1. Cleaning and Shaping of the Root Canal System
Edit by Hou Tiezhou

2. Objectives of Canal Preparation
Start with the end in mind

3. Objectives of root canal preparation
The root canal system must be:
Cleaned of its organic remnants
Shaped to receive a three dimensional filling of the entire root canal space

4. Objectives of root canal preparation
The canal is
Cleansed primarily by irrigation
Shaped primarily by instrumentation

5. Hence cleansing and shaping

6. Cleansing of the root canal
Objectives
Removal of organic debris
Elimination of bacteria

7. Irrigation An ideal irrigant: Is nontoxic
Dissolves vital and necrotic tissue
Is bactericidal
Lubricates the canal
Removes the smear layer

8. Sodium hypochlorite Dissolves vital and necrotic tissue
Is bactericidal
Lubricates the canal

9. Cannot be considered non-toxic!!!
Sodium Hypochlorite
Cannot be considered non-toxic!!!

10. Prolube
EDTA and carbamide peroxide in a water soluble base

11. Prolube Facilitates placement of file Entraps debris
Aids in removal of the smear layer

12. EDTA
Chelating agent
Effectively removes smear layer

13. Shaping of the root canal
Canal shape – produced by instrumentation
Objective is a smooth tapered preparation

14. Shaping of the root canal

15. Instruments Instruments differ according to: Metal Taper Tip design
Cross sectional geometry
Length of cutting blades
Sizing

16. Metals Nickel titanium Stainless steel
Excellen flexibility Less flexible
Conforms to canal Straightens and
curvature transports canal
Plastic deformation Permanent deformation

17. Metals
Stainless steel files demonstrate permanent deformation

18. Metals
Nickel titanium files demonstrate plastic deformation

19. Taper
Definition
Increase in diameter per unit length

20. What is Taper? D16 D1 0.32 mm diameter increase D16 D1

21. What is taper?

22. Taper Taper of instruments in U of M file kit
Stainless steel files – 0.02 taper
OS – variable tapers ranging from 0.05 to 0.08
Series 29 rotary Profiles – 0.06 taper
NiTi hand files – 0.04 taper

23. Tip Design Non-cutting tip Bullet nose (60 degree) tip
Smooth transition angle where tip meets flat radial lands

24. Tip Design Designed to follow a pilot hole
Guides instrument through canal during preparation

25. Tip Design

26. Cross-sectional geometry
Three radial lands
Each contains bidirectional cutting edges
Keep instrument centered in the canal
Cutting edges scrape dentin

27. Cross sectional geometry

28. Cross sectional geometry

29. Cross sectional geometry
Radial lands separated by three u-shaped flutes
Provide space for accumulation of debris
Moves debris out of canal

30. Length of cutting blade
Traditionally 16 mm
Orifice shapers – 10 mm

31. Sizing of instruments ISO sizes
Number refers to tip diameter in tenths of mm
The tip diameter increases by 0.05 mm from sizes 10 to 60, then by 0.10 mm

32. Sizing of instruments
% increase in diameter from #10 to #15 file is 50%
Difference between #55 and #60 is only 9%

33. Sizing of instruments Series 29
Progressive 29% increase in tip diameter
Instruments are better spaced
More instruments in smaller sizes and fewer large instruments

34. Crown Down Technique
The coronal portion is prepared before the apical portion
Follows medical principle of cleansing before probing a wound

35. Crown Down Technique

36. Crown Down Technique Eliminates constrictions in the coronal region
Reduces effect of canal curvature
Improves tactile awareness during apical preparation

37. Crown Down Technique Allows more effective irrigation
Removes majority of tissue and microbes before apical third is approached
Reduces change in working length during apical preparation

38. Crown Down Technique Coronal third Orifice shapers
Middle third 0.06 taper rotary Profiles
Apical third 0.04 taper hand Profiles

39. Clinical Procedure Estimate working length Parallel radiograph
Estimated working length is the distance from the reference point to the radiographic apex

40. Parallel Radiograph

41. Clinical Procedure
Establish straight line access to apical third

42. Clinical Procedure Explore canal patency
Ensure that canal is negotiable to radiographic apex
Small file – #10 K-file
May need to precurve these SS files

43. Clinical Procedure
Files used in a push/pull or quarter turn pull motion
Never rotate these files through 360 degrees

44. Clinical Procedure

45. Clinical Procedure

46. Clinical Procedure Estimate canal size Radiographic appearance
Crown/root morphology
Standardized tables

47. Estimation of canal size

48. Estimation of canal size
See Table in manual

49. Clinical Procedure Actual WL determination
Preparation should terminate at
Apical constriction
1 mm short of radiographic apex

50. Clinical Technique
Actual WL determination
Radiograph
Apex locator

51. Clinical Procedure
Actual Working Length Determination

52. Clinical Procedure

53. Clinical Procedure
Apex Locator

54. Clinical Procedure
Crown down cleaning and shaping of canals

55. Clinical Procedure
This technique applies only to teeth ranging from 18 – 23 mm in length
Coronal third measurement is WL minus 8 mm
Middle third measurement is WL minus 4 mm
Apical third measurement is WL

56. Preparation of the coronal third
Coronal third measurement is working length minus 8 mm
Prepared using Profile orifice shapers

57. Preparation of the coronal third
Profile orifice shapers
In sequence larger to smaller

58. Preparation of coronal third
Measure WL minus 8 mm on largest OS
Lubricate the canal with Prolube

59. Preparation of coronal third
Rotate OS at 300 rpm
Note: Orifice shaper should be rotating at 300 rpm before it is placed in the canal
Advance the OS in 1 mm increments
When resistance is encountered retract OS while still rotating
Never force any instrument apically

60. Preparation of the coronal third
This OS will not extend to WL minus 8 mm
Irrigate copiously

61. Irrigation

62. Preparation of coronal third
Move to next smallest OS
This will extend further than previous instrument
Repeat the steps described for largest OS
Continue this sequence until working length minus 8 mm is reached

63. Preparation of coronal third
Return to largest OS
This will now extend further into the canal than it did previously
Repeat this sequence until this (the largest) OS reaches WL minus 8 mm

64. Preparation of the coronal third
Never force any instrument apically
Irrigate after every instrument
Use copious amounts of Prolube

65. Preparation of coronal third

66. Preparation of middle third
Middle third measurement is WL minus 4 mm
Prepared using 0.06 taper Series 29 rotary Profiles in sequence larger to smaller

67. Preparation of middle third
Prepared with 0.06 Series 29 NiTi rotary Profiles

68. Preparation of middle third
Measure working length minus 4 mm on the largest 0.06 taper series 29 rotary file
Set green rubber stop at that length
Lubricate the canal with Prolube

69. Preparation of middle third
Rotate at 300 rpm
File must be rotating at 300 rpm before it is placed in canal
Advance file in 1 mm increments
When resistance is encountered retract file while still rotating
Copious irrigation with NaOCl

70. Preparation of middle third

71. Preparation of the apical third
Prepare to actual working length
Use 0.04 taper NiTi hand files in sequence smaller to larger

72. Preparation of apical third

73. Preparation of apical third
Measure working length on #15 file
Set rubber stop at that length
Lubricate the canal with Prolube

74. Preparation of apical third
Advance size 15 file to working length
Rotate file through 360 degrees
Irrigate copiously with NaOCl after each file

75. Preparation of the apical third
Advance size 20 file to working length
Continue through sequence, seating each file to working length

76. Preparation of apical third
The largest file that extends to working length is the Master Apical file (MAF)
For large canals – minimum MAF #
For small canals – minimum MAF #

77. Master Apical File Take a radiograph with MAF in place. This confirms:
Length
Placement

78. Mission accomplished
Smooth tapered preparation