Endodontics Lec 6: Cleaning and Shaping of Root Canal (PDF)

Lec 6 Endodontics Cleaning and Shaping of Root Canal By: Faisal Alhuwaizi Dr.Cube I Fourth Stage I 2024  Cleaning and Shaping of Root Canal The major biologic aim of endodontic therapy is to eliminate apical periodontitis by disinfection and sealing of root ca...

Lec 6 Endodontics Cleaning and Shaping of Root Canal By: Faisal Alhuwaizi Dr.Cube I Fourth Stage I 2024  Cleaning and Shaping of Root Canal The major biologic aim of endodontic therapy is to eliminate apical periodontitis by disinfection and sealing of root canal systems. Endodontic treatment mainly consists of three steps: 1. Cleaning and shaping of the root canal system. 2. Disinfection of the canal system. 3. Obturation and 3D closure and seal of the complete canal space. Cleaning and shaping is one of the most important step in the root canal therapy for obtaining success in the root canal treatment. www.drcube.org Cleaning It comprises the removal of all potentially pathogenic contents from the root canal system including the necrotic pulp tissue, dentine debris and microbes. Shaping The establishment of a specifically shaped cavity which maintain the original shape and taper of the canal and allow three-dimensional progressive access into the apical part to permit the final obturation instruments and materials to fit easily. For the success of endodontic treatment the contents of the root canal must be completely removed, to prevent any communication from the root canal system and periodontal space that may act as a portal of exit and can lead to formation of periodontal lesions of endodontic origin. www.drcube.org Apical region contains most of the lateral canals that connect the canal into the surrounding periodontium. Communication route between the periodontal pocket and the root canal. www.drcube.org Schilder in early 1960s described 5 mechanical and 4 biological objectives for successful root canal therapy. Mechanical Objectives 1 The root canal preparation should develop a continuously tapering cone. This shape mimics the natural canal shape. 2 Making the preparation in multiple planes which introduces the concept of “flow”. This objective preserves the natural curve of the canal. 3 Making the canal narrower apically and widest coronally. To create a continuous tapers up to apical third which creates the resistance form to hold gutta-percha in the canal. 4 Avoid transportation of the foramen. There should be gentle enlargement of the foramen while maintaining its position. Unprepared canal Prepaired canal 5 Keep the apical opening as small as possible. Since over- lapping of the foramen contributes to number of iatrogenic problems. Doubling the file size apically increases the surface area of foramen for four folds (πr2). www.drcube.org Biological Objectives 1) Confinement of instrumentation within the root canals only. 2) Ensure not to force necrotic or instrumentation debris beyond the apical foramen. 3) Optimum debridement of the root canal space. 4) Creation of sufficient space for intra-canal medicaments. www.drcube.org  Basic Principles in Root Canal Instrumentation 1. Before starting the endodontic treatment, proper Straight access of the canal diagnosis and evaluation of the tooth has to be perform to ensure that the tooth has favourable treatment prognosis. 2. During preparation of the access cavity, a straight line access from the coronal to the apical regions of the canal must be obtained. This can be performed by removing the overlying dentine to ensure flaring and smooth internal walls of the cavity with straight line access to the root. This dentine shoulder should be removed to straighten the canal access www.drcube.org 3. Ensure glide path of the canal and apical patency before starting canal preparation. This can be performed by passing a small size K-file (usually a size #8 or #10) beyond the apex. The glide path file can help to ensure complete opening of the canal and facilitate working length estimation. 4. Precurved instrument: In case of a curved canal, the instrument should be precurved to estimate the curvature of the canal. This is true only in case of stainless steel instrument, but nickel titanium instrument is flexible and cannot be curved. www.drcube.org 5. The use of intracanal irrigation solutions that serve many advantages: ▪ Dissolving and flushing out of the debris from the root canal. ▪ Lubrication for the cutting motion of the files within the canal. ▪ Antimicrobial activities. The most popular intra-canal irrigation solution is Sodium hypochlorite (NaOCl) 2.5-5.25%. The irrigation solution can be delivered inside the canal by using hypodermic syringe. www.drcube.org 6. Instrument examination: each instrument should be examined each time before insertion inside the root canal to verify the presence of any sign of fatigue, stressor damage, so any instrument showing such a sign should be discarded. 7. After each insertion and removal of the file, its flutes should be cleaned regularly, to ensure efficient cutting action of the file and prevent debris accumulation, canal blockage or extrusion of debris beyond the apical foramen. 8. Never force the instrument in the canal. Forcing or continuing to rotate an instrument while its bind to the canal wall may break the instrument. www.drcube.org 9. Use of instruments in sequential order. Root canal preparation is done gradually by using successively larger files (never skip any size of instrument) e.g. size 20 followed by size 25 then 30 and so on, but not size 20 then size 30. 10. Over preparation and too aggressive over enlargement of the curved canals should be avoided. 11. Creation of an apical stop should be maintained during instrumentation procedures by maintaining the apical size as clean and small as possible. Over enlarging of the apical foramen should be avoided because it destroy the apical stop and cause apical extrusion of the irrigation and obturation material and cause failure of endodontic treatment. www.drcube.org  Manual or Hand Instrumentation Techniques Standardized Technique Step-Back Technique Step-down Technique Balanced Force Technique Crown Down Technique 1. Standardized Technique This technique is developed by Ingle and uses the same working length (WL) definition for all instruments introduced into a root canal. Therefore, relies on the inherent shape of the instruments to impart the final shape of the canal. It is also called ‘single-length technique’. www.drcube.org Disadvantages of Standardized Technique 1) Chances of loss of working length due to accumulation of dentin debris. 2) Possibility of uncompleted debridement of the wider part of the canal (coronal part). 3) Difficult to irrigate apical region. 4) More chances of pushing debris periapically. 5) Increased incidences of ledging, zipping and perforation in curved canals. 6) Increased incidences of file fracture due to heavy contact and friction with canal walls. www.drcube.org 2. Step-Back Technique Realizing the importance of a canal shape larger than that produced with the standardized approach, the step-back technique was introduced by Clem and Weine in 1960. This technique relies on stepwise reduction of WL for larger files, typically in 1 or 0.5-mm steps, resulting in flared shapes with 0.05 and 0.10 taper, respectively. The final result is a preparation with small apical enlargement and marked taper from apical to coronal. www.drcube.org Advantages of Step-Back Technique More flare at coronal part of root canal with proper apical stop. Disdvantages of Step-Back Technique 1- Difficult to irrigate apical region. 2- More chances of pushing debris periapically. 3- Time consuming. 4- Increased chances of iatrogenic errors for example ledge formationin curved canals. 5- Difficult to penetrate instruments in the canal. 6- More chances of instrument fracture. 7- More chance of change in WL after finishing of coronal flaring especially in the curved canal. www.drcube.org  3. Step-Down Technique This technique was developed to shape the coronal part (coronal preflaring) of the canal before instrumentation of the apical part. The objectives of this Technique 1- To permit straight access to the apical region of the canal by eliminating coronal interference. 2- To remove the bulk of necrotic tissue and microorganisms before apical shaping to minimize extruded debris through the apical foramen during instrumentation. 3- To allow deeper penetration of irrigant deeply into the apical part of the canal. In addition, it provide coronal escape way for apical debris with less chance for extrusion from the apex. 4- The WL is less likely to change with less chance of zipping near the apical constriction. www.drcube.org  Procedure ▪ Preparation of two coronal root canal thirds using Hedstrom files of size #15, #20, and #25 to 16 to 18 mm or where they bind. These files are used with circumferential filing motion on the canal walls. ▪ Thereafter, increasing the coronal flaring of the canal by using Gates-Glidden drills size 2, 3, and 4, in sequential order with 1 mm shorter for each larger file. ▪ Followed by canal WL estimation, then instrumentation of the remaining apical part of the canal. This includes using small K- file # 15, 20 and 25 to prepare the apical seat. ▪ Combining the two parts, step-down and apical shape, by stepwise decreasing of WL of incrementally larger files. Frequent recapitulation with a #25 K-file to WL is advised to prevent blockage. www.drcube.org 4. Balanced Force Technique This technique was introduced after the development of new file ‘Flex- R file’. This file has “safe tip design” with a guiding land area behind the tip. This design help the file to be guided within the canal, especially the curved one, and prevent engaging the wall and ledge formation. This technique can be described as positioning and preloading an instrument through a clockwise rotation and then shaping the canal with a counterclockwise rotation. www.drcube.org Procedure 1- In balanced force technique, preparation is completed in a step-down approach. 2- After that, the balanced force hand instrumentation begins in the apical preparation by placing, cutting, and removing instrument using only rotation motion. 3- File motion include: a) Placement (apical pushing with 1/4 clockwise rotation). b) Cutting (repeated 3/4 counterclockwise rotation). c) Removal (1/4 clockwise rotation with pulling for removing debris). C www.drcube.org 4- The original Balanced Force concept then refers to apical control zones, for example, first using sizes #15 and #20 files to the periodontal ligament (i.e., through the apical foramen) and then reducing the working depth by 0.5 mm for subsequent sizes #25, #30, and #35. The apical shape is then completed 1 mm short using sizes #40 and #45 under continuing irrigation with NaOCl. Advantages Lesser chances of creating a ledge, blockage or canal transportation. www.drcube.org 5. Crown Down (Pressure-less) Technique The crown-down instrumentation concept based on the canal shaping technique moving from the crown toward the apical portion of the canal. This concept was the introductory for the most recent rotary instrumentation technology. Procedure www.drcube.org Biological Advantages of Crown Down Technique 1 Removal of tissue debris coronally, thus minimizing the extrusion of debris periapically. 2 Reduction of postoperative sensitivity which could result from periapical extrusion of debris. 3 Greater volumes of irrigants can reach in canal irregularities in early stages of canal preparation because of coronal flaring. 4 Better dissolution of tissue with increased penetration of the irrigants. www.drcube.org Clinical Advantages of Crown Down Technique 1- Enhanced tactile sensation with instruments because of removal of coronal interferences. 2- Flexible (smaller) files are used in apical portion of the canal; whereas larger (stiffer) files need not be forced but kept short of the apex. This decrease the chance for canal ledging, transportation and perforation. 3- Straight line access to root curves and canal junctions. 4- Provides more space for irrigants. 5- Enhance canal debridement and decrease frequency of canal blockages. 6- Desired shape of canal can be obtained that is narrow apically and wider coronally. This provides better room for Gutta Percha condensation to obtain proper three dimensional obturation of the root canal. www.drcube.org Thank You For Your Attention The First and Largest Educational Platform for Students of The Medical Group in Iraq www.drcube.org