When we find ourselves working on a tooth where barely anything is left—just precarious walls clinging on, and destruction has reached truly advanced stages—we inevitably begin to ask that critical question: is this tooth destined for extraction? In the vast majority of cases, the answer is a reassuring “no.” And right here, our hero steps in to save the day: the Post and Core.
A Post and Core is a restorative dentistry procedure we perform when a tooth is severely damaged and requires additional reinforcement before we can place a crown on it. In simple terms, the “post” acts like a foundational column that we insert into the root canal. This provides the essential support for the “core,” which is the part we meticulously build up to prepare the tooth to receive its definitive crown.
When Do We Need a Post & Core?
Quite simply, a Post & Core becomes necessary when the remaining enamel and dentin structure of the tooth isn’t sufficient to provide adequate support and stability for the final crown. In these situations, the post essentially serves as the primary pillar, embedded within the root canal, to robustly support the core as we reconstruct the tooth’s shape.
Is the Tooth Restorable? Key Assessment Factors
Determining if a tooth is genuinely “restorable” hinges on several absolutely crucial factors. Primarily, the thickness of the remaining tooth walls should ideally be no less than 1 mm, and their height should be at least 1-2 mm.
To simplify this even further, if you can comfortably place and securely stabilize a rubber dam clamp on the tooth, it’s highly probable that the tooth is indeed restorable.
What if the Tooth Appears Non-Restorable? Exploring Alternatives
Just because a tooth initially seems non-restorable doesn’t mean we should immediately resort to extraction. Absolutely not! There are still viable alternative solutions worth considering, such as:
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Extrusion: This process is typically achieved through orthodontic treatment.
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Crown Lengthening: This involves a minor surgical intervention.
However, a critically important condition must be met before embarking on either of these steps: we must ensure that the root length to crown length ratio is not less than 1:1. This is vital for guaranteeing the long-term success of the procedure.
Optimal Post Dimensions: Length and Width Guidelines
When determining the ideal dimensions for the post, there are two fundamental rules we absolutely must adhere to:
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Length: The guiding principle here is “as long as possible.” Nevertheless, it’s essential to leave 3-5 mm of gutta-percha filling material at the apical end of the root canal to meticulously preserve the apical seal.
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Width: We must ensure the post’s width does not exceed one-third of the external root width. This is a critical measure to prevent any undue weakening of the root structure itself.
How to Select the Right Post? Material, Shape, and Surface Considerations
Choosing the correct post is a decision that primarily depends on three key attributes: its material, shape, and surface characteristics.
1. Material Types
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Metal Post: These are exceptionally strong. However, a significant drawback is that any occlusal discrepancies can potentially lead to a root fracture.
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Fiber Post: Generally considered a safer option. Their flexibility closely mimics that of natural dentin, meaning if excessive pressure occurs, the post itself is more likely to fracture before the root is harmed.
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Zirconia Post: These posts offer a blend of the metal post’s strength with the aesthetic appeal of a fiber post.
2. Post Shape
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Parallel Post: These posts provide superior retention compared to tapered posts. Yet, they demand a more aggressive canal preparation, which regrettably can weaken the tooth structure.
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Tapered Post: Given the concerns with parallel posts, we often prefer using a tapered post, especially one that is tapered towards its tip.
3. Post Surface Characteristics
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Threaded Post: These posts are inserted into the canal with a rotational motion. This can generate significant stress and potentially lead to a root fracture.
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Serrated Post: Inserted using a pushing force, this type is generally considered less risky.
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Smooth Post: While posing the least risk, smooth posts also offer the weakest retention.
It’s also worth noting that modern post designs are specifically engineered to minimize stress on the root.
Post & Core Fabrication Methods
We primarily utilize two fundamental methods for Post & Core fabrication: the direct method and the indirect method.
The Direct Method (Chairside)
This approach is entirely completed in a single clinical appointment right in the dental chair.
The Steps:
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X-ray: First, an X-ray is taken to assess the root angulation and the overall tooth condition.
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Isolation: The tooth is completely isolated using a rubber dam.
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Canal Preparation: A Peeso reamer is used to prepare the post space. It’s crucial that the post’s diameter matches that of the reamer. The post length should be approximately 3-5 mm shorter than the full root canal length to preserve the apical seal.
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Post Trial & X-ray: The post is test-fitted, and an X-ray is taken to confirm its accurate placement.
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Post Sterilization: The post is sterilized using either sodium hypochlorite (NaOCl) or chlorhexidine (CHX).
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Etching: The root canal is etched with phosphoric acid for 15 seconds, followed by thorough rinsing and drying.
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Bonding Agent: A dual-cure bonding agent is applied and meticulously distributed with a microbrush and an air syringe, then light-cured.
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Resin Cement: A dual-cure resin cement, such as GC Bond, is used to cement the post into the canal, which is then light-cured.
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Core Build-Up: The core is then built up until the desired shape and size are achieved.
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Tooth Preparation: The tooth is prepared for the crown. A critical detail here is ensuring the finish line rests on sound tooth structure, not on the restorative material.
The Indirect Method (Chairside & Labside)
This method typically involves two distinct phases: a chairside component in the clinic and a labside component in a dental laboratory.
The Steps:
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X-ray: An X-ray is taken to evaluate the root canal filling and canal angulation, and to determine an initial post size estimate.
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Crown Preparation: The crown portion of the tooth is prepared, ensuring smooth surfaces and a butt-joint margin. It’s also important to create an anti-rotation feature in the preparation to prevent crown rotation.
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Root Canal Preparation: A portion of the gutta-percha is removed, and the canal is widened using a Peeso reamer. Crucially, 3-5 mm of gutta-percha must be left apically to maintain the apical seal. A post-preparation X-ray is then taken to verify the accuracy of the work.
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Canal Walls Cleaning: A Peeso reamer is used with a brushing motion to meticulously remove any remaining gutta-percha or sealer from the canal walls.
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Pin Trial: A pin is inserted into the canal to confirm it reaches the desired length, then it is removed.
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Canal Rinse & Dry: The canal is rinsed and dried using a paper point, followed by the application of a lubricant inside the canal.
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Acrylic Resin & Pin Placement: Acrylic resin powder and liquid are mixed. A small amount is applied to the tip of the pin, which is then inserted into the canal.
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Core Build-Up: The pin is withdrawn, more acrylic resin is added, and it is reinserted. This step is repeated until the core is built to the desired size and shape. Crucially, avoid leaving the pin in the canal for too long to prevent resin adhesion to the canal walls, and be careful not to overheat the tooth.
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Core Preparation: The acrylic resin core is then prepared as if it were a natural tooth, ensuring the finish line is on sound tooth structure, not on the resin.
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Send to Lab: The completed pattern is sent to the dental laboratory for the fabrication of the permanent Post & Core from the material chosen by the clinician.
Note on Cementation: The specific cementation method will depend directly on the type of material used to fabricate the Post & Core.
While another indirect method involves using an additional silicone impression, the detailed technique described above is generally preferred and more commonly utilized.
A Critical Factor for Post & Core Success
To guarantee the absolute highest success rate for this treatment, you must ensure that the post makes direct contact with the gutta-percha at the apical end of the root canal. If there is any gap or space between the post and the gutta-percha, the success rate will be significantly reduced.
