1) There are several techniques for cleaning and shaping root canals during endodontic procedures, including step-back, crown-down, and hybrid techniques. 2) The step-back technique involves first enlarging the apical third of the canal with small files, then using larger files to step back and flare the middle and coronal thirds. 3) The crown-down technique starts with flaring the coronal third, then preparing the middle and apical thirds with progressively smaller files moving from the crown toward the apex.

1. Cleaning and Shaping

2. Endodontic instrumentation procedures: 1) Intra coronal preparation; -Endodontic access should facilitates: - Visual inspection of the pulp space. - Direct access to the canal orifice. - Complete control over the instrument. - Maximum convenience during the filling phase.

3. 2)Working length determination3) pulp extirpation4) Intra-radicular preparation

4. Intra-radicular preparation:A) Basic instrumentation motion.B) Techniques for the preparation.

5. A) Basic instrumentation motion: It is the type and direction of the motion that the operator performs while holding the instrument and works in the canal space;Filling motion: This is a linear motion in the form of push and pull action with effective action during pulling.

6. It is the most effective cutting motion for dentin, especially with H-file. It is recommended for enlarging the coronal 2/3 of the canal (circumferential filling).2) Reaming motion: It indicates clockwise rotation (90-180°). It denotes insertion, rotation then retraction of the instrument. It is indicated to be used in the apical third to prepare circular cross section to best fit the master cone.

7. 3) Turn and pull motion: This is a combination of reaming and filling where the instrument is inserted with quarter turn clockwise(reaming) and file is withdrawn(filing).4) Watch winding motion: It is the back and forth oscillation of the file through 30 -60° of rotation.

8. 5) Balanced force motion (Roane concept): - The instrument is inserted with quarter turn clockwise rotation until the working length is reached. - The instrument is then rotated counter-clockwise (cutting dentine) with apical pressure to prevent outward movement of the instrument. - Then clockwise turn is made to load debris on the file and pull it away.

9. - Flex-R-file is the instrument of choice to be used with this motion, due to its: triangular cross section and non cutting tip. - Simultaneous apical pressure and counter-clockwise rotation of the file strikes a balance between the tooth structure and the instrument. This keeps the instrument centralized inside the canal and prevents canal transportation.

10. -The problem with the counter clockwise rotation are; 1- The debris that are pushed towards the apical foramen. 2- The file tends to fracture (brittle fracture).

11. B) Techniques for preparation: 1) Apical coronal technique: It starts by enlarging the apical third followed by flaring of the coronal third.

12. Step-back technique (telescopic or serial root canal preparation):It includes three phases:A) Phase I: Apical preparation:Tooth length determination.

13. Selection of the initial file.

14. I.F is inserted into the canal to the full working length using a watch winding motion until it becomes loose. The procedure is repeated until the apical area is prepared at least three successive files after the I.F. Master apical file: is the largest file that will reach the full working length.B) Phase II; (stepping back): It is the stepping backward using larger size files while shortening working length to obtain a flared preparation.

15. N.B: Recapitulation: It must be done between each step through returning back to the working length with the MAF after each step back to loose the debris and smooth the wall with the irrigation to prevent blockage.C) Phase III; Flaring:The coronal third is flared using latch type rotary instrument or H File.

16. Modified step back technique:It is the same as the step back technique but in phase II (stepping back) the working length is shortened 3-5 mm to leave retention form for gutta-percha cone.

17. Advantages of step-back technique: 1. Shaping the apical 1/3 with small flexible files while larger stiffer files are used away from the apex. 2. Maintain a proper resistance form.3. Create spaces for multiple cones.

18. Disadvantages of step-back technique: 1. Extrusion of the debris beyond the apex. 2. Apical blockage. 3. Tendency for canal deviation.

19. 2) Coronal apical technique:Advantages:1. Early debridement of the coronal part of the canal.2. Better and deeper penetration of the irrigant.3. Elimination of the coronal and middle dentine resistance.4. Shorten the preparation time.

20. Crown down technique : A) Phase I: Coronal flaring using gates glidden drills no 3,2,1 with increase in depth of the penetration respectively.B) Phase II: (body of the canal)Accomplished by filling action starting with larger files and gradually decrease in the size of instrument with gradual increase in length.

21. C) Phase III): It includes preparation of the apical third of the canal till reaching the master file.

22. 3) Hybrid preparation:(Modified double flared): 1) Phase I: Coronal flaring 2) Phase II: Apical preparation 3) Phase III: Body of the canal is prepared in a step back manner