Circumferential Filing Technique Quiz

Objectives of Root Canal Preparation

• Confine instrumentation to the root canal apex
• Avoid forcing necrotic material beyond the foramen during canal preparation
• Remove all pulp tissue, bacteria, and their by-products, debris from the root canal system
• Create sufficient space to receive intra-canal medicament and for irrigants to flow

Cleaning and Shaping of Root Canal System

• Cleaning refers to the removal of all contents of the root canal system before and during shaping
• Includes removal of:
  • Organic substances
  • Microflora
  • Bacterial by-products
  • Caries
  • Pulp stones
  • Dense collagen
  • Previous root canal filling material
• Shaping refers to a specific cavity form with specific objectives, such as:
  • Three-dimensional access into the canal
  • Creating an apical preparation
  • Permitting final obturation instrument and materials to fit easily

Schlider's Mechanical Objectives

• Develop a continuously tapering cone
• Make the preparation in multiple planes, introducing the concept of "flow"
• Make the canal narrower apically and widest coronally
• Avoid transportation of the foramen
• Keep the apical opening as small as possible

Clinical Objectives of Cleaning and Shaping

• Direct access should be obtained along the straight lines
• The length of the tooth should be accurately determined
• Instruments should be used in a sequence of sizes with periodic recapitulation and without skipping of the sizes
• Instruments should be used with a quarter to half turn and withdrawn with a full stroke
• Barbed broaches should be used cautiously and only when the root canal is wide enough to permit their insertion and rotation without binding

Instrumentation Techniques

• Circumferential filing: moving the file around the circumference of the canal space while stroking the instrument in a 1-3 mm amplitude
• Reaming: using a clockwise or right-hand rotation of an instrument with spiral cutting edges
• Step-back technique: refining the root canal by using a master apical file and circumferentially filing the canal walls to achieve a smooth taper

Advantages and Disadvantages of Step-Back Technique

• Advantages:
  • Less likely to cause periapical trauma
  • Facilitates removal of more debris
  • Allows creation of a small apical preparation with larger instruments
  • Facilitates packing of additional gutta percha cones
  • Minimizes procedural errors
• Disadvantages:
  • Significant apical extrusion of debris
  • Apical blockage
  • Canal deviation
  • Time-consuming
  • Alteration of working length
  • Apical extrusion of debris during root canal instrumentation may be associated with postoperative pain or discomfort