coronal interferences with the files

Christie WH, Peikoff MD. Conservative treatment of apical foramen. J Canad Dent Assn 1980;3:187

Goerig "Step-down" technique

• Reduces canal curvatures allowing straighter access to the apex

• Removes the bulk of radicular tissue without penetrating apex

• Ideal emergency treatment

Initial opening• Traditional openings were too small, in the wrong

areas• Canals were missed• Tooth structure misdirected files

Ingle JI, Beveridge EE. Endodontics 2nd Ed.

Let the tooth dictate your access –Simply enlarge access to match pulp chamber

Messing JJ, Stock CJR. A Colour Atalas of Endodontics

Access improved

Traditional anterior cingulum access


Frequent result – perforation!


Missed lingual canal


Again - simply enlarge access to match pulp chamber

Again - simply enlarge access to match pulp chamber

Messing JJ, Stock CJR. A Colour Atalas of Endodontics

Access improved

Initial openingNeed straight-line access to the apical 1/3


File types and File types and File types and File types and techniquestechniquestechniquestechniques

Stainless Steel K-Files• Square blank twisted to produce the

spiral shaped cutting edges• Flexible in small sizes• Stiffness increases rapidly in larger

sizes• Can be pre-curved

• Excellent for pathfinding, bypassing obstructions and dealing with procedural accidents

•Can cause transportation and perfs

• Square blank twisted to produce the spiral shaped cutting edges

• Flexible in small sizes• Stiffness increases rapidly in larger

sizes• Can be pre-curved

• Excellent for pathfinding, bypassing obstructions and dealing with procedural accidents

•Can cause transportation and perfs

Stainless Steel Hedstrom Files

• Round blank cut to produce very sharp cutting edges

• Very aggressive, fast dentin removal• Must NEVER be twisted into canal• Insert and cut by pulling outward• Somewhat less strong than K-files due to

cut edges

• Round blank cut to produce very sharp cutting edges

• Very aggressive, fast dentin removal• Must NEVER be twisted into canal• Insert and cut by pulling outward• Somewhat less strong than K-files due to

cut edges

Nickel Titanium Files•Increased flexibility•Conforms to canal curvature•Memory – straight!•Cannot precurve•Too flexible for pathfinding,

bypassing obstacles, etc.

• Increased flexibility•Conforms to canal curvature•Memory – straight!•Cannot precurve•Too flexible for pathfinding,

bypassing obstacles, etc.

Stainless Steel K-File

Kink

Nickel Titanium

No kink

This can be good or bad, depending on what you are

trying to accomplish• If you are instrumenting a canal,

the file tends to stay centered –good…

• If you are trying to bypass an instrument or ledge, the file tends to stay centered – bad!

Taper

No, this is not crown and bridge!

What is Taper?

0.96 mm diameter increase

0.02 taper

D16

0.06 taper

0.32 mm diameter increase

D16 D1

D1

Taper is expressed in mm diameter increase per mm length

How much is enough?

• Schilder said we need to develop a continuously tapering form for debridement and resistance form

• Black’s principles, modified by Ingle and Bakland, said our form must be dictated by the internal anatomy of the canal

• Some canals do NOT have a continuously tapering form

• So, the taper we select must match the anatomy of the canal.

Some canals have a lot of taper…

1

2

3

4

5

6

7

8

1mm 40

2mm 60 .20

3mm 100 .40

4mm 110 .10

5mm 100 -.10

6mm 110 .10

7mm 130 .20

8mm 150 .20

Distance from Size Taperapex

Average taper = 0.157 mm/mm

Some canals have very little

1mm 30

2mm 30 0

3mm 30 0

4mm 30 0

5mm 30 0

6mm 35 .05

7mm 45 .10

8mm 55 .10

9mm 60 .05

10mm 50 -.10

Distance from Size Taperapex

Average taper = 0.027 mm/mm

Files tend to bind and cut coronally, where they are largest, and not apically where we think they are binding, leaving the coronal

portion overinstrumented and weak, and the apical portion underinstrumented and

infected.

The problem with excessive taper

Binds here

Not here

All files with a long cutting edge exhibit taper, and the modern trend is to more and

more taper. This, however, is not appropriate for all canals. For those canals a non-tapered (LightSpeed), or minimally tapered (0.02) file

must be used

The problem with excessive taper

Misconception about Ni-Ti• “Superflexibility” somehow negates

characteristics of other metals– Increasing size -> increasing stiffness– Increasing taper -> increasing stiffness

• Reality – There is no magic!

Do those look flexible to you?

How do we create taper if we don’t use very tapered instruments?

Step - Back Technique

By increasing file size in “steps” of 1mm as you “back out” coronally

Taper = 0.05

Proper taper

• The appropriate taper for a canal is that which it had initially

• Occasionally we have to increase the taper slightly to allow for our obturation technique

• Any dentin we remove, however, will weaken the tooth

• So, we must err toward conservatism

• The appropriate taper for a canal is that which it had initially

• Occasionally we have to increase the taper slightly to allow for our obturation technique

• Any dentin we remove, however, will weaken the tooth

• So, we must err toward conservatism

Proper taper

• For most molars and some premolars, rotary files having 0.04 and and 0.06 taper will produce approximately the correct taper

• Excessive taper will cause strip perforations

• Insufficient taper is not really a problem• So, err toward less taper

• For most molars and some premolars, rotary files having 0.04 and and 0.06 taper will produce approximately the correct taper

• Excessive taper will cause strip perforations

• Insufficient taper is not really a problem• So, err toward less taper

Proper file size

• Some rotary systems are available with only small tip sizes (e.g. <40)

• This is due to an erroneous belief that:– All canals are tapering– All canals are small at the apex

• Research shows that these assumptions are not true

• Therefore, the apical portion may need to be prepared with hand instruments or LightSpeed Taper?

Proper file size

• In rotary systems that are available with tip sizes >40, tapers larger than 0.02 can lead to excessive coronal sizes and resulting strip perfs

Principles & Practice of Endodontics, Walton & Torabinejad, Saunders, 2002

But I thought more taper was better?

• 0.06 taper means the file size enlarges by 0.06 mm/mm

• If the tip size is 40, and• The length is 16mm, then• 16 x 0.06 = 0.96• Add to tip size 40 = size 136 • A GT 0.12 would be 40 + 1.92 = size 231!

Proper file size

Since file taper should match canal taper– The only reason to exceed the natural

taper is to facilitate GP cone placement– In larger canal sizes, this is no problem

• Therefore, in teeth with large canals, less tapered files are indicated

Canal is BIG and almost straight!

Proper file size

• This means that in many maxillary anteriors and many premolars rotary instruments are not indicated or needed

• It is often faster to instrument teeth with large canals with Hedstrom files than with rotary instruments!

Be sure you instrument to a large enough size apically!

Why is the preparation size important?

Why is the preparation size important?

Bacteria!Bacteria!Bacteria!Bacteria!Bacteria!Bacteria!Bacteria!Bacteria!

Apical size chart

• Based on morphological studies• Not a rule but a starting point• Adjust for each individual tooth

Tooth Initial file size Final file size

MAXILLARY ARCH

Central 45 60

Lateral 40 (30 if curved) 55 (45 if curved)

Canine 45 60

Premolar B: 25, P: 30; 1 canal: 40 B: 40, P: 45; 1 canal: 55

Molar MB: 25, DB: 25, P: 40 MB: 40, DB: 40, P: 55

MANDIBULAR ARCH

Anterior B: 25, L: 25; 1 canal 40 B: 40, L: 40; 1 canal 55

Canine 40 55

Premolar B: 25, L: 30; 1 canal 45 B: 40, L: 45; 1 canal 60

Molar MB: 25, ML: 25, D: 40 MB: 40, ML: 40, D: 55

Clinical ProceduresClinical Procedures

Clinical Procedures

1. Determine canal

configuration

Clinical Procedures

1a. Estimate working length

Expose a parallel X- Ray

Pre-op film employs the XCP instrument to produce a parallel radiograph

Why parallel?

Clinical Procedures

Parallel films have the least distortionand allow measurements to be made

with reasonable accuracy

Clinical Procedures

Purple – tooth planeRed – Film planeLight blue – bisecting angle

a b

A - with instrumentB – without instrument

Paralleling requires a film holder

Bisecting angle reduces but does not eliminate distortion

Clinical Procedures

Do not fixate on the apex only!

Evaluate root curvature!

1b. Estimate canal curvature

Clinical Procedures

http://www.gearjammin.com/twisty/

Clinical Procedures

Do NOT use rotaries in highly curved canals!Do NOT use rotaries in highly curved canals!

1c. Determine canal form

Clinical Procedures

http://www.holylandmarket.com/html/731.htm

Determine canal form

Small Medium Large

Rotary - OK Rotary - OK Rotary - NO

2. Obtain straight line access

Clinical Procedures

What burs do we need?

• #4 or #6 high-speed round carbide

• D11-T equivalent diamond or Endo-Z bur

• #4 or #6 high-speed round carbide

• D11-T equivalent diamond or Endo-Z bur

Access the chamber…Access the chamber…

Then let the internal anatomy dictate your outline formThen let the internal anatomy dictate your outline form

Initial opening• Remove caries and defective

restorations

• High speed round #4 or 6 for penetration into pulp chamber

• Aim for largest canal


Watch for procedural errors!


Initial opening• After penetration,

enlarge by cutting on withdrawal

• Locate largest canal, follow road map on chamber floor

• Endo explorer to locate canals

Cohen S, Burns RC. Pathways of the Pulp, 7th Ed.

AnteriorsXXXXIncorrect Correct


Penetrate, then cut on

withdrawal

Posteriors


Penetrate, then cut on

withdrawal

Enlargement

• Access preparation is a dynamic process

• Conservation of tooth structure is SECONDARYto convenience form

• Access opening should NEVER bind or guide instruments


Oops!

Binding

Remove the cervical bulge!


Pull up

Then smooth

Completed access

• Continuously tapering, conical form desired

• Use a 1 DT diamond for outline form


3. Explore canal patency

Clinical Procedures

Pass a small, precurved file to the apex

Clinical Procedures

4. Estimate canal size (use chart + x-ray)

Clinical Procedures

Tooth Initial file size Final file size

MAXILLARY ARCH

Central 45 60

Lateral 40 (30 if curved) 55 (45 if curved)

Canine 45 60

Premolar B: 25, P: 30; 1 canal: 40 B: 40, P: 45; 1 canal: 55

Molar MB: 25, DB: 25, P: 40 MB: 40, DB: 40, P: 55

MANDIBULAR ARCH

Anterior B: 25, L: 25; 1 canal 40 B: 40, L: 40; 1 canal 55

Canine 40 55

Premolar B: 25, L: 30; 1 canal 45 B: 40, L: 45; 1 canal 60

Molar MB: 25, ML: 25, D: 40 MB: 40, ML: 40, D: 55

Apical Size Chart

Notice the variation in canal size

Rotaries are not designed for large canals!

5. Establish initial working length (IWL)

Clinical Procedures

Initial working length• Study pre-op radiographs to determine the

approximate length to the apex• Subtract 4mm; this is the IWL

IWL4mm

Rotary technique

• NEVER force a rotary instrument• Use only light pressure (similar to

writing)• Use intermittent tapping motion• Listen to handpiece, reduce pressure if

it slows down (this does NOT work in non-battery powered handpieces)

• Always use a torque-reverse handpiece

Rotary technique

• All instrumentation is PASSIVE• Instruments are chosen because they

very nearly fit to length (1-2mm)• As they rotate, they clean and smooth• 3 sizes allows sufficient dentin removal

for mechanical disinfection and smoothing without weakening the tooth

• All instrumentation is PASSIVE• Instruments are chosen because they

very nearly fit to length (1-2mm)• As they rotate, they clean and smooth• 3 sizes allows sufficient dentin removal

for mechanical disinfection and smoothing without weakening the tooth

6. Prepare coronal 1/3 with orifice shapers

Clinical Procedures

Prepare coronal 1/3 with Orifice Shapers:

Initial working length minus 4mm (apex – 8 mm)Begin with size that nearly reaches the IWL – 4 mm passively, increase 3 sizes (less if too much binding occurs)

Clinical Procedures

STRAIGHT-LINEACCESS

IWLIWL

IWL - 4IWL - 4

Coronal Flaring: Orifice ShapersCoronal Flaring: Orifice Shapers

Irrigation & RC Prep are essential!

Clinical Procedures

Why irrigate and recapitulate?

Mud here…Causes perf hereAnd failure here!

Recapitulation and Apical clearing

• Canal is like a snow globe• An absorbent point would

remove the liquid but not the snow

• It would pack into the bottom of the globe, or apex of the tooth

• Snow, or dentinal “mud”, must be removed mechanically

Instrument with a “tapping” motionLight pressure (like writing with a pen)NO MORE THAN 1MM AT A TIME !!!!!!!

Clinical Procedures

Prepare coronal 1/3 with Orifice Shapers:Initial Working Length minus 4 mmIrrigation & RC PrepInstrument with a “pecking” motionLight pressure (like writing with a pen)NO MORE THAN 1MM AT A TIME !!!!!!!Small to large orifice openers until largest at approximately IWL - 4

Clinical Procedures

Important note!

• The Virginia technique is PASSIVE• NEVER force an instrument• If it doesn’t tap easily to the IWL-4,

accept the new, shorter length• Continue to tap the instruments only as

far as they go without causing the handpiece to autoreverse

Very large, non-tapered canals

• If you can insert all the orifice openers to the IWL-4 or beyond, the canal is too large for rotary instrumentation with a long cutting edge instrument like a ProFile

• Hand instrumentation or the LightSpeed system should be used

• Consult your instructor before proceeding

0.06 taper files

Clinical Procedures

7. Prepare mid 1/3 with 0.06 tapers

IWL

Prepare coronal 2/3 with 0.06 tapersSelect size that passively almost reaches IWL, instrument 3 sizes moreEndpoint is the Initial Working Length

Prepare coronal 2/3 with 0.06 tapersSelect size that passively almost reaches IWL, instrument 3 sizes moreEndpoint is the Initial Working Length

Clinical Procedures

8. Determine the exact length to foramen

Clinical Procedures

How long should we go?

Cementum

Dentin

Mesial view of an anterior tooth

The Apical Foramen

"Natural" constriction in the apical area 0.25 to 0.5 from the

radiographic apex = MINOR FORAMEN

Minor foramen

Mesial view of an anterior tooth

0.5 to 1 mm

Standard radiographic view

The Apical Foramen

Cementum

Dentin

Note: File is long, but it looks

short on the radiograph!

Instrument Length

Aim:As close to minor foramen as

possible. Realize that the radiographic apex is not necessarily

the anatomic apex!

Instrument Length

Ideal

Instrument Length

Final Working length

will be ~1mm from radiographic

apex

Instrument Length

Can I "feel“ the apex?-Only useful with crown-down technique

-Not reliable

-Use only in conjunction with

other techniques

How about apex locators?

Studies suggest ever-increasing accuracy

Still remain technique-sensitive

Do not work in all cases

Useful adjunct, but can be difficult to interpret

Need a combination of techniques for accuracy

Radiographic DeterminationStill the “gold standard”!

“Endo Ray” instrument allows paralleling radiograph with instruments in place

Radiographic Determination

Ideal placement


Short Long

Shift shot

• Always make 2 radiographs from slightly different angles

• Aids in overcoming 2-D limitation


Hedstrom and K files make canal identification easy!

9. Prepare apical 1/3 with 0.04 ISO

tapers from small to large

Clinical Procedures

Working lengthWorking length

Prepare the apical 1/ 3Prepare the apical 1/ 3

Coat a 0.04 hand file the same size as the file you used to take your FWL radiograph with RC PrepPlace it to the FWL using a watch-winding motionRotate it clockwise until it is loose in the canal

Instrumentation of the apical 1/3Instrumentation of the apical 1/3

Irrigate copiouslyCoat the next larger file with RC PrepWork it to the FWL using a watch-winding motionRotate it clockwise until it is loose in the canal


Continue to repeat these steps for three file sizes.Recapitulate – after irrigating, replace the original file size to the FWL and watch wind to place if necessary. Then irrigate.This will remove any accumulated dentinal “mud”

Continue to repeat these steps for three file sizes.Recapitulate – after irrigating, replace the original file size to the FWL and watch wind to place if necessary. Then irrigate.This will remove any accumulated dentinal “mud”


Now, begin step back as follows:Place the next larger size in the same fashion, but only to the FWL – 1mm.Work the file in the same fashion as previously


Repeat this twice, with the next larger size, to FWL –2and FWL –3This will give you a “step back” taper


Finally, recapitulate, irrigate, and smooth the steps by using the last size you took to the FWL in an up-and-down filing motionThis file size is your master apical file, which will dictate the size of your master gutta percha cone


Important note…

• Instrumentation near the apex is dangerous• Many endodontists complete the apical 1/3

entirely with hand instruments• However, the use of carefully controlled

rotaries can result in a smoother transition• Once you have sufficient experience, the

alternate technique for finishing should provide a smoother preparation

• After instrumenting to the WL for three file sizes past the file used to determine your FWL, instead of the stepback, simply:

• Place the next larger size 0.04 taper Profile in the handpiece and gently tap it to the WL

• Be careful not to pass the WL!

Instrumentation of the apical 1/3: alternative to step-back

Instrumentation of the apical 1/3: alternative to step-back

Remember:• NEVER attempt to instrument a canal

with a rotary instrument that you have not already instrumented to the FWL with at least a size 25 hand instrument

Remember:• Always use any instrument, hand or

rotary, with RC Prep for lubrication• Be sure to irrigate copiously after each

file

Remember:

• Apical clearing is NOT recapitulation!

• It consists of:– Drying the canal– Rotating (by hand) without

pressure the last size file used(master apical file)

Irrigate copiously, dry, apically clear, and you are…

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