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Dental Plaque Dental Plaque Dr.Ghada Maghaireh Dr.Ghada Maghaireh BDS,MS,ABOD BDS,MS,ABOD
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Page 1: Dental Plaque

Dental PlaqueDental Plaque Dr.Ghada MaghairehDr.Ghada Maghaireh

BDS,MS,ABODBDS,MS,ABOD

Page 2: Dental Plaque

Dental Plaque as a Dental Plaque as a microbial biofilmmicrobial biofilm

Dental plaque is an example of biofilm.Dental plaque is an example of biofilm. The term biofilm is used to describe The term biofilm is used to describe communities of communities of

microorganisms attached to a surfacemicroorganisms attached to a surface.. Such organisms are organized into three dimensional Such organisms are organized into three dimensional

structure enclosed in a matrix of extracellular material structure enclosed in a matrix of extracellular material derived from both the cells themselves and the derived from both the cells themselves and the environment.environment.

Bacteria growing into Bacteria growing into biofilmsbiofilms are more resistant to the are more resistant to the effect of host defense mechanisms and antimicrobial effect of host defense mechanisms and antimicrobial agents when compared to the same cells in a liquid agents when compared to the same cells in a liquid suspension.suspension.

So it is important to mechanically disturb the biofilm when So it is important to mechanically disturb the biofilm when utilizing antimicrobial therapy (Brushing and professional utilizing antimicrobial therapy (Brushing and professional cleaning)cleaning)

Page 3: Dental Plaque

Dental Plaque and DietDental Plaque and Diet A carbohydrate-rich diet increases the growth A carbohydrate-rich diet increases the growth

rate of many oral bacteria.rate of many oral bacteria. It has been shown that the accumulation of It has been shown that the accumulation of

dental plaque dental plaque after 4 days is higher when after 4 days is higher when individuals consume a diet supplemented with individuals consume a diet supplemented with sucrose compared with a control diet without sucrose compared with a control diet without added sucrose.added sucrose.

A sucrose rich diet change the composition of A sucrose rich diet change the composition of the microflora into a more aciduric species.the microflora into a more aciduric species.

In addition, sucrose can be converted by In addition, sucrose can be converted by bacteria into glucans which can enhance plaque bacteria into glucans which can enhance plaque attachment and contribute to the plaque matrix. attachment and contribute to the plaque matrix.

Page 4: Dental Plaque

Dental Caries & Dental Plaque

Carbohydrates (Sucrose)Cariogenic bacteria such as S. mutans

Glucans Acids

Plaque formation Demineralization

+

Page 5: Dental Plaque

Formation and Structure of Formation and Structure of Dental PlaqueDental Plaque

The development of dental plaque can be divided The development of dental plaque can be divided into different stages:into different stages:

1. Pellicle formation.1. Pellicle formation. 2. Attachment of single bacteria cells.2. Attachment of single bacteria cells. 3. Growth of attached bacteria leading to the 3. Growth of attached bacteria leading to the formation of distinct microcolonies.formation of distinct microcolonies. 4. Microbial succession and co-aggregation leading 4. Microbial succession and co-aggregation leading

to to increased species diversity with continued increased species diversity with continued

growth of growth of microorganisms.microorganisms. 5. Climax community /mature plaque (2 weeks or 5. Climax community /mature plaque (2 weeks or

older).older).

Page 6: Dental Plaque

Pellicle FormationPellicle Formation Microorganisms do not colonize directly on the Microorganisms do not colonize directly on the

mineralized tooth surface.mineralized tooth surface. The teeth are always covered by a layer called The teeth are always covered by a layer called

““the pelliclethe pellicle””.. It is an acellular proteinaceous film that forms It is an acellular proteinaceous film that forms

on the on the ““nakednaked”” tooth surface within minutes to tooth surface within minutes to hours.hours.

In uncolonized areas the pellicle reaches a In uncolonized areas the pellicle reaches a thickness of 0.01-1 µm within 24 h.thickness of 0.01-1 µm within 24 h.

The major constituents of the pellicle are The major constituents of the pellicle are salivary glycoproteinssalivary glycoproteins, , phosphoproteinsphosphoproteins, , lipidslipids and components from the and components from the gingival cervicular gingival cervicular fluidsfluids. .

Page 7: Dental Plaque

Microbial ColonizationMicrobial Colonization Microbial colonization of teeth requires Microbial colonization of teeth requires

that bacteria adhere to the surface.that bacteria adhere to the surface. Mechanism involved in the adherence Mechanism involved in the adherence

is very complex and not fully is very complex and not fully understood.understood.

Initial microbial colonization.Initial microbial colonization. Microbial succession.Microbial succession.

Page 8: Dental Plaque

Initial Microbial Initial Microbial ColonizationColonization

The tooth surface is initially colonized by a The tooth surface is initially colonized by a highly selected part of the oral microflora, highly selected part of the oral microflora, mainly Smainly S.sanguis.sanguis, S, S.orals.orals, and S., and S.mitismitis..

Together theses three streptococci Together theses three streptococci accounts for 95% of the streptococci and accounts for 95% of the streptococci and 56% of the total initial microflora.56% of the total initial microflora.

Bacteria contain a recognition system on Bacteria contain a recognition system on their surfaces that enables components of their surfaces that enables components of the bacteria surface (adhesins) to bind to the bacteria surface (adhesins) to bind to complementary molecules (receptors) in complementary molecules (receptors) in the pellicle.the pellicle.

Page 9: Dental Plaque

Microbial SuccessionMicrobial Succession As the microbiota ages, a shift occur from a As the microbiota ages, a shift occur from a

Streptococcus-Streptococcus-dominateddominated plaque to a plaque plaque to a plaque dominated by dominated by ActinomycesActinomyces..

Such microbial shifts are known as Such microbial shifts are known as microbial microbial successionsuccession..

Pioneer bacteria create an environment that Pioneer bacteria create an environment that is either more attractive to secondary is either more attractive to secondary invaders or unfavorable for themselves invaders or unfavorable for themselves because of a lack of nutrients or because of a lack of nutrients or accumulation of inhibitory metabolic accumulation of inhibitory metabolic products.products.

Page 10: Dental Plaque

Microbial SuccessionMicrobial Succession As the bacterial deposits become As the bacterial deposits become

thicker, the oxygen concentration thicker, the oxygen concentration decreased.decreased.

Progressive shift from aerobic in the Progressive shift from aerobic in the early stages to a situation in which early stages to a situation in which anaerobic organisms are predominant anaerobic organisms are predominant after 9 days.after 9 days.

After some weeks of undisturbed After some weeks of undisturbed growth, the microbial community growth, the microbial community develops into a climax community develops into a climax community that harbors a broad range of that harbors a broad range of bacterial species.bacterial species.

Page 11: Dental Plaque

Dental Plaque and CariesDental Plaque and Caries

Two main school of thought on the Two main school of thought on the role of plaque in the etiology of role of plaque in the etiology of caries.caries.

1. The specific plaque hypothesis.1. The specific plaque hypothesis.

2.The non-specific plaque 2.The non-specific plaque hypothesis.hypothesis.

The ecological plaque hypothesis.The ecological plaque hypothesis.

Page 12: Dental Plaque

The Specific Plaque HypothesisThe Specific Plaque Hypothesis Only a few species of the diverse collection of Only a few species of the diverse collection of

organisms comprising the plaque microflora are organisms comprising the plaque microflora are actively involved in the disease.actively involved in the disease.

A considerable amount of evidence supports the A considerable amount of evidence supports the association between organisms of the Streptococcus association between organisms of the Streptococcus mutans group and caries incidence and prevalence.mutans group and caries incidence and prevalence.

The cariogenic potential of S. mutans is probably The cariogenic potential of S. mutans is probably due to the unique combination of properties with due to the unique combination of properties with which this microorganism is capable. which this microorganism is capable.

The pathogenic potential can be modified by changes The pathogenic potential can be modified by changes in the environment.in the environment.

Lactobacilli play a major role in the development of Lactobacilli play a major role in the development of a lesiona lesion. .

Page 13: Dental Plaque

The Specific Plaque The Specific Plaque HypothesisHypothesis

The specific plaque hypothesis has important The specific plaque hypothesis has important implications because the association between S. implications because the association between S. mutans, lactobacilli and dental caries can be mutans, lactobacilli and dental caries can be used in diagnosis, treatment and prevention of used in diagnosis, treatment and prevention of the disease in groups of subjects as well as in the the disease in groups of subjects as well as in the individual case.individual case.

It focused efforts on controlling disease by It focused efforts on controlling disease by targeting preventive measures and treatment targeting preventive measures and treatment against a limited number of organisms.against a limited number of organisms.

Page 14: Dental Plaque

The non-specific plaque The non-specific plaque hypothesishypothesis

For more than 100 years, investigators have tried to For more than 100 years, investigators have tried to identify the bacteria responsible for dental caries identify the bacteria responsible for dental caries formation and to determine whether their role is one of formation and to determine whether their role is one of specificity.specificity.

Frequent association ofFrequent association ofStreptococcus mutansStreptococcus mutans

Lactobacillus sLactobacillus s and with caries activity gave acceptance and with caries activity gave acceptance to their being specific cariogens.to their being specific cariogens.

However, dental caries occurrence in their absence, and However, dental caries occurrence in their absence, and

the presence of other bacteria able to produce the presence of other bacteria able to produce substantial amounts of acid from fermentable substantial amounts of acid from fermentable carbohydrate, provided arguments for carbohydrate, provided arguments for non-specificitynon-specificity. .

Page 15: Dental Plaque

The non-specific plaque The non-specific plaque hypothesishypothesis

Disease is the outcome of the overall Disease is the outcome of the overall activity of the total plaque activity of the total plaque microflora.microflora.

A heterogeneous mixture of A heterogeneous mixture of microorganisms could play role in microorganisms could play role in the disease.the disease.

Page 16: Dental Plaque

The Ecological Plaque The Ecological Plaque HypothesisHypothesis

This hypothesis propose that the organisms This hypothesis propose that the organisms associated with disease may also be present at associated with disease may also be present at sound sites, but at levels too low to be clinically sound sites, but at levels too low to be clinically relevant.relevant.

Disease is a shift in the balance of the Disease is a shift in the balance of the resident resident microflora microflora driven by a change in driven by a change in local local environmental conditionsenvironmental conditions..

In case of dental caries, repeated conditions of In case of dental caries, repeated conditions of low pH in plaque following frequent sugar intake low pH in plaque following frequent sugar intake will favor the growth of acidogenic and aciduric will favor the growth of acidogenic and aciduric species, and therefore predispose a site to caries. species, and therefore predispose a site to caries.

Page 17: Dental Plaque

The Ecological Plaque The Ecological Plaque HypothesisHypothesis

The hypothesis also acknowledge the dynamic The hypothesis also acknowledge the dynamic relationship that exists between the microflora relationship that exists between the microflora and the host.and the host.

So that the impact of alterations in key host So that the impact of alterations in key host factors (such as saliva flow) on plaque factors (such as saliva flow) on plaque composition is also taken into account. composition is also taken into account.

The disease can be controlled not only by The disease can be controlled not only by targeting directly the pathogen (e.g. mutans targeting directly the pathogen (e.g. mutans streptococci), but also by interfering with the streptococci), but also by interfering with the factors that are the shift in the balance of factors that are the shift in the balance of microflora (e.g. lowering the acid challenge).microflora (e.g. lowering the acid challenge).

Page 18: Dental Plaque

The Ecological Plaque The Ecological Plaque HypothesisHypothesis

Stress Environmental Change

Ecological Shift Disease

Remineralization

Demineralization

Excesssugar Neutral

pHS.sanguisS.oralis

Acid production

LowpH

MSLactobacilli

Page 19: Dental Plaque

Midterm ExamMidterm ExamThe First six lectures will The First six lectures will

be covered with the exam.be covered with the exam.Monday 2-4-2012 from Monday 2-4-2012 from

3:15-4:15.3:15-4:15.10H1,10H2,10H3.10H1,10H2,10H3.