IV. STRUCTURED ABSTRACT
In orthopedic dentistry, removable dentures are widely used, designed to replace the dentition of different lengths, as well as to restore the functions of chewing and speech. For the manufacture of removable dentures with a cast base, noble alloys have become more widely used, since due to their good thermal conductivity, it is possible to maintain the perception of cool and hot at a significant level. [1] The article deals with the use of cast basis in removable prosthetics. Advantages regarding plastic-based prostheses. Considerable attention is paid to research and experiments. The article also describes the materials from which prostheses are manufactured with cast basis. These include alloys of noble and base metals. Precious metals are attributed to: gold, silver, platinum. To the ignoble - iron, lead, etc. There are such alloys as cobalt-chromium, silver-palladium alloys, etc. Currently, titanium alloys have gained popularity. Their most important advantage is their excellent biocompatibility with the human body
VII. Goal
Justification for the use of modern cast bases in the clinic of orthopedic dentistry for the production of removable dentures.
VIII. Materials and methods.
Alloy of gold AU 900 blanks.
STRUCTURE: 90% gold, 4% silver, 6% copper.
PROPERTIES: melting point 1063°C. The alloy is characterized by ductility, easy to machine under pressure (stamping, forging). The gold alloy is made in the form of a disk. The alloy is easily erased. Therefore, when manufacturing stamped crowns from the inside, solder is poured on the chewing surface or cutting edge. They are available in the form of disks and blocks.
Gold alloy of 750 samples.
COMPOSITION: gold-75%, silver and copper-8%, platinum-9%.
PROPERTIES: Platinum gives this alloy elasticity and reduces shrinkage during casting.
Silver-palladium alloys have a higher melting point - 1100-1200 C. Their physical and mechanical properties are similar to gold alloys of gold. The corrosion resistance is lower. Alloys are ductile and malleable. Soldered with gold solder.
Alloy Pd-250.
COMPOSITION: silver-75.1%, palladium-24.5%, some alloying metals (zinc, copper, gold).
Alloy Pd-190.
COMPOSITION: silver-78%, palladium-18.5% , etc.
Alloy Pd-150. Reduced the amount of palladium to 14.5%, increased the amount of silver.
Base metal alloys:
* STEEL GRADE 1X18N9T (EYA-1)
COMPOSITION: carbon-1.1%; nickel-9%; chromium-18%; manganese-2%, titanium-0.35%, silicon-1%, the rest-iron.
* STEEL GRADE 20X18N9T.
STRUCTURE: carbon-0.2%, 9% nickel, chromium-18%, manganese-2%, titanium-1%, silicon-1%, the rest-iron.
* STEEL GRADE 25X18N102. COMPOSITION: carbon-0.25%, nickel-10%, chromium-18%, 2.0% manganese, silicon-1.8%, the rest-iron.
Cobalt-chromium alloy.
STRUCTURE:
• cobalt - 66-67%, the basis of the alloy, solid, durable and lightweight metal.
* chromium - 26-30%, to increase corrosion resistance.
* nickel - 3-5%, increases ductility, ductility, viscosity, improves the technological properties of the alloy.
* molybdenum - 4-5. 5%, increases the strength of the alloy.
* manganese-0.5%, increases the strength, quality of casting, lowers the melting point, helps to remove toxic sulfur compounds from the alloy.
* carbon - 0.2%, reduces the melting point and improves the fluidity of the alloy.
* silicon-0.5%, improves the quality of castings, increases the fluidity of the alloy.
• iron - 0,5%, increases fluidity, improves the quality of castings.
Properties of KHS-dental alloy:
It is characterized by good physical and mechanical properties, low density. The melting point is 1458C. The alloy is resistant to abrasion and retains its mirror-like luster for a long time. [3]
Titanium alloys. In dentistry, both pure (99.5%) and its alloys are used. Its mechanical characteristics are no worse than those of some noble alloys used for dental purposes. The titanium coating forms a resistant oxide film, thanks to which it is resistant to corrosion and biologically compatible with the soft tissues of the human oral cavity.
For the manufacture of removable dentures with cast bases, metals and their alloys are used. Such materials include alloys of noble (to a greater extent) and base (cobalt-chromium alloys) metals. But despite this, they continue to be used because of their excellent biocompatibility with the human body. Gold-based alloys are strong, withstand heavy chewing loads, have an antibacterial effect, do not cause an allergic reaction, darkening and inflammation of the gums. They are not subject to corrosion, do not react with saliva, do not cause intoxication. In its pure form, gold is not used because of its softness and is therefore used exclusively with additives.[4]
Cobalt-chromium alloys (CCS) were used in general orthopedics for prosthetics of large joints, and from there came to dental prosthetics. The advantage of these prostheses is high strength, rare cases of individual intolerance, and cost-effectiveness. The disadvantage is the need to turn the teeth (their service life is reduced), as well as the overload of the supporting nodes, which sometimes leads to the destruction of their periodontal. The melting point of CCS is slightly less than 1500°C. The alloy is suitable for casting complex structures in terms of configuration, although it creates some difficulties in manufacturing. According to the "price-quality" parameter, cobalt-chromium alloys are considered one of the best dental materials for prosthetic frames. They are characterized by the following properties: high biocompatibility with oral tissues. In rare cases, individual intolerance to individual components, such as nickel, may be observed. Good physical and mechanical properties (strength, corrosion resistance, high wear resistance). Satisfactory properties of injection molding. They are inferior to nickel-chromium alloys, but if the technology is followed, they can cast accurate, but at the same time openwork designs. Economical (cheaper than gold and zirconium dioxide).
Titanium has taken its rightful place among modern materials. With an increase in allergic reactions to various alloys and metal alloys used in medicine and dentistry, titanium is considered as the main alternative. Titanium has attracted the attention of orthopedists due to its remarkable biocompatibility and good stability. High biocompatibility is determined by the ability of titanium to form a protective oxide layer on its own surface in a fraction of a second, so that it does not release free metal ions that are ready to cause pathological processes around the implant or prosthesis. At the moment, titanium gives us the ability to use only 1 metal in the oral cavity. We can make almost any design. There are no chemical interactions between the various elements of the prostheses, but the tissues around the prosthesis remain independent of metal ions.[5]
Titanium is a pure chemical element, a metal; it has the ability, while in the body, to be inert for a long period; in dental prosthetic equipment, pure titanium is used in 4 gradations (from T1 to T4); hardness, depending on the gradation, from 140 to 250 units.
As long-term practical activity has shown, having numerous positive properties, metals have every chance to have negative effects in the tissue of the prosthetic bed and the body as a whole.[6,7] Factors of metal intolerance in the rarest cases are considered: mechanical trauma of the oral mucosa with removable dentures, exposure to the oral mucosa with bacteria that are present in the plaque of the prostheses, allergic and toxic-chemical effects of substances that make up the prostheses, internal organ disease, hormonal disorders, psychogenic factors. An important obstacle to the entry of allergens, toxic elements, bacteria and their waste products into the human body is the epithelium, in this case, mechanical trauma of the mucous membrane is one of the main factors of intolerance to removable dentures .[8] The epithelium is subjected to mechanical trauma, under the influence of a wide range of temperatures, fluctuations in PH values, and exposure to irritating and damaging factors. It is known that the basis of the removable prosthesis should clearly reproduce the microrelief of the mucous membrane of the tissues of the prosthetic bed. But, in the course of metal casting, its linear-volume changes inevitably occur due to shrinkage. There are discrepancies between the relief of the base of the prosthesis and the relief of the tissues of the prosthetic bed [9].
Thus, research data from Russian and foreign sources of literature suggests that a large range of basic materials is used today, which are subject to high requirements for quality, comfort, and high aesthetics. It is necessary to emphasize that such materials must have high hygienic properties, the characteristics of which have a great influence on the operational properties.
IX. Results.
The patient with a plate prosthesis does not fully feel the taste of food and temperature changes, since the base of the structure is covered by the mucous membrane of the hard palate. And, consequently, the area of receptors that respond to external stimuli decreases. Dentures with a metal base differ from plate dentures and have their own advantages. The patient feels less foreign body in the mouth, because the metal base is thinner than the plastic one. The perception of cold and hot food is preserved due to the fact that the metal base has good thermal conductivity. The metal-based prosthesis is suitable for patients with allergies to acrylic and plastic.
One of the main reasons for choosing metal is the frequent failure of the prosthesis with a plastic base. Over time, it ceases to withstand the chewing load and breaks into two parts.
Any prostheses in the mouth affect the mucous membrane and disrupt the process of salivation. In patients with a metal base, dry mouth is less common than in patients with a plastic prosthesis.
Also, inflammation of the mucous membrane of the upper jaw with a metal prosthesis is less common than with a plastic one.
For oral hygiene, it is better to have a prosthesis with a metal base. Its surface is smooth, unlike plastic, so the plaque on it does not settle much. And on a metal base, this will be more noticeable, so the patient will have to carefully monitor the quality of cleaning.[10]
It can be summarized that prostheses with a cast base are preferable to plastic ones. Patients with such prostheses feel more confident and do not have additional costs for the repair of the prosthesis.
X. Discussion
The advantages of choosing a cast base for the production of food products are shown by the following properties: :
* precise fit and secure fixation in the oral cavity ;
* quick habituation and the possibility of constant wear (even during a night's sleep );
* uniformity of the base material, lack of hygroscopicity, non-susceptibility to food color and absorption of foreign substances;
* the strength of the prostheses and the rational distribution of mechanical loads when placed only on one side of the jaw;
• maintaining the temperature sensitivity;
* biochemical equality of oral fluid.[11,12,13]
XI. Conclusion
Thus, prostheses with a cast base have a higher chewing efficiency, they can be used for allergies to acrylic plastics, with an increased gag reflex, repeated fractures of plastic bases, low clinical crowns. This all allows the orthopedic dentist to use removable dentures with a cast base.
