The Microbiology of Dental Caries

1. The Microbiology of Dental Caries

2. Caries defined • 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 5--11 years to 67% among persons aged 12--17 years and 94% for dentate adults (with >1 natural teeth) aged >18 years.

3. The original model

4. A more recent model

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

6. The caries culprits • 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. • Sobrinus means “distant cousin on mother’s side”. • Lactobacillus produces lactic acid at higher concentrations than “helpful” bugs

7. Streptococcus mutans What is it?

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

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

10. 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.

11. 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?

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

14. The Mutans Streptococcus

15. How does Strep mutans attatch to teeth and cause caries?

16. Biofilm Formation

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

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

19. S. mutans structures

20. Adhesin • A surface structure or macromolecule that binds a bacterium to a specific surface. • Antigen (Ag) I/II or SpaP • 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. • Enables P. gingivalis to adhere to streptococci, enabling secondary colonizers to be incorporated into plaque communities.

21. S. mutans structures

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

23. S. mutans structures

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

25. 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.

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

27. Cell walls

28. Vaccines Against Dental Caries

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

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

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

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

33. Role of IgA • Prevents colonization • Key in vaccine development • 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.

34. Vaccines • 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. • Recombinant strains methods also reduce cross-reactivity problems and help prolong IgA response as well.

35. Target Antigens • Subunit vaccination • Bacerial antigens • Synthetic peptides • Proteins • Target Gtf

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

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

38. Public considerations • 1950’s-4 vaccines; 1:10,000 autism • 1980’s-8 vaccines; 1/2,600 • 1990’s-10 vaccines; 1/350 • 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

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

40. Thank You!