1. Alloys for cast prostheses: bare-metal alloys metal-ceramic alloys

2. Metal-Ceramic Alloys

3. porcelain-fused-to-metal alloys pfm alloys ceramic alloys

4. Porcelain advantages matches enamel color translucent like enamel well tolerated by soft tissues

5. Porcelain disadvantages difficult to form acceptable margins brittle fractures in tension

6. Metal-Ceramic Alloys Desirable properties melts at high temperature bonds with porcelain compatible with the thermal expansion of porcelain does not discolor porcelain does not sag

7. Metal-Ceramic Alloys Desirable properties melts at high temperature Fusing Ranges: High gold alloys: 950 – 1050 o C Dental porcelains:1000 – 1050 o C Metal-ceramic alloys:1150 – 1300 o C

8. Metal-Ceramic Alloys Desirable properties melts at high temperature bonds with porcelain

9. Porcelain Alloy Noble alloys – Fe, Sn, or In form surface oxides In some systems there may be mechanical component to the bonding Metal oxide

10. Metal-Ceramic Alloys Desirable properties melts at high temperature bonds with porcelain compatible with the thermal expansion of porcelain

11. Compatible thermal expansion: porcelain adapts well to the alloy at the sintering temperature 1050 o C porcelain contracts less than the alloy 25 o C

12. Compatible thermal expansion: porcelain adapts well to the alloy at the sintering temperature 1050 o C porcelain contracts less than the alloy 25 o C

13. Metal-Ceramic Alloys Desirable properties melts at high temperature bonds with porcelain compatible with the thermal expansion of porcelain does not discolor porcelain

14. Discoloration Copper - blue or blue-green reaction product at P/M interface.

15. Discoloration Nickel Alloys - Dark gray or black oxides on castings - can be removed

16. Discoloration Silver Alloys - colors porcelain light green greenish gingival margin

17. Metal-Ceramic Alloys Desirable properties melts at high temperature bonds with porcelain compatible with the thermal expansion of porcelain does not discolor porcelain does not sag

18. SAG SAG : distortion of the alloy under its own weight at the porcelain firing temperature.

19. SAG: Noble Alloy : high SAG Base Metal Alloys : low SAG

20. Metal Ceramic Alloys Au-Pd-Pt Au-Pd-Ag Au-Pd Pd-Ag Ni-Cr

21. Au-Pd-Pt Metal-Ceramic Alloys 75% - 98% Au trace of iron, Sn, In

22. Metal Ceramic Alloys Au-Pd-Pt Au-Pd-Ag Au-Pd Pd-Ag Ni-Cr

23. Au-Pd-Ag Metal Ceramic Alloys 50-60% Au 25-30% Pd 10-15% Ag trace of Sn and In

24. Metal Ceramic Alloys Au-Pd-Pt Au-Pd-Ag Au-Pd Pd-Ag Ni-Cr

25. Au-Pd Metal Ceramic Alloys 50-60% Au 35-40% Pd trace of Sn or In

26. Metal Ceramic Alloys Au-Pd-Pt Au-Pd-Ag Au-Pd Pd-Ag Ni-Cr

27. Pd-Ag Metal-Ceramic Alloys 50 - 65% Pd 30 - 40% Ag trace of Sn or In

28. Pd-Ag Metal-Ceramic Alloys Pd-Co 79 - 88% Pd 4 - 5% Co In, Sn

29. Pd-Ag Metal-Ceramic Alloys Pd-Cu-Ga 79% - 81% Pd 10% Cu 9% Ga

30. Metal Ceramic Alloys Au-Pd-Pt Au-Pd-Ag Au-Pd Pd-Ag Ni-Cr

31. Ni-Cr Metal-Ceramic Alloys 75-80% Ni 9-20% Cr sometimes beryllium

32. Nickel-Chromium Alloys Bonding Mechanisms Intermediary oxides (e.g., Cr 2 O 3 ; BeO; NiO; mixed Ni and Cr Oxides) Mechanical bonding

33. Co-Cr & Ni-Cr alloys: functions of elements Cr – forms adherent, nonporous oxide layer; “passivates” the alloy

34. If oxide forms with larger or smaller volume than alloy it consumes, Oxide will be crumbly, porous If oxide has nearly the same volume as the alloy it consumes, it may be nonporous & adherent. alloy said to be “passivated”

35. Co-Cr & Ni-Cr alloys: functions of elements Cr - forms adherent, nonporous oxide layer; “passivates” the alloy Ni & Co – interchangeable C – small enough greatly increases hardness & strength Mo – strengthens alloys Be – lowers casting temperature of Ni- based alloys by 100 o C

36. Base Metals: nickel chromium iron copper titanium cobalt tin indium zinc Ni, Co, & Fe become corrosion resistant when alloyed with Cr All except Ti will corrode vivo when unalloyed

37. Biocompatibility: nickel-based alloys - nickel contact dermatitis – more frequent in women – sometimes extra oral possible cancers of the lung and nasal passages (industrial dust; none reported in dental settings) Most frequent problem for patients Possible problem for dental technicians; seen in other industries - not reported in dentistry.

38. Biocompatibility Nickel Contact dermatitis: 12 – 15 % women in U.S. Long-term exposure to dust - possible cancers of lung and nasal passage

39. Nickel biocompatibility: nickel-based alloys - Be contact dermatitis chemical pneumonitis from fumes & dust (coughing, chest pain, pulmonary dysfunction - sometimes fatal) danger is to lab technicians, not to dentists or patients in 2003 the ADA withdrew seal of approval for Be-containing Ni-based alloys

40. Nickel-Chromium Alloys Advantages cost SAG resistance rigidity strength

41. Nickel-Chromium Alloys Disadvantages hard to cast hard to finish not biocompatible