Anterior post and core crowns

Restoring a tooth that has undergone root canal treatment presents unique clinical challenges. Anterior teeth, in particular, often suffer extensive loss of coronal tooth structure due to caries, trauma, previous restorations, or endodontic access preparations. When insufficient coronal dentin remains to retain a crown, the clinician may need to use a post-and-core system to provide retention and support for the final restoration. Although posts can be valuable tools in restorative dentistry, their use must be carefully considered: posts do not strengthen weakened teeth. In fact, improper use of posts may increase the risk of root fracture or complicate future endodontic retreatment.

Why Posts Are Needed in Endodontically Treated Teeth

An endodontically treated tooth is structurally compromised for several reasons:

  • Loss of internal tooth structure through access preparation and canal shaping
  • Loss of coronal tooth structure due to caries, trauma, or previous restorations
  • Changes in dentin characteristics post-endodontically, including decreased moisture content
  • Occlusal stresses, especially in anterior teeth that may be involved in guidance

 

Posts are primarily used for retention of the core, and the core in turn supports the crown. It is critical to emphasize that:

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Posts do NOT reinforce or strengthen teeth.

They simply retain the core. Any forces are transmitted along the post into the root, which can increase the risk of root fracture if design principles are ignored.

A ferrule effect—a 360-degree encirclement of tooth structure by the crown—is essential for long-term success. A ferrule height of at least 1.5–2 mm significantly improves fracture resistance.

Before placing a post, the clinician must ensure that:

  • The root canal filling is adequate
  • The apical seal is intact (ideally leaving ≥5 mm of gutta-percha)
  • No unresolved pathology exists
  • The root morphology is suitable for post preparation

 

If doubts exist regarding endodontic quality, retreatment should be considered before placing a post.

 

Preliminary Preparation

Preparing a tooth to receive a post involves several important steps. Each step is intended to preserve tooth structure while preparing a stable platform for the final restoration.

1. Coronal Tooth Preparation

The aim is to prepare the crown of the tooth for a full-coverage restoration while retaining as much coronal dentin as possible. Excessive reduction will weaken the remaining structure and reduce ferrule effectiveness.

Weakened or decayed tooth structure is removed. However, the root face should not be flattened during preparation, as this can compromise ferrule and retention.

2. Removal of Coronal Gutta Percha

A heated instrument or Gates–Glidden bur may be used, ensuring the apical seal is not disturbed. Typically:

  • Minimum 4–5 mm of gutta percha should remain apically
  • Canal length and preparation depth should be verified using silicone stops, periodontal probes, or radiographs

 

3. Canal Preparation

Canal preparation varies depending on the type of post system being used. The general aim is to:

  • Create parallel-sided or appropriately shaped walls
  • Avoid excessive dentin removal
  • Follow the canal’s natural anatomy to minimize perforation risk
  • Maintain the apical seal

 

As a rule, the post length should be approximately equal to the anticipated crown height, but anatomy and safety limit this in many cases.

 

Types of Post and Core Systems

There is no single perfect system. Each has advantages and limitations depending on the clinical situation.

1. Prefabricated vs. Custom-Made Posts

Prefabricated Posts

These are mass-produced and ready for immediate use.
Advantages:

  • Quick and easy to place
  • Economical
  • Many designs and materials available

 

Disadvantages:

  • Less adaptable to unusual canal shapes
  • Often require more removal of dentin than custom options
  • May not provide ideal adaptation

 

Custom-Made Posts

Usually cast metal.

Advantages:

  • Precisely matches canal anatomy
  • Excellent adaptation, reducing cement thickness
  • Suitable for complex or irregular canals

 

Disadvantages:

  • Requires laboratory stage
  • More expensive
  • Increased chairside and fabrication time

 

Custom posts are preferred for extremely elliptical or flared canals where prefabricated posts cannot achieve intimate adaptation.

2. Materials: Metal vs. Non-Metal Posts

Metal Posts

Traditionally used for decades.

Pros:

  • High strength
  • Established long-term success
  • Excellent for high-stress situations

 

Cons:

  • May cause root fracture due to stiffness
  • Poor esthetics in anterior region
  • Potential corrosion with certain alloys

 

Metal posts are available as:

  • Parallel serrated (e.g., ParaPost®)
  • Parallel threaded (e.g., Radix®, Kurerâ„¢)
  • Tapered threaded (e.g., Dentatusâ„¢ screw)—least desirable because they cause high stress concentration

 

Threaded posts must be cemented passively since active threading into the canal dramatically increases fracture risk.

Non-Metal Posts (Fiber-Reinforced)

These have become highly popular for anterior teeth.

Advantages:

  • More flexible, closer to dentin modulus of elasticity
  • Lower risk of catastrophic root fracture
  • More esthetic—no gray shine-through under all-ceramic crowns
  • Failures tend to be adhesive debonding rather than root fracture, allowing easier retreatment

 

Disadvantages:

  • Technique-sensitive bonding
  • Long-term fatigue resistance may be lower than metal
  • Requires thorough cleaning of canal wall (no residual sealer)

 

Common systems: LightPost™, ParaPost® FiberWhite, RelyX™ FiberPost.

 

Post Designs: Parallel-Sided vs. Tapered

Parallel-Sided Posts

Generally preferred due to:

  • Superior retention
  • Less stress concentration
  • More predictable long-term results

 

Tapered Posts

Match natural canal anatomy but:

  • Provide poorer retention
  • Are associated with increased stress near the apex
  • Useful for small tapered roots such as lateral incisors

 

Surface Texture: Threaded, Serrated, or Smooth

  • Threaded: High retention but increase stress; use only passively cemented
  • Smooth: Less retention; relies more on cement
  • Serrated: Provide retention while minimizing stress concentration

 

Indirect Custom-Made Posts

These cast metal posts require precise impressions and laboratory fabrication. They are especially useful when:

  • The canal is extremely flared
  • A strong core is needed
  • Coronal tooth structure is extremely limited

 

There are two fabrication techniques:

1. Direct Pattern Technique

The clinician fabricates a wax or burn-out resin pattern inside the canal.
Advantages:

  • Directly matches canal anatomy
  • Reduced risk of impression inaccuracies

 

Disadvantages:

  • Technique sensitive
  • Requires careful manipulation in the mouth

 

2. Indirect Impression Technique

A plastic impression post is placed into the prepared canal, and an impression is taken.

Advantages:

  • Less chairside time
  • Simpler in some situations

 

Disadvantages:

  • Difficult to maintain a good coronal seal while awaiting the laboratory stage
  • Higher risk of impression errors

 

3. Direct Prefabricated Posts

Prefabricated posts can be placed immediately after canal preparation.

Fibre Posts (Non-Metal)

These require adhesive cementation. Therefore:

  • All residual sealer (especially eugenol-based) must be removed
  • Alcohol rinse or post-space conditioning may be needed
  • Dual-cure or chemical-cure composite is recommended since light may not penetrate deeply

 

Advantages include:

  • Immediate placement after RCT
  • Reduced risk of microleakage
  • Lower risk of catastrophic root fracture

 

After bonding the post, the core can be built with composite resin.

Metal Prefabricated Posts

Various designs exist (parallel serrated, parallel threaded, tapered threaded). They are cemented using conventional cements unless the system requires adhesive bonding.

Some systems include a prefabricated core head that integrates with the post, while others require the clinician to build up a core with composite or amalgam.

 

Practical Considerations and Management of Common Problems

Even with careful planning, complications can arise.

1. Subgingival Tooth Loss

Possible solutions:

  • Orthodontic extrusion to bring margins supragingivally
  • Crown lengthening surgery
  • Cast post and core with an extended post to engage the defect

 

2. Extensive Tooth Loss or Calcified Canal

Examples: Dentinogenesis imperfecta, severe wear.
Solutions:

  • Use adhesive techniques with composite core materials
  • Consider porcelain-bonded crowns or crown lengthening

 

3. Perforation of Root During Post Preparation

Management depends on severity:

  • If the post can be removed, seal perforation with MTA using magnification and illumination
  • If alignment is incorrect, re-prepare with correct angulation
  • Severe cases may require surgical repair

 

Coronal third perforations generally have a poorer prognosis.

4. Loss of Post

Evaluate cause:

(i) Insufficient length → remake with increased length
(ii) Loose fit or too much canal taper → sandblast post, use adhesive cement (e.g., Panavia™ 21), or remake post
(iii) Perforation-related loosening → radiographic assessment
(iv) Root fracture → extraction

5. Apical Pathology

If root canal treatment is satisfactory, consider periradicular surgery.
If not satisfactory, retreatment and new post placement are advised.

 

Causes of Failure in Post and Core Crowns

A survey found:

  • Many posts fail within the first year
  • If a post crown survives 3 years, prognosis for a 10-year survival is favorable

 

Common failure modes include:

  • Caries
  • Root fracture
  • Mechanical failure of post
  • Loss of retention
  • Debonding (especially in fibre posts)

 

The presence of ferrule significantly reduces these risks.

 

Removal of Old Posts and Cores

Old posts may need removal due to failure, recurrent pathology, or need for retreatment.

Methods:

  • Forceps removal (gripping with Spencer–Wells forceps) — limited to loose posts
  • Post removers that use root face anchorage — good for cemented posts
  • Ultrasonic vibration — often effective but requires aggressive water cooling to avoid heat damage
  • Masseran kit or similar systems — create a channel around the post for removal; useful for fractured posts

 

Caution: Excessive force or inadequate cooling can cause perforation or heat injury.

 

Clinical Decision-Making: Choosing the Best Post System

The ideal system depends on:

  • Amount of remaining tooth structure
  • Presence or absence of ferrule
  • Esthetic demands
  • Root anatomy
  • Operator skill
  • Type of crown planned (ceramic vs. metal-ceramic)

 

General Rules of Thumb

  • For anterior esthetic cases → fibre posts work very well
  • For severely flared canals → custom cast post and core
  • For short roots or thin roots → avoid threaded posts especially tapered threaded
  • Maintain ≥2 mm ferrule whenever possible

 

Clinicians should be familiar with multiple systems, as one system alone cannot meet every clinical need.

 

Key Principles for Success

To maximize success and longevity:

Retention

  • Adequate post length
  • Parallel walls when possible
  • Proper cementation protocol

 

Resistance and Ferrule

  • Maintain maximum coronal dentin
  • Aim for ≥2 mm ferrule circumferentially
  • Avoid excessive tooth removal during preparation

 

Material Selection

  • Choose fibre posts for esthetic areas and lower fracture risk
  • Choose cast posts for flared or irregular canals

 

Endodontic Quality

  • Ensure the root filling is ideal
  • Correct any pathology before restoring
  • Preserve at least 4–5 mm of gutta percha apically

 

Conclusion

Anterior post and core crowns remain an important part of restorative dentistry, especially for teeth that have undergone significant structural compromise. While modern adhesive dentistry has reduced the frequency of post placement in some cases, posts are still essential when coronal tooth structure is inadequate to support a crown.

Understanding the biomechanics of root-filled teeth, choosing an appropriate post system, preserving tooth structure, and respecting endodontic principles are all critical to long-term success. By mastering multiple systems and techniques, the clinician is better prepared to manage the wide variety of clinical scenarios encountered in practice.

 

References

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