Energy Resources. ( B. Pharmacy, 1st Year, Sem-II) Natural Resources
alloys_and_base_metals_pavan.pptx
1.
2.
3.
4. • HIGH NOBLE ALLOYS “PRECIOUS METALS”
• ◦ AT LEAST 60% NOBLE. 40% OF WHICH IS GOLD. THE
REMAINING 40% IS BASE METAL
• NOBLE ALLOYS(SEMIPRECIOUS)
• ◦ AT LEAST 25% NOBLE (NO GOLD REQUIREMENTS).
75% BASE METAL
• BASE METAL ALLOYS
• ◦ LESS THAN 25% NOBLE
6. ALLOY TYPE BY MAJOR ELEMENT: Gold-
based, palladium based, silver-based, nickel-
based, cobalt-based and titanium based
ALLOY TYPE BY PRINCIPAL THREE
ELEMENTS: Such as Au-Pd-Ag, Pd-Ag-Sn,
Ni-Cr-Be, Co-Cr-Mo, Ti-Al-V and Fe-Ni-Cr.
ALLOY TYPE BY DOMINANT PHASE
SYSTEM: Single phase [isomorphous],
eutectic, peritectic and intermetallic.
10. Biocompatible : The material must tolerate oral fluids and not
release any harmful products into the oral environment.
Should have good corrosion resistance
Good tarnish resistance
Non-allergic
Good aesthetics
Must have adequate thermal properties
Melting range should be low enough to form smooth surface with
the mould walls
Economic and easily available
19. They should be able to
bond with porcelain
Its coefficient of thermal
expansion should be
compatible with that of
porcelain
Its melting temperature
should be higher than the
porcelain
It should not stain or
discolor porcelain
25. Cobalt main constituent
• further harden the alloy and also to impart corrosion
resistance.
Chromium no less than 25%
• refine the grain structure and improve the behaviour of base
metal alloys during casting
Molybdenum no less than 4%
Cobalt + nickel + chromium no less than 85%
Iron - 0 to 5%
• controls the brittleness and ductility
Carbon - upto 0.4%
• Silicon – Increases ductlity
Tungsten, Manganese, Silicon and Platinum in
traces
The chemical
composition of
these alloys
specified in
the ISO
Standard for
Dental Base
Metal Casting
26. lighter in weight – lesser density 8 to
9 gms/cm3.
Fusion temperature: The casting
temperature of this alloy is
considerably higher than that of gold
alloys. 1250C to 1480C
A.D.A. specification No. 14 divides it
into two types, based on fusion
temperature
Type-I (High fusing) – fusing
temperature greater than
1300C
Type-II (Low fusing)– fusing
temperature lower than
1300C
27. • YIELD STRENGTH: IT IS HIGHER THAN THAT OF GOLD ALLOYS. 710MPA
(103,000PSI).
• ELONGATION: DUCTLITY IS LOW RANGES FROM 1 TO 12%.
• THESE ALLOYS WORK HARDEN VERY EASILY, SO CARE MUST BE TAKEN
WHILE ADJUSTING THE CLASP ARMS OF THE PARTIAL DENTURE
• HARDNESS: 432 VHN. THUS, CUTTING, GRINDING AND FINISHING IS
DIFFICULT
• HIGH MODULUS OF ELASTICITY, CASTING CAN BE MADE MORE THINNER,
THUS DECREASING THE WEIGHT OF THE R.P.D. ADJUSTMENT OF CLASP
IS NOT EASY.
• TARNISH AND CORROSION RESISTANCE: FORMATION OF A LAYER OF
CHROMIUM OXIDE ON THE SURFACE OF THESE ALLOYS PREVENTS
TARNISH AND CORROSION IN THE ORAL CAVITY.
• SOLUTIONS OF HYPOCHLORITE AND OTHER COMPOUNDS THAT ARE
PRESENT IN SOME DENTURE-CLEANING AGENTS WILL CAUSE
CORROSION IN SUCH BASE METAL ALLOYS.
29. • NICKEL MAIN CONSTITUENT
• CHROMIUM NO LESS THAN 20%
• MOLYBDENUM NO LESS THAN 4%
• BERYLLIUM NO MORE THAN 2%
• NICKEL + COBALT + CHROMIUM NO LESS THAN 85%
38. Formed from very thin
pressed/rolled sheets of
wrought stainless steel.
The wrought stainless-steel
sheets have high values of
modulus of elasticity and
proportional limit.
This enables sufficient
rigidity to be achieved with
a very thin sheet of
material.
Conducts heat through
metallic plates thus
ensuring the patient retains
normal reflex reaction to hot
and cold
