STRUCTURE OF MATTER

1
STRUCTURE OF MATTER PRINCIPLES OF ADHESION

• PRESENTED BY-
• DR LAKSHYA KUMAR
• ASSISTANT PROFESSOR
• PROSTHODONTICS

BDS FIRST YR DENTAL MATERIALS TIMING- 1000
1100 AM DATE- 15/09/2014
2
STRUCTURE OF MATTER

• Material Properties to be considered
• 1. BIOCOMPATIBILITY (whether material can be
  used intraorally)
• 2. PHYSICOCHEMICAL Properties
• 3. HANDLING CHARACTERISTICS (ease of
  handling)
• 4. AESTHETICS (relating to beauty)
• 5. ECONOMY (cost effectiveness)

3

• To understand DM Basic Knowledge of
  Matter
• Bcoz behavior of DM depends on atomic
  structure (ceramic, plasticizer, metal)
• Atoms Molecules are held together by
  ATOMIC INTERACTIONS

4
Change of State
Melting Temp.
Heat of Vaporization

• SOLID LIQUID
  GAS
• Heat of Vaporization when water boils quantity
  of energy needed to transform Liquid to Vapour
• Amount of heat needed to evaporate 1 gm of liquid
  to vapour (at given temp pressure)
• Ex- 540 cal. of heat is req. to vaporize 1 gm
  of H2O (at 100 C pressure of 1 atom)
  

Latent heat of Fusion
5
KINETIC ENERGY

• Gaseous state possesses more KE than does the
  Liquid state
• If the KE of liquid decreases sufficiently when
  temp is decreased, 2nd Transformation in state
  may occur Liquid can change to solid
• KE is released (in form of heat) when Liquid
  freezes Latent Heat of Fusion
• 1gm of H2O freezes, 80 cal. Of heat is released

6

• 1 gm of solid is changed to liquid input of
  energy is req
• For Metals the temp. at which Change occurs is
  k/as Melting Temperature

7
Interatomic Bond Distance Bonding Energy

• 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
• Bonding Energy Energy can be defined as a force
  integrated over a distance

8

• Thermal Energy KE of atoms/molecules at a given
  temp. atoms are is constant state of vibration
• If higher the temp. greater the amplitude so,
  greater is the KE/ Internal Energy.
• Gross effect is expansion k/as Thermal Expansion

9
Crystalline Structure

• Atoms are bonded by Primary / Secondary forces,
  Na attract Cl- results in regularly spaced
  configuration Space Lattice/ Crystal.
• Any arrangement of atoms such that every atom is
  situated similar to every atom

10
Non Crystalline Structure

• Waxes may solidify as amorphous materials such
  that the molecules are distributed at random.
• Glass its atoms tends to develop a short order
  instead of long range order (Crystalline
  Structure)
• Ordered arrangement of glass is more/less locally
  interspersed with a considerable no. of
  disordered units because this arrangement is
  typical of liquids such solids (glass)are
  sometimes called Supercooled Liquids

11
Glass Transition Temperature

• The temp. at which there is an abrupt increase in
  the thermal expansion coefficient,
  indicating increased molecular mobility is called
  Glass Transition Temperature(Tg)
• It is characteristic of the particular glassy
  structure.
• Also k/as Glass Temperature

12
Diffusion

• In Gases Liquid is well-known
• Atoms/Molecules diffuse in solid state as well .
• Diffusion in Crystalline structure at room temp.
  is very low. At increased temp. prop. of metals
  may be changed radically by atomic diffusion
• Diffusion in Non-crystalline structure may occur
  at rapid rate (b.coz of disordered structure)
• Diffusion Coefficient D
• Defined as Amount of Diffusion that takes place
  across a given unit area

13
ADHESION BONDING

• In complete denture retention Adhesion between
  Denture Saliva Soft tissue
• 2 substances brought into Intimate contact, one
  adhere to the other, this Force is
• Adhesion In / When Unlike molecules are
  attracted
• Cohesion In / When Like molecules are
  attracted
• Material / film produced for Adhesion is Adhesive
  (fluid/semiviscous is best)
• Material to which it is applied is Adherend

14

• In Mechanical bonding there is Strong attachment,
  ex Screws, Bolts, Undercuts
• Internal surface of Crown / Post with
  cement irregularities with Air abrasion
• Enamel Acid Etching Phosphoric Acid (10-20
  secs) forms minute pores resin flows into pores
• Increased /improved Mechanical Retention
  Decreased Marginal Leakage, Stains, Secondary
  Caries Irritation of Pulp

15
Principles of Adhesion

• Surface Energy
• Wetting
• Contact Angle of Wetting ()

16

• Surface Energy
• At surface of lattice, energy is greater
  (outermost atoms are not equally attracted)
  increase in energy per unit area of surface is
  referred to as Surface Energy/ Tension
• Greater Surface energy greater capacity of
  Adhesion

17
Principles of Adhesion

• Wetting
• Liquid must flow easily over entire surface
  adhere to solid
• Contact Angle of Wetting

18
(No Transcript)
19
(No Transcript)
20
ACID ETCHING

• Procedure
• Surface treatment
• Application of acid
• Acid concentration
• Type of acid
• Etching time
• Washing stage
• Drying stage

21
ACID ETCHING
The pattern of Enamel etching is categorized as
Type 1 (preferential prism center etching) Type
2 (preferential prism periphery etching) Type 3
(mixed). There appears to be no difference
in micro-mechanical bonding of the different
etching patterns. The etched surface develops a
frosty appearance
22
ACID ETCHING
Etching of dentin surfaces primarily
dissolves hydroxyapatite crystals within the
surface of the intertubular dentin and along the
surface of the outermost peritubular dentin. A
smear layer exists from cavity preparation that
is typically 1 to 2 um thick with smear plugs
23
(No Transcript)
24
Interatomic Bonding

• The forces that hold atoms together
  are called cohesive forces. These interatomic
  bonds may be classified as primary or secondary.
  The strength of these bonds and their ability to
  form after breakage determine the physical
  properties of material.

25

• Primary Bond
• A bond that forms between atoms and that
  involves the exchanging or sharing of electrons.
• Secondary Bond
• A bond that involves attraction between
  molecules. Unlike primary bonding, there is no
  transfer or sharing of electrons.

26
(No Transcript)
27
Interatomic Primary Bonding

• Interatomic primary bonding may be of three
  different types
• 1. Ionic Bonds
• Result from the mutual attraction of positive and
  negative charges.
• The classic example is sodium chloride (NaCl-).
• In dentistry, ionic bonding exists in certain
  crystalline phases of some dental materials, such
  as gypsum and phosphate based cement .

28
(No Transcript)
29
(No Transcript)
30
2. Covalent Bonds

• In many chemical compounds, two valence
  electrons shared by adjacent atoms.
• The hydrogen molecule H2, is an example of
  covalent bonding.
• Covalent bonding occur in many organic compounds,
  such as dental resin.

31
(No Transcript)
32
3. Metallic Bonds

• It is the attraction force between positive metal
  ions and the delocalized (freely moving)
  electrons, gathered in an electron cloud.
• These free electrons are responsible for the high
  electric and thermal conductivities of metals
  also for their ability to deform plastically.
• Found only in metals.

33
(No Transcript)
34
Interatomic secondary Bonding

• In contrast with primary bonds, secondary
  bonds dont share electrons. Instead, charge
  variations among molecules or atomic groups
  induce polar forces that attract the molecules.

35
1. Hydrogen Bonding

• Bonds between hydrogen atom and atoms of the most
  electronegative elements (N, O, F) are called
  hydrogen bonds.
• When a water molecule intermingle with other
  water molecules, the hydrogen (positive) portion
  of one molecule is attached to the oxygen
  (negative) portion of its neighboring molecule
  and hydrogen bridges are formed. Polarity of this
  nature is important in accounting for the
  intermolecular reaction in many organic
  compounds, such as the absorption of water by
  synthetic dental resins.

36
(No Transcript)
37
2. Van der Waals Forces

• Van der Waals Forces form the basis of a dipole
  attraction.
• Normally, the electrons of the atoms are
  distributed equally around the nucleus and
  produce an electrostatic field around the atom.
  However this field may fluctuate so that its
  charge becomes momentarily positive and negative.
  A fluctuating dipole is thus created that will
  attract other similar dipoles. Such interatomic
  forces are quite weak .

38
(No Transcript)
39

• In general, materials can be subdivided into two
  categories according to their atomic arrangement.
  In crystalline materials there is a
  three-dimensional periodic pattern of the atoms,
  whereas no such long range periodicity is present
  in noncrystalline materials, which possess only
  short-range atomic order.

40
Crystalline Structure

• Atoms are bonded to each other by either primary
  or secondary forces. In the solid state, they
  combine in a manner that ensures minimal internal
  energy. The result is that they form a regularly
  spaced configuration known as a space lattice or
  crystal.

41

• A space lattice can be defined as any arrangement
  of atom in space in which every atom is situated
  similarly to every other atom. Space lattices may
  be the result of primary or secondary bonds

42

• There are 14 possible lattice types or forms, but
  many of the metals used in dentistry belong to
  the cubic system that is, the atoms crystallize
  in cubic arrangements. All dental amalgams, cast
  alloys, wrought metals, gold foil are
  crystalline. Some pure ceramics, such as aluminia
  and zirconia core ceramics, are entirely
  crystalline

43

• Other ceramics, such as porcelains, consists of
  noncrystalline glass matrix and crystalline
  inclusions that provide desired properties,
  including color, opacity, and increase in thermal
  expansion coefficients, radiopacity, strength,
  fracture toughness .

44
(No Transcript)
45

• Simple cubic

46
Body centered cubic

• In the body-centered cubic (BCC) array,
• All angles are 90 degrees and all atoms are
  equidistant from one another in the horizontal
  and vertical directions. Metallic atoms are
  located at the corners of the unit cell, and one
  atom is at the center of the unit cell
• Eg. iron and common for many iron alloys

47
The face-centered cubic

• This array has 90- degree angles and atomic
  centers that are equidistant horizontally and
  vertically, but atoms are located in the centers
  of the faces with no atom in the center of the
  unit cell
• Eg Most pure metals and alloys of gold,
  palladium, cobalt, and nickel

48

• Face centered orthorhombic

49

• Body centered orthorhombic

• Simple triclinic

50

• Simple monoclinic

• Base centered monoclinic

51
Noncrystalline Solids and their Structures

• Structures other than crystalline forms can occur
  in the solid state. For example,waxes may
  solidify as amorphous materials so that the
  molecules are distributed at random..
• A resin based composite consists of resin matrix,
  filler particles and an organic coupling agent
  that bond the filler particles to the resin
  matrix. In some cases, the filler particles are
  made from radiopaque glasses that are
  nancrystalline.

52

• Composites have a noncrystalline matrix and may
  or may not contain crystalline filler particles.
• The structural arrangements of the noncrystalline
  solids dont represent such low internal energies
  as do crystalline arrangements of the same atoms
  and molecules. Noncrystalline solids do not have
  a definite melting temperature, but rather they
  gradually soften as the temperature is raised .

53
(No Transcript)
54
THANK YOU