Role of crowns in dental bridges
A dental bridge is a fixed prosthetic structure that restores dental arch integrity in small and medium bounded defects. Artificial crowns act as the main abutments here. They are fixed onto previously prepared natural teeth, roots, or implants.
Between the abutment crowns lies the intermediate part (pontic), which directly replaces the missing teeth. In relation to the mucous membrane, it can be:
- Saddle-free (tangent) — used in the anterior region to ensure phonetics and aesthetics.
- Sanitary (ovate/hygienic) — used in the posterior region, leaving space for adequate hygiene.
- Saddle-shaped — tightly contacts the alveolar ridge (rarely used, primarily in ceramic structures).
Based on the fabrication material, prostheses with abutment crowns can be metal, plastic, ceramic, metal-ceramic, and metal-plastic. Based on manufacturing technology, stamped-soldered, cast, milled (CAD/CAM), and adhesive structures are distinguished.
Alternative abutment structures
In addition to the classic full crown, more conservative structures can be used as prosthesis abutments:
- Half-crowns — cover the hard dental tissues from 3–4 sides, leaving the vestibular surface exposed to preserve natural aesthetics.
- Inlays (Inlay, Onlay, Overlay) — microprostheses that restore only the lost part of the clinical crown. Their use allows for minimal preparation of the abutment teeth.
Clinical stages of working with crowns
The prosthetics process involves a strict sequence of steps requiring specialized instruments. For example, dental tweezers (straight, angled on the flat, or with a locking mechanism) are used for securely holding small items; their working part may feature serrations and a diamond coating.
- Preparation. Begins with the separation of contact surfaces and reduction of the occlusal plane, taking into account the thickness of the future prosthesis. Then the vestibular and oral walls are prepared, a cervical shoulder is formed (if required by the design), and sharp edges and angles are thoroughly smoothed.
- Try-in (fitting). The finished structure is first evaluated on the working cast (an exact replica of the patient's jaw on which the technician fabricated the prosthesis). Then the crowns are placed onto the abutment teeth in the oral cavity. The dentist checks the marginal fit to the tooth neck or shoulder (using a hook-shaped explorer) and controls occlusal and articulation contacts with articulating paper. Adjustments are made if necessary.
- Fixation. The operational field is isolated from saliva, and the tooth stumps are dried. The prosthesis also undergoes medical treatment and drying. Mixed luting cement is placed inside the crowns, after which the prosthesis is firmly pressed onto the teeth while controlling the bite. Once the cement sets, excess is carefully removed.
Removal of artificial crowns
If the structure has failed or complications have developed (e.g., apical periodontitis, pulpitis of the abutment teeth, or pressure sores under the pontic), the crown must be removed.
To section the framework, the following are used:
- Carbide burs (for cutting metal).
- Diamond burs (for working with ceramics).
- Carborundum discs and shaped stones.
For direct removal, a Copp crown remover with an active spring-loaded bolt is used, along with special crown-removal pliers, elevators, and straight explorers used to pry open the edges of the sectioned structure. Ultrasonic devices help break down the old luting cement structure.
How to memorize the steps of tooth preparation for a crown: SOVUS — Separation of contact surfaces, Occlusal reduction, Vestibular and oral reduction, Under-shoulder/shoulder formation, Smoothing of edges.
Class and exam questions
In what cases are bridge prostheses on crowns contraindicated?
Contraindications include distal extension defects, large bounded defects, mobility of abutment teeth (in severe periodontitis), un санированная oral cavity, and inflammatory processes in the periapical tissues.
Why is a hook-shaped explorer needed during crown try-in?
This type of dental explorer is used for precise determination of the marginal fit of an artificial crown to the tooth tissues or the prepared shoulder.
What complications can occur after crown fixation?
Possible complications include decementation, chipping of the veneering material, fracture of the pontic, as well as biological complications: pulpitis, periodontitis of the abutment teeth, local periodontitis, and pressure sores beneath the intermediate part.
What else to study on this topic
- Kennedy and Gavrilov classifications of dental arch defects.
- Differences between working and diagnostic dental models.
- Types and purposes of periodontal probes (ball-ended and sickle).
- Components and retaining elements of removable partial dentures (clasps, attachments, telescopic crowns).
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