Artificial teeth By Dr Rashid Hassan

By

Dr. RASHID HASSAN

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ARTIFICIAL TEETH

ARTIFICIALTEETH

DESIRED PROPERTIES OF ARTIFICIAL TEETH

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Aesthetics.

Adhesion between artificial teeth and denture base.

Compatibility with denture base material.

Low density.

Resistant to fracture.

Abrasive resistant.

MATERIALS FOR ARTIFICIAL TEETH4

ACRYLIC

RESINSPORCELAIN

ACRYLIC TEETH5

Produced in reusable metal moulds.

Can be produced by,

1. Dough moulding

technique.

2. Injection moulding

technique.

Resins used is highly cross linked.

Tooth coloured pigments are added.

ACRYLIC TEETH6

Based on polymethyl methacrylate composition.

More cross linked than polymerized denture base.

PORCELAIN TEETH7

Standard shapes and sizes.

Moulds are 30% larger than normal size.(to overcome firing shrinkage)

Small holes or metal pins are present in the base of the porcelain teeth.

Wearing up of enamel of opposing tooth.

PROPERTIES OF ARTIFICIAL TEETH8

PROPERTIES ACRYLICTEETH

PORCELAINTEETH

Density (g/cm³) 1.2 2.4

Coefficient of thermal expansion (ppm/°C)

80 7

Modulus of elasticity (GPa)

2.5 80

Hardness (VHN)

20 500


1. AESTHETICS:

Both materials give a realistic appearance.

Translucency and colour of porcelain teeth is better than acrylic teeth.

Vast variety of colours, shapes, sizes and shades are available for both the materials.

2. CLICKING SOUNDS:

Clicking sounds are produced when opposing porcelain teeth come into contact.

No such sounds are heard in case of acrylic teeth.


3. ATTACHMENT TO THE DENTURE BASE:

Chemical adhesion to the denture base in case of acrylic teeth.

Mechanical adhesion through pins and holes in case of porcelain teeth.

Complete boiling out of wax is important for retention with the denture base.

33% of all denture repair is due to debonding of teeth from the denture base.

Cont…


Acrylic teeth bind more effectively to the heat cure acrylic than self cure acrylic.

Bonding of acrylic teeth to self cure acrylic can be improved by, Making grooves into the acrylic teeth.

Making grooves followed by using solvent/monomer mixture to soften the tooth base and then impregnate it with MMA.


4. COEFFICIENT OF THERMAL EXPANSION:

Acrylic teeth are more compatible with the denture base due to similar coefficient of thermal expansion.

Crazing can occur in case of porcelain teeth due to high difference in coefficient of thermal expansion.

5. DENSITY:

Porcelain teeth has density twice as high as compared to acrylic teeth.

Porcelain teeth dentures are heavier.


6. HARDNESS:

Porcelain teeth are harder than acrylic teeth. A disadvantage in case of porcelain teeth

when adjustments and grinding is required. Acrylic teeth are abrasive as compared to

porcelain teeth.7. BRITTLENESS:

Porcelain teeth are brittle. Teeth may fracture or chip off in case of

porcelain teeth.


8. FORCES ON SOFT TISSUES:

Porcelain teeth transmit higher forces on underlying soft tissues.

Greater modulus of elasticity is the cause of high forces.

9. COST:

Acrylic teeth are much more cost effective as compared to porcelain teeth.

Artificial teeth By Dr Rashid Hassan

Health & Medicine

Transcript of Artificial teeth By Dr Rashid Hassan