Dental materials

1. STRUCTURE OF
MATTER
Dr. Shiva

2. EVALUATION OF MATERIALS
• American Dental Association (ADA)
• International Standard Organization (ISO)
• Federation Dentaire Internationale (FDI).

4. INTERATOMIC BONDS
• The forces of attraction between atoms or molecules may be divided into:
• Primary bonds
• Ionic
• Covalent
• Metallic.
• Secondary bonds
• Hydrogen bond
• van derWaals Forces

5. Interatomic bond distance
 Bond Distance : Limiting factor which prevents atoms /
molecules from approaching each other too closely
 If Distance reduces – Repulsion
 If Distance increases – Attraction
 If forces of Attraction increases – Interatomic space decreases

6. CRYSTALLINE STRUCTURE
• Crystal lattice can be defined as an arrangement of atoms in space such
that in every atom it is in similar relation to every other atom.
• crystal lattice may be the result of primary or secondary bonds.
• There are 14 possible types of lattice forms, but three relatively cubic crystal
structure of lattice are found for most of the metals.
E.g:
1. Simple cubic
2. Face centered cubic
3. Body centered cubic.

8. NONCRYSTALLINE
STRNONCRYSTALLINE STRUCTURE
• Noncrystalline solids lack a systematic and regular arrangement of atoms
over relatively large atomic distances.
LINE STRUCTURE

9. Surface Properties

10. ADSORPTION vs ABSORPTION

11. Absorption
• the substance adsorbed is sucked into or
penetrates in a type of diffusion process.
• When the dry grapes are being kept
immersed in water, it imbibes water and
hence swells.
• Application in dentistry:
• hydrocolloid impression is being stored in
the presence of moisture (water), they
absorb water and swell.
• Calcium sulfate hemihydrate is hygroscopic
material and easily absorbs moisture from
the humid atmosphere to form calcium
sulfate dihydrate. Formation of dihydrate on
the hemihydrate powder results in
lengthening of the setting time.

12. • Adsorbent: The material which takes up or
adsorbs the molecules onto its surface is called
as “adsorbent”.
• Ex: denture, gold foil, calculus, plaque.
• Adsorption process is of two types. They are:
1. Physical adsorption or physisorption
2. Chemisorption.
• In physisorption, the process consists of just a
physical phenomenon where just the van der Waals
force is in action.
• In chemisorption, it involves a chemical process
where exists a chemical interaction between the
surface atoms of adsorbent and the atoms of
adsorbate.

14. Sorption
• This is a process in which both adsorption and
absorption
• Eg:The sorption of water alters the dimensions of
acrylic dentures.This change in dimension is
reversible and plastic may go through numerous
expansions and contractions when alternately
soaked in water and dried.

15. DIFFUSION
• Diffusion is the movement of solvent
molecules from a region of higher
concentration to a region of lower
concentration.
• Application in dentistry:
• Salts and dyes diffuse through dentin.
• Stains and discoloring agents will diffuse
through plastic restorative materials.

16. Surface tension
• Surface tension may be defined as the force
acting tangentially to the liquid surface and
perpendicular to the unit length of an
imaginary line drawn on the surface.

17. • Applications in dentistry:
• These detergents improve the ability of
the dentifrice to wet the tooth surface
and thus it aids in removing debris from
tooth surface.

18. WETTING
• To produce adhesion, the liquid must
flow easily over the entire surface and
adhere to the solid; this character is
referred to as “wetting”.
• Factors affecting wetting:
1.The surface of the adherent.
2. Surface energy
3. Irregularities.

19. ANGLE OF CONTACT
• the angle formed by the adhesive with the adherent at their interface.

20. • If Surface area increases the angle of contact decreases

22. ADHESION
• Adhesion occurs when two unlike molecules join together on being brought into
contact due to force of attraction between them.
• Zinc phosphate cement
• Zinc polycarboxylate cement

23. • Bonding may be achieved by one of the two mechanisms:
• 1. Mechanical bonding
• 2. Chemical bonding.

24. COHESION
• Cohesion occurs when two like molecules or substances join together on being
brought into contact due to the force of attraction between them.
• Application in dentistry: Pure gold restoration

26. Thank you
Drshivasai