Cleaning & Shaping

3. CONTENTS
• Introduction
• History
• Guidelines for S & C
• Schilder’s Objectives
• Principles
• Variations in Morphology
• Functional Motions
• RC working width
• Instrumentation Techniques
• Standardized
• Conventional Stepback
• Modified Stepback
• Passive Stepback
• Crown-down
• Crown-down Pressureless
• Double Flared
• Modified Double Flared
• Balanced Force

4. CONTENTS
• Instrumentation Techniques
• Modified Balanced Force
• Reverse Balanced Force
• Hybrid
• Canal Master Technique
• Non Instrumentation
• Laser Assisted Instrumentation
• Ultrasonic Instrumentation
• Sonic Instrumentation
• Special Anatomic Problems
• Curved Canals
• Calcified Canals
• C-shaped Canals
• S-shaped Canals
• Evaluation Criteria of Canal Preparation
• Iatrogenic Errors
• Conclusion
• References

5. Introduction
• Success – how well the canals are shaped and cleaned.
• S & C – important phase in endodontic treatment
• Root canal system must be:
• Cleaned of pulp tissue & debris
• Shaped to receive a 3-D filling of the entire RC space
Baumgartner & Madder
We shape the canals with instruments and clean the canals with irrigants.
Instruments are sharp, dentin is soft, so at most cautious use of instruments are advised.

6. • Pulp Space :
• Organic Substances, Microflora, Bacterial Byproducts
• Food, Caries, Pulp Stones
• Previous RC fillings & Dentinal filings from RC Preparation
Of all the phases of anatomic study in the human system, one of the most
complex is the pulp cavity morphology.
- M.T. Barrett

7. • Principle :
• To remove all organic debris & microorganisms from the root canal systems
• and to shape the walls of the canals to facilitate further cleaning
• and subsequent obturation of the entire RC space.
• Numerous Shaping Techniques – designed : produce a tapered preparation of the RC.

8. History
1733 Pierre Fauchard Trephination of teeth, preparation of root canals & cauterization of pulps -
“ Le Chirurgien Dentiste “
1838 Edward Maynard Endodontic hand instruments
1852 Arthur Used small files for root canal enlargement
1885 Gates Glidden Gates Glidden drills
1889 William H Rollins First endodontic handpiece for automated RC preparation
1915 Kerr K-files
1957 Richmann Ultrasonics in endodontics
1967 Ingle Standardized Technique
1969 Clem First decribed Stepback Technique
1971 Weichmann & Johnson Lasers in endodontics

9. History
1974 Schilder Gave detailed description of Stepback Technique
1979 Mullaney Stepback Technique
1980 Georig Stepdown (Crown-down) Technique
1980 Marshall & Pappain Crown-down Pressureless Technique
1980 Abou Rass, Glick & Frank Anticurvature Filing
1983 Fava Double Flared Technique
1986 Roane & Sabala Balanced Force Technique
1993 Lussi Non Instrumentation Technique
1994 Torabinejad Passive Stepback Technique
2002 Sequeria Alternate Rotary Motion

10. Guidelines for Shaping of a RC (Grossman)
I. Preinstrumentation
• Direct access into root canals along a straight line
• Working length : accurately determined
II. Instrumentation
• Instruments : fitted with instrument stops
• Sequential order of instruments & recapitulation
• Sterile instruments in a wet canal only
• Cautious use of barbed broaches : only when wide canal
• Checked for deformation, discarded if strained

11. Guidelines for Shaping of a RC (Grossman)
III.Cleaning & Shaping
• Instruments : confined to the RC, prevent injury to periradicular tissues
• Don’t force an instrument if it binds
• Recapitualtion : prevent packing of debris
• Apical portion : enlarged to facilitate flow of irrigants
• Remainder of canal enlarged – maintain original tapered canal configuration
• Debris should not be forced through the apex
• Precurve file : curved canals – prevents ledging

12. Functional Motions of Instrumentation
• Reaming:
• Clockwise rotation – pushing motion
• Limited to quarter to half turn
• Disengaged with a mild pulling motion when bound
• Penetration – Rotation - Retraction
• Filing:
• Push-pull motion
• Passive insertion and active withdrawal of the instrument

13. • Combination of Reaming & Filing:
• File is inserted quarter turn clockwise and apically directed
pressure (reaming) and then subsequently withdrawn (filing).
• Files edges get engaged into dentin during withdrawal.
• By combination of these reaming and filing repeatedly, canal
enlargement takes place.

14. • Watch-winding:
• Aka, Twiddling motion
• Instrument reciprocated back and forth in counter-clockwise direction
• Then retracted to remove debris
• Movement with quarter turns using small K-files(#8 / #10) to reach till
working length before coronal flaring
Ingle

15. • Circumferential Filing:
• Instrument is inserted upto the apex
• Laterally pressed against one side of canal
• Withdrawn with a pulling motion to file the dentinal wall
• Procedure is repeated until the next file/reamer is used
• Narrow canals, reamer is used alternatively with files

16. • Anticurvature Filing:
• By Abou Rass et al
• Prevent perforation of the furcal wall of the mesial root of
molars. (Danger Zone)
• Top of Handle : pulled into the curvature
• Shank : pushed away from the inside of the curve
• Balances the cutting flutes against the safer part of the
root

17. • Serial Shaping Motion:
• Follow :
• Movement of smallest instrument to reach the apical foramen
• Negotiating any obstructions or curvatures
• Follow-withdraw :
• As apical foramen is reached, instrument is withdrawn or pulled coronally.
• Carting :
• Transporting dentinal debris & pulp remnants coronally
• Using reamer or F-flex files

18. • Carve :
• Shaping or sculpting the canal to form a continuously tapering cone
preparation without apical pressure using reamers
• Smoothening :
• Circumferential filing using K flex files
• Patency files :
• Smallest file that does not bind to the canal wall at the minor diameter
• Used to check the patency of the canal up to the apical foramen

19. • Scouting :
• Estimating the gauge and anatomy of root canal with help of instrument.
• Gauging :
• Knowing the cross sectional diameter of the foramen that is confirmed by the
size of the instruments that fits snugly at working length.
• Tuning:
• Ensuring that each sequentially larger instrument uniformly backs out of canal
by 0.5mm.

20. Schilders Objectives of Cleaning & Shaping
1. Continuously tapering canal from the apex to the access cavity
2. Maintain original anatomy
3. To leave as much radicular dentin(0.2mm-critical)
4. Maintain the position of apical foramen
5. Keep apical foramen as small as practically possible

21. Biological Objectives
• To confine the instrumentation within the apical foramen
• No extrusion of necrotic debris beyond the foramen
• Removal of all tissues and debris from the root canal space
• Creation of sufficient space for the placement of intra-canal medicament and
for irrigation purposes

22. Principles
I. Outline form
• Basic preparation throughout its length, dictated by the canal
anatomy
• Initial anatomy must be maintained throughout the procedure
II. Convenience form
• Access has to be expanded if instruments starts to bind
III. Sanitation of the cavity
• Meticulous cleaning of the cavity walls until they feel glass-smooth
• Accompanied by continuous irrigation
Anil Kohli

23. Principles of Cleaning & Shaping
IV. Retention form
• Nearly parallel walls in the apical 2-3mm of the canal
• To ensure firm seating of the GP point
V. Resistance form
• Development of apical stop at the CDJ against which the
obturation must terminate
VI. Extension for prevention
• Extension of cavity preparation throughout its entire length and
breadth

24. A. Radiographic Apex
B. Resistance Form
: development of apical stop at CDJ
C. Retention Form
: to retain primary filling point
D. Convenience Form
: subject to revision as needed to accommodate
larger, less flexible files
E. Outline Form
: basic preparation throughout its length dictated by
canal anatomy

25. Variations in Canal Morphology
Curved Canals

26. Variations in Canal Morphology
• Double curved canal
• Common : max. lateral incisors, canines & premolars, mand. molars
Bayonet / S-shaped Canals

27. Variations in Canal Morphology
• Due to failure of HERS to fuse on the lingual / buccal root surface
• Formed by coalescence of cementum deposition
• Common : Mand. 2nd molars > max. molars > mand. premolars
C-shaped Canals

28. Melton’s Classification:
• Category I
• Continuous C-shaped canal running from the
pulp chamber to the apex.
• Category II
• Semicolon shaped (;) in which dentin separates
a main C-shaped canal from one mesial distinct
canal.
C-shaped Canals

29. • Category III
• 2 or more discrete and separate canals.
• Subdivision I
• C-shaped orifice in coronal 3rd that divides into 2 or
more discrete and separate canals that joins
apically.
• Subdivision II
• C-shaped orifice in coronal 3rd that divides into 2 or
more discrete and separate canals in the mid-root
to the apex.

30. • Category III
• Subdivision III
• C-shaped orifice in coronal 3rd that divides into 2 or
more discrete and separate canals in the coronal 3rd
to the apex.
• Category IV
• Only one round / oval canal in that cross-section
• Category V
• No canal / lumen can be observed.

31. Variations in Canal Morphology
• Narrow, ribbon-shaped communication between two root canals that
contains pulp or pulpally derived tissue.
• Classification ( Kim et al)
• Type I
Incomplete isthmus; faint communication between two canals.
• Type II
Characterized by two canals with definite connection between
them.
Isthmus

32. • Type III
Very short complete isthmus between two canals.
• Type IV
Complete or incomplete isthmus between two or more canals.
• Type V
Marked by two or three canal openings without visible
connections

33. Classification of Endodontic Instruments (Grossman)
Group 1
Hand Operated
A. Barbed Broaches & Rasps
B. K-type Reamers & Files
C. Hedstroem Files
Group 2
Low speed instruments with latch type attachments
A. Gates-Glidden drills
B. Peeso Reamers
Group 3
Engine driven instruments
A. Rotary NiTi endo instruments
B. Reciprocating instruments
C. Self Adjusting File (SAF)
Group 4 Ultrasonics & Sonic Instruments

34. Instruments Used For Cleaning And Shaping
• Broaches
• Rasp
• K- files
• H –files
• GG drills
• NiTi rotary
• Light speed
• Profile

35. Root Canal Working Width
• RC should be widened for following reasons:
• To eliminate microorganism on the canal surface mechanically
• Completely removing the pulp tissue
• Increase the capacity of root canal to permit irrigation and
debridement of apical 3rd of root canal
• To shape the root canal to receive gutta-percha, wider canal
are easy to fill particularly if its narrow initially

36. • Traditional Concept
• Enlarge the canal atleast 3 sizes beyond the size of the first instrument that binds.
• Enlarge the canal until clean, white dentinal shavings appear in the flute of the
instrument.
• NOT RECOMMENDED ANYMORE
• The color of the dentinal shaving is no indication of presence of infected dentin or organic
debris.
• Root canals should be enlarged regardless of initial width to remove irregularities of dentin
and make smooth and tapering canal.
Grossman

37. • Current Concept
• Minimum size to which a root canal should be enlarged cannot be standardized and
varies from case to case.
• Factors affecting the size of canal while enlarging at working length
• Peri-apical pathology or resorption
• Narrow canals - initial canal width has to be assessed radiographically
• Whether root canal is vital / calcified / infected
• Radius of canal curvature which could make the canal preparation difficult
• Complex canal anatomy like C-shaped canals and the isthmus region
Grossman

38. • A study showed that molar tooth canals should be enlarged upto #40 for effective cleaning
• Canals shaped with greater taper NiTi allow irrigants to reach the apical third without much
enlargement of apex too much
• Study shown that canals shaped with 6% taper instruments upto #30 have cleaner canals
without smear layer or debris
Grossman

39. Narrow Apex
Benefits Drawbacks
• Minimal risk of Canal transportation • Little removal of infected dentin
• Minimal Extrusion of irrigants • Questionable rinsing effect in apical areas
during irrigation
• Minimal Extrusion of filling material • Possibly compromised disinfection during
inter appointment medication
• Can be combined with tapered
preparation to counteract some
drawbacks
• Not ideal for lateral condensation
Cohen

40. Wide Apex
Benefits Drawbacks
• Removal of infected dentin • Risk of preparation errors and extrusion of
irrigants and filling material
• Access of irrigants and medications to
apical third of root canal
• Not ideal for thermoplastic obturation
Cohen

41. Root Canal ShapingTechniques
Apico-CoronalTechniques Corono-ApicalTechniques
• StandardizedTechnique • Crown-downTechnique
• Stepback Preparation • Crown-down Pressureless
• Passive Stepback • Double FlaredTechnique
• Balanced ForceTechnique
• HybridTechnique

42. StandardizedTechnique
• First formal RC preparation technique
• Ingle (1961)
• Canals prepared by enlarging sequentially to selected size.
• Final result : preparation similar in size, shape and taper of a standardized instrument
• Technique:
• Working length
• Canal negotiated with smallest size instrument, worked upto WL with sequentially
larger file
• Finally a canal shape is produced which is similar to the last instrument used.

43. • Two factors of variations
• Canals shaped with standardized technique end up wider than the instrument size
would suggest.
• Production quality is insufficient, both for instruments and for gutta-percha cones,
leading to size variations.
Ingle

44. Conventional Stepback Preparation
• Telescopic / Flare / Serial RC preparation
• Mullaney, Walton, Weine & Martin : 1979
• Preparation : from the apex with fine instrument which is enlarged first to a size 25/30 and
then consecutively larger instruments are used for shaping the middle and coronal part of
the canal.
• Technique:
Mullaney divided into 2 phases:
Phase I
Phase II A & B

45. • Phase I :
• Patency
• Working length
• Initial Apical File (IAF)
• Watch-winding motion with copious irrigation
• Recapitulation
• Canal enlarged upto No. 25 at the working length

46. • Phase II A :
• Next file size No.30 used 1mm short of WL
• Recapitulation (No. 25)
• Next file (No. 35) used 2mm short of WL
• Preparation steps back by 1mm till straight mid-canal is reached

47. • Phase II B :
• Coronal portion is prepared using GG/Orifice openers
: remove coronal constriction

48. • Phase II B (Refining Phase):
• For smoothing the canal walls
• To get taper from coronal portion till apex and will be larger
repilca of original canal
• Last apical instrument (No.25) used to smoothen the walls with
push-pull strokes with copious irrigation.
• This Preparation gives 5% taper to the canal.

49. • Serial Canal Preparation:
• By Walton & Torabinejad
• After apical preparation, preparation steps back by 0.5mm & one larger instrument
at a time.
• This Preparation gives 10% taper to the canal.

50. ADVANTAGES:
• Creates only small apical preparation with larger instruments used at
successively decreasing lengths to create a taper.
• Taper can be altered by changing the interval between consecutive
instruments.

51. DISADVANTAGES:
• Difficult to irrigate apical region
• More chances of apical extrusion of debris
• Time consuming
• It has tendency to straighten the curved canal
• Increased chances of iatrogenic errors
• Loss of working length

52. Modified Stepback Preparation
• After apical preparation, stepback preparation begins 2-3mm up the canal
• Provides short parallel retention form to the master GP point
ADVANTAGES :
• Reduced apical transportation
• Increases the percentage of canal walls being prepared
Nisha Garg

53. Modified Stepback Preparation
DISADVANTAGES :
• Passing a precurved instrument in a coronally tight canal straightens the
instrument leading to ledge formation.
• Holds only a minimal volume of irrigant and so accumulation of dentinal mud
leads to blockage of the foramen.
• WL is most likely to change as coronal constriction is removed.

54. • When GG drills and Peeso drills are advanced past the middle third of
root canal : Resulting shape is – “COKE BOTTLE”.
• GG drills and peeso drills - deep into the canal : risk of fracture as they
are not very resistant to fatigue occuring in curved canals.
• Strip perforations and over preparation
Ingle

55. • Coffae and Brilliant
• Use of #35 till working length, stepwise reduction of WL for subsequent
files upto #60.
• Then use of GG drills no. 2 and 3 approximately 16 and 14mm
approximately into the canal - showed superior debridement.
Ingle

56. Passive StepbackTechnique
• Developed by Torabinejad
• Combination of hand and rotary files : to attain an adequate coronal flare before apical RC
preparation
• Provides gradual enlargement of root in an apical to coronal direction without applying
force, thereby reducing procedural errors.

57. Passive StepbackTechnique
• Technique:
• Access preparation and WL determination using No.15 file
• Additional files of 20, 25, 30, 35 and 40 are inserted passively into the canal :
removes debris and mildly flared preparation for insertion of GG.
• Copious irrigation
• No. 2 GG inserted to a point where it binds slightly, pulled back 1 – 1.5mm and then
activated – canals walls get flared.
• Similarly GG No. 3 and 4 are used coronally.

58. Passive StepbackTechnique
• Reconfirmation of WL
• No. 20 file is inserted upto WL and prepared by filing with instruments progressively
short of WL.

59. Passive StepbackTechnique
ADVANTAGES:
• Removal of debris and minor canal obstructions
• Knowledge of canal morphology
• Gradual passive enlargement of canal in apico-coronal direction
• Can be used with ultrasonic instruments
• Reduced incidence of procedural errors.

60. Crown-DownTechnique (Step Down)
• Aka; Reverse flaring (Weine), Coronal 2/3rd enlargement (Cohen), Cervical Flaring (Goreig)
• Shaping of the coronal aspect of root canal first before apical instrumentation.
• Technique:
• Patency with No.8/10 K file
• Coronal 2/3rd prepared using H-files
(#15,20,25) to a WL depth of 16-18mm or to
a point where the file starts to bind.

61. • Flaring coronal segment with GG #2, #3 or #4, each drill being
sequentially shorter.
• WL determination
• Remaining canal prepared in step-down approach, using
descending file sequence, progressing by 1mm.

62. • Apical portion of canal is then enlarged to appropriate MAF which can vary from
canal to canal and from tooth to tooth.
• Final taper attained by the MAF is used in circumferential filing.

63. • Modifications:
• Crown-down pressureless technique
• Double flare technique
• Balanced force technique

64. Crown-Down PressurelessTechnique
• By Marshall and Pappain
• Early coronal flare with GG drills followed by incremental removal of dentin from coronal to
apical direction : hence termed “CROWN DOWN”
• Straight K-files are used in a large to small sequence with a reaming motion and no apical
pressure. : hence termed “PRESSURELESS”
• Morgan and Montgomery found this technique resulted in rounder shape when compared to
usual stepback technique.

65. • Technique:
• After coronal access, provisional WL
• #35 K-file introduced into the canal with no apical pressure
• GG # 2 is used for coronal flaring upto or short of point where #35 file explored.
• Followed by GG # 3 & 4 : this shortens the WL.
• Crown-down preparation, #60 file used with no apical pressure & reaming action
is employed to enlarge the canal.

66. • Followed by use of sequentially smaller files, deeper into the canal
• Radiographs are taken when instrument penetrates the provisional WL
• Final step to enlarge the apical area to appropriate MAF at WL

67. Balanced ForceTechnique
• By Roane & Sabala (1985)
• Involves the use of instrument with non-cutting tip
• Flex-R files are recommended for this technique.
• Technique described as “Positioning and Preloading” an instrument through clockwise
rotation and then shaping the canal with a counter clockwise rotation.

68. • Technique:
• Coronal and middle thirds prepared using crown-down technique,
using GG.
• First file that binds short of WL is inserted into the canal
• Rotated clockwise (quarter turn) using only light pressure
• This movement causes flutes to engage a small amount of dentin
• Now file is rotated counter-clockwise with apical pressure to keep the
file at the same depth.

69. • This causes shearing off small amount of dentin engaged during
clockwise rotation.
• Dentinal shavings are removed with a characteristic “CLICKING
SOUND”
• After 2/3 cycles, file is loaded with dentinal shavings and is
removed from the canal with a prolonged clockwise rotation. (loads
debris into the flutes)
• Sequential files are used in crown-down fashion before preparing
the apical third.

70. • Roane recommends minimum enlargement of size 45, 1.5mm short of apical
foramen in curved canals.
• Size 80 in single rooted teeth, carrying the preparation through full length of
the radiographic apex of the root.
• This technique has shown to reduce canal transportation and ledging.

71. Modified Balanced ForceTechnique
• Earlier called Alternated Rotary Movements
• Does not recommend withdrawal of instrument after each set of rotations
• Emphasized incremental apically directed movement and withdrawal when the file
has reached the working length.

72. Reverse Balanced Force Preparation
• NiTi greater Taper hand files are used.
• Flutes of Greater taper files are machined in a reverse direction unlike other files.
• Technique:
• File inserted and rotated 60° in anti-clockwise direction
• Then 120° in clockwise direction with apical pressure.
• Files are used in sequence from largest to smallest in crown-down sequence
upto the WL.
• WL determination
• Apical portion prepared using 2% taper ISO files in balanced force technique.

73. Double FlareTechnique
• By Fava
• Canals prepared in crown-down manner using K-files in decreasing sizes.
• Followed by stepback technique in 1mm increments with increasing file sizes.
INDICATIONS:
• Straight root canals
• Straight portions of curved canals
CONTRAINDICATIONS:
• Calcified canals
• Young permanent teeth
• Open apex

74. • Technique:
• WL determination using small K-file
• Crown-down Preparation : Apical third is enlarged using larger to smaller K-files
until WL is reached.
• Apical enlargement done till MAF size
• Stepback preparation with descending files with frequent recapitulation with MAF.

75. ADVANTAGES:
• Greater taper in cervical and middle third such that the removal of canal contents
is more effective and RC is better cleaned.
• Improved quality of root canal filling compared to conventional technique.
• Flared technique maintains the RC shape and produces neither the hour glass
appearance nor apical zip.
• Facilitates irrigation procedure and easier placement of posts.

76. Modified Double FlareTechnique
• By Saunders & Saunders
• Uses non cutting tipped instruments with stepback technique.
• Technique:
• Preparation starts in the coronal part of the canal
• #40 Flex R file with balanced force introduced into straight part of the canal
• Sequential larger sizes used to instrument the straight part
• Coronal 4-5mm instrumented with GG (No. 2 & 3)
• #20 file extended to WL

77. • Canal prepared sequentially with balanced force technique.
• Preparation is continued until clean dentinal shavings are obtained.
• MAF varies between #40 - #45 file.
• Stepback with balanced force done to prepare remaining curved portion.

78. ADVANTAGES of Crown-DownTechnique
• Shaping of canal is subjectively easier than stepback
• Removal of coronal obstructions allows removal of bulk of tissue, debris and micro-
organisms before apical shaping.
• Minimizes extrusion of debris
• Allows better access and control over the apical enlarging instrument, thus
decreasing incidence of zipping
• Allows better penetration of irrigants
• WL is less likely to change while employing this technique

79. HybridTechnique
• Combination of Stepdown followed by Stepback.
• Both rotary and hand instruments are used
• Technique:
• Patency with #10 K file
• Coronal third preparation using hand or GG till point of curvature
• WL determination
• Apical portion prepared using stepback technique
• Recapitulation and irrigation

80. ADVANTAGES:
• Ability to shape canal predictably
• Less chances of ledge formation
• Maintains the integrity of dentin by avoiding excessive removal of
radicular dentin.
• Optimises the advantages of crown down & step back techniques

81. Canal MasterTechnique
• By Wildey & Senia
• Instrument used is Canal Master Instrument (SW)
• Here cutting portion is reduced to 1-2mm with 0.75mm non-cutting pilot tip
• Cutting portion resembles a reamer with blunted edges.
• Rest of the instrument is parallel sided shank of round cross section
• Maximum efficiency is with clockwise rotary motion

82. ADVANTAGES:
• Prevents transportation of the canal
• Small cutting head provides minimum cutting surface with maximum control
• Increased flexibility
• Instrument stays centered in the canal
• Gives finer tactile perception
• Does not require recapitulation

83. Non-InstrumentationTechnique
• By Lussi et al
• Minimal Invasive Technique
• Uses controlled cavitation & hydrodynamic turbulence in the RC so as to clean them.
• Technique uses:
• Vaccum pump
• A Hose
• A special valve to pump irrigant which generates bubbles & cavitation
that loosen the debris
• Debris is removed by suction.
• Enhances the ability of NaOCl to dissolve the organic pulp tissue.

84. • Technique:
• First reduced pressure at 0.7 bar generated, producing macroscopic &
microscopic voids (5-50μm)
• Followed by quick pressure rise to 0.1 bar leading to collapse of bubbles,
thus building up cavitation and turbulence.
• Allows irrigant to penetrate the whole of RC system
• Smooth exchange of irrigant is obtained using double tubing.

85. ADVANTAGES:
• Cleaning of canal, similar or better than hand instrumentation
• Better results in curved canals
• Less chances of extrusion of irrigant beyond the apex
• Treatment duration is independent of the number of RCs in the tooth
DISADVANTAGES:
• Does not shape the canal
• Tooth has to be insulated

86. Laser Assisted Canal Preparation
• By Weichmann & Johnson (1971)
• Nd.YAG, Argon, Excimer laser, Erbium Laser
• Nd YAG laser energy better absorbed by dark tissue and is transmitted by water.
• Excimer lasers and Erbium lasers are strongly absorbed by dental hard tissue.
• Dederich et al showed the melting and recrystallizing the dentin surface can create
clean and penetrable canal.
• Delivered through optical fibres which have a diameter of 200 – 400 μm equivalent to
#20-40 files

87. MECHANISM :
• Melting the dentin surface
• Vaporization of debris and pulpal tissue remnants.
INDICATIONS :
• Straight / Slightly curved canals
• Wide root canals
CONTRAINDICATIONS :
• Heat generated may injure the peripical tissues
• Curved canals cannot be assessed
• Expensive

88. Canal Preparation with Ultrasonic Instrumentation
• Introduced by Richman in 1957
• Barbed broach is connected to an ultrasonic delivery system for use in canal
preparation and apical resection.
• Howard Martin and Walter Cunningham in 1976
• Developed a device, tested and marketed it in 1976.
• Named the Cavitron endodontic system (Dentsply).
• Endosonics refers to the endodontic treatment by sonic, supersonic or subsonic
system (Martin & Cunningham).

89. • Based on sound as an energy source (20-25khz) that activates endodontic files.
• Energy source – piezoelectric or magnetostrictive.
• Files oscillate at the frequency of 20,000- 25,000 vibrations /seconds.
• Magnetostrictive Unit
• Electromagnetic energy is converted into mechanical energy.
• It needs water coolant because it generates more heat.
• Expensive, more clumpsy and less powerful.

90. • Piezoelectric energy is induced by subjecting crystals of quartz or Rochelle salts to
physical force or pressure.
• Generates less heat
• Doesn’t require water as coolant
• Transfers more energy to the file, making it more powerful.
• Used for
• Location of calcified canals
• Retrieval of broken instrument
• Root end preparation.

91. • Handpiece holds a K-file, when activated produces movement of
shaft of file between 0.001” & 0.004” at freq. of 25-30KHz.
• Oscillating movement produces cutting action & creates ultrasonic
waves of the irrigant.
• Ultrasonic vibration - heat : increases the chemical effectiveness
of irrigant solution.

92. • 2 significant physical processes that occur :
• Cavitation
• Acoustic Streaming

93. • Growth and collapse of bubbles (Implosion) with resulting increase in
mechanical cleansing activity of the solution.
• Negative pressure : within the exposed cells of intracanal materials,
implosion breaks the cells.
• Irrigant/coolant : washes out broken cell parts.
• Increase in mechanical & thermal activity of irrigants
• Removal of debris & tissues from the isthmus
• Removal of smear layer are more efficient.

94. • Formation of small but intense eddy currents or fluid movement
around the oscillating instrument.
• Improves the cleaning ability of the irrigant : hydrodynamic
shear stress
• Eddying occurs closer to the tip than in the coronal end of the
file, with an apically directed flow at the tip.

95. Ultrasonics : Adv & DisAdv
ADVANTAGES
• Less time consuming.
• Produces cleaner canals because of synergetic effect.
• Heat produced increase the chemical effectiveness of sodium hypochlorite.
DISADVANTAGE
• Increased frequency of canal transportation.

96. Canal Preparation with Sonic Instrumentation
• Sonic endodontic handpiece attach to the regular handpiece at a
pressure of 0.4 Mpa
• Air pressure can be varied with an adjustable ring on the
handpiece to give an oscillatory range of 2 to 3 kHz.
• Tap water irrigant / coolant is delivered into the preparation from
handpiece.

97. • Sonically powered files oscillate in large elliptical motion at the tip.
• When loaded into the canal oscillation motion changes into a longitudinal
motion, up and down (Walmsley et al); efficient form of vibration for
preparing root canal. (Ingle)
• Types of files used in Sonic system
• Rispi Sonic, Shaper Sonic, Trio Sonic, Helio Sonic Files.
• Files have spiral blades protruding along their lengths and non cutting tips.

98. SONICS : Adv & DisAdv
ADVANTAGES
• Better shaping of canals than ultrasonic preparation.
• Due to constant irrigation, amount of debris extruding beyond apex is less.
• Produces clean canals free of debris and smear layer.
DISADVANTAGES
• Walls of prepared canals are rough.
• Chances of transportation more.

99. Special Anatomic Problems in Canal Cleaning and Shaping
• Management of Curved Canals
• Management of Calcified Canals
• Management of C-shaped Canals
• Management of S-shaped Canals

100. Management of Curved Canals
• First step : estimate the angle of curvature
• It estimates only the mesio-distal curve but not the bucco-lingual curve.
Degree of Curvature
Interior angle formed by intersection of 2 straight lines, one
drawn from the orifice through the coronal portion of the
root and another from the apex through the apical portion of
the curve

101. • Curved canals : occurrence of uneven cutting and cause errors.
• To avoid occurrence of such errors, there should be even contact of file to the dentin
• This can be done by:
1. Decreasing the force by means of which straight files apt to bend against the
curved dentin surface.
2. Decreasing the length of file which is aggressively cutting at the given span.

102. • Decreasing the force by means of which straight files apt to bend against the curved
dentin surface :
• Precurving the file
• Extravagant use of smaller number of files
• Use of intermediate sizes of files
• Use of flexible files

103. I. Precurving the File
2 types of precurving:
• Placing an extremely sharp curve near the tip of an instrument
• Degree of curvature is estimated by holding the file over the
preoperative radiograph and increasing the curvature until the
configurations of the file and canal match.
• Short sharp curve of 30 – 40 degrees is given.
• Uses :-
• To bypass a ledge
• To prepare a tooth with dilacerations
• When retreating a failing case.

104. • Gradual precurve for the entire length of flutes
• RC instrumented with the precurved files : significantly lower debris
score than those prepared with straight files.
• Matching the curvature of the file to the curvature of the canal
facilitates its insertion.
• Tear drop shape rubber stop can be used, with the point showing the
correct direction of the curve.

105. • Smaller files follow canal curvature because of their flexibility.
• They should be used until larger files are able to negotiate the canal without force.
II. Extravagant Use Of Smaller Files

106. III. Flexible files
• Use of flexible files cause less alteration of canal shape than stiffer files.
• Maintain the shape of curve and avoid occurrence of errors.

107. IV. Intermediate files
• By cutting off a portion of the file tip, a new instrument size is
created which has the size intermediate to two consecutive
instruments.
• In severely curved canals clinician can cut .05 mm of the file to
increase the instrument diameter by .01mm.
• This allows smoother transition of instrument sizes to cause
smoother cutting in curved canals.

108. • Decreasing the length of file which is aggressively cutting at the given span
• Anticurvature filing
• Modifying the cutting edges of the instrument
• Changing the canal preparation techniques

109. • Cutting edges of curved instrument can be modified by dulling the flute of outer portion of
apical third and inner portion of middle third.
• Dulling of the flutes can be done with diamond file.
II. Modifiying Cutting Edges

110. • Crown-down technique
 Removes the coronal interferences and allow the files to reach up to the apex
more effectively.
III. Changing Canal PreparationTechniques

111. Management of Calcified Canals
• Common occurrence
• Pulpal Calcifications: signs of pathosis, but not the cause.
• Occur nearest to irritant to which pulp is reacting
• Most are seen in coronal portion of pulp and least in apical part into the canal
• Etiological Factors: caries, trauma, drugs and aging.

112. • Access preparation
• Location of canal orifice
• DG – 16 explorer
• Canal pathfinder
• Penetration and negotiation of calcified canals
• No .8 K file
• Before inserting, precurve the file in its apical 1mm.
• Forceful probing – false canals – perforation.
• Confirm the position of instrument with radiograph.

113. Guidelines For Negotiating Calcified Canals
• Copious irrigation with 2.5% -5.25% NaOCl.
• Always advance the instrument slowly in calcified canals.
• Always clean the instrument on withdrawal & inspect before reinserting.
• When a fine instrument reaches canal length, obtain a radiograph immediately.
• Use chelating agents to assist canal penetration.

114. • Flaring of canal orifice and enlargement of coronal third of canal space improves tactile
perception.
• Avoid removing large amount of dentin in the hope of finding a canal orifice.
• Small round burs should be used to create a glide path to the orifice.

115. Management of C-shaped canals
• Difficult to remove pulp tissue & necrotic debris, excessive haemorrhage,
persistent discomfort during instrumentation.
• Continuous circumferential filing + 5.25% NaOCl for tissue removal and
control of bleeding.

116. • If bleeding is continuous, ultrasonic removal of tissue or placement of
Ca(OH)2 between appointments.
• Over preparation should be avoided : only little dentin between external
root surface and canal system.

117. Management of S-shaped / Bayonet shaped canal
• Involves at least two curves with the apical curve having maximum deviations in anatomy.
• Usually identified radiographically : mesiodistally
• Buccolingually
• Multi-angled radiographs
• When IAF is removed : simulates multiple curves
• Common :
• Maxillary lateral incisors, canines, premolars
• Mandibular molars

118. • 3D nature of the canals must be visualised
• Failure may lead to stripping along inner surface
• Unrestricted access to initial curve : Flared access preparation.
• Once entire canal is negotiated, passive shaping of coronal curve is done first.
• Constant recapitulation and copious irrigation.

119. • Gradual use of small files with short amplitude strokes is essential to manage these canals.
• To prevent stripping, anticurvature filing is recommended, with pressure being placed away
from curve of coronal curvature.

120. Evaluation Criteria of Canal Preparation
• Canal should exhibit “glassy smooth” walls
• There should be no evidence of unclean dentin filings, debris, or irrigant in the canal.
• Spreader should be able to reach within 1mm of the working length.

121. Iatrogenic Errors
Those unfortunate occurrences that happen during treatment, some owing to
inattention to detail, others totally unpredictable. - INGLE
• Ledge formation
• Perforation
• Zipping / Elliptication
• Canal Blockage
• Separated Instruments

122. Ledge
• An artificially created irregularity on the surface of the root canal wall that prevents
the placement of instruments to the apex of an otherwise patent canal.
Causes:
• Forcing and driving the instrument into the canal
• Attempting to prepare calcified root canals
• Excessive enlargement of curved canal with files
• Packing debris in the apical portion of the canal
• Anatomic complexities - roots curved towards buccal or lingual side.

123. Perforation
• Creating a ledge in the canal wall during initial preparation and perforating
through the side of the root at the point of obstructions / root curvature.
• Using too large or too long an instrument and either perforating directly
through the apical foramen or wearing a hole in the lateral surface of the root
by over instrumentation.

124. Zip / Elliptication
• Transportation of the apical portion of the canal
ie. an elliptical shape formed in the apical foramen during preparation of curved canals.
• Creation of an ‘elbow’ is associated with zipping – at the narrow region of the root canal
at the point of maximum curvature
Ie. the irregular widening that occurs coronally along the inner aspect and apically
along the outer aspect of the curve.

125. Canal Blockage
• Due to lack of recapitulation
• Insufficient irrigation
Instrument Separation
• Overuse of instruments
• Instrumentation in a dry canal
• Excessive pressure applied
• Manufacturing defects

126. Conclusion
• Shaping and cleaning are important interdependent steps in the root canal
treatment.
• The combination of anatomic, biologic & pathophysiologic knowledge of the tooth
and the skill of the operator play a major role in optimizing the quality of the
root canal treatment.

127. Keep in Mind
• Do no harm to the tooth structure
• Totally clean the canal system
• Create a continuous taper
• Do not alter the minor diameter
• Assume curvature in all canals
• Avoid aggressive apical instrumentation
• Avoid overzealous shaping
• Accurately pre-bend files
• Avoid apical blockage
• Develop a tri-dimensional image through
visual & tactile awareness.

128. References
• Textbook of Endodontics – Ingle
• Principles & Practice – Walton & Torabinejad
• Pathways of the Pulp – Cohen
• Textbook of Endodontics – Nisha Garg
• Endodontic practice – Grossman
• Endodontics – Stock, Walker, Gulabivala
• Endodontic Science – Carlos Estrela

129. “Cleaning and Shaping is a game and, as such, can be played at
various skill levels. Visualizing and executing great play can
move the clinician towards mastery and winning the inner game
of endodontics.”
- Clifford J. Ruddle