Porcelain-fused-to-metal restorations are the most widely spread and reliable prosthesis method. Affordable prices, high strength, and good aesthetic properties make these types of dental prosthetics popular. Professionalism, quality materials as well as an appropriately chosen furnace for firing porcelain-fused-to-metal restorations - are the keys to success.
BiMedis Company highlights the aspects that one should take into account when choosing the right furnace and keeping patients satisfied with high-quality products.
Firing metal with porcelain is a complicated process that involves sintering of a dental porcelain mass with a metal subframe. The crown subframe can be made of cobalt-chrome or nickel-chrome alloys, which have an excellent biocompatibility with gum tissue and affordable price. The prostheses can also be made of noble metals like gold or platinum. Precious metal alloy dental restorations have considerably greater longevity, and better aesthetic properties (due to the yellowness of the alloy the crown color look more natural), but are more expensive. There are also alloys made of zirconium and aluminum oxides. These compositions are better because their properties are almost identical to the natural translucence of a tooth. Therefore, ceramic prostheses do not look artificial, as is often the case with restorations made of cheaper materials. The crown material plays a determinant role in the firing process since all the materials require special conditions.
The process of sintering is impossible without a dental furnace. Sintering of porcelain requires high temperatures. Accordingly, a furnace should provide excellent temperature control in addition to an appropriate vacuum level in the furnace chamber. The metal subframe is covered with porcelain layers of equal thickness. Moreover, each layer requires specific sintering conditions. The temperature stability, accurate regulation of the temperature variability, and the peak temperature value and durability of its retention are the main conditions. Accurately set vacuum level and the gradation of air rarefaction in a furnace are important as well. All the mentioned parameters directly influence the quality of metal-ceramic constructions.
To appropriately choose a furnace and select its characteristics, one should identify the following aspects:
1. Universality of use - If the chosen furnace is universal, you can work with subframes of different types.
2. The diversity of materials used - Before buying a furnace, you should determine what materials you will work with since all of the materials have their own physical and chemical properties and special requirements for sintering. The sintering procedure results in the material hardening, the degree of which depends on the initial powder dispersity, temperature maintenance, and the duration of the sintering process.
3. Technical capabilities - In the course of sintering, physical and mechanical properties are changed. Sintering takes place in a deoxidizing atmosphere consisting of hydrogen, carbon dioxide; argon or nitrogen, or just air to prevent oxidation of powder. Increasing the temperature and duration of sintering improves shrinkage, material density, and the bonds between raw materials. We highly recommend using only high-quality materials for production to preserve your reputation.
4. The function of pressing - The majority of modern furnaces are equipped with a pressing function, which allows crowns to be molded without a subframe. In this case, the fabrication involves press-injections of pre-heated porcelain mass. The pressure of injections is automatically or manually regulated
The good quality of firing is one of the main tasks that not every furnace will cope with. To get aesthetic crowns, you should apply the porcelain mass with equal layers, each of which has to be separately fired in a vacuum furnace. In order to avoid cracks on ceramics, one should select the right firing program while taking into account the technical capabilities and parameters of the furnace. Otherwise, the process needs to be started over again.
You can find a wide variety of offers of furnaces for metal-ceramics with a broad range of prices on the BiMedis Company site , and our specialists will eagerly advise you on any issues and answer any questions you may have.
Stanislav Tsaryk, doctor, BiMedis company