When dealing with severely decayed teeth, dental professionals often face the choice between using fiber posts or cast metal cores. While fiber posts are versatile, cast cores—especially metallic ones—are generally more robust and durable. This article provides a step-by-step guide to preparing and placing cast metal posts, ideal for cases requiring enhanced strength, especially in highly visible areas where aesthetics are a priority.
Advantages and Disadvantages of Cast Metal Posts
Cast metal posts provide excellent support for compromised teeth structures. However, the key disadvantage lies in their modulus of elasticity, which is much higher than that of dentin, potentially leading to stress concentration and root fractures. This is why cast metal posts are carefully considered and typically applied only in situations where the advantages outweigh the risks.Step-by-Step Guide to Preparing Cast Metal Posts
1. Initial Root Canal Preparation
Begin by preparing the root canal, similar to other types of posts. Use radiographic images to identify the appropriate depth for filling material removal. This preparation lays the groundwork for proper core fitting.
2. Pattern Creation for Casting the Core
To fabricate a cast core, create a pattern using an acrylic or wax core. Insert a prefabricated acrylic or plastic post into the canal and adjust as needed. This pattern allows for an accurate core shape during casting.
3. Lubrication of Remnant Tooth Surface
Apply petroleum jelly to the remnant tooth surfaces, both in the canal and around other areas, using absorbent paper points and brushes. This prevents the acrylic or wax from adhering to the tooth during the hardening process.
4. Application of Acrylic/Wax Beads
Add small beads of acrylic or wax inside the canal and on the post surface to form a preliminary pattern. Carefully place the post into position, creating the initial foundation of the core.
5. Adjusting for Polymerization Shrinkage
Remove and reinsert the acrylic pattern multiple times during polymerization to avoid resin trapping in irregularities within the canal. This step is essential to ensure a perfect fit without internal stress points.
6. Shaping the Core
After forming the pattern, check for correct modeling. Apply additional acrylic or wax beads as needed to achieve the desired anatomic shape. At this stage, you can already visualize the final preparation shape.
7. Refining the Core Pattern
Trim any excess material, checking if more material is needed for a precise fit. Properly shaping the core pattern now reduces adjustments after casting.
8. Preparing for the All-Ceramic Crown
Prepare the cast core pattern for the all-ceramic crown, following the general guidelines for anterior crown preparation. This stage allows for minor corrections, either by adding or grinding material, ensuring minimal adjustments after casting.
9. Laboratory Casting and Try-In
The laboratory casts the core using the lost-wax technique, typically with noble or semi-noble metal alloys. Perform any minor adjustments needed during try-in to avoid stress during cementation.
10. Final Cementation of the Core
Once the core is suitably adapted and adjusted, perform either conventional or adhesive cementation, depending on the practitioner’s preference. This final step secures the core in place, setting the stage for the ceramic crown.