Metals in dentistry
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Metals are commonly used in dentistry due to their hardness, strength, and corrosion resistance. The main metals used are gold, platinum, palladium, silver, and titanium. Gold is often used on its own or in alloys due to its biocompatibility, corrosion resistance, and ability to form solid solutions with other metals. This changes the properties of gold for different applications. Titanium is also widely used for implants and prosthetics due to its strength, corrosion resistance, and ability to integrate with bone. Dental amalgam is a mixture of silver alloy powder and liquid mercury that hardens into a filling material.
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Metal alloys – classification criteria according to ANSI/ADA
(American National Standards Institute /American Dental Association)
< 25any
With advantage of
noble metals
> 25anyNoble
> 60> 40Very noble
Nobel metal
content
Gold content
[weight %]
Alloy type](https://image.slidesharecdn.com/metalsindentistry-171217101945/85/Metals-in-dentistry-32-320.jpg)
![36
Metal alloys – alloy density
Density of dental alloys are in the range from 4,5 g/cm3 (titanium alloys)
to 18,5 g/cm3 (some nobel alloys)
7,5
7,5
4,5
1275
1400 – 1500
1700
With excess of nobel
metals
Based on nickel
Based on cobalt
Based on titanium
12,4
10,6
10,6
865 – 925
1100 – 1190
1020 – 1100
Nobel
Silver- gold- copper
Palladium – copper
Silver -palladium
18,5
15,6
1045 – 1140
910 – 1065
Higly nobel
Gold - platinum
Gold- copper- silver
Density [g/cm3]Melting range [oC]Alloy type](https://image.slidesharecdn.com/metalsindentistry-171217101945/85/Metals-in-dentistry-36-320.jpg)
![38
Metal alloys – hardness
Influences polish of alloy
Hardness is related to yield point.
Hardness is express in kg/mm2.
-it means amount of mass [kg] needed to be apply to make
notch of 1 mm2 area
hardness of dental alloys is in the range:125 – 425 kg/mm2
Enamel hardness is 343 kg/mm2](https://image.slidesharecdn.com/metalsindentistry-171217101945/85/Metals-in-dentistry-38-320.jpg)
Metals in dentistry
- 2. 2 Metals properties Usually are: Hard Luster High density is dependent on molar mass of molecule as well as structure type of crystalline which determines amount of atomes to be able to be packed in lattice. Good heat nad electricity conductors because of metalic bonds presence
- 3. 3 Metallic bond Elecetron configuration Na - 1s22s22p63s1 Valence elctron 3s1 is surranded by Na+ sodium elctron’s cloud Accumulation of more amount of atoms being in sodium crystal is causing that valence elctrons are moving within entire crystal volume Electron gas which penetrates inter-ions space as a result of electrostatic interaction attracts positive charged ions making them densely packed Sodium atom Na2 molecule Sodium crystal
- 4. 4 Metallic bond Presence of metalic bond in structure determines its: • Opaqueness • Metalic gloss • Good electrical conductivity • Good thermal conductivity • Ductililty
- 5. 5 Metals used in dentistry Noble metals: Gold, palladium, platinum High resistivity to corrosion Non-noble metals Titanium, nickel, copper, silver, zinc Provide modulus of elasticity and abrasion resistance of dental alloys.
- 6. 6 Main type of metals used in dentistry Gold Gold belongs to copper „family” Density 19,3 g/cm3 Melting temperature 1062oC Boiling temperature 2600oC Very soft, melleable, and ductile Good elctrical and heat conductor With silver, platinum and palladium makes solid solution
- 7. 7 Main type of metals used in dentistry Gold Dissolves in: Aqua regia (mixture of hydrochloric and nitrate acids in 3:1 proportion, has very oxidative properties and has ability to dissolve gold, platinum, palladium and other nobel metals) Au + HNO3 + 4 HCl HAuCl4 + NO + 2H2 Chlorine water (water saturated with chlorine)
- 8. 8 Main type of metals used in dentistry – Platinum • Belongs to platinum „family”. • Density - 21,45 g/cm3 • Melting point - 1773oC • Boiling point - 4300oC • Average hardness • Easy to forging and rolling • High resistance to chemicals • Dissolves only in aqua regia making chloroplatinous H2PtCl6 acid
- 9. 9 Main type of metals used in dentistry Platinum To expensive to be used in dentistry. Used as an additive to gold in the amount of 5-10% Platinum changes gold properties: Adds elasticity Changes color Increases melting point Gold-platinum alloys are used for making : Arches Wire dental aplliances
- 10. 10 Main type of metals used in dentistry Iridium Density - 22,42 g/cm3 Melting point - 2440oC Boiling temperature - 4400oC Silver-white metal, very fragile but hard High chemical resistance: reacts only with chlorine and fluorium DOES NOT dissolve in aqua regia
- 11. 11 Main type of metals used in dentistry Irydium Alloys of irydium (10%) with platinum are more hard, more resistant and have more chemical resistance than pure platinum Used for „stifts” for porcelain crowns
- 12. 12 Main type of metals used in dentistry – Palladium Density - 11,97 g/cm3 Melting temperature - 1549oC Boiling point - 2540oC Not very hard Plastic Melleable
- 13. 13 Main type of metals used in dentistry Palladium Chemical reactivity Dissolves in: Nitric acid Sulpuric acid, Very easily in aqua regia Addition of 20% palladium to gold with platinum gives „white gold”. Alloy of palladium with silver in 9:1 proportion is used for making parts of porcelain crowns Palladium is a part of platinum soldier
- 14. 14 Other metals used in dentistry – Silver Chemical and physical properties: Not very hard Resistant to loads Easy to undergo chemical and thermal changes, ductile The best heat and electricity conductor Dissolves in nitric and sulphuric acid Makes alloys with many metals: With palladium and gold mix in any ratio in solid and liquid state Combines with H2S and makes silver sulphide (Ag2S) Combines with chloride and makes silver chloride (AgCl) In oral cavity
- 15. 15 Silver in pure form is not used in dentistry Silver salts are poisones ! Can be applied unless there will be no contact with oral cavity fluids. (e.g.: in stifts) Application : • as a stift for crowns • for temporary dental work • as a component of dental gold Other metals used in dentistry – Silver
- 16. 16 Permanent protetic suplement - porcelain crowns on the base made from metal or steel
- 17. 17 Permanent protetic suplement Porcelain crowns fused to steel or gold base
- 18. 18 Crown and bridge on metal alloy base
- 20. 20 Other metals used in dentistry Mercury In room temperature it is thick fluid metal Belongs to zinc”family” Density 13,54 g/cm3 Freezing temperature -38,89oC Boiling temperature 356,90oC Dissolves all metals except ferrum and platinum „families” Reacts with nitric acid only
- 21. 21 Other metals used in dentistry Titanium atomic number 22 posseses high mechanical strength, corosion resistant (including sea water and chlorine) gray color can be added as an addition to iron, aluminum, vanadium, molibdenium and other alloys. Titanium alloys are used in airspace industry ( engines), in military, metalurgic processes, moto, medical ( dentures, orthopedic braclets), in sports (bicycle frames and components, tennis rackets, baseball bats, hiking equipment, golf clubs) http://images-of-elements.com/titanium.php http://www.gtagaming.com/downloads/gta-san-andreas/weapon-mods/10718
- 22. 22 • Used in dentistry • Posesses much more lower thermal conductivity than traditional prosthetic materials • High hardness, mechanical strength and longevity • Hypoalergenic and corrosion resistant • For bones treatments alloys of titanium and Al, Nb (niobum). For example Blount braces with longevity about 20 years are made from alloy of Titanium (43-47%) and Nickel (53-57%) • Other application of Ni-Ti alloys are implants plates and for curing bite in chieldren Other metals used in dentistry Titanium
- 23. 23 Titanium is a metal very often used in implants and more often in protetic Main adventure is to create oxidation layer on the surface which protects against corrosion and interaction of cell fluids with chemical reaction. After implant is introduced directly to bone contact osteogenesis starts - process which is building up of bone directly on the implant surface. That leads to the direct structural and functional connection between living bone and the surface of implant - osteointegration
- 24. 24 Osteointegration on the surface of implant
- 25. 25 Dental implants A dental implant, sometimes called a tooth implant, is an artificial tooth root (synthetic material) that is surgically anchored into jaw to hold a replacement tooth or bridge in place
- 27. 27 Metal alloys – classification criteria Alloys can be divided in respect to: 1. Amount of noble or non-noble components. For example: 60% Au, 10% Pl, 5% Pt i 25% Cu – combined „nobility” of alloys is 75%. (Copper is not noble and does not count) 2. Dominant metal. For example: alloys based on gold. 3. Color – alloys in yellow or silver color sometimes are called „white” . 4. Application – alloys for making fillings or solders
- 28. 28 Metal alloys Metal alloys have crystal structure. During solidification of melted alloys crystals are formed and become larger Smaller grains gives better alloy properties. In order to have the smallest possible grains other components are added such as iridium or ruthenium. In alloys with high quantities of non-nobel metals crystals with large diameter are dominant.
- 29. 29 Alloy properties are usually not an average from properties of metalic components Addition of even small amount of any metal to alloy can cause dramatic change in its properties For example: small amount (5-10%) of platinum in gold alloy increases hardness and elasticity of alloy. Palladium and nickel increase hardness of alloy. Alloy properties are determined by many factors: composition, manufacturing condition, mechanical and thermal treatment, crystal structure etc.
- 30. 30 Requirements for metal alloys Alloys should posses: • Ease of melt • Ease to make a cast (melted alloys with high density and good flow are easier to be cast) • Ease of processing • Corrosion resistance and dullness in oral cavity environment • Biocompatibility : should not be toxic and cause allergy
- 31. 31 Proper mechanical properties, especially: • High plastic resistance, especially for alloys exposed to high stress • Proper ductility protecting against breaking during the fixing • Proper hardness which results in milling dificulties and its resistance to grinding • Should not be expensive. Ideal alloy shoud not be expensive in terms of material and processing Requirements for metal alloys
- 32. 32 Metal alloys – classification criteria according to ANSI/ADA (American National Standards Institute /American Dental Association) < 25any With advantage of noble metals > 25anyNoble > 60> 40Very noble Nobel metal content Gold content [weight %] Alloy type
- 33. 33 Metal alloys - the most important parameters Melting temperature range Density Strength and hardnes
- 34. 34 Metal alloys – melting temperature range Metal alloys are melting in specific temperature range. During the heating melting temperature range: 950o -1000oC 950oC first symptoms of melting 975oC part of the alloy is liquid but some of the components are still solid 1000oC entire alloys become liquid
- 35. 35 Metal alloys – melting temperature range liquidus - temperature in which alloy entirely become liquid solidus – temperature in which alloy during the cooling became solid Alloy may be used for casting when its temperature is higher than liquidus. Solidus is important during soldering. If soldering will make alloy warmer above solidus than shape change may occur
- 36. 36 Metal alloys – alloy density Density of dental alloys are in the range from 4,5 g/cm3 (titanium alloys) to 18,5 g/cm3 (some nobel alloys) 7,5 7,5 4,5 1275 1400 – 1500 1700 With excess of nobel metals Based on nickel Based on cobalt Based on titanium 12,4 10,6 10,6 865 – 925 1100 – 1190 1020 – 1100 Nobel Silver- gold- copper Palladium – copper Silver -palladium 18,5 15,6 1045 – 1140 910 – 1065 Higly nobel Gold - platinum Gold- copper- silver Density [g/cm3]Melting range [oC]Alloy type
- 37. 37 Metal alloys – alloys strength Yield point – indicates force applied to the surface unit at which permanent deformation will appear Yield point unit is Mega pascal (MPa) Yield point for alloys is in th erange of: 260-1150 MPa Alloy deformation – magnitude express in percentage (%) Yield point 750 MPa and deformation 0,2% - it means that force of 750 MPa is causing deformation of alloy by 0,2%
- 38. 38 Metal alloys – hardness Influences polish of alloy Hardness is related to yield point. Hardness is express in kg/mm2. -it means amount of mass [kg] needed to be apply to make notch of 1 mm2 area hardness of dental alloys is in the range:125 – 425 kg/mm2 Enamel hardness is 343 kg/mm2
- 39. 39 Amalgam Amalgam – it is the mixture of silver alloy with liquid mercury Sillver alloy – it is the powder consisting of silver, tin and copper After mixing silver alloy with mercury chemical reaction takes place which gives amalgam: silver alloy + mercury -> amalgam At the begining it is plastic and after it hardens it is harder than other dental filling
- 40. 40 Amalgam Currently alloys with high quantity of copper are used (13 – 30%) Amalgams made of silver alloy with high content of copper (in comparison to small amount of Cu 2 – 4%) are: More resistant to crushing and elongation Less resistant to corrosion More susceptible to edge ckracking Example of composition of silver alloy with high content of copper: Silver 40 – 60% Tin 27 – 30% Copper 13 – 30%
- 41. 41 Amalgamation Combining silver alloy with mercury starts process of dissolving alloy in mercury During dissolving process chemical reaction takes place which leads to mixture cristalization which results in thickening and hardening of amalgam Hardening of amalgam starts before all alloys molecules are totally dissolved Fixed amalgam contains large amount of silver alloy surrounded by new product of chemical reaction which took place in amalgam Simplified reaction schematic: Silver alloy (tin - silver - copper) + mercury Silver alloy (unreacted) + copper-tin + silver-mercury After amalgamation process ends there is no „free” mercury in amalgam
- 42. 42 THE END