The Microbiology of Dental Caries

Caries defined Dental caries- an infectious disease that damages the structures of teeth. Dental caries- an infectious disease that damages the structures of teeth. The prevalence of dental caries (i.e., the percentage of persons with >1 decayed, missing, or filled teeth) in permanent teeth increases with age, from 26% among persons aged years to 67% among persons aged years and 94% for dentate adults (with >1 natural teeth) aged >18 years. The prevalence of dental caries (i.e., the percentage of persons with >1 decayed, missing, or filled teeth) in permanent teeth increases with age, from 26% among persons aged years to 67% among persons aged years and 94% for dentate adults (with >1 natural teeth) aged >18 years.

The original model

A more recent model

Criteria for Cariogenicity An organism must acidogenic An organism must acidogenic An organism must be aciduric An organism must be aciduric An organism must exhibit tropism for teeth An organism must exhibit tropism for teeth An organism must utilize refined sugar (sucrose) An organism must utilize refined sugar (sucrose) (Newburn, 1983)

The caries culprits The main microorganism involved in the initial caries process is S. mutans. The main microorganism involved in the initial caries process is S. mutans. S. sobrunis and lactobacillus are also involved, but must have s. mutans present to colonize. S. sobrunis and lactobacillus are also involved, but must have s. mutans present to colonize. Sobrinus means “distant cousin on mother’s side”. Sobrinus means “distant cousin on mother’s side”. Lactobacillus produces lactic acid at higher concentrations than “helpful” bugs Lactobacillus produces lactic acid at higher concentrations than “helpful” bugs

Streptococcus mutans What is it?

Streptococcus mutans What is it? A gram + facultative anaerobe characterized by 8 serotypes, a-h.

Streptococcus mutans What is it? A gram + facultative anaerobe characterized by 8 serotypes, a-h. Prevelance?

Streptococcus mutans What is it? A gram + facultative anaerobe characterized by 8 serotypes, a-h. Prevelance? The most prevelant serotype in the USA is c.

Streptococcus mutans What is it? A gram + facultative anaerobe characterized by 8 serotypes, a-h. Prevelance? The most prevelant serotype in the USA is c. Groups?

Carbohydrate Antigens Carbohydrate heteropolymers that contain glucose and galactose. Carbohydrate heteropolymers that contain glucose and galactose. Antibody specificity Antibody specificity Bind glucosyltransferase to bacterial cell Bind glucosyltransferase to bacterial cell

The Mutans Streptococcus SpeciesSerotypeSource S. mutans c,e,fHuman S. sobrinus d,g,hHuman S. cricetus a Sometimes human, mostly rats and hamsters S. rattus b Sometimes humans, mostly rats S. downei h Macaque monkey S. macacae c Macaque monkey S. ferus cRats

How does Strep mutans attatch to teeth and cause caries?

Biofilm Formation

Environment Require a non-shedding Require a non-shedding Needs nutritionally rich media for growth. Needs nutritionally rich media for growth. Optimum temp for growth is 37° C, or 25-42°C. Optimum temp for growth is 37° C, or 25-42°C. Low pH Low pH Transmission: Vertical and Horizontal Transmission: Vertical and Horizontal

Transmission Vertical Parent to child Horizontal Non-parent same species transfer Role of mutacin Window of infectivity

S. mutans structures

Adhesin A surface structure or macromolecule that binds a bacterium to a specific surface. A surface structure or macromolecule that binds a bacterium to a specific surface. Antigen (Ag) I/II or SpaP Antigen (Ag) I/II or SpaP Attatches to salivary pellicle receptors, salivary agglutinins, and other bacteria. Attatches to salivary pellicle receptors, salivary agglutinins, and other bacteria. Also provides mechanism for binding of salivary agglutinin glycoprotein to the streptococcal cell surface-generates receptor for other bacteria to adhere. Also provides mechanism for binding of salivary agglutinin glycoprotein to the streptococcal cell surface-generates receptor for other bacteria to adhere. Enables P. gingivalis to adhere to streptococci, enabling secondary colonizers to be incorporated into plaque communities. Enables P. gingivalis to adhere to streptococci, enabling secondary colonizers to be incorporated into plaque communities.

S. mutans structures

Extracellular enzymes 1. Gtf-I 1. Gtf-I Forms insoluble glucans with mostly α1,3 links between glucose polymers (mutans). Forms insoluble glucans with mostly α1,3 links between glucose polymers (mutans). 2. Gtf-S 2. Gtf-S Forms water soluble glucans with mostly α 1,6 links between glucose polymers (dextrans). Forms water soluble glucans with mostly α 1,6 links between glucose polymers (dextrans). 3. Gtf-SI 3. Gtf-SI Forms both water soluble and insoluble glucans. Forms both water soluble and insoluble glucans. 4. Ftf 4. Ftf Forms water soluble fructose Forms water soluble fructose

S. mutans structures

Glucans Tooth adherence Tooth adherence Promotes aggregation Promotes aggregation Biofilm accumulation Biofilm accumulation Retention of bacterial nutrients Retention of bacterial nutrients Some antibodies prevent GTF function and are protective. Some antibodies prevent GTF function and are protective.

Dextranases  Can convert glucan into glucose for glycolysis.  Break down α-1,6 linkages of glucose into α-1,3 linkages.  Glucans can serve as attachment mechanisms and energy stores.

LTA Lipoteichoic acid is an amphipathic constituent of the gram-positive bacteria outer-envelope. Lipoteichoic acid is an amphipathic constituent of the gram-positive bacteria outer-envelope. Can stimulate inflammation-TLR2 Can stimulate inflammation-TLR2 Analgous to LPS in gram negative bacteria. Analgous to LPS in gram negative bacteria. May help in adherence May help in adherence Key in virulence. Key in virulence. Area for possible vaccine? Area for possible vaccine?

Cell walls

Vaccines Against Dental Caries

Effective Vaccines Identify the bad guy. Identify the bad guy. Identify the best target to destroy the bad guy. Identify the best target to destroy the bad guy. Identify the component of the immune system that should be targeted. Identify the component of the immune system that should be targeted.

Vaccines: Whole or part? Early vaccinations involved patients swallowing boluses of killed S. mutans. Early vaccinations involved patients swallowing boluses of killed S. mutans. This induced heart cross-reactive antibodies. This induced heart cross-reactive antibodies. Cardiolipin (diphosphatidyl glycerol) Cardiolipin (diphosphatidyl glycerol) May no longer be a concern? May no longer be a concern? Removed using a preadsorption technique Removed using a preadsorption technique More recent efforts have focused on protein expression and secretion. More recent efforts have focused on protein expression and secretion.

Effective Vaccines Identify the bad guy. Identify the bad guy. Identify the best target to destroy the bad guy. Identify the best target to destroy the bad guy. Identify the component of the immune system that should be targeted. Identify the component of the immune system that should be targeted.

Effective Vaccines Identify the bad guy. Identify the bad guy. Identify the best target to destroy the bad guy. Identify the best target to destroy the bad guy. Identify the component of the immune system that should be targeted. Identify the component of the immune system that should be targeted. Should NOT harm the host! Should NOT harm the host!

Role of IgA Prevents colonization Prevents colonization Key in vaccine development Key in vaccine development More IgA produced daily than any other immunoglulin. More IgA produced daily than any other immunoglulin. Finding ways to prolong the availability of antigens in the secretory IgA will improve dental caries vaccinations. Finding ways to prolong the availability of antigens in the secretory IgA will improve dental caries vaccinations.

Vaccines Ag I/II vaccine would prevent binding. Ag I/II vaccine would prevent binding. Molecules that act as adjuvants, such as cholera toxin B and E coli. heat-liable toxin, improve the longevity of the IgA response to antigens from S. mutans. Molecules that act as adjuvants, such as cholera toxin B and E coli. heat-liable toxin, improve the longevity of the IgA response to antigens from S. mutans. Recombinant strains methods also reduce cross-reactivity problems and help prolong IgA response as well. Recombinant strains methods also reduce cross-reactivity problems and help prolong IgA response as well.

Target Antigens Subunit vaccination Subunit vaccination Bacerial antigens Bacerial antigens Synthetic peptides Synthetic peptides Proteins Proteins Target Gtf Target Gtf

Enteric Pathway Put antigens in a harmless enteric bacteria Put antigens in a harmless enteric bacteria Natural proliferation in gut; greater power than capsules with the antigen Natural proliferation in gut; greater power than capsules with the antigen Considerations Considerations Is the bug really harmelss? Plasmid vectors can encode resistance

Active or Passive? Which is better? Active immunity will produce higher titer’s. Route? Oral and intranasal favored thus far.

Public considerations 1950’s-4 vaccines; 1:10,000 autism 1950’s-4 vaccines; 1:10,000 autism 1980’s-8 vaccines; 1/2, ’s-8 vaccines; 1/2, ’s-10 vaccines; 1/ ’s-10 vaccines; 1/350 Today-13 vaccines, given in 33 shots before a child is 2 years of age Today-13 vaccines, given in 33 shots before a child is 2 years of age 1/100 boys, 1/400 girls is diagnosed with autism

Considerations Debate similar to fluoride? How would one more vaccine be received?

Thank You!