Main factors affecting the bonding of gold and porcelain and their treatment methods

Updatetime: 2023-12-01

Baked porcelain alloy and porcelain powder combination form

1. Chemical bonding: refers to the chemical reaction between the oxide layer on the surface of the metal bottom crown and the oxide and amorphous glass interface in the metal baked porcelain material, and the combination formed by chemical bonds such as metal bonds, ionic bonds and covalent bonds. It is very important to form a transition layer of certain thickness on the interface of metal and ceramic in the process of porcelain baking to form a good bond. However, the binding force is reduced if the transition layer is too thick.

2. mechanical combination: refers to the metal surface after coarsing (such as sandblasting) to form a bumpy surface, expand the contact area, so that the metal ceramic powder after melting and firing play a mechanical Mosaic, but its role is relatively small.

3. physical combination: mainly refers to the van der Waals force between the two, that is, the attraction between molecules. But this combination has little effect.

4. Pressure combination: when the thermal expansion coefficient of the porcelain material is slightly less than that of the porcelain alloy, the compression force of the porcelain material is greater than the induced tension, so that when the porcelain repair is cooled, the compression effect will be generated and the combination between the porcelain material and the metal will be enhanced.

Among the above four binding forms, chemical binding is the main binding form.

The main factors affecting the combination of gold and porcelain and the treatment methods

1, casting melting temperature is too high to make the casting loose metal is not dense, easy to lead to casting fracture or porcelain bubbles. Dental porcelain alloy in the heating melting of the correct melting method: the metal surface will have obvious shadow and gradually disappear, when the metal center of the dark red dot completely disappeared, the alloy edge Angle passivation, flat slide (do not have to melt into a group), for the best casting time, can not wait until broken film. Porcelain alloy melting must not overburn.

2. the metal surface is polluted, there are impurities, dust, oil stains and other residues. The right way: First of all, select the right polishing material to place the metal crown bridge. After placement, clean white corundum sand with 40-80 mesh is used, the pressure is 3-4bar, the injection Angle is obtuse with the casting, and the surface of the metal crown bridge is evenly sprayed. Do not touch the metal crown bridge with your hands after spraying to avoid oil stains. Wash with steam or ultrasonic. (In special cases, it can be soaked in high concentration alcohol, acetone or 30% hydrochloric acid before steam and ultrasonic cleaning to increase the bonding of gold and porcelain and reduce sintering bubbles)

3. The surface of the metal crown bridge has sharp edges and acute angles, and the axes are not streamlined, resulting in stress concentration and porcelain cracking. Treatment method: Avoid the above situation when the metal is polished in place.

4. pre-oxidation degassing treatment is not correct. The correct treatment method: The company's products of baked porcelain alloy contains trace elements that are conducive to improving the bonding force of gold and porcelain, and will naturally form an oxide film during the porcelain process, without pre-oxidation. But degassing is a must. The degassing pre-oxidation method is: preheating time 1min, initial temperature 600℃, heating to 950-980℃, holding for 3min, cooling time more than 2min. It is normal for the metal surface to appear dark after pre-oxidation of degassing (in vacuum), which needs to be removed by blasting with clean corundum sand.

5. porcelain powder mixing or plastic porcelain pollution. Treatment method: Refer to the ceramic powder instructions for correct use.

6. sintering temperature, heating rate is not correct. Treatment: Dental porcelain nickel-chromium alloy sintering please refer to the ceramic powder manual for correct use. Dental porcelain cobalt-chromium bioalloy should pay special attention: the starting temperature is 500℃, the preheating time is 3min, the heating rate cannot be higher than 55℃ per minute, the maximum temperature is referred to the porcelain powder instructions, the cooling rate cannot be higher than 55℃ per minute, the cooling temperature is 500℃, and the cooling time is 3min.

7. OP coating improper: the consistency of the OP mixture, the thickness of the OP coating, the initial temperature of pre-drying, the highest temperature, and the improper pre-drying time will make the first layer of OP sintering effect is not good, resulting in bubbles. Treatment method: According to different circumstances refer to the porcelain powder manual for treatment.

Prev： What are the causes of incomplete casting of dental hard cobalt chromium castings?