1. Conclusion of first part of dental materials

2. Conclusion 1/ Why is better to use dental alloys than pure metals? - the composition of individual chemical elements or metal in alloy are so, that the properties of whole alloy are the best 2/ When was began to use dental alloys? -the development of metal alloys arrived at the ending of 19. Century, when Mr. Bing constructed the first inlay°s bridge 3/ What is the main criterium for distribution of dental alloys? -the main criterium for this distribution and for assigning of ISO standard is hardness of material - the hardness of dental material can characterised by the Vickers and by the Brinell

3. Conclusion 4/ Write the distribution of dental alloys – according to standard ISO (hardness material) - The alloys with the high content of aurum and platinum ( ISO 1562) - The alloys with flat content of aurum and platinum, they are the alloys of argentum and palladium ( ISO 8891) - The alloys of general metals ( cobalt, nickel ) ( ISO 6871) - The alloys for ceramic burning ( titanium too) ( ISO 9693) - The alloys as a aluminium bronze

4. Conclusion 5/ Characterise the properties of gold-platinum, ISO ( ISO 1562). -they are indicated for large bridges - they contetnt of aurum 75-90 %, 8-19% pllatinum, 4-10 % palladium, iron, iridium -iridium easy oxidate and make adhesion to the ceramic - palladium has a high temperature of melting, higher mechanical resistence and lower price - disadvantage is that palladium discolors the yelllow color of aurum -typical color of these alloys after oxidation is grey or brown-grey

5. 6/ Write the main characteristic of general metal alloys - the basic of these alloys is cobalt or nickel - next they include chrom (min 20-25 %), molybdenum (4%), iron, mangan, wolfram, berilium, titanium, carbon, nitrogen, silicium - the content of nickel or cobalt, must be minimally 85% - chrom very increased the hardness of material - these alloys are indicate for metal construction of removable partial denture, large bridges, metaloceramic construction - very heavy disadvantage is volumetric contraction by the freezing Conclusion

6. 7/ What is the galvanism? - it is a complex of processes, which are result from elektrochemical reactions - in general, it is rise of electric tension between two electrodes, which are coupled with fluid -the basic of galvanism is ability of metals to release the cations from surface of metal alloy 8/ How can you characterise the stomatitis galvanica? -they are clinical manifestation of galvanic stimulus on the mucosa surface - to the symptoms belong : parestesia, stripes, disorders smack, strog attack of pain neuralgiform character - it is glossitis or stomatitis Conclusion

7. 9/ Describe the chemical chracteristic of cobalt-chrom alloys. -after standard ISO, cobalt alloys have to contain at least 25% Cr, 4% Mo -reorganisation of atoms into the atomic lattice are the cause of volume expansion - the casting temperature of cobalt alloys is 1400°C 10/ Explain the mechanical properties of cobalt alloys. - the Co-Cr dental alloys are very strong and hard, because size of atoms of Co, Cr and Mo is similar (Co 0,25; Cr 0,26; Mo 0,28 mikrometra) - atomic lattice is very resistant to the external forces Conclusion

8. 11/ What is the cause of resistance before corrosion. - protection before corrosion is passive layer, which create by the chrome - the cobalt alloys are more resistant before corrosion than nickel alloys, because the cobalt alloy dont make easy free cations 12/ Why the nickel alloys support hypersensitievity? - metal cations react with anions surrounding medium. So they can make macromolekules. These elementary parts from alloys are trasported to the various parts of body. - solubile compound of Ni-alloys are absorbed very quick and ca make change in structure of DNA and so support damage Conclusion

9. 13/ Describe the main characteristic of solders for Ni-Cr alloys. - the solder must have the melting temperature about 100°C decreased than is the melting temperature of origin alloy ( for protect of origin alloy) - a chemical composition of solder is similar as a composition of origin alloy - from it results, that the place of connection is not very different from whole cast - the different composition solder and origin alloy produces the base for galvanic current Conclusion

10. 14/ How can you describe the fineness of gold alloys? - it is the proportion of gold in gold alloys. - into the fineness belong the rate of platinum too - the main measurement of fineness is thousandth or carats - we distiguish 5 gradus of fineness 15/ Explain the chemical properties of gold alloys. - they are without change on air and in water - they are resistant before oxidation, it means they are resistant before corrosion - they do not react with all of acids ( as a concentrate or as a solutions) - only one solution, which can dissolve gold alloys, is solution of nitric acid and hydrochloric acid in volumetric rate is 1:3 Conclusion

11. 16/ Write the distribution of gold alloys according to hardness of material. - It is distribution at four classes ( type 1 – 4) -Type 1 is smooth alloys with high content of gold; type 4 is very strong alloys with high content of pllatinum and palladium 17/ How can be changed the physical properties in gold alloys, when is added palladium and pllatinum? - palladium and pllatinum provide higher casting temperature, higher mechanical resistance and narrower price - their disadventages is decoloration from yellow on white color -typical color of these alloys after oxidation is grey or grey-brown Conclusion

12. 18/ Describe the general properties of titanium. - titanium is very good biocompatible material - it has a exeptional resistance before corrosion - it can be use as a bioactive material, which can make adhesion with vital tissue - It is one metal, which is in nature as binary alloys and in dental prax is used as a pure metal 19/ When began the indutrial production of titanium? - at 1932y. – as a chemical reaction between TiO2 and calcium or magnesium - it was in America, Japan and in Russia Conclusion

13. 20/ Characterise the physical properties of titanium. -titanium is the metal of steel color with high brightness - difference from steel is in the weight. It is result from unequal density - the density of pure titanium is about 4,51 g/cm 3, and Ti – alloys is 4,40 – 4,80 g/cm 3. - in equation with cobalt alloys, which have density about 8,2 g/cm 3, the weight of the metal titanium cast is less about 43% than weight of similar cobalt cast ( according to large and shape) Conclusion

14. 21/ What is the main principle of melting titanium ? - the melting of titanium is by the mercury arc in vacuum - this metod names as a „skull melting“ - other type of melting titanium is during the induction current - this melting is running in the vacuum with special inert gas, argon (colorless and odorless gas) 22/ Explain the soldering of titanium. - soldering of titanium parts is by the welding - according to very strong chemical reaction of titanium by the temperature above than 500°C, must be soldering very quick and with high thermal energy, by laser ray Conclusion

15. 23 / Which type of plaster is the main type for using in dental practice, for making others type of plaster. - It is plaster of Paris 24/ What is the chemical base of plaster of paris? - it is anhydric beta polyhydrate of gypsum: CaSO 4. 1/2H 2 O - it is produced by the process of dehydration of gypsum - chemical reaction is following CaSO 4.2H 2 O CaSO 4. 1/2H 2 O + 1/2H 2 O Conclusion

16. 25/ Write the dividing of dental plaster according to chemical properties: - from chemical view can be divided : 1. plaster of Paris ( soft plaster) 2. hydrocal plaster ( hard plaster) 3. densite plaster ( super hard plaster) 26/ Characterise the hydrocal plaster - the base of this plaster is the alfa polyhydrate plaster of paris - this plaster is more hardness than plaster of paris - chemical and physical properties of both type are similar, but atomic lattice is different - the beta plaster has a high porosity, but hydrocal plaster has nonporosity crystals Conclusion

17. 27/ Explain the setting of plaster. - Setting is exotermic reaction, it is hydration: CaSO 4. 1/2H 2 O + 1,5 H 2 O CaSO 4.2H 2 O + heat - by the setting is mixed the powder with water - by the setting create the volume expansion - the condition of this expansion is mashing of rising crystals - the name of this expansion is hydroscopic expansion 28/ How can be accelerated the setting of plaster? - accelerating of setting can be secured with the : - hot water - chemical regulators of setting - change of mixing speed (intensive mixing) - changen of mixing rate Conclusion

18. 29/ Why is important the hydroscopic expansion at the setting of plaster? - it is necessary for compensation of contraction of metal alloys at the cooling 30/ What is the base for determination of plaster hardneess? -the hardness is depend on character, large and shape of atomic crystals - the plaster of paris is adorned with a crystals in shape of needles, this atomic lattice need for mixing a lot of water and from physical properties it is soft type of plaster - superhard plaster is squars as a shape of atomic lattice and for mixing need a very little volume of water Conclusion

19. 31/ Explain the mixing rate W/P (water/powder). it is volume of water to content of powder, which is necessary for making slurry plaster matter, for making prosthetic models 32/ Which type of plaster is the best for dental use and why? - it is superhard plaster, type IV - mixing rate is V/P 18,5-24 - hardness is 60 MPa - volume expapnsion at the setting is 0,1% -according to high hardness and mechanical resistance it is a good type for working models at fixed bridge and crown Conclusion

20. End.