Transcript برنامج خادم الحرمين الشريفين للابتعاث الخارجي (الولايات المتحدة

Summary of Lecture # 1
September 19, 2007
Abdullah S. Al-Swuailem BDS, MS, MPH, Dr PH
Preventive Dentistry
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Why Prevention?
Definition of Health.
Types of Prevention
Remedies if prevention fails
Categories of oral diseases
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Strategies to prevent plaque diseases:
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Dental caries and periodontal disease are caused by bacteria and
hence are considered infectious diseases.
Virulent bacteria in sufficient number can cause disease in
susceptible individuals.
Dental plaque Composition :
salivary components ( proteins) + bacteria + end products of bacterial
metabolism .
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Primary Prevention in Dentistry
Time
Host
Bacteria
Caries
Diet
Primary Prevention in Dentistry
- Fluoride
- Sugar and diet
- Pit and fissure sealants
- Public education
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Read the summary of the Surgeon
General Report on “Oral Health in
America” p-2 in primary Preventive
Dentistry by N. Harris
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Demineralization and remineralization
phases of dental caries
Bacterial Plaque
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Learning Objectives:
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Understand the concept of bacterial biofilm in the
process of causing disease
Know and differentiate between subsurface pellicle
and acquired pellicle
Know the stages of dental plaque formation and
factors that may affect its build-up
Differentiate between sub-gingival and supragingival calculus
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Bacterial Plaque
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Unlike most diseases, dental caries and
periodontal disease are caused by a
variety of bacterial species
Bacterial Plaque
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Microbial biofilm:
All living cells are negatively charged
Biolfim bacteria behave differently from
Planktonic (liquid-phase) cells. Bacteria
growing in biofilm are more resistant to host
defence mechanisms and exogenous
antimicrobial agents. Thus mechanical
removal of bacterial biofilm is needed to have
effective antimicrobial therapy
Bacterial Plaque
- Prior to tooth eruption, microscopic voids on
the enamel surface is filled by organic
material of endogenous origin (subsurface
pellicle)
- After tooth eruption, a thin coating of salivary
film covers the tooth exposed surface and
subsequently become colonized by oral
bacteria. This exogenous film is called
acquired pellicle
Bacterial Plaque
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If the acquired pellicle is removed it
begins to reform immediately and it
takes about a week for the pellicle to
develop its condensed and mature
structure
The acquired pellicle is also formed on
artificial surfaces, e.g. dental
restorations
Bacterial Plaque
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The carbohydrate components of
certain pellicle glycoproteins may serve
as receptors for bacterial-binding
protein such as adhesin
Bacterial Plaque
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Factors influencing the build-up of dental
plaque:
Mechanical displacement (chewing, tongue
movement, oral hygiene aids)
Stagnation (colonization in sheltered
environments, e.g. inter-proximal area)
Availability of nutrients
Interactions between the microbes and the
host’s inflammatory immune system
Bacterial Plaque
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Plaque formation:
Within 2 hours, initial plaque formation begins as a
series of isolated bacterial colonies confined to tooth
surface irregularities
In about 2 days, the plaque double in mass and
bacterial colonies coalesce
In the first 4-5 days of plaque formation, the number
of bacteria increase significantly
After approximately 21 days, bacterial replication
slows so that plaque accumulation becomes relatively
stable. Bacteria in the deeper portion of the
developing plaque are either facultative or obligate
anaerobes
Bacterial Plaque
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Plaque formation:
In individuals with poor oral hygiene, superficial dental
plaque may contain food debris and mammalian cells such
as desquamated epithelial cells and leukocytes. This debris
layer is called materia alba “white matter”
First bacteria to adhere to tooth surface are called
primary colonizers, and are typically non-pathogenic
Secondary colonizers bacteria colonize on existing
bacterial layer
Early colonizers are cocci (47-85% streptococci), followed
by short rods and filamentous bacteria. These are mainly
aerobic bacteria
Sucrose is used to synthesize intracellular and
extracellular polysaccharides
Bacterial Plaque
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Dental Plaque metabolism:
Upon exposure of dental plaque to sucrose, acid forming
organism such as S. mutans produce:
Acids
Intracellular polysaccharides
Extracellular polysaccharides [ glucans (dextran) and
fructans (levan)]
20% of plaque dry weight is made up of glucans, 10%
levans, and 70-80% bacteria
Dental plaque and dental caries and periodontal disease
initiation
Bacterial Plaque
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Dental calculus:
From Latin word meaning stone
Tartar refers to accumulated sediment or crust on the
sides of a wine cask
Calculus in itself is not harmful, but harm comes from
overlying dental plaque
Smokers, children with asthma and cystic fibrosis,
mentally handicapped individuals, and patients who are
tube-fed over long periods have greater calculus deposits
Patients taking medications such as beta-blockers,
diuretics, and anticholinergics have significantly reduced
levels of calculus
Bacterial Plaque
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Dental calculus:
Supra-gingival calculus:
located coronal to gingival margin and frequently
develops opposite to duct orifices of major salivary glands.
30% mineralized. Yellow to white chalky mass
Sub-gingival calculus:
Located below the gingival margin and derived its
minerals from crevicular fluids within the gingival sulcus.
It is thinner and harder (60% mineralized) than supragingival calculus. Gray to black in color.
Calculus formation can be inhibited by using agents
containing pyrophosphate or metal ions such as zinc