WHY STUDY DENTAL MATERIALS

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FUNDAMENTALS




     WHY STUDY DENTAL
        MATERIALS

REFERS TO THE SCIENCE WHICH
DEALS WITH THE PROPERTIES,
PROPER MANIPULATION AND
STORAGE OF MATERIALS
WHY DO WE STUDY DENTAL
MATERIALS?




BASIC COMPOSITION OF THE
        UNIVERSE

Matter—anything that has weight
Matter—
and occupies space
  T      f   tt
• Types of matter
   Solid
   Liquid
   Gas
Energy—
Energy—the ability to do work




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  STRUCTURE OF MATTER
Types of materials
  Non-               amorphous—
• Non-crystalline or amorphous—no definite
  atomic structure.
                       lattice—
• Crystalline or space lattice—a definite atomic
  structure
Atom
Element
Compound
Molecule
Alloy




 EVALUATION PROGRAMS

ADA Council on Dental Materials and
Devices
  Certificate Program
• C tifi t P
• Acceptance Program
Federation Dentaire Internationale




Dentists and consumers have long recognized the American
Dental Association (ADA) Seal of Acceptance as an
important symbol of a dental product's safety and
effectiveness. For more than 125 years, the ADA has
sought to promote the safety and effectiveness of dental
products. The first Seal of Acceptance was awarded in
1931. In 1984, President Ronald Reagan gave the
Association a certificate of commendation for the
             self-
outstanding self-regulatory efforts of its Seal program.

       g              y         y,                   p
Although it is strictly voluntary, more than 100 companies
participate in the Seal program. Participating companies
commit significant resources to test and market products in
the Seal program. More than 400 dental products that are
sold to consumers carry the Seal of Acceptance. These
         toothpaste,         floss,
include toothpaste, dental floss, manual and electric
toothbrushes,
toothbrushes, mouth rinse and chewing gum.gum.




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FACTORS MAKING DEMANDS
ON DENTAL MATERIALS

 G. V. Black is responsible for many of
 the theories used in testing dental
 materials for the mouth still used
 today.
 It includes both the physical and
 chemical changes




PHYSICAL LIMITATIONS

 Biting forces
   The average biting force of a person with
   natural dentition is approximately 150
        d In th         t i    that b
   pounds. I the posterior , th t becomes
   approximately 30,000 psi of pressure on
   a single cusp of a molar.
   Materials considered for use in restoring
   the occlusal surfaces must have sufficient
   strength to withstand these forces.




MECHANICAL PROPERTIES

 STRESS—THE INTERNAL FORCE
 THAT RESISTS ANOTHER FORCE
 EXTERNALLY APPLIED.
 STRAIN IS THE AMOUNT OF
 MOVEMENT OR CHANGE OF
 SHAPE CREATED BY A FORCE.




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FORCE



 ANY PUSH OR PULL UPON MATTER
 STRESS AND STRAIN IS A
 RESPONSE TO FORCE.




TYPES OF STRESS AND
STRAIN


 COMPRESSIVE—PUSHES THINGS
 TOGETHER
 TENSILE—PULLS AND STRETCHES
 SHEAT—SLICES APART




ELASTICITY



 THE ABILITY TO REGAIN SHAPE
 WHEN STRESS IS REMOVED




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TYPES
 ELASTIC—ELASTICITY
 INELASTIC—MATERIAL REMAINS
 PERMANENTLY DEFORMED
 ELASTIC LIMIT—THE MAXIMUM
 STRESS A MATERIAL CAN
 WITHSTAND WITHOUT BEING
 DEFORMED PERMANENTLY
 MODULUS OF ELASTICITY (YOUNG’S
 MODULUS)




ELASTIC LIMIT (HOOK’S LAW)
 YIELD STRENGTH
 PERMANENT DISTORTION OCCURS
 BEYOND THE PROPORTIONAL LIMIT
ULTIMATE STRENGHT—THE
MAXIMUM STRENGHT OBTAINED
BASED ON THE ORIGINAL
DIMENSION OF THE OBJECT
TOUGHNESS—THE ABILITY OF A
MATERIAL TO RESIST FRACTURE




DUCTILITY—ABILITY OF A
MATERIAL TO WITHSTAND
PERMANENT DEFORMATION
UNDER TENSIL STRENGTH.
MALLEABILITY—HAMMERED OR
ROLLED INTO SHAPE
FLOW, CREEP OR SLUMP—
DEFORM PERMANENTLY UNDER A
CONSTANT LOAD.




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HARDNESS—RESISTANCE TO
PENETRATION
  BRINEL HARDNESS NUMBER
    BHN IS HIGH THE MATERIAL IS HARD
    BHN IS LOW THE MATERIAL IS SOFT
  VICKERS
  KNOOP HARDNESS NUMBER
  MOHS—ALSO KNOWN AS THE
  STRATCH HARDNESS
DISTORTION




THERMAL PROPERTIES

 THE TOOTH IS AN EXCELLENT HEAT
 INSULATOR WHICH MEANS THAT IT
 HAS A LOW THERMAL CONDUCTIVITY
 VALUE
 THERMAL CONDUCTIVITY
 THERMAL EXPANSION




ADHESION
 FORCE THAT CAUSES UNLIKE
 MOLECULES TO ATTRACT
 ADHESION ACTION OF A LIQUID
  VISCOSITY
  WETTING
 FILM THICKNESS
 SURFACE TENSION ENERGY




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         PHYSICAL
       LIMITATIONS
•   MOISTURE
•   TEMPERATURE CHANGES
•   INERT
•   AESTHETIC FACTORS
•   RETENTION
•   GALVINISM




       BIOILOGICAL
       LIMITATIONS

•   TOXIC EFFECTS OF MATERIALS
•   ACIDITY/ALKALINITY
•   TEMPERATURE CHANGES
•   MICROLEAKAGE




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