This document discusses various physical properties of dental materials including brittleness, ductility, malleability, and hardness. Brittleness refers to a material's inability to plastically deform before fracturing. Ductility is the ability to sustain deformation under tension without fracturing, while malleability refers to the ability under compression. Hardness is measured by a material's resistance to indentation or scratching. Common tests for properties include Vickers, Knoop, and Rockwell tests.

1. PHYSICAL PROPERTIES OF
DENTAL MATERIAL
BRITTLENESS, DUCTILITY, MALLEABILITY AND HARDNESS

2. 1. BRITTLESNESS
• IT IS THE RELATIVE INABILITY OF A MATERIAL TO SUSTAIN PLASTIC
DEFORMATION BEFORE FRACTURE OF A MATERIAL OCCURS.
• • OR A BRITTLE MATERIAL FRACTURES AT OR NEAR ITS PROPORTIONAL LIMIT.

4. DUCTILITY AND MALLEABILITY
• DUCTILITY REPRESENTS THE ABILITY OF A MATERIAL TO SUSTAIN LARGE
PERMANENT DEFORMATION UNDER A TENSILE LOAD BEFOR IT FRACTURE
• MATERIAL WHICH SUSTAINS TENSILE STRESS AND
CONSIDERABLEPERMANENT DEFORMATION WITHOUT RUPTURE, IT IS
DUCTILE
• THE ABILITY OF A MATERIAL TO SUSTAIN CONSIDERABLE PERMANENT
DEFORMATION WITHOUT RUPTURE UNDER COMPRESSION, IS TERMED AS
MALLEABILITY

5. • THERE ARE THREE COMMON METHODS FOR THE MEASUREMENT OF DUCTILITY
1. THE PERCENT ELONGATION AFTER FRACTURE.
•
• 2. THE REDUCTION IN AREA OF TENSILE TEST SPECIMENS.
3. THE MAXIMUM NUMBER OF BENDS PERFORMED IN A COLD BEND TESTS.

7. HARDNESS
• THE RELATIVE HARDNESS OF A SUBSTANCE IS BASED ON ITS ABILITY TO RESIST
SCRATCHING.
• “RESISTANCE TO INDENTATION”
• THE PROPERTIES THAT ARE RELATED TO THE HARDNESS OF A MATERIAL ARE
COMPRESSIVE STRENGTH, PROPORTIONAL LIMIT AND DUCTILITY.

8. VICKERS AND KNOOP
• VICKERS IS USED TO MEASURE THE HARDNESS OF VERY HARD AND BRITTLE
MATERIALS, SUCH AS CAST DENTAL ALLOYS, BUT IS ALSO APPLICABLE TO
SOFTER MATERIALS. KNOOP HAS BEEN USED FOR A WIDER RANGE OF
MATERIALS, FROM AMALGAM AND CERAMICS TO RESIN-BASED COMPOSITES,
BUT IS ALSO USEFUL FOR MATERIALS THAT VARY IN HARDNESS OVER AN AREA
OF INTEREST, SUCH AS ENAMEL AND DENTIN.

10. TEST FOR HARDNESS
• HARDNESS TESTS THAT MEASURE THE RESISTANCE OF A MATERIAL TO INDENTATION
BY AN INDENTING PROBE (E.G. BRINELL, VICKERS AND SHORE DUROMETERS): SOME
TESTS MEASURE THE INDENTATION WITH THE LOAD APPLIED AND SOME MEASURE
THE RESIDUAL INDENTATION AFTER THE LOAD IS REMOVED.
• HARDNESS TESTS THAT MEASURE THE RESISTANCE OF A MATERIAL TO SCRATCHING
BY ANOTHER MATERIAL (E.G. THE BIERBAUM SCRATCH TEST, THE MOH HARDNESS
TEST): SIMILAR TECHNIQUES ARE COMMONLY USED IN PAINT TESTING AND INVOLVE
PULLING THE SAMPLE BENEATH A LOADED INDENTER.
• HARDNESS TESTS THAT MEASURE RECOVERY EFFICIENCY OR RESILIENCE (E.G. THE
VARIOUS ROCKWELL TESTERS).

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