Endodontics Quiz

Cleaning and Shaping

• The goal of endodontic therapy is to cure or prevent periradicular periodontitis and maintain natural tooth function and aesthetics.
• Cleaning involves removing all contents from the root canal system, including organic substances, micro-organisms, bacterial by-products, debris, caries, denticles, pulp stones, and root canal filling materials.
• Shaping refers to creating a specific cavity form with design objectives.

Outline

• Principles of Cleaning and Shaping
• Endodontic Instruments
• Steps of Cleaning and Shaping
• General Considerations
• Criteria to Evaluate Cleaning and Shaping

Brief History

• 1852: Arthur used small files for root enlargement.
• 1885: Gates Glidden drills were introduced.
• 1889: William Rollins developed the first endodontic hand piece.
• 1974: Schilder introduced the concept of "cleaning and shaping."

Endodontic Instruments

• Hand Instruments: Broaches and files.
• Rotary Instruments: Gates Glidden drill, Protaper, Profile, K3, Reciproc.
• Automated Instruments: Sonic and ultrasonic lasers.

Filing Motions

• Push and Pull action: Effective during pulling, best used with H-Files.
• Reaming Motion: Insertion, rotation, then retraction to prepare circular cross section.
• Turn and Pull (combination reaming/filing): Insertion with a quarter turn (reaming), followed by withdrawal (filing).
• Watch Winding Motion: Back-and-forth oscillation.

Reaming Motion

• Repeated clockwise rotation of the instrument shaves canal walls, producing a roughly circular cross-section.

Turn and Pull/Reaming

• File is inserted with a quarter turn clockwise and apically directed pressure, then is subsequently withdrawn.

Watch Winding Motion

• Gentle right and left rocking motion cuts while light inward pressure keeps the file engaged and progresses toward the apex.

Steps of Cleaning and Shaping

• Initial files are the first file that binds at the apex at full working length.
• MAF is the last file used for apical preparation(usually 3 sizes larger than the initial file).
• Recapitulation: A small file is used to clean the apical portion, removing debris.
• Definitions of Initial Files, MAF, and Recapitulation.

Access Principles

• Over-enlargement or gouging during access procedures significantly weakens structural strength.
• Employ appropriate cylindrical burs and tapered fluted burs to avoid root fracture or non-restorable conditions.

Coronal Modification

• Tools for pre-flaring include Gates Gliddens and dedicated NiTi instruments.
• Benefits of coronal modification include unimpeded apical access, improved tactile control during small file negotiation, improved access for disinfecting irrigations, and reduced working length changes during canal preparation.

Coronal Modification Continued

• If a canal is constricted, mineralized, or difficult to access, enlarging the coronal portion before deep entry into the root canal is beneficial.
• Pre-enlargement of the coronal portion of a root canal facilitates apical access.

Working Length Determination

• Radiographs, tactile sensation, moisture on paper points, and knowledge of root morphology are used to establish working length.
• The electronic apex locator is a reliable tool to determine working length.

Working Length Determination Continued

• Traditional treatment terminates canal preparation at the apical constriction, the narrowest section, believed to coincide with the cementodentinal junction.
• The position and anatomy of the CDJ can vary significantly from tooth to tooth, root to root, and even between different walls of the same root canal.

Working Length Determination Continued

• Terminating the preparation in necrotic cases 0.5 to 1 mm short of the radiographic apex and 1-2 mm short of the radiographic apex for irreversible pulpitis is recommended.

Apex Locator Tips

• Dry canals
• Appropriate file size
• Pulling the file from the filling/crowns, metal
• Radiographs
• Charge the tool/instrument.

Patency File

• A small K-file (usually size #10 or #15 ) is used to passively extend 1mm beyond the apical foramen without enlarging .
• Small patency files help clean up debris at the canal terminus through chemomechanical procedures.

Patency File and Glide Path

• A glide path is a path to the canal terminus to allow access of subsequent instruments.
• Glide path is created and secured with K-Files size #10 and #15, using a watch winding or balanced force motion .

Recapitulation

• Irrespective of the technique used, recapitulation is accomplished by using a small file to the correct working length to loosen debris and flush with irrigant (sodium hypochlorite). It is critical between successive enlargening files.

Canal Enlargement/Preparation

• The initial canal size is a critical determinant of the desired apical diameter.
• Adequate canal preparation is crucial for successful antimicrobial agent delivery to the apical third of the root canal.
• Maintaining the original path of the canal during preparation is important

Canal Enlargement/Preparation continued

• The shape of the access cavity in canals is extremely vital to ensure that instruments have unimpeded access .
• The size of the initial canal also determines the final apical diameter and affects proper irrigation needle penetration

Canal Enlargement/Preparation continued

• Apical enlargement has been broken down into three phases: Pre-enlargement, Apical enlargement, and Apical finishing
• The most teeth are between 19-25mm along their length, with clinical crown between 10mm.

Danger Zone

• Vertical root fractures and perforations are possible outcomes of excessive removal of radicular dentin.
• This sensitive area , or danger zone, refers to areas of concern at the root tip.

Final Apical Size

• Shuping et al. found that the additional antibacterial impact of sodium hypochlorite (NaOCl) only became apparent after instrumentation reached ISO size 30-35.

Criteria for Evaluating Cleaning and Shaping

• Following cleaning and shaping procedures the canal should exhibit "glassy smooth” walls, without unclean debris, or irrigant.
• This is verified by pressing the MAF against each wall in an outward stroke.

Criteria for Evaluating Cleaning and Shaping continued

• Shaping is evaluated by assessing canal taper and checking apical configuration, used for obturation with lateral compaction, and warm vertical compaction.

Step Back Technique

• Incorporates a stepwise reduction of the working length for larger files, typically 1 mm or 0.5 mm steps.
• Includes the use of a stainless steel K-Files exploring the apical constriction and establishing working length and incrementally reducing the working length.

Step Back Technique continued

• The use of larger and stiffer instruments during preparation reduces the incidence of errors, especially for curved canals.

What Does That Mean?

• Tooth length determination and initial file selection.
• The procedure repeating until the apical area is prepared using successive files.
• MAF (largest file) reaching full working length.

Step Back Technique Phase I (Apical Preparation)

• The procedure involves determining tooth length, selecting the initial file, inserting it to full working length, and using a watch-winding motion until it becomes loose.
• The treatment is repeated using successive files until the apical area is prepared.
• The last file used denotes the master file.

Phase I-Preparation of Apical Constriction

• Apical preparation is performed until 3 files after initial file
• Recapitulation with smaller file to full working length.
• The last file in phase 1 is the master file.

Phase II-Preparation of the Rest of the Canal

• Stepping backwards using larger size files while shortening working length to obtain a flared preparation.
• Recapitulation and irrigation occur between each file.
• Size increases, length decreases.

Crown Down Technique

• Enlarge the coronal third with progressively smaller GG drills or rotary instruments.
• The technique focuses first on flaring the coronal portion of the canal before the working length is established.
• It uses an exploratory action with a small file to help locate canals and evaluate preparation.

Limitations of Crown Down Technique

• After preflaring, the canal orifices should be inspected with Gates-Glidden drills or nickel-titanium rotary instruments.
• The procedure beings with larger Gates-Glidden instruments (size #4 or #5). Additional one-millimeter expansion (into the crown) is used to complete the coronal flaring.
• Be cautious not to carry the Gates-Glidden drills to the same level to prevent excessive cutting of dentin.

Crown Down Technique Advantages

• Removing tissue debris coronally minimizes extrusion of debris periapically.
• Reduces postoperative sensitivity from periapical debris extrusion.
• Increased irrigant volume penetration into canal irregularities and better tissue dissolution.

Crown- Down Technique: Clinical Advantages

• Enhanced tactile sensation, because of removal of coronal interferences.
• Flexible smaller files are used in apical portions, preventing large file damage in the apical part of the canal.
• Straight line access is beneficial for root curves and junctions.
• Space increases for irrigants and canal debridement frequency.
• Desired shape can be accomplished, creating the needed space for condensation.

General Considerations

• Initial canal exploration using smaller files to gauge size and shape, always performed with irrigant or lubricant present, never a dry canal.
• Copious irrigation between each instrument insertion and use of precoronal flaring techniques allow easy placement of working length files.
• Gradual canal enlargement, from coronal to apical, irrespective of flaring technique is recommended.
• Instrument binding should be avoided—files are teased to length using a watch winding action.

Evaluating Cleaning and Shaping Continued

• Post-procedure, the canal exhibits a smooth "glassy" appearance, absent of debris, fillings, or irrigant.
• Assessing this is done with the master apical file (MAF), which is pressed against each wall in an outward stroke.
• Evaluation of canal taper and apical configuration are also relevant measures.
• For warm vertical compaction, the plugger should reach within 5 mm of the working length, and for lateral compaction, the finger spreader should contact approximately 1 mm short.