1. Special anatomic problems in canal cleaning and shaping (complication)
Name: Seyedsaeid Seyedraoufi
Subject: Phantomic endodentic
Lecturer: Prof.Doctor Nino Korsantia
Garg N., Garg A. - Textbook of Endodontics ,2011
June 2020

2. Cleaning and Shaping of root canal
Cleaning and shaping the root canal consists of removing the pulp tissue and debris from the canal and shaping the canal to receive an obturation material
Using sequentially larger size of files and irrigating and disinfecting the canal to clear it of debris , one shapes the canal to receive a well condensed filling that seals the root canal apically and laterally to prevent any leakage

3. Principles of endodontic cavity preparation
List of preparations of endodontic cavity preparation is established by slightly modifying “Principles Of Cavity Preparation“ established by G.V.Black
Endodontic preparations consists of both coronal and radicular preparation each prepared separately but ultimately flowing together into a single preparation:
Endodontic coronal cavity preparation:  
1.Outline form 2. Convenience form 3. Removal of the remaining carious dentine(and defective restoration)4.Toilet of the cavity
Endodontic radicular cavity preparation:
1.Outline form and convenience form(continued) 2. Toilet of the cavity(continued)
3. Resistance form 4. Retention form

4. Anatomic problems
Curved Canals
Calcified Canals
C-shaped Canals
S-shaped Canals

5. Curved Canals
Unfortunately, not all root canals are straight. Clinicians regularly encounter curves of different degrees and in various places all along the root canal system
Management of curved Canals:
Estimate and calculate angle of curvature, imagine a straight line from orifice towards canal curvature and another line from apex towards apical portion of the curve.
The internal angle formed by interaction of these lines is the angle of curvature.

6. Factor affecting success of negotiation of a curved canal:
File can cut dentine evenly only if it engages dentine around its entire circumference. Once it becomes loose in a curved canal, it will tend to straighten up and will contact only at certain points along its length.
Factor affecting success of negotiation of a curved canal:
Degree of curvature
Flexibility of instrument
Size of root canal
Width of root canal
Skill of operator
This can lead to occurrence of procedural errors. To avoid occurrence of such errors there should be even contact of file to the canal dentine.
Also we need to decreased Filing force to prevent any kind of errors during working.

7. Decrease in the Filing Force can be done by:
A. Pre-curving the file.
B. Use of smaller number files.
C. Use of intermediate sizes of files: It has been seen that increment of 0.05 mm between the instruments is too large to reach the correct WL in curved canals. To solve this problem, by cutting off a portion of the file tip a new instrument size is created which has the size intermediate to two consecutive instruments.
There is increase of 0.02 mm of diameter per millimeter of the length, cutting 1 mm of the tip of the instrument creates a new instrument size, for example, cutting 1 mm of a number 15 file makes it number 17 file.
D. Use of flexible files.

8. Decrease in length of actively cutting file can be done by:
A. Anti-curvature filing:
Anti-curvature filing was introduced to prevent excessive removal of dentin from thinner part of curved canals, for example, in mesial root of mandibular molar and mesio buccal root of maxillary molar.
The walls of opposite side from curve are instrumented more than the inner walls resulting in a decrease of the overall degree of canal curvature.
B. Changing the canal preparation techniques (using Crown down technique).

9. Management of calcified Canals
Calcifications in the root canal system are commonly met problem in root canal treatment.
Various etiological factors seem to be associated with calcifications are caries, traumas and aging.
Success in negotiating small or calcified canals is predicted on a proper access opening and identification of the canal orifice.
The distance from the occlusal surface to the pulp chamber is measured from the preoperative radiograph.

10. Management of calcified Canals
At this suspected point a fine instrument number 8 or 10 K- file, is placed into the orifice, and an effort is made to negotiate the canal.
An alternative choice is to use instruments with reduced flutes, such as a canal pathfinder which can penetrate even highly calcified canals.
The most common sign of accidental perforation is bleeding, but bleeding may also indicate that the pulp in the calcified canal is vital.
If there is any doubt as to whether the orifice has actually been found, place a small instrument in the opening and take a radiograph

11. Guidelines for Negotiating Calcified Canals:
Copious irrigation all times with 2.5 to 5.25 percent NaOCl enhances dissolution of organic debris, lubricates the canal, and keeps dentin chips and pieces of calcified material in solution.
Always advance instruments slowly in calcified canals.
Always clean the instrument on withdrawal and inspect before reinserting it into the canal.
When a fine instrument reaches the approximate canal length, do not remove it; rather obtain a radiograph to ascertain the position of the file.
Use chelating agents to assist canal penetration to full WL.
Flaring of the canal orifice and enlargement of coronal third of canal space improves tactile perception.

12. Management of C-shaped Canals
Though the prevalence of C-shaped canals is low, but those requiring endodontic treatments present a diagnostic and treatment difficulties to the clinician.
Some C-shaped canals are difficult to interpret on radiographs and often are not identified until an endodontic access is made.
These are commonly seen in mandibular second molars and maxillary first molars especially when roots of these teeth appear very close or fused.
In maxillary molars, includes MB and palatal canals or the DB and palatal canals. In the mandibular second molar, the C- shaped canal includes MB and distal canals.

13. Major problems come across during bio-mechanical preparation of C- shaped canals are difficulty in removing pulp tissue and necrotic debris, excessive hemorrhage, and persistent discomfort during instrumentation.
Because of large volumetric capacity of the C-shaped canal system, along with transverse anastomoses and irregularities, amounts of 5.25 percent NaOCl is necessary for maximum tissue removal and for control of bleeding.
Over preparation of C-shaped canals should be avoided, because of presence of only little dentin between the external root surface and the canal system in these teeth.

14. Management of S-shaped Canals
S-shaped or bayonet shaped canals pose great problems while endodontic therapy, since they involve at least two curves, with the apical curve having maximum deviations in anatomy.
These double curved canals are usually identified radiographically with multi-angled radiographs, or when the initial apical file is removed from the canal and it simulates multiple curves.
S-shaped canals are commonly found in maxillary lateral incisors, maxillary canines, maxillary premolars, and mandibular molars.

15. Access preparation is flared to allow for a more direct entry.
During initial canal penetration, it is essential that there be an unrestricted approach to the first curve.
Once the entire canal is negotiated, passive shaping of coronal curve is done first, to facilitate the cleaning and shaping of the apical curve.
To prevent stripping in the coronal curve, anti curvature or reverse filing is recommended, with primary pressure being placed away from curve of coronal curvature.
Gradual use of small files with short amplitude strokes is essential to manage these canals effectively.
Constant recapitulation with small files and copious irrigation is necessary to prevent blockage and leading in the apical curve.
Over curving the apical 3 mm of the file aids in maintaining the curvature in the apical portion of the canal as the coronal curve becomes almost straight during the later stages of cleaning and shaping.