Aetiology of Periodontitis

Question 1

Definition of aetiology

Answer 1

The science behind the study of factors causing disease - contribute, modify or cause development.

Question 2

Prevention and treatment

Answer 2

Relationship between the aetiological factors and pathogenesis

Question 3

What is the main aetiological factor in the development and progression of inflammatory periodontal disease?

Answer 3

Dental biofilm - no plaque control contributes to increase prevalence and severity.

Question 4

What are the plaque theories?
(WALTER LOESCH 1976)

Answer 4

1. Specific Plaque theory
2. Non-specific Plaque theory

Question 5

Non-specific plaque hypothesis states that:

Answer 5

The degree of gingival inflammation = to the amount of plaque present as well as all plaque has the same potential to cause disease.

MORE PLAQUE –MORE DISEASE

Hypothesis?
Sometimes Less plaque have more periodontal destruction
Sometimes more plaque causes less destruction.

Question 6

Specific Plaque Theory

Answer 6

Only certain plaque is pathogenic and its pathogenicity depends on the presence of or an increase in specific microorganisms”

Further studies lead to the realisation that the microflora in affected and non infected areas differ in composition

Question 7

Dental Plaque definition

Answer 7

Specific but highly variable structural entity that develops due to sequel of events of micro-organism inhabitation of tooth structures, restoration and other parts of oral cavity. Composed of: salivary components - mucins, micro-organisms, debris, desquamated epithelial cells that are embedded in extracellular matrix.

Question 8

Composition of Dental Plaque:

Answer 8

1) WATER 80%
2) MICRO- ORGANISMS INTERCELLULAR MATRIX 20% (20-30% OF PLAQUE MASS)

-INORGANIC MATERIALS:
Calcium, phosphorus
Sodium, potassium
fluoride

-ORGANIC MATERIALS:
Polysaccharides,
glycoproteins, proteins,
lipids

-BACTERIA
MYCOPLASMA
PROTOZOA
YEAST
VIRUSES

Question 9

What are the 4 categories of bacteria characteristics?

Answer 9

1) Cell wall composition
2) Oxygen environment
3) Metabolism
4) Morphotypes (group of bacterial strains within a single species that are distinguishable by morphological characteristics)

Question 10

Cell wall
characteristics of bacteria

Answer 10

Gram-positive (Gr +ve) and gram-negative bacteria (Gr -ve). Named according to permeability of cell wall.

Gr -ve = external membrane lipopolysaccharide layer(LPS layer) under capsule. Release of LPS layer (endotoxin) causes tissue destruction.

G +ve bacteria have NO LPS layer.

Question 11

Bacterial Metabolism types

Answer 11

1. Saccharolytic (fermenting) - break down CHOs (carbohydrates)
2. Asaccharolytic (non-fermenting) - uses amino-acids, peptides & proteins to grow.

Question 12

Oxygen environment of bacteria

Answer 12

O2 availability influences ability of bacterial growth and number.

1. Aerobic organisms need O2.
2. Facultative anaerobes can use O2, can also grow anaerobically.
3. Aerotolerant anaerobes do not use O2 but can tolerate an oxidizing environment.
4. Obligate anaerobes cannot survive in an O2-rich environment.

Question 13

Morphotypes of bacteria

Answer 13

Structural properties.
Name usually describes form:
Cocci = spherical
Bacilli = rods, filaments
Spirochetes = spiral formed

Question 14

Plaque as biofilm

Answer 14

Bacteria binds to surface developing sessile, mushroom-shaped colonies attached with narrow bases. The microcolony has various types of bacteria that are compatible and independent.

Question 15

Steps for supragingival plaque development into dental biofilm:

Answer 15

1 Pellicle formation:
An amorphous membrane that coats all surfaces of oral cavity, made up of glycoproteins (saliva).
Attaches to Ca and PO4 ions of the hydroxyapatite of tooth.

2 Initial colonization of the pellicle:
Within hours, Bacteria in saliva contact and bind by using receptor- molecules.
Initially bacteria are mainly cocci, binding in a mono layer and later proliferate to form colonies.
Bacilli and filaments attach to the cocci. Colonies become larger leading to a bacterial mass.

3.Growth and maturation of plaque:
Unpleasant odor/Maturity
Inter-microbial matrix formed from:
- saliva material
- gingival exudate
- other microbial substances

Non-specific bacteria also caught in this extra-cellular matrix.

These bacteria are different from initial colonizers. Colonization and growth of new bacterial species
Change in initial aerobic environment: gram positive - gram negative.

4. Bacterial co-aggregation:

2 bacteria species becoming one.
Brought about by the direct interaction between the surface components of two species.
E.g. Filaments covered with cocci, called “corncob” formation; others resemble test-tube brushes, where filamentous bacterium acts as central axis and gram negative rods forming the hairs of a brush

5 Bacterial succession:

With plaque maturation - initial bacteria proliferate(rapid increase in number) and grow.
- the environment changes – this allows new and different types of bacteria to move into developing plaque.

Question 16

Forces involved in pellicle formation:

Answer 16

Van der Waal forces
Electrostatic forces
Hydrophobic forces

Question 17

UNDISTURBED PLAQUE WILL:

Answer 17

• Increase in Thickness
• Increase in Amount of bacteria
  -Increase in different types of bacteria
  -be visible after 24hrs (no food required)

Question 18

Late bacteria colonizers:

Answer 18

1. motile gram-negative rods
2. Porphyromanas gingivalis

Question 19

Early bacteria colonizers:

Answer 19

1. Streptococci
2. Capnocytaphaga species
3. gram positive rods
4. actinomyces species

Question 20

Sub-gingival plaque formation steps:
(More aggressive organisms)

Answer 20

1. Initiated by mature supra-gingival plaque
2. Leads to gingival inflammation that may lead to gingival attachment loss
3. Supra-gingival plaque then grows apically into the sulcus
4. = Sub-gingival plaque
5. Bacteria multiply as the environment changes

Question 21

Iatrogenic factors

Answer 21

orthodontic brackets
partial dentures
restorations
crowns
pontics

Question 22

Tooth position &
anatomy factors

Answer 22

enamel pearls
grooves
malocclusion

Question 23

Poor plaque control factors

Answer 23

ignorance
retardation
economic

Question 24

Systemic factors

Answer 24

alcohol
diet
smoking
saliva

Question 25

Tooth pathology factors

Answer 25

caries

Question 26

Inorganic composition of calculus: (70-80%)

Answer 26

EARLY CALCULUS
Brucite

LATER CALCULUS
Octacalcium phosphate

MATURE CALCULUS
Hydroxyapatite &
Whitlokite

Question 27

Organic structure (10-15%)

Answer 27

PROTEINS
POLYSACCHARIDE COMPLEXES
DESQUAMATED EPITH CELLS
LEUCOCYTES
VARIOUS M/ORGANISMS

Question 28

BOOSTER CONCEPT Calculus Theory

Answer 28

Mineral precipitation results from a local rise in the degree of saturation of calcium and phosphate ions
A rise in the pH of the saliva causes the precipitation of calcium phosphate salts by lowering the precipitation constant.

Question 29

BACTERIOLOGICAL THEORY

Answer 29

Oral microorganisms are the primary cause of calculus formation.
Involved in the attachment to the tooth surface.

Question 30

INHIBITION THEORY

Answer 30

Calcification at specific sites - because of inhibiting mechanism at non-calcifying sites.

Alkaline pyrophosphatase enzyme involved in controlling mechanism.
Pyrophosphate inhibits calcification - prevents the initial nucleus from growing, possibly by poisoning the growth centers of the crystals.

Question 31

TRANSFORMATION THEORY

Answer 31

Hypothesis - hydroxyapatite need not arise exclusively via epitaxis or nucleation.

Question 32

EPITACTIC CONCEPT

Answer 32

According to this concept, seeding agents induce small foci of calcification which enlarge and coalesce to form a calcified mass.

Question 33

Enzymatic theory

Answer 33

Calculus formation is the resultant of the action of phosphatases derived from either oral tissues or oral microorganism on some salivary phosphate containing complex.