endo sheet # 11- Nataliya Komashynska

بسم الله الرحمن الرحيم

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بسم الله الرحمن الرحيم

Objectives of root canal preparation:
1. mechanical objectives
2. biological objectives
Root canal preparation techniques:
1. coronal-apical approach
2. apical-coronal approach

-The final shape should be continuously tapering funnel following the shape of the original canal; this was termed as the "concept of flow".
- The concept of flow will allow good irrigation and will allow 3- dimension filling .
- There are many challenges of root canal preparation, and the most important one is complex anatomy of a root canal system. If we don't work carefully we might have errors in preparation like :
1. apical transportation
2. perforation
By using large and stiff instruments , perforation of the root may occur,
and this perforation will cause the periodontal inflammation.
3. Apical zipping. It is the result of the tendency of the instrument to straighten inside a curved root canal, resulting in over-enlargement of the canal along the outer side of the curvature . This also may cause perforation.
4. Ledging
A ledge has been created when the working length can no longer be negotiated and the original patency of the canal is lost. This means that we can’t insert the file until the apical construction. It’s very difficult to clean and fill, we have a stopper at that level .So we can’t clean it properly.

CAUSES OF LEDGE FORMATION

1-Inadequate straight line access into the canal
2-Incorrect working length determination.
3-Filing of a curved canal short of working length.
4-Over enlargement of a small curved canal.
5-Loss of patency by debris packed in the canal.
6-Larger files plus curved canal equals a ledge


It’s very important to maintain the apical patency (keep the apical foramen open) in order to maintain the integrity of the apical part of the canal.
Apical patency: the main idea of it is to insert a very small file
(size 8 or 10) inside the canal until it a little bit over extended beyond the apical foramen (0.5mm) to ensure that there is no apical debris close the apical foramen( that will become like a rock (very hard) later on and it will be difficult to remove).


Conclusions (for the previous lec’s)

• The successful outcome of root canal therapy depends on a considerable extent of good preparation (cleaning and shaping).More correctly to say shaping and cleaning because a good shaping or continuously taper shape will allow adequate cleaning.
• Remove agents which initiate or perpetuate periapical inflammation.
• You don’t have to complete all root canal treatment –cleaning, shaping and filling- in one visit, but it is better to complete cleaning and shaping in the same visit to prevent flare up which make swelling and pain.
• Coronal followed by apical preparation.
• Keep all instrumentation with root canal and avoid extrusion into periapical tissues.
• No amount of chemotherapy in the absence of good instrumentation will produce a successful outcome.
** Instruments should be used sequentially
-Prepared canal should include (encompass) original canal-not straightened or transported.
-Prepared canal should end in apical narrowing.
-Preparation should taper smoothly from crown to apex.


• Problems are easy to create; their prevention is the challenge.

• Any new technique, no matter how easy it first appears to be, has a learning phase for every operator before it may be used in most efficient manner.
**new technique does not mean a better one.
Drawbacks of Conventional Hand Stainless Steel Preparation Techniques:

1.TIME CONSUMING
2 .LESS PREDICTABLE SHAPES IN CURVED CANALS
3.DEBRIS EXTRUSION WITH FILING MOTION
4.MISHAPS(ledges, canal blockade, zipping of foramen)
-If the hand technique used in improper way it will cause errors.

**The recent technique is Rotary Nickel Titanium Instruments which added a lot in endodontic treatment .

Advantages of Rotary NiTi Techniques

1.LESS CANAL TRANSPORTATION
2.LESS DEBRIS EXTRUSION (LESS Post Or PAIN)
3.FASTER THAN HAND PREPARATION
4.MORE PREDICTABLE RESULTS

-The rotary nickel titanium has a lot of systems (may be more than 30 systems) but basically they are divided in to 2 categories:

1- Constant taper ( all instrument ) : In previous lectures we talked about
standardization and about O2 or 2% taper. (02 taper means that the instrument diameter increases by 0.02 mm with each 1 mm back from instrument tip)

Constant taper is divided into : -cutting active bland with sharp cutting edges
- Not cutting bland (with Radial Land )
Cutting edge becomes like areas called radial land areas rather than a sharp cutting edge



-some systems have a non-cutting blades or lands
(profile , GT and A3 systems ).
-other systems may have cutting blades without lands
(Hero 642, HeroShaper, Mtwo, Alpha File, RaCe)

2- Variable taper ( ProTaper which we use )


** Rotary Instruments with a Constant taper and Cutting Blades
have a tendency to screw-in


** Rotary Instruments with a Constant taper and a Radial Land.(Cutting edge isn’t sharp but like an area) Requires more pressure to cut and are subjected to more stress.
(surface contact is increased)

**Rotary Instrument with a large cross-section(central mass) and a constant taper are too stiff in taper higher than 4% to shape curvatures without risks of mishaps.

**Any Niti should be used with a special type of hand piece , with a special speed (not more than 300 RPM),and with a special torque.

One of the systems is X-Smart :
-it is safe
-torque control and autoreverse function.

Another system that are widely used in clinic is ProTaper system
-ProTaper is the only system that has Variable Taper .
- Prevent screw-in effect
-Allows increased apical tapers (Finishing Files)
-Allows excellent shaping with few instruments


* Basically we have 6 files, 3 shaping files and 3 finishing files.
There design works on coronal apex approach concept.

Shaping files; S1, S2, Accessory Sx
1- S1 → purple in color .
tip diameter is 0.18 mm.
-because it is very thin apically and have a wider taper coronaly the active segment of the file is the coronal segment (the part that cuts once inserted inside the canal is the coronal part of the file)
It should be passed passively in order to inter inward without any resistant, and with brush like motion it will shape the canal upward.

2- S2 → white in color .
tip diameter is 0.20 mm , so it is equal to yellow one in manual series.
-the taper is wider in the middle part of the file so we use it to shape the middle part of the canal .
So by using S1 ,S2 files we shape the coronal and middle part of the canal .

3- Sx. Its tip diameter is 0.19mm, this file is used only when needed.(If we don’t have very straight line access cavity we can use Sx in order to relocate canal to become straight line).
-In slide 149we use Sx to remove dentinal shelf to make straight line access.
-In slide 150 we can see lower 4,5,6 and 7 ,Clamp , file is inserted into the canal. Distally we have 1 canal and Mesially we have 2 canals .MB canal is the carved one and ML is straight.
In slide 151 we see lower 4,5,6,7. With lower 6 root canal treated and filled.



-Design of shaping files is called Eiffel tower shape .
It resembles its shape downward wide gives it resistance,
upward very thin gives it flexibility
-to prepare the apical part of the canal we use finishing
files .
Finishing files :
-Basically they are F1, F2, F3 files with an increase in the diameter as we move from 1-3 .
They are used according to they size of the apical part of the canal.
Type of the file is the same as standardized.
F1 20 , F2 25 , F3 30
F1→ yellow
F2→ red
F3→ blue

-for very large canals we use F4, F5 files, but commonly
we use F1, F2, F3 files .
-this system is good for cleaning and shaping curved
canals.
Their taper is fixed at the last 3 mm:
F1 → 0.07 mm taper
F2 → 0.08 mm taper
F3 → 0.09 mm taper
They are larger than the taper in normal files which is
0.02mm ,but we can't continue with this large taper cause
we will have a thick file coronaly .That's why those files
have fixed taper only in the apical part ,then the taper will
decrease as we move towards the handle (coronaly).

ProTaper Universal Characteristics
-Cutting blade (no radial land). This will increase Efficiency.
-Safe non cutting tip which will act as a guide.
-cross section differs between S1, S2,F1,F2,F3
-in smaller sizes → convex cross section .
-in larger sizes → concave cross section to increase
flexibility .
- So it is convex in S1, S2, SX, F1, F2 .And Concave in F3, F4, F5

-Triangular concave cross-section will increase Flexibility.
-Triangular convex cross-section will increase Resistance.

***before using any rotary instrument you have to establish glyde path with size 10 and 15 hand files or ProFinder files because rotary instrument can not open classified canals .Then enlarge it by using ProTaper S1.

ProFinder Files
• Variable Decreasing Taper
(avoids taper lock effect)
• Smoother Progression in Tip Diameter
• Silicone Handle
• Depth Marks

Treatment Sequence
1-Scout the canal with hand files10 & 15 or with ProFinder Files 13 & 17 to the level they are accepted in the canal.
The lubricating action of Glyde helps the instruments to slide in the canal.

2-Use S1 with a brushing motion and enlarge the canal no deeper than the level of the penetration of size 15 hand File (to make sure that the tip of S1
is never blocked)

3-If needed, use Sx with a brushing motion to relocate the orifice of the canal and create a straight line access
(Don’t use Sx deeper than S1 because its tip is very thin and can fracture)

4-Use stainless steel hand files 10 & 15
Or ProFinder Files deeper in the canal and determine working length .

5-After going to length with a stainless steel file size 15, use S1 to working length, using a brushing motion.

6-When S1 reaches working length, use S2 to working length
using a brushing motion.

7-When S2 reaches working length, use F1 to working length.

8-Gauge the diameter of the foramen with stainless steel files and if the foramen is larger than 20, use F2, F3, F4 or F5 to working length, according to the real apical diameter.
CAUTION !
NEVER USE A BRUSHING ACTION WITH THE FINISHING FILES .
When a finishing file reaches length, It is immediately withdrawn.


There are2 types of ProTaper files:
1-Hand using files (manual files )
2-Rotary files.

PROTAPER For HAND USE files have advantages for Hand SS File Users; there will not be Canal Transportation
-Less Extruded Debris
-Excellent Apical Taper
For NiTi Rotary Users: In Case of Contra Indication to Continuous Rotation (Example : Apical Hooks)


In slide 165 we see apical hook .If we use rotary file the chance of fracture will be high so we use manual protaper file.


PROTAPER For HAND USE
Shaping files
1- S1 → purple in color .
tip diameter is 0.18 mm.
2- S2 → white in color .
tip diameter is 0.20 mm
**Important .The color coding is completely different than that in manual instruments.

-F1 , F2 ,F3 files have fixed taper at last 3 mm
-color coding is the same for a manual instrument.

7 % in 20(F1)
8 % in 25(F2)
9 % in 30(F3)
**increasing taper will add advantages to mechanical and biological goals of our perforation , it will allow us to make cleaner, wider and easy to filling canal.






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DONE BY:Nataliya Komashynska
28/11/2010
LEC #:11