Dental alloys

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Gold teeth made of dental gold ( Uzbekistan )

Dental alloys are alloys of defined compositions that are used in dentistry .

In dental alloys, a distinction is made between precious metal alloys ( precious metal ; gold , silver , palladium or platinum ) and non-precious metal alloys (non-precious metal; cobalt , iron , nickel , copper , chromium , molybdenum , titanium , tungsten , tin , zinc , rhenium , indium , gallium) , Tantalum , boron , iridium , manganese , ruthenium , silicon , yttrium or rhodium ). Within these groups, a distinction is made according to the respective main component. Over 1400 dental alloys are approved in Germany (as of 2009).

Dental standards

The following standards apply to dental alloys:

  • DIN EN ISO 1562 Dentistry - Gold casting alloys for alloys with a precious metal content of more than 75%.
  • DIN EN ISO 8891 for alloys with a precious metal content between 25% and 75%.
  • DIN EN ISO 969327 for alloys for the production of metal-ceramic (VMK) (metal-ceramic alloy).
  • DIN EN ISO 6871-1 Precious metal-free dental casting alloys - Part 1: Cobalt-based alloys
  • DIN EN ISO 22674 CoCrMo model casting alloys
  • DIN EN ISO 15841 Dentistry - Wires for orthodontics
  • DIN EN ISO 10271 Dentistry - Corrosion test method for metallic materials
  • DIN EN 29333 dentistry - hard solders and DIN EN ISO 9333 dentistry - dental solders

Classification

Classification of precious metal casting alloys according to the standards DIN EN ISO 1562 and DIN EN ISO 8891:

  • Type 1: low strength - for cast objects that are only subjected to very little stress (e.g. inlays).
  • Type 2: medium strength - for cast objects that are exposed to moderate loads (e.g. three-quarter crowns, onlays, bridge anchors, pontics, fully cast crowns and saddles).
  • Type 3: high strength - for cast objects that are subject to heavy loads (e.g. inlays, thin three-quarter crowns, thin facet backs, cast plates, pontics, full cast crowns and saddles).
  • Type 4: extra high strength - for cast objects that are exposed to very high loads and have thin cross-sections (e.g. saddles, bars, clips, telescopic crowns, caps, one-piece castings and model casting frameworks).

history

Early finds

Replica of a Phoenician denture from Sidon , around 700 BC BC, World Museum Liverpool , Mayer Collection

In 2700 BC Teeth are said to have been decoratively covered with thin gold leaf , as can be seen from finds from a tomb dating from around 2700 BC. ( Hili Tomb ) in the Hili Archaeological Park collection in the Al Ain National Museum in Abu Dhabi . It is one of the last vestiges of the mysterious Umm al-Nar culture, which existed between 3000 and 2000 BC. BC first established a major civilization epoch in the region. Already 1000 BC The Chinese used tooth fillings made of the finest gold leaf, which was stamped into the caries holes. The first prosthetic work was done in 500 BC. Made by the Phoenicians . In Eastern Europe, for example in Tajikistan and the Orient, gold teeth on the front were considered a sign of wealth.

19th century

Upper and lower partial dentures based on aluminum, 1858–1880, front teeth are Waterloo teeth, molars made of porcelain

In May 1869, William N. Morrison described the ring-cap crown ( Morrison crown ) named after him in the Missouri Dental Journal . These metal band crowns, also called band sleeve crowns, were widely used before the establishment of the casting technology. For this purpose, a gold band was adapted to the ground tooth in a ring shape and soldered. The chewing surface (“lid”) was cast separately and then soldered to the tape. In 1876, Cassius M. Richmond from San Francisco developed the ring pin crown ( Richmond crown ) named after him , which could also have a porcelain bowl as a veneer. 1907 William H. Taggert invented a casting machine and a investment material containing a modeled directly in the casting metal by means of lost wax process ( lost wax casting ), and casting method with lost form could result. The cast objects had a previously unknown accuracy of fit. However, the cast crowns produced in this way were not widely used until the 1950s.

20th century

Partial upper denture made of gold. Visible parts of the gums made of pink rubber, teeth made of porcelain (1st half of the 20th century)

During the Second World War in 1817, the volume of production and the value of dental gold produced and partly exported in the United States was determined and listed by the Bureau of the Census at the request of the Federal Reserve Board.

After numerous attempts, M. Weinstein, S. Katz and AB Weinstein were the first to apply for a patent in the USA in 1952 for a ceramic ceramic in which stability is created by a metal framework (mostly made of a gold-platinum alloy) under the ceramic, however, it often flaked off. The coefficient of thermal expansion (CTE) of metal and ceramic differed greatly when they cooled down from the firing temperature of 880 ° C, which led to tension. In 1962 it was possible to adjust the CTE between metal and ceramic, thereby considerably reducing the risk of breakage. At the same time, the company developed Whip Mix Corporation , the phosphate-bonded investment material with which the first high melting gold - platinum - alloys of JF Jelenko Company and J. Aderer Company were cast, which (as a scaffold for keramikverblendete crowns crowns PFM ) are used. The VMK crowns and bridges that have been used worldwide since then were born (composite metal-ceramic) .

At the end of the 19th century, the American Elwood Haynes developed a cobalt -based alloy (starting point for the stellite group ), which he applied for a patent in 1907. It forms the basis of the chrome-cobalt-molybdenum alloys that are still used in dentistry today for model cast prostheses and for crown and bridge technology. As a rule, the ceramic-on cobalt-chromium alloys differ from the model casting alloys in that tungsten is added . One of the first cobalt-chromium alloys that can be veneered with the low-melting and high-expansion ceramics was developed by the Bremer Goldschlägerei BEGO in 1999.

William J. Buehler and Frederick Wang examined the first nickel-titanium arc in 1963, which was named Nitinol , which is an acronym for Nickel Titanium Naval Ordinance Laboratory . The first discovery of shape memory alloys goes back to the 1920s, but this discovery was initially forgotten. It was not until 1971 that this new material was introduced into orthodontics by Andreasen and Hillemann. This was a work-hardened nickel-titanium alloy, which is martensite at mouth temperature and has a transformation temperature of over 100 ° C.

Metal alloys

A distinction is made between precious metal alloys, which contain gold, silver, palladium or platinum, and non-precious metal alloys (non-precious metal), which are made from cobalt, iron, nickel, copper, chromium, molybdenum, titanium, Tungsten, tin, zinc, rhenium, indium, gallium, tantalum, boron, iridium, manganese, ruthenium, silicon, yttrium or rhodium.

Precious metal alloys

Dental gold

Color variations of different dental gold alloys in platelet form of one gram each

Dental gold, d. H. Dental gold alloys (also known as "dental gold alloys"), colloquially "dental gold", or gold casting alloys, are alloys that mainly consist of gold and additional metals and are used in dental technology to create inlays , partial dentures or, in some cases, entire teeth . Dental gold is commercially available for this in plate form ("crown sheet", thickness approx. 0.25 mm) or as platelets (thickness approx. 1 to 2 mm with a weight of approx. 1 g).

There are around 30 manufacturers and suppliers of gold casting alloys in Germany.

  • Dental gold plate (edge ​​length: ~ 6 mm; weight: ~ 1 g)

  • Gold crown

  • Gold filling (gold inlay)

Chemical composition and physical properties

Due to their defined composition, different dental gold alloys are characterized by different physical properties such as hardness and melting point as well as different colors. The following two tables with the data of five different alloys allow an exemplary comparison of chemical composition and physical properties.

Composition of dental gold alloys

alloy Gold (%) Silver (%) Platinum (%) Palladium (%) Copper (%) Zinc (%)
Degulor A 87.5 11.5 - 1.0 - -
Degulor B 75.7 15.0 1.4 3.3 4.1 0.4
Degulor S. 79.3 12.3 0.3 1.6 5.5 1.0
Degulor M 70.0 13.5 4.4 2.0 4.1 1.2
Degulor M0 65.5 14.0 8.9 1.0 10.0 0.5

Physical properties of dental gold alloys

alloy Melting range
° C		 Brinell hardness
kg / mm 2 		Tear strength
kg / mm 2 		Yield point
kg / mm 2 		Elongation
%		 Specific
weight		 hardness
Degulor A 990-1080 58 30th 12 36 17.4 extra soft
Degulor B 960-1040 82 41 21st 36 16.1 soft
Degulor S. 910-990 80 39 20th 42 16.0 soft
Degulor C 860-920 115 49 30th 43 15.6 medium hard
Degulor M 900-970 145 59 38 34 15.7 hard
Dental gold as an exchange currency

Dental gold in the form of 1 g heavy, small platelets is also suitable as a means of payment in times of severe crisis ( national bankruptcy , hyperinflation ), as this is better suited as a means of payment in barter or as a substitute currency for daily needs than gold bars , which are hardly ever in small portions split up. Dental gold alloys with a high fine gold content (e.g. BIOcclus : about gold / platinum group metals 88.2%) are particularly suitable for this. A plate would currently correspond to a (theoretical) material value of around € 37 (at a sales price of € 58.60), which, however, is likely to increase sharply in the aforementioned crises.

Bonding alloy

If dental alloys are used for metal-ceramic veneers (VMK, composite metal ceramics; ceramic-clad tooth crowns), metals such as zinc, indium or tin that form adhesive oxides are added in concentrations of 0.5 to 2% to ensure that the ceramic adheres well to the carrier alloy to guarantee. The copper content is low or absent. It is also essential that the alloy has a coefficient of thermal expansion that is coordinated with the ceramic material .

  • Bridge framework made from a bonding alloy

  • Ceramic-veneered bridge

Implant

Titanium dental implant

Implants are made from titanium or tantalum alloys, cobalt-chromium or cobalt-chromium-nickel alloys, but also from zirconium. The “gold standard” is currently still titanium alloys.

Model cast prosthesis

Partial denture in the upper jaw, framework made of a chrome-cobalt-molybdenum alloy

A model cast prosthesis is an inexpensive, aesthetically rather unsatisfactory partial prosthesis. Its metal frame (including the holding and supporting elements - so-called brackets) is cast in one piece from a chrome-cobalt-molybdenum alloy , which consists of 65% Co, 30% Cr and 5% Mo. The prosthetic saddles with the artificial teeth are attached to this very stable framework .

Electroplating

With the electroplating in the can Dental restorations are manufactured, which consists of thin gold cap and is veneered with ceramic. The electrochemical process produces self-supporting metal frames from gold. In the Auro-Galvano-Crown-Process (AGC), a gold layer of approx. 200 µm is deposited on the tooth stumps prepared with silver powder in the dental laboratory. The frameworks have a purity of 99.99% gold. Electroplating is suitable for the production of single crowns , denture bases , ceramic veneered partial crowns and inlay fillings (inlays / onlays), telescopic crowns , dental bridges for replacing a tooth and dental implant superstructures.

Base metal alloys

Lot

DIN EN ISO 4063 defines soldering as a thermal process for materially bonded joining or coating of materials, whereby a liquid phase is created by melting a solder or by diffusion at the interfaces. The solidus temperature of the base materials is not reached. DIN 13928 specifies the requirements and test methods that the solders for dental technology themselves and in combinations of various dental alloys must at least meet. They differ mainly in the melting interval, which can depend on the time of application (e.g. before or after the ceramic firing). They must also be determined according to the alloys to be soldered.

The individual alloy components of the solders are divided into the following areas of application:

  • Gold casting alloys:
  • Reduced gold casting alloys:
    • Gold, silver, copper, indium, zinc and platinum metals.
  • Copper-free gold casting alloys:
    • Gold, silver, zinc and platinum metals.
  • Silver-palladium-gold casting alloys:
    • Silver, copper, gold, indium, zinc and platinum metals.
  • Ceramic Alloys:
    • Gold, palladium, copper, indium, zinc.
  • so-called steel gold solders for combination soldering EM / Co-Cr-Mo:
    • Gold, nickel and zinc as pre-solders.
    • Gold, silver, copper, indium, manganese and platinum metals as the main solder.
  • Base metal alloys:
    • Nickel, chromium, molybdenum and iron as high-melting solder.
    • Gold, silver, nickel, zinc and copper as low-melting solder.

amalgam

Old amalgam fillings containing γ2

For tooth fillings , γ2-free amalgams are used, which are produced from master alloys by mixing mercury with chips. The master alloys consist of 40 to 70% silver, 10 to 30% copper, the remainder of tin, low contents of precious metals or zinc. Mixing produces Ag 3 Hg 4 and Cu 6 Sn 5 . Amalgams used before 1970 were high in silver and low in copper. When these amalgams harden, Sn 8 Hg, the γ2 phase, is formed , which tends to corrode. This led to a dark discoloration of the filling.

Orthodontics

Orthodontic brackets with an integrated arch
Orthodontic arches

Orthodontic archwires are made from several alloys, most commonly stainless steel, a nickel-titanium alloy (NiTi), or a beta-titanium alloy composed primarily of titanium and molybdenum.

See also

literature

Individual evidence

  1. ↑ Dental Vademecum, chap. 9.6 Alloys, pp. 715–892, Institute of German Dentists , Deutscher Ärzteverlag 5th edition 1995, ISBN 3-7691-4058-3 .
  2. ↑ The Metals: Materials science with its chemical and physical principles . Verlag Neuer Merkur GmbH, 1999, ISBN 978-3-929360-44-8 , p. 56.
  3. ↑ a b c d Currently replaced by the version DIN EN ISO 22674: 2016-09: Dentistry - Metallic materials for fixed and removable dentures and applications ; Retrieved December 5, 2016.
  4. ↑ DIN EN ISO 15841: 2014-12 ; Retrieved December 5, 2016.
  5. ↑ DIN EN ISO 10271: 2011-10 ; Retrieved December 5, 2016.
  6. ↑ Currently replaced by the version DIN EN ISO 9333: 2006-10 ; Retrieved December 5, 2016.
  7. ^ Walter Kamann: Material science and clinical investigations of the filling therapy of the teeth with plastic gold. Habilitation thesis, 2000, University of Witten / Herdecke.
  8. ↑ James Harrison Prothero, Prosthetic dentistry online . Retrieved November 10, 2016.
  9. ↑ KW Alt, Historical Development of Crown and Bridge Replacement. In: Strub JR, Türp JC, Witkowski S, Hürzeler MB, Kern M: Curriculum Prosthetics Volume II. 2nd ed. Quintessenz, Berlin, Chicago, London (etc.), 1999, pp. 661–663, ISBN 978-3 -86867-027-1 .
  10. ^ Christian Bruhn, F. Gutowski, A. Gysi, Christian Bruhn, F. Gutowski, A. Gysi et al .: Dental prosthetics . Springer Berlin Heidelberg, April 18, 2013, ISBN 978-3-642-99582-8 , p. 624.
  11. ↑ Wolfgang Strübig, History of Dentistry. An introduction for students and dentists. Deutscher Ärzte Verlag, Cologne, 1989, pp. 96–114. ISBN 3-7691-1099-4 .
  12. ↑ Annual Report of the Director of the Census to the Secretary of Commerce for the Fiscal Year Ended ... . US Government Printing Office, 1918, p. 13.
  13. ↑ K. Krumbholz, Status and Development of Dental Ceramics. ZWR 3, 193-199 (1996)
  14. ^ Karl Eichner: Dental materials and their processing. 1. Basics and processing . Georg Thieme Verlag, 2005, ISBN 978-3-13-127148-8 , p. 329.
  15. ↑ Lee M. Pike, 100+ Years of Wrought Alloy Development at Haynes International, 8th International Symposium on Superalloy 718 and Derivatives, 2014. Retrieved November 14, 2016 ( February 9, 2015 memento in the Internet Archive ) (PDF).
  16. ↑ Thorsten Hoopmann, Influence of the wash firing temperature on the temperature and load behavior of burnable cobalt-chromium alloys (PDF) Dissertation 2012. Accessed on November 14, 2016.
  17. ↑ WJ Buehler, JW Gilfrich & RC Wiley, "Effects of low-temperature phase changes on the mechanical properties of alloys near composition TiNi," Journal of Applied Physics 34 (1963) p 475. doi: 10.1063 / 1.1729603
  18. ^ FE Wang, WJ Buehler & SJ Pickart, "Crystal structure and a unique martensitic transition of TiNi," Journal of Applied Physics 36 (1965) p 3232-3239.
  19. ^ GF Andreasen, TB Hilleman: An evaluation of 55 cobalt substituted Nitinol wire for use in orthodontics. In: Journal of the American Dental Association (1939). Volume 82, Number 6, June 1971, pp. 1373-1375, PMID 5280052 .
  20. ^ RJ Hazel, GJ Rohan, VC West: Force relaxation in orthodontic arch wires. In: American journal of orthodontics. Volume 86, Number 5, November 1984, pp. 396-402, PMID 6594062 .
  21. ↑ Roland Strietzel: The material science of metal-ceramic systems . Verlag Neuer Merkur GmbH, 2005, ISBN 978-3-937346-14-4 , p. 49.
  22. ↑ Bundesfinanzhof, judgment of April 17, 1986 (file number IV R 115/84): surplus calculation ; Exchanges; Dentist; Fine gold; Operational cause ; Retrieved November 9, 2016.
  23. ↑ The Metals: Materials science with its chemical and physical principles . Verlag Neuer Merkur GmbH, 1999, ISBN 978-3-929360-44-8 , p. 176.
  24. ↑ a b c Fathi Zereini ,: Emissions of platinum metals: analysis, environmental and health relevance . Springer-Verlag, March 7, 2013, ISBN 978-3-642-58611-8 , p. 69.
  25. ↑ Degulor S , Degudent. Retrieved March 10, 2019.
  26. ↑ Alloys , Degudent. Retrieved March 10, 2019.
  27. ↑ Price for one ounce of fine gold $ 1,222, corresponds to € 1138. 1 troy ounce = 31.1 g. 87% fine gold content of a plate. As of November 14, 2016.
  28. ↑ Herbert v. Eich: Emergency Currencies: How to Remain Tradable in a Total Crisis . BookRix, 13 October 2016, ISBN 978-3-7396-6366-1 , p. 31 ff.
  29. ↑ BIOcclus , Degudent.
  30. ↑ Alloy price .
  31. ↑ Gold Charts . AG Precious Metals.
  32. ^ Gabriele Dietrichs, Paul Rosenhain, Gabriele Diedrichs, Paul Rosenhain: Galvanoforming: Bio-aesthetics in restorative dentistry . Verlag Neuer Merkur GmbH, 1995, ISBN 978-3-921280-99-7 , p. 25.
  33. ↑ Hans-Joachim Burkhardt, Dental soldering . Retrieved November 12, 2016.