dental casting alloys (1).pptxh du fu u it iitv

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1. DENTAL CASTING ALLOYS

2. DEFINITION Alloy : It is defined as crystalline substance with metallic properties that is composed of two or more elements, at least one of which is metal. Noble metal : They are resistant to corrosion in the mouth.eg: gold, platinum, palladium, rhodium, ruthenium, iridium, osmium and silver Base metals: These are non –noble metals. A metal that readily oxidizes or dissolves to release ions. Eg. Chromium, cobalt, nickel, iron, copper, manganese

3. CLASSIFICATION AND COMPOSITION OF DENTAL CASTING ALLOYS: I) ALLOY CLASSIFICATION OF THE AMERICAN DENTAL ASSOCIATION (1984): Alloy type Noble metal content High noble Must contain  40%Au and  60% of noble Metals. Noble Must contain  25% of Noble metals Base metal alloys Contain < 25% wt of Noble metals.

4.   ACCORDING TO THE NUMBER OF ALLOYING ELEMENTS a . Binary alloy – if two elements are present b.  Ternary alloy – if three elements are present c.  Quaternary alloy – if four elements are present

5. ACCORDING TO ADA SPECIFICATION NO.5 Type I (Soft): These alloys are limited to use in inlays that are subject only to slight stress during mastication. Type II (Medium): These medium alloys can be used for all types of cast inlays and onlays . Type III (Hard): These alloys are most acceptable for crowns , thin 3/4 th crowns, and anterior and posterior bridge abutments Type IV (Extra hard): These alloys are designed to have sufficient strength and adequate properties for cast removable partial dentures with clasps, precision cast fixed bridges and ¾ crowns.

6. ACCORDING TO USE Alloys for all metal and resin veneer restorations (eg inlays, posts, resin and composite veneered crowns and FPDs) Alloys for metal ceramic restoration (eg PFM crowns and FPDs) Alloys for removable dentures (eg RPD frames and complete denture bases)

7. ACCORDING TO MAJOR ELEMENTS Gold alloys Silver alloys Palladium alloys Nickel alloys Cobalt alloys Titanium alloys

8. ACCORDING TO THREE MAJOR ELEMENTS Gold-palladium-silver Palladium-silver-tin Nickel-chromium-molybdenum Cobalt-chromium-molybdenum Iron-nickel-chromium Titanium- Aluminium -vanadium

9. REQUIREMENTS OF CASTING ALLOYS Corrosion resistance. Tarnish resistance. Biocompatible. Sufficiently strong for intended purpose. Easy to fabricate. Flow well and duplicate fine details during casting. Minimal shrinkage on cooling after casting. Easy to solder.

10. USES & TYPES USES Inlays and onlays Crowns and FPDs Partial denture frames (Type IV) Post- cores TYPES High Noble : Gold Alloys Noble: Silver Palladium Alloys Base Metal : Nickel-chrome Alloys, Cobalt- Chrome Alloys, Titanium And Its Alloys, Aluminium Bronze Alloys

11. REMOVABEL DENTURE ALLOYS REQUIREMENTS: They should be light in weight They should have high stiffness They should have good fatigue resistance They should be economical They should not react to commercial denture cleansers

12. REMOVABLE DENTURE ALLOYS TYPES 1) cobalt-chromium alloys 2) nickel-chromium alloys 3) Aluminium and its alloys 4) Type IV noble alloys 5) Titanium

13. COBALT-CHROMIUM ALLOYS APPLICATIONS: Denture base Cast removable partial denture framework Crowns and fixed partial dentures Bar connectors

14. Properties of base metal alloys Extremely high yield strengths and hardness, makes difficult to polish. Less corrosion resistance. Less biocompatible .