Metal-ceramic crown restoration

June 5, 2023 Време за четене ~ 5 min Брой прочетени текстове: 11853

Metal-ceramic crowns are considered one of the most durable restorations. They consist of 2 layers: a metal base and a ceramic veneer. The metal perfectly withstands even high chewing loads, while the ceramic gives the structure a natural look.

Unfortunately, ceramics are not as strong as dental alloys, and chipping of the top layer in crowns occasionally occurs.

Causes:

• Violation of fabrication technology;
• Improper (overvalued) occlusion;
• Change in bite;
• Strong mechanical impact;

Indications for repair

Repair of a chipped crown is only possible if the problem is located in the ceramic layer. In these cases, restoration is possible even with large fragments. But if the metal part is affected, it is impossible to restore the old structure, it can only be replaced.

Therefore, dentists urge to treat dentures with care, their replacement is a long and expensive process.

1. If the chip is very small or it is just a crack in the ceramic, the edges are ground, the entire surface is polished and smoothed.
2. In the case of a large chip, the problem area is sanded and restored with composite materials.
3. If the broken off part is saved, the dentist can glue it back together. The joint is then sanded and polished.
4. If the metal framework is damaged, it is cut, the denture is removed, and the restoration is restored.

Restoration methods

A damaged denture can only be repaired by direct restoration. The work is done in the dentist’s chair, in one appointment. This makes the dentist’s work much more difficult. For the first time, the construction was made from individual impressions, on a model, with excellent access and a wide choice of material.

During the repair, access to the prosthesis is limited by the width to which the patient can open his mouth. Of the materials, only composite can be used. To achieve a color match in such conditions is quite difficult. Therefore, it is important to choose a clinic whose doctors have extensive experience in artistic restoration.

Indirect method of restoration is used if the crown needs to be replaced. This happens when the metal base is damaged. Then impressions are taken from the patient again and a technician in the laboratory makes a new prosthesis based on them.

Restoration of a metal-ceramic crown – stages

The dentist faces several tasks at once:

• To recreate the aesthetics;
• Restore the integrity of the veneer;
• To preserve the contact points and not to overbite.

The work begins with an assessment of the damage. The dentist then proceeds directly to the repair:

1. Isolates the tooth.

Composite is a hydrophobic material. If moisture (saliva) gets on it, the bonding strength will drop dramatically. Such a restoration will not last very long.

2. Cleans the surface with an abrasive paste.

Uses an attachment for grinding.

3. Forms the bevel of the ceramic.

To increase the area of interaction between the composite and the ceramic and to enhance bonding, the edges are machined so that a 45-degree bevel is formed.

4. Sandblasts the framework and bevel of the ceramic.

The procedure is necessary to clean the surface, give it a matte and rough surface.

5. Etches the surface with acid.

The acid enhances the roughness of the surface and any residual moisture is evaporated. The surface is considered ready for work.

6. Applies primer.

The primer molecules are double molecules. They contain a hydrophobic component to bond well with the composite and a hydrophilic component to bond with the ceramic.

7. Adds an adhesive.

This is a special compound that acts as an adhesive. The adhesive is illuminated with a lamp.

8. Coating the metal with an opaque composition.

If this is not done, it will show through the composite layer, making the repair obvious. The composition primes the metal, masking it.

9. Matching the color of the composite.

The dentist applies drops of composite in different shades to the neighboring tooth to make the restoration as inconspicuous as possible. Once the selection is made, the drops are easily removed.

10. The composite is applied in layers.

Each layer is illuminated with a lamp.

11. Etches, dries and glazes the surface of the restoration.

If the framework is damaged, the crown is replaced by taking an impression and fabricating a new prosthesis.

Service life of the restoration

Correctly performed repairs will extend the service life of the denture for several years. However, it should be remembered that composite restorations require careful treatment. The dentist will necessarily give recommendations for care. The patient is required to follow these recommendations.

Composites do not like products with a high content of pigments. They absorb dyes, and the metal-ceramic restoration becomes noticeable. To avoid this, it is necessary to limit, or better exclude from the diet dark berries, red wine, coffee and tea. After their consumption, be sure to rinse your mouth.

2 times a year it is necessary to come to the clinic for polishing and preventive examination.

Do not expose your teeth to excessive stress. This is facilitated by hard foods: dried goods, breadcrumbs, candy, nuts.

Cost of repair

The higher the quality of the materials, the less noticeable the repair will be. At the same time, this means that the price of restoration will cost more. In addition, only a dentist with high qualifications can perform a quality restoration. Not every dental clinic will do this kind of work. This also affects the final cost.

Doctor’s opinion