June 5, 2023 読書時間 ~ 5分 リード数 11853
メタルセラミッククラウンは最も耐久性のある修復物の一つと考えられています。金属ベースとセラミックベニヤの2層構造になっています。金属は高い咀嚼負荷にも完璧に耐え、セラミックは自然な外観を与えます。
残念ながら、セラミックは歯科用合金ほど強くはなく、クラウンの表層に欠けが生じることがあります。
原因がある:
- Violation of fabrication technology;
- Improper (overvalued) occlusion;
- Change in bite;
- Strong mechanical impact;
Indications for repair
欠けたクラウンの修復は、問題がセラミック層にある場合にのみ可能です。このような場合、大きな破片でも修復は可能です。しかし、金属部分に問題がある場合、古い構造を修復することは不可能で、交換するしかありません。
Therefore, dentists urge to treat dentures with care, their replacement is a long and expensive process.
- 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.
- In the case of a large chip, the problem area is sanded and restored with composite materials.
- If the broken off part is saved, the dentist can glue it back together. The joint is then sanded and polished.
- 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:
- Isolates the tooth.
- Cleans the surface with an abrasive paste.
- Forms the bevel of the ceramic.
- Sandblasts the framework and bevel of the ceramic.
- Etches the surface with acid.
- Applies primer.
- Adds an adhesive.
- Coating the metal with an opaque composition.
- Matching the color of the composite.
- The composite is applied in layers.
- Etches, dries and glazes the surface of the restoration.
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.
Uses an attachment for grinding.
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.
The procedure is necessary to clean the surface, give it a matte and rough surface.
The acid enhances the roughness of the surface and any residual moisture is evaporated. The surface is considered ready for work.
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.
This is a special compound that acts as an adhesive. The adhesive is illuminated with a lamp.
If this is not done, it will show through the composite layer, making the repair obvious. The composition primes the metal, masking it.
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.
Each layer is illuminated with a lamp.
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
Restoration of a metal-ceramic crown is a painstaking work that requires skill and time. Therefore, my advice is to take care of your fixed dentures. Do not subject them to unnecessary stress. Follow the recommendations of your prosthodontist. May you never need to have your dentures repaired.