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Stomatologic Materials Medical Chemistry and Biochemistry Dentistry - First year - Winter term © Institute of Medical Biochemistry and Laboratory Diagnostics of the General University Hospital and of The First Faculty of Medicine of Charles University in Prague

Stomatologic materials 2015/2016 Stomatologic materials  Metallic  Dental alloys  Dental amalgams (download from:  Non-Metallic  Dental plasters  Dental porcelains (silicates)  Dental cements  Imprinting materials  Dental resins  Dental waxes

Stomatologic materials 2015/2016 Metals Pure metals are only infrequently used in dentistry. Sometimes pure gold (Au) is used as high quality (but relatively expensive) inlay. Au is biologically well tolerated, but too soft material. Gold is very stable, no corrosion occurs in it. For prosthetic purposes, other metals are added usually, to get a material with better properties, especially, more hard and with higher melting point.

Stomatologic materials 2015/2016 Gold Alloys The content has to be: Au + Pt-metals (Pt, Pd, Ir, Ru and Rh) ≥ 75 % Au ≥ 65 % Ni ≤ 0.1 % Be, Cd ≤ 0.02 % Composition of typical gold alloys Au, Cu, (Ag) Au, Pt, Cu, Zn Au, Pd, Cu ISO 1562:2004 (gold alloys with at least 60 % mass fraction of gold and at least 75 % mass fraction of gold plus specified platinum group metals)

Stomatologic materials 2015/2016 Dental alloys The addition of Cu to Au increases the hardness of the resulting alloy. On the other hand, too much of Cu increases the corrosion of the alloy in oral cavity. The strongest and most durable ally is reached in combination of Au - Ag - Cu - Pt. Sn, Zn, Fe, In, Si – improve the smelting quality of the alloy The main disadvantage of gold alloys is their high price!

Stomatologic materials 2015/2016 Alloys with lower content of Au Ag - Au – Pd – Cu – In Ag – Pd – Cu Ag – Pd – In - Zn ISO 8891:1998 Dental casting alloys with noble metal content of 25 % -75 %

Stomatologic materials 2015/2016 Alloys based on common metals Co – Cr – Mo – Si – Mn Co – Cr – Mo – W – Si Co – Cr – Mo – Ti ISO :1994 Dental base metal casting alloys -- Part 1: Cobalt-based alloys a) Co – very hard! Especially in combination with Cr! and Mn! Ni – Cr – Mo – Si - Different to make exact casting ISO :1994 Dental base metal casting alloys -- Part 2: Nickel-based alloys b) Ni – (!!Allergies!!) Very high melting point ( o C) Cu – Al – Ni – Mn - Fe No ISO! c) Aluminium bronzes – nice yellow color, extremely high corrosion in oral cavity Many patients do not tolerate aluminium bronze at all!! Very often allergic reactions

Stomatologic materials 2015/2016 Metal ceramic restorative systems This type of alloy has to have high melting (>1000 o C), because most of the ceramic materials are baked at 900 o C. Example: Au – Ag - Pd - In - Sn (Safibond - ISO 9693) <1% 27.4% 60% 4% 7% Common metal alloy - less suitable e.g., oralium ceramic Co (61%)+Cr(26 %)+Mo(6%)+W(5%)- Without Ni !

Stomatologic materials 2015/2016 Casting of Dental Restoration The lost-wax casting process – the most commonly used (for inlays, crowns, bridges) 1.Preparation of the tooth (teeth) to receive cast restoration 2.Make an impression of the prepared tooth 3.Pour gypsum slurry into the impression to make a positive cast, which is an exact replica of the dental arch from which the individual parts, representing the prepared tooth or teeth, are sectioned 4.Make a wax pattern that will be representative of the lost tooth structure (laboratory) 5.Sprue (Fix in space) the wax (see Figure) 6.Invest the wax pattern ty 7.Eliminate the wax pattern by burning the wax out of the investment in a furnace thus making a mold 8.Force molten metal into the molt (overpressure or vacuum – centrifugation) 9.Clean the cast 10.Remove the sprue from the casting 11.Finish and polish the cast on die – end of the laboratory phase 12.Cement the prepared cast restoration on the prepared tooth (teeth) – dentist's office The mold after burning out of the wax