Post and core systems

Indications and contraindications

Cast post and cores with intracanal retention are indicated when successful placement of crowns and fixed partial dentures is impossible without prior root reinforcement.

Main indications:

• Destruction of a significant portion of the crown due to caries or other pathological processes.
• Traumatic fracture of the major part of the tooth.
• Anomalies in the position of anterior teeth in adults (when orthodontic treatment is not applicable).
• Pathological tooth wear.
• Tooth inclination greater than 15° in secondary deformities.
• Microdontia (short clinical crowns).

Contraindications:

• Moderate to severe periodontitis with root mobility.
• Softening of root tissues at the cervical level and below.
• Insufficient root length.
• Curvature, obliteration, or obstruction of the canal.
• Root shortening following apicoectomy.

Root canal preparation

Thorough preparation is performed prior to fabricating the buildup:

1. Diagnostics: Assessment of the number, direction, and patency of roots, as well as periodontal status (including radiography).
2. Preparation: Removal of destroyed tooth tissues.
3. Primary canals: Widening of well-patent canals (palatal in the maxilla, distal in the mandible) to 2/3 of their length.
4. Accessory canals: In multirooted teeth, accessory canals (buccal in the maxilla, mesial in the mandible) are widened by 1–2 mm strictly parallel to the primary canal. A endo-bur or carbide fissure bur is used for this purpose.

Methods for fabricating cast core buildups

There are two main approaches to creating core buildups:

• Direct method: The wax (or acrylic resin) pattern is modeled directly in the patient's oral cavity. Softened wax is injected into the canal under pressure, excess is trimmed, the core is formed (allowing for a 1.5–2 mm clearance to antagonists), a metal post is inserted, and the assembly is retrieved for subsequent casting.
• Indirect method: The clinician prepares the canal and takes an impression. Based on the impression, the dental technician pours a working gypsum cast on which the buildup is modeled in the dental laboratory.

Cementation of the restoration

Permanent cementation of the buildup follows a strict protocol:

1. Tooth preparation: Thorough drying and degreasing of the canal and core.
2. Placement of cement: The canal is filled with luting material (often using a lentulo spiral).
3. Preparation of the post: Cement is applied to the post and the root-facing surface of the core.
4. Se_ating: The buildup is inserted into the canal and firmly pressed into place.

The luting cement must have a fluid consistency to allow excess to escape freely. Cement residues are carefully removed after 10–15 minutes to avoid traumatizing the marginal periodontium. Following cementation, the patient should follow a gentle regimen (avoid eating, keep teeth clenched) for 2–3 hours.

Class and exam questions

What else to study on this topic

• Classification of post systems and threaded pins
• Features of using prefabricated posts for direct restorations
• Materials and alloys for cast cores (cobalt-chromium, gold-platinum, etc.)
• Clinical and technical requirements for the finished core buildup
• Complications during preparation and service of post-retained restorations (perforations, fractures)

Other topics in "Chapter 9. Restoration of anatomical form and function of the tooth"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.