1. Techniques of Biomechanical Preparation
Assalaam Alekom
Techniques of Biomechanical Preparation
Dr. Gaurav Garg
Lecturer, College of Dentistry, Al Zulfi

2. Objectives of Canal Preparation
Start with the end in mind : cleaning and shaping
Removal of pulp &
necrotic debris
Shaping- conical/
Funnel shape
Good Obturation

3. Shilder’s Five Mechanical Objectives
To develop a continuously tapering cone.
2. To have the narrowest cross-sectional diameter at the apical terminus
3. To maintain the original flow of the canal.
4. Do not transport the foramen
5. To keep the apical opening as small as is practical.

4. Biological objectives
Four biologic objectives
Confinement of instrumentation to the roots themselves
No forcing of necrotic debris beyond the foramen
Removal of all tissues, bacteria and bacterial products and substrates from the root canal space
Creation of sufficient space for intra canal medicaments

5. Criteria for adequate cleaning
Clean dentinal shavings
Clean irrigating solutions
Glassy smooth walls
For apical preparation - apical stop

6. Reference point Reduce occlusal table (flatten cusp tips) for
reproducible reference
Points
Straight-line access to
eliminate obstructions from
canal orifices
Use safe-ended burs

7. Techniques of canal preparation
Step Back/ Telescopic technique
Crown Down/ Step Down

8. Step Back Technique Phase I- Apical preparation/ enlargement
Phase II- Stepping Back & Refining

9. Phase I- Apical enlargement
Determine working length
Negotiation of full length.
Determine Initial Apical file ( IAF)
File with size 10 to WL

10. File with size 15 to WL

11. File with size 20 to WL

12. File with size 25
(Master Apical File) to WL

13. Phase II-Stepping back
Stepping back by 1mm from
WL at size 30
Stepping back by 2mm from
WL at size 35
Stepping back by 3mm from
WL at size 40

15. Phase II-Refining Phase
A. Refining coronal flare with Gates Glidden B. Smoothen the walls (Steps) using a flexible 25 no. K file or H-file.

17. Crown Down Technique
The coronal portion is prepared before the apical portion

18. Steps in preparation Explore canal patency and estimate size
Establish working length
Remove coronal obstructions: Radicular access: gates glidden burs
Crown down preparation: from coronal-middle-apical.

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

20. Working length determination
Actual WL determination: Preparation should terminate at
Apical constriction
1 mm short of radiographic
apex
Radiograph
Apex locator

21. Estimate canal size Estimate canal size (Gauging)
1st binding instrument :
initial apical file
Master apical file: 3 sizes
larger
Radiographic appearance
Crown/root morphology

22. Preparation of coronal third
Enlarge orifice: with G-G drills
Mesio-buccal, mesio-lingual, disto-buccal
canals: #1,#2, #3 Gates-Glidden(GG)
Distal, palatal canals-
#1, #2, #3, #4 GG's
G-G drills

23. Crown down preparation
Introduce larger file (35) about 14mm coronal portion of the canal
File with no. 30, 1mm deeper than size 35
Continue deeper till WL reached with smaller file
W.L. determined

24. Crown down preparation
Step down with smaller instruments
till they reach complete W.L. : #15 at WL
Enlarge apex till #30
Step back from apical to
coronal

25. Recapitulation ( using smaller
size instruments between successive larger instruments)
Anti curvature filing
Filing preferentially away
from the inner curve or
furcal aspect
(danger zone)

26. 5. 4. 3. 2. 2. 1.
Patency: EWL
Coronal enlargement
Middle third enlargement
Apical enlargement: CWL
Blending

27. Advantages of crown down technique
Eliminates constrictions in the coronal region
Reduces effect of canal curvature
Improves tactile awareness during apical preparation
Allows more effective irrigation
Removes majority of tissue and microbes before apical third is approached
Reduces change in working length during apical preparation

28. Golden rules!! Create reliable, reproducible reference points
Never force instruments
Frequently re-establish patency
Use copious irrigation

29. Mission accomplished
Smooth Tapered Preparation

30. THANK YOU !