plaque and calculus

Question 1

What is the current model for the development of periodontal diseases?

Answer 1

Bacteria->host immune response->destructive mechanisms-> c. tissue and bone metabolism

Question 2

What is plaque?

Answer 2

Bacterial aggregations on teeth and other solid/oral structures

Soft, concentrated mass of mainly a large variety of bacteria together w cell debris which develops shortly after not brushing teeth

Can’t be removed by rinsing w water

Separate structure from food debris

Question 3

What are two types of plaque?

Answer 3

Supra-/sub-ginigival

Question 4

What is the structure of plaque?

Answer 4

70% microorganisms

30% inter bacterial matrix inc. extracellular polysaccharides and host cells

Question 5

What is the inter bacterial matrix?

Answer 5

Cuticle
Epithelial cells
Polymorphonuclear leukocytes 
Carbohydrates 
Lipids (LPS)
Protein
Immunoglobulins 
Enzymes

Question 6

What bacteria can be found in plaque?

Answer 6

P. gingivalis
P. micros
A. actinomycetemcomitans
F. nucleatum
T. forsythensis 
P. intermedia

Question 7

What happens in 0-20mins of plaque formation?

Answer 7

Pellicle/cuticle formed by opposite charges in salivary macro-molecules
Large amounts of acidic AAs and glycoproteins from saliva
Small amounts of basic and sulphur containing AAs

Passive transport of microorganisms
Adhesion receptors provide reversible adhesion
Weak London forces holding plaque to tooth

After this,
Primary and secondary colonisers can provide irreversible adhesion
Tertiary colonisers can act in unison
(Early and late colonisers)

Question 8

What’s the the steps to plaque formation?

Answer 8

Reversible adhesion
Colonisation
Co adhesion
Multiplication
Detachment and recolonisation

Question 9

What happens in 2-4 days of plaque formation?

Answer 9

PRIMARY COLONISATION
Cocci are predominant and there’s an increase in gram +ve filamentous and rod shaped organisms

Formation of ECM for attachment to tooth surface and protection

Question 10

What happens in 1-2 days of plaque formation?

Answer 10

ATTACHMENT
Dental pellicle formed
Selective colonisation of salivary and planktonic organisms, primarily gram +ve cocci

Question 11

What happens in 4-7 days of plaque formation?

Answer 11

SUCCESSION
Increase in no of filamentous organisms and bacterial species forming mixed and diverse flora
Thickening of biofilm
Colonisation of gram -ve such as vibrios and spirochetes

Question 12

What happens in 7-14 days of plaque formation?

Answer 12

SECONDARY COLONISATION/PROLIFERATION
More gram -ve and anaerobes (spirochetes and fusiform)
More expression of virulent factors by bacteria
Formation of well organised biofilm colonies
Clinical inflam visible

Question 13

What happens in 14+ days of plaque formation?

Answer 13

MATURATION
Proliferation of gram -ve in deeper layers of plaque
Organisms densely packed w well organised protective ECM
Clinical inflam well established

Question 14

What happens in 3-8 hours of plaque formation?

Answer 14

10^3-10^4 organisms/mm^3

90% gram positive cocci and rods, actinomyces species

Question 15

What happens in 24hours of plaque formation?

Answer 15

Clinically evident
Changes in proportions of organisms-
~Streptococci <45% 
~Gram -ve 20%
~Others 35%

Question 16

What is sub gingival plaque?

Answer 16

Derived from supra plaque
Low O2 favour anaerobes
Nutrients from crevicular fluid
Organisms can exist w/o attachment

Question 17

What is the difference in plaque flora of gingivitis and periodontitis?

Answer 17

GINGIVITIS
~25% streptococci
~25% actinomyces
~25% gram -ve rods
~2% spirochetes
~23% other

PERIODONTITIS
~more than 800 species
~90% anaerobes
~up to 50% spirochetes

Question 18

What is the pathogenicity of plaque?

Answer 18

Endotoxin- LPS induces bone resorption
Enzymes- metalloproteinases, collagenases, hyaluronidases etc
Cytotoxic metabolites- volatile sulphides (H2S), urea, organic acids (eg. Lactic, pyuric)

Question 19

What is calculus?

Answer 19

The calcified, of calcifying deposits on teeth or other solid structures present in the mouth

Supra-gingival-
White/yellow/stained, forms rapidly and easier to remove

Subgingival-
Darker/harder, more difficult to remove, slower to form

Question 20

How can calculus be detected?

Answer 20

Visual- direct, airstream
Tactile- WHO probe/curette
Radiography- bitewing etc
Electronic devices eg. Detectar

Question 21

What is the composition of calculus?

Answer 21

70-80% inorganic/crystalline (hydroxyapatite, whitlockite, brushite etc)
20% organic (proteins, carbs, lipids)

Question 22

What is the structure of calculus?

Answer 22

Layered 
Varying amounts of calcification
Random arrangement of crystals
Outline of calcified microorganisms 
Plaque on surface

Question 23

How does calculus attach to the tooth surface?

Answer 23

Calcification of pellicle
Intimate contact of crystals between enamel/cementum/dentine due to ionic attraction
Micromechanical interlocking

Question 24

How does calculus form?

Answer 24

Preceded by plaque
Crystals form in matrix
Crystal nos rise, bacteria becomes mineralised

CO2 hypothesis-
High levels of CO2 in saliva as it leaves glands
CO2 leaves saliva, rises pH, Ca and PO4 ions
Precipitates into plaque

Ammonia production hypothesis-
Research- rapid calculus + raised salivary urea
Increase in pH
Ca and PO4 ions come out
Precipitates into plaque

Nucleation hypothesis-
Nucleation of crystal formation by unknown compounds

Question 25

What is the pathogenicity of calculus?

Answer 25

Associated w perio but doesn’t cause it
Calculus is a plaque retentive factor
There may be viable bacteria within lacunae in calculus