plaque and calculus Flashcards
What is the current model for the development of periodontal diseases?
Bacteria->host immune response->destructive mechanisms-> c. tissue and bone metabolism
What is plaque?
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
What are two types of plaque?
Supra-/sub-ginigival
What is the structure of plaque?
70% microorganisms
30% inter bacterial matrix inc. extracellular polysaccharides and host cells
What is the inter bacterial matrix?
Cuticle Epithelial cells Polymorphonuclear leukocytes Carbohydrates Lipids (LPS) Protein Immunoglobulins Enzymes
What bacteria can be found in plaque?
P. gingivalis P. micros A. actinomycetemcomitans F. nucleatum T. forsythensis P. intermedia
What happens in 0-20mins of plaque formation?
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)
What’s the the steps to plaque formation?
Reversible adhesion Colonisation Co adhesion Multiplication Detachment and recolonisation
What happens in 2-4 days of plaque formation?
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
What happens in 1-2 days of plaque formation?
ATTACHMENT
Dental pellicle formed
Selective colonisation of salivary and planktonic organisms, primarily gram +ve cocci
What happens in 4-7 days of plaque formation?
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
What happens in 7-14 days of plaque formation?
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
What happens in 14+ days of plaque formation?
MATURATION
Proliferation of gram -ve in deeper layers of plaque
Organisms densely packed w well organised protective ECM
Clinical inflam well established
What happens in 3-8 hours of plaque formation?
10^3-10^4 organisms/mm^3
90% gram positive cocci and rods, actinomyces species
What happens in 24hours of plaque formation?
Clinically evident Changes in proportions of organisms- ~Streptococci <45% ~Gram -ve 20% ~Others 35%
What is sub gingival plaque?
Derived from supra plaque
Low O2 favour anaerobes
Nutrients from crevicular fluid
Organisms can exist w/o attachment
What is the difference in plaque flora of gingivitis and periodontitis?
GINGIVITIS ~25% streptococci ~25% actinomyces ~25% gram -ve rods ~2% spirochetes ~23% other
PERIODONTITIS
~more than 800 species
~90% anaerobes
~up to 50% spirochetes
What is the pathogenicity of plaque?
Endotoxin- LPS induces bone resorption
Enzymes- metalloproteinases, collagenases, hyaluronidases etc
Cytotoxic metabolites- volatile sulphides (H2S), urea, organic acids (eg. Lactic, pyuric)
What is calculus?
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
How can calculus be detected?
Visual- direct, airstream
Tactile- WHO probe/curette
Radiography- bitewing etc
Electronic devices eg. Detectar
What is the composition of calculus?
70-80% inorganic/crystalline (hydroxyapatite, whitlockite, brushite etc)
20% organic (proteins, carbs, lipids)
What is the structure of calculus?
Layered Varying amounts of calcification Random arrangement of crystals Outline of calcified microorganisms Plaque on surface
How does calculus attach to the tooth surface?
Calcification of pellicle
Intimate contact of crystals between enamel/cementum/dentine due to ionic attraction
Micromechanical interlocking
How does calculus form?
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
What is the pathogenicity of calculus?
Associated w perio but doesn’t cause it
Calculus is a plaque retentive factor
There may be viable bacteria within lacunae in calculus
