Endodontically Treated Teeth Restoration

Treatment of Endodontically Treated Teeth (ETT)

Endodontically Treated Teeth (ETT) are teeth that have undergone root canal treatment. These teeth oftenpresent unique challenges for restoration due to altered dentin properties and reduced structural integrity.

I. Introduction and Alternatives

Many severely destroyed teeth can be treatedwith fixed prostheses. The decision to maintain or replace an ETT depends on several factors.

Factors Influencing Tooth Maintenance vs. Replacement:

• Periapical pathology

• Extent of canal filling

• Type of tooth (anterior vs. posterior)

• Age and sex of the patient

• Quality and time of root canal filling

• Tooth type (maxilla or mandible)

• Pulp status (vital or non-vital)

• Use of intracanal medication

• Filling material

Impossibility to Perform RootCanal Treatment:

• Calcified or anatomically complex root canals

• Inability to retreat (e.g., removal of old posts, broken endodontic files, silver tips, previous failed retreatments)

Anterior Teeth Considerations:

• With crown placement: A post may be needed to increase retention.

• Without crown placement: A post is generally not needed.

Posterior Teeth Considerations:

• Often treated with an onlay or inlay without a post.

II. Characteristicsof Endodontically Treated Teeth

1. Dentin Modification:

• Dentin inherently resists crack propagation and has fracture-toughening mechanisms.

• ETT dentin undergoes changes:

  • Dehydration: Increases fragility.

  • Collagen fibers reduction and degeneration: Further increases fragility.

• Consequence: Dentin is less fatigue-resistant, more brittle, and has a higher fracture risk, especially in older ETTs.

2. Reduction of Structural Integrity:

• Caused by caries, old restorations, fractures, and loss of the pulp chamber roof.

• Effects of endodontic treatment and irritants (e.g., NaOCl, EDTA, CaOH) over dentin contribute to structural loss.

• Alwaysavoid unnecessary removal of tooth structure!

• Opposing teeth can cause separation of ETT cusps, leading to vertical fractures.

• Clinical Data: Lower molars and upper premolars with MOD restorations and endodontic therapy show 50% fracture rates in5 years without cusp coverage. With cusp coverage, success rates increase significantly (Sorensen and Martinoff, 1984).

3. Reduction of Sensitivity:

• Reduced proprioception and higher pain threshold.

• Lowered capability of recording stimuli and lesscontrol over applied forces.

• Requires twice the forces to elicit a reaction, leading to inadequate behavior under high occlusal loads.

III. Assessment of Endodontically Treated Teeth

1. Must Be a Healthy Tooth:

• Clinically:

  • No fractures extending beyond restoration boundaries.

  • Periodontal health.

  • No infection (fistula, oozing).

• Radiographically:

  • No root fractures.

  • No internal or external resorption.

  • Good apical seal.

  • No radiolucent periapical areas (assessed 6 months post-treatment).

2. Quantity and Quality of Remaining Tooth Structure:

• Assess large caries and the amount of losttooth structure.

• Small destruction: Regular reconstruction without a post.

• Small to medium destruction: Prefabricated post.

• Great destruction: Cast post and core.

A coreis material placed on the tooth to rebuild missing coronal structures above the root canal space.

A post is placed inside the root canal space when insufficient lateral tooth tissue supports a core.

3. Anatomy of the Pulp Canal:

• Pulpcanal section (cylindrical/oval) and diameter:

  • The post must adapt to the canal, not vice-versa.

  • Always select the largest and straightest canal (e.g., palatal canal for upper molars, distal for lower molars).

• Direction of the canal relative to the occlusal plane:

  • Great inclination: Prefabricated post.

  • No great inclination: Depends on the canal, prefabricated or cast post and core.

4. Biomechanical Needs for the Restoration:

• Consider the position and type of the tooth.

• Function of the future restoration (solitary or bridge abutment) dictates flexural and compressive forces.

• Every posterior ETT requires a cusp-coverage restoration (ideally onlays/crowns) to reduce fracture risk.

5. Ferrule Effect:

• Crucial for long-term success. Requires ofnatural tooth structure on the finish line, not composite.

• A healthy cervical dentin collar of coronal to the crown margin.

• Purpose:

  • Optimizes biomechanical behavior.

  • Elevates resistance of the crown.

  • Reduces and better transmits stress.

  • Dissipates forces concentrated at the tooth circumference.

  • Stabilizes the restored tooth and optimizes resistance form.

• The more ferrule height and uniformity, the better the prognosis. A non-uniform ferrule is still better than none, especially on palatal and buccal surfaces.

• In case of no ferrule effect:

  • Evaluate options: crown lengthening, orthodonticextrusion, post (if viable), or extraction.

  • Historically, cast post and core (CP&C) was preferred; today, many authors favor prefabricated posts.

  • If none are viable, extraction and restoration with an implant or bridge may be necessary.

6. Subgingival Destruction:

• Amount and depth of subgingival destruction dictate solutions.

• Solutions: Crown lengthening, orthodontic extrusion, or tooth extraction.

• Requires ferrule effect plus respecting the biological width, leading to a minimum of of supra-alveolar tooth structure.

Surgical Crown Lengthening:

• Increases crown-to-root ratio (increases effective crown length, reduces effective root length and root dentin volume).

• Evaluate aesthetic outcome, especially for anterior teeth. Good option for molars.

• Delays treatment (3-6 months).

Orthodontic Extrusion:

• Reduces bone support. Should be considered before surgical options.

• More favorable mechanical behavior, preferable for premolars and incisors.

• Delays final treatment.

IV. Treatment Planning: Post Utilization

Posts are used for:

• Retention of the core.

• Optimization of resistance.

• Transfer and dispersion of loads into the root.

• Controversially, for strengthening the tooth and restoration (though the crown is what truly reinforces).

Gutta-percha, MTA, and composite do not reinforce the tooth or restorations.

Indications for Post Placement:

• Large defects requiring crowning or partial coverage.

• Narrow abutment diameter.

• Immature root with a large root canal.

A) Anterior Teeth:

• Intact tooth (minor proximal cavities, only access cavity): Sometimes no post is needed. Upper central incisors are 3x tougher without a cast post and core.

• With loss of tooth structure:

  • Consider translucency for final restoration material.

  • Alternatives: Prefabricated post with composite resin and crown/onlay/overlay, or endocrown.

• Abutment Reconstruction and Tooth Preparation: Shillinburg recommends cusp coverage.

• Minor tooth structure loss (e.g., cavity just accesses canal): Composite resin, onlay, or endocrown. The pulp chamber can be used to increase retention and adhesion.

• Moderate tooth structure loss (50%): E.g., big occlusal/proximal caries, increased severity with cervical lesions. Treatment: Prefabricated post with composite resin restoration and crown, onlay, overlay, or endocrown.

• Severe tooth structure loss (>50%): Two or fewer walls remaining (e.g., MOD caries or cusp loss). Apost is recommended. Options: prefabricated post and crown. Always remember the ferrule effect.

• If no ferrule effect: Prefabricated post + composite resin + cusp coverage; or crown lengthening + CP&C + crown; or CP&C withadditional post for stability (controversial).

B1) Premolars:

• Smaller teeth with less structure and smaller pulp chambers for retention.

• Subject to lateral masticatory forces; a post is usually indicated.

B2) Molars

:

• A post is more indicated when coronal structure is totally missing or the pulp chamber is too small for retention/adhesion (e.g., for an endocrown).

C) Considerations for Teeth as Denture Abutments:

• ETTshould not be abutment teeth for free-ended RPDs (4x higher fracture risk).

• ETT should not be used for cantilever bridges (high failure/fracture risk).

• ETT as bridge abutments fracture twice as often as vital teeth or single-tooth FDPs, even with aferrule effect.

• Not to be used as single retainers.

• Use of ETT as abutments for bridges with more than one pontic is questionable.

V. Prefabricated Posts

A) Classification:

Prefabricated posts are classified by their material, shape, and surface.

Material:

Metals Posts:

A metallic post is a rigid metal rod placed inside the root canal to retain the core when very little tooth structure remains. It offers strong retention but can transmit stress to the root and is lessesthetic.

Esthetic Posts:

Esthetic posts, such as glass fiber or zirconia, are used inside the root canal when good esthetics are required. They are more flexible, distribute stress better, and reduce the risk of root fracture compared to metal posts. Fiberposts blend with the tooth and avoid darkening, while zirconia posts offer higher stiffness with excellent esthetics.

Shape:

• Cylindrical:

  • Greater retention (more friction).

  • Can create a weaker area of the root at the posttip.

• Tapered:

  • Fits the pulp canal better, more respectful of canal shape.

  • Less weakening of the root.

  • Lower retention; potential wedge effect if not deep enough.

Surface:

B) Purposes:

• Intraradicular retention.

• Better dispersion of forces.

• The post does not reinforce the tooth per se, the crown is what truly reinforces the tooth.

Retention depends on multiple factors:

• Length: Minimum of crown height, maximum of , or of tooth length. Leave at least of apical seal.

• Shape and Surface: Best shape is cylinder/tapered. Most retentive surface is threaded but with high fracture risk. Prefabricated posts are typically fluted.

• Diameter: Greater diameter provides greater retention, but not greater than of the root diameter.At least of root wall thickness must be maintained. The post must adapt to the canal, not vice versa.

Procedure:

1. Make a radiograph of the tooth.

2. Confirm apical seal and performance of endodontic treatment.

3. Calculate working length ( of apical seal).

4. Remove endodontic sealing material (gutta-percha) with Gates-Glidden drills.

5. Shape the pulp canal with drills (increasing diameter, contra-angle handpiece)up to the desired width.

6. Insert the post into the canal and take a radiograph to check fit and ensure all gutta-percha has been removed.

7. Check for enough space to the antagonist tooth.

8. Cement the post:

   • Fiberposts: Cemented with composite resin cements (translucent with dual-cure, opaque with self-cure).

   • Metal posts: Cemented with zinc phosphate or glass ionomer cements.

9. Build up the core.

10. Perform crown preparation.

11. Take an impression.

12. Place a provisional restoration.

13. Cement the definitive crown.