Assessment of Endodontically Treated Teeth

Assessment of Endodontically Treated Teeth

• The quality of the endodontic treatment, amount of remaining tooth structure, periodontal health, occlusal forces, and esthetic requirements influence the success of restoring endodontically treated teeth (ETT).

Quality of The Endodontic Treatment

• A good apical seal, no coronal leakage, no pain upon percussion or biting, no missed canals, no periapical pathosis or widening of the periodontal membrane space, no exudate, sinus tract or perforation, and no over or underfilling indicate quality endodontic treatment.

Amount of Remaining Tooth Structure

• The strength of ETT is directly proportional to the amount of remaining tooth structure.
• A minimum of 3 mm length and 1.5 mm thickness of tooth structure is considered restorable.
• Ferrule effect is essential for restoring ETT.
• Crown/root ratio, affected by horizontal and vertical bone resorption, should ideally be 1:2, with a normal ratio of 2:3 and a minimum of 1:1.
• Biological width, starting from the base of the sulcus to the alveolar bone crest, includes the epithelial and connective tissue attachments.
• Grade 2 mobility negatively affects the longevity of restorations.
• Occlusal and parafunctional stresses, including type of occlusion, parafunctional habits, if the tooth is an abutment, and its position in the arch, should be considered.

Esthetic Requirements

• Discoloration of ETT can result from remnants of degenerated pulp or endodontic fillings.

Treatment Planning

• Restoration options range from core only, endocrown, to extra-coronal restorations with or without a post, depending on remaining tooth structure and stress levels.

Anterior + Premolar Teeth

• Favorable loading, no parafunctional habits, and not acting as a bridge retainer:
  • Access cavity only, one axial wall, bonded composite restoration, and a crown.
• High stresses, parafunctional habits, or acting as a bridge retainer:
  • Access with three axial walls, post, core, and crown.

Molar Teeth

• Access cavity only, one axial wall, bonded composite restoration, and a crown.
•  Access with four axial walls, post, core, and crown.

Post Crown System

• A full coverage restoration retained by a post accurately fitted inside the prepared root canal.
• Components include post (dowel), core, and extra-coronal part.
• Ideal post characteristics include good retention for the core, minimal stress transfer, bonding to dentin, high strength, accurate fit, tooth structure conservation, easy removal for retreatment, high esthetic properties, biological compatibility, and efficient procedures.

Indications for Post Crown System

• Individual restoration for badly mutilated ETT.
• Retainer for short span bridge.
• When other restoration types are not suitable.
• Presence of good roots in ETT.

Contraindications

• Improper root canal filling.
• Periapical pathosis.
• Short, thin, curved, or weak roots.
• Inadequate bone or periodontal support.
• Abnormal occlusion and bad habits.

Advantages

• Excellent retention and aesthetics.
• Restoring any tooth, even with complete loss of coronal structure.
• Correction of mal-aligned teeth.
• Strengthening of badly mutilated ETT.

Disadvantages

• Limited to non-vital teeth.
• Root weakening due to improper canal widening.
• Root fracture due to improper canal preparation or post selection.

Classification of Post Crown Systems

• According to material:
  • All metallic
  • All non-metallic
  • Combination
• According to retention:
  • By post only
  • By post and pin(s)
  • By post and collar
• According to attachment:
  • Attached post crown
  • Detached post crown (two pieces, three pieces)
•  According to method of construction:
  • Ready made
  • Custom made

Attached Post Crown (One-Piece Post Crown)

• Not currently used.

Principles of Post Preparation

• Tooth preparation:
  • Conservation of tooth structure: Root canal preparation and coronal portion preparation.
  • Retention form: Root canal geometry, post design, post length, post diameter.
  • Resistance form: Stress distribution and rotation resistance.

Preservation of Tooth Structure

• Post space preparation: Minimal tooth structure should be removed to prevent perforation or weakening of the root.
• Coronal tissue preparation: Internal reduction to eliminate undercuts and external reduction to accommodate a complete crown.

The Ferrule Effect

• Binds tooth structure together, increasing resistance to lateral and occlusal forces.
• Decreases stress concentration at the post/core junction.
• Maintains cement seal integrity and increases resistance to dislodgement.

Factors Affecting Ferrule Functionality

• Ferrule height: 1.5-2 mm of vertical tooth structure.
• Ferrule width:  At least 1 mm thickness.
• Number of walls: Uniform ferrule is superior; a non-uniform ferrule is better than no ferrule.
• Tooth type, lateral load, and ferrule location: Functional cusp should have a ferrule on posterior teeth; palatal ferrule for maxillary and labial ferrule for mandibular teeth in anterior teeth.
• Type of post and core materials:

How To Gain Ferrule

• Surgical crown lengthening.
• Orthodontic extrusion.

Retention Form

• Resistance to displacement along the path of insertion.
• Factors influencing retention form:
  • Post length
  • Post surface texture
  • Post diameter
  • Luting agent
  • Preparation geometry

Post Length

• Longer posts provide more retention.
• Guidelines for post length:
  • Equal to the occlusal-gingival dimension of the crown.
  • Longer than the crown.
  • One and one-third of the crown length.
  • Specific fraction of the root length.
  • Ending halfway between the crestal bone and root apex.
  • As long as possible while maintaining apical seal.
• Considerations:
  • At least 3-5 mm of apical gutta-percha should be retained.
  • Post should extend at least 4 mm apical to the bone crest to decrease dentinal stress.
  • Molar posts should not exceed 7 mm apical to the canal orifice to avoid perforation.

Post Surface Texture

• Threaded or serrated posts offer more retention than smooth posts.
• Controlled grooving or roughening of the post and canal increases retention.

Post Diameter

• Different theories exist:
  • Minimal canal preparation.
  • Minimum of 1 mm sound dentin around the post.
  • Post width should be less than one-third of the root width at its narrowest point.

Luting Agent

• Limited effect on retention.
• Important for poor-fitting posts only.
• Adhesive resins may be used for dislodged posts.

Preparation Geometry

• Nearly circular canals can be prepared with twist drills or reamers for parallel walls or minimal taper.
• Elliptical canals require minimal taper (6-8 degrees) to ensure adequate retention and avoid undercuts.
• Parallel-sided canals are more retentive than tapered canals.
• Parallel posts offer more retention than tapered posts.

Post Design

• Threaded posts are more retentive than serrated posts, which are more retentive than smooth posts.

Resistance Form

• Resistance to displacement during function.
• Factors influencing resistance form:
  • Stress distribution
  • Rotational resistance

Stress Distribution

• Stresses concentrate at the cervical part of the root and the apex of the post. 

This quiz evaluates the key factors influencing the success of restoring endodontically treated teeth (ETT). Important considerations include the quality of endodontic treatment, remaining tooth structure, and periodontal health. Test your knowledge on the criteria for effective restoration and the implications of structural integrity.