Root Canal Treatment: Objectives and Methods

• Endodontics Department: Deals with the preparation of root canals.
• The main goal of root canal treatment is to maintain periradicular health by preventing infection or restoring health by eliminating microorganisms.
• Root canal treatment includes removing necrotic pulp, tissue debris, inflamed pulp, or healthy pulp tissue.

Learning Objectives

• Root canal treatment aims and objectives
• Determining the working length of a root canal
• Choosing instruments based on the purpose and principles of root canal preparation
• Understanding the application steps in detail

Biocentric Approach to Root Canal Treatment

• Removal of tissues, microorganisms, by-products, and substrates
• Shaping the root canal system for irrigation, medication, and filling
• Filling the shaped canal system with coronal restoration

Endodontic Triad

• Achieves cleaning, shaping, and canal filling while preserving tooth structure.

Pre-Treatment Examination

• Clinical and radiographic examination required.
• Radiographs provide information on caries, coronal restoration quality, pulp chamber dimensions, pulp stones, canal numbers, and root curvature.

Diseases on Radiographs

• Periodontitis appears on radiographs
• Pulpitis does not

Determining Working Length

• Accurate determination of root canal length is essential for cleaning, disinfection, and filling.
• Meta-analysis studies show both overfilling and incomplete filling have negative effects on prognosis.

Radiographic Method

• Initial working length is calculated from measurements on preoperative radiography.
• Insert a file (ISO 15 or larger) to an estimated length and take a radiograph.
• The working length is adjusted based on where the preparation should end.

Defining Working Length

• Distance from a fixed reference point (incisal edge or cusp tip) to the apical constriction.

Key Terms

• Apical Foramen (Major Foramen): Main opening where the root canal reaches the periodontal ligament.
• Physiological Foramen (Apical Constriction, or Minor Foramen): The point where cementum reaches the root dentin or periodontal tissue.
• Anatomical Apex: Farthest point of the tooth crown morphologically.
• Radiological Apex: Farthest apical point seen in radiology, may differ from anatomical apex due to root morphology differences.
• Black Range: Funnel-shaped part from cementum-dentin border to the periodontal ligament.

How to Determine Working Length

• Radiographic methods
• Electronic apex locator
• Tactile sense/feeling resistance

Apical Constriction Area

• The minor diameter is the ideal point to end endodontic treatment.

• It has the narrowest diameter, least blood supply, and intertwining of pulpal and periodontal tissues.

• Recommended that root canal treatments be 0.5-1 mm behind the radiographic apex.

• Radiographic images are two-dimensional, the file tip may exit the apical foramen.

Electronic Apex Locators

• These measure impedance at different frequencies and are accurate within 0.5mm in >90% of cases.
• Using apex finders can reduce the number of radiographs, but radiography gives anatomy information.

Paper Point Technique

• This technique is used depending on the state of the root canal dryness
• It is not suitable as a primary method for determining run length.

Root Canal Preparation

• Root canal systems are inclined in one or more planes. The degree and amount of curvature varies from root to root. The apical portion of the root canal system is generally the least cleaned and prepared.
• Preserving the original canal shape and preventing complications is important.

Purposes of Mechanical Root Canal Preparation

• Removing vital and necrotic tissue
• Creating space for irrigation and medication
• Preserving apical root anatomy
• Protection from iatrogenic damage
• Facilitating obturation
• Maintain dentin for tooth function

Outline Form of Canal

• The natural curvature is maintained while enlarging the canal
• Prepared canal shows the outline of the original canal.
• The canal should be wide to create maximum resistance.

Resistance Form of Canal

• Important to create an apical stop in the apical foramen while preparing the apical third of the canal.
• In most cases, the area is 0.5 mm behind the radiographic apex.

Foramen Apicale

• Not always located at the apex.

Retention Form of Canal

• Preparation of this form without hurting the apical foramen.

Flaring Form of Canal

• Expansion of the root canal from the funnel-shaped retention form to the access cavity preparation.

Instrumentation Techniques

• Crown-down: Preparation from the coronal part to the apical part and reduces the risk of apical obstruction.
• Step-back: Preparation of the apical part to the coronal part, creates a tapered formula.
• Hybrid: Begins with coronal preparation (crown-down) and enlarges of the apical part.

Balanced Force Technique

• Relies on rotational movements
• Provides superior protection of canal curvature and prevention of procedural errors.
• Provides adequate apical control and ensures good centering ability of the handpiece in the root canal.

Filing for Guide Path (Apical Patency)

• The Apex constriction must remain unblocked
• The guide file should be a small flexible K-type that passively passes through the apical constriction without widening it.

Techniques compared

• Crown-down Technique: Enlarges the coronal part, minimizes the passage of canal contents out of the apical area.
• Step-back Technique: Prepares the canal starting from the apical part.
• Balanced Force Technique: Uses various handpiece manipulation strategies.

Terminology of instruments

• Initial Apical File (IAF): Smallest file that attaches to the walls at the working length
• Master Apical File (MAF): Largest file that attaches to the walls at the working length, three .sizes larger than the first file.
• Recapitulation: Reuse of the MAF
• Irrigation: Rinsing the root canal.

Preparation in Root Canal Treatment

• An unobstructed path is created using diamond or tungsten carbide burs.
• Canal orifices can be located using a K-type file (#6-8 or 10).

Working Length Calculation

• Uses apex finder and radiography
• The working length determined depends on the canal diameter.
• The rubber stop on the file is placed at the reference point, and radiography is taken.

Radiography

• The part from the incisal edge to the root tip is measured, as is the distance from the incisal edge to where the file ends.
• The real length of the tooth is calculated, working length is 1mm shorter.

Hybrid Preparation Technique

• Stage 1: Coronal Enlargement (Gates-Glidden Burs)
• Stage 2: Apical Gauging
• Stage 3: Step-back

Coronal Enlargement Stage

• Use a number 4 Gates Glidden bur, and other sizes as required.
• The bur is withdrawn slightly when tightness is felt, then its length is measured.
• Then switch to #3 GG, then #2 GG, adjusting the rubber stopper each time.

Additional Considerations

• The device should not be stopped while the bur is in the root canal
• Finally, the root canal has to be irrigated

Apical Gauging stage

• IAF selection and MAF determination must be done before this technique.
• File which will be used in canal length measurement, is short/long in the root canal; then choose a smaller/larger size file
• Generally, the root canal instrument should be 3 sizes larger than the IAF is the MAF.
• Irrigate!

Step-Back stage

• After MAF, preparation can be done up to another 3 file sizes.
• Each file is used on 1 mm shorter than the previous file
• Then, immediately perform intracanal irrigation, increase instrument size,return to the MAF at working length.
• Irrigate!