This document discusses the relationship between dental plaque and dental caries, defining caries as a bacterial disease characterized by demineralization of tooth structure. It details the roles of various microorganisms, including Streptococcus mutans and lactobacilli, in the initiation and progression of caries, and presents hypotheses explaining the involvement of plaque in oral diseases. Factors such as sugar consumption, tooth surface susceptibility, and saliva's protective role are also addressed, underscoring the multifactorial nature of dental caries.

1. Microbiology
Dental Caries
Dr. Ali Yaldrum
SEGi UC, KD

3. Learning Outcomes
At the end of this session students should be
! Describe rela4onship between plaque and oral diseases
! Describe role of plaque in development of caries
! Define Dental Caries
! Describe the ae4ology and the role different factors
play in ini4a4on and progression of the disease
! Describe the role played by different microorganisms

4. Relationship of
Plaque bacteria to Caries

5. Plaque & Caries
Historically for any microbe to be considered responsible
for a given condi4on, Koch s postulate was applied

6. Koch s Postulate
1. The microbes should be found in all cases of the disease with a
distribu4on corresponding to the observed lesions
2. The microbes should be grown on laboratory media for several
subcultures
3. A pure subculture should produce the disease in the suscep4ble
animal
4. A high an4body 4ter to the microbe should be detected during
infec4on; this may provide protec4on on subsequent reinfec4on

7. Koch s Postulate
1. A microbe should be present in sufficient numbers to ini4ate
disease
2. The microbe should generate high levels of specific an4bodies
3. The microbe should produce relevant virulence factors
4. The microbes should cause disease in an appropriate animal
model
5. Elimina4on of the microbe should result in clinical improvement

8. Role of Plaque
! The Specific Plaque Hypothesis (fig.1)
! The Non-­‐Specific Plaque Hypothesis (fig.2)
! The Ecological Plaque Hypothesis (fig.3)

9. Specific Plaque Hypothesis
Plaque
{ few species out of diverse resident
flora are actively involved in disease
X problem
( disease can still occur in absence of these
organisms
)
Disease
fig.1

10. Non-Specific Plaque Hypothesis
Plaque
{ out come of the overall activity of
the total plaque microflora
( )
plaque mediated diseases are polymicrobial but one
problem
specific organism predominate
Disease
fig.2

11. Ecological Plaque Hypothesis
Plaque
{
organisms associated with disease
are already present on teeth but very
low to detect
fig.3
Disease ( disease only initiates as a result of shift in
the balance of resident microf lora )

12. Dental Caries

13. Dental Caries
! It is bacterial disease of calcified 4ssue of the teeth characterized
by demineraliza4on of the inorganic and destruc4on of the
organic substance of the tooth.
Dental Caries is known as disease of civilization

14. Dental Caries
The Early theories
! The legend of Worms
! Endogenous Theory
! Chemical Theory
! Parasitic Theory
! Chemoparasitic Theory

15. Dental Caries
! Chemoparasitic theory
Miller in 1890 suggested that oral bacteria converted dietary
carbohydrates into acid which solubilized the calcium phosphate of
enamel to produce a caries lesion

16. Aetiology of Dental Caries

17. Saliva
Caries
Susceptible Surface
P laque
Saliva
Saliva
Time Bacteria
Sugar
Saliva
fig.4 aetiology of caries

18. Role of Saliva

19. Role of Saliva
Saliva plays a vital role in the maintenance of oral health
and the integrity of oral 4ssues
Saliva contains:
• exfoliated epithelial cells
• oral microorganisms
• food residues (carbohydrates)
• an4microbial factors
• minerals

20. Role of Saliva
! Mechanical washing ac4on of saliva is very effec4ve for
cleaning of teeth
! high buffering capacity neutralizes acid
! supersaturated with Calcium and phosphorus helps in
remineraliza4on
Salivary flow rate: 0.8 mm /min on upper labial surface
5.0 -­‐ 8.0 mm/min on lower lingual surface

21. Susceptible Surface

22. Susceptible Surface
Some areas of the tooth are more suscep4ble to developing caries
than others, known as susceptible areas
Suscep4bility is related to several factors
! Mineral & Fluoride Content
! Structure of that par4cular area

23. Susceptible Surface
Susceptible tooth surfaces includes
! Pits & Fissures (fig.5)
! Approximal Enamel cervical to contact point (fig.6)
! Exposed root surface (fig.7 & 8)
! Margins of Restora4on (fig.6 & 9)
! Cervical margins of tooth (fig.10)

24. pits & fissures caries
fig.5

25. Caries under restoration Approximal Caries
fig.6

26. Root surface Caries
fig.7

27. Root Surface Caries
fig.8

28. Caries under restoration Amalgam restoration
fig.9

29. white spot lesions
fig.9

30. From white spot to cavity formation
white spot lesion Cavitation
earliest clinical evidence (reversible) Later clinical stage (irreversible)

31. Time &
Sugar Substrate

32. Sugar Substrate
! Direct rela4onship between intake of Carbohydrates
(sugar) & Caries
! Glucose, Fructose & Sucrose are cariogenic
! Sucrose is the most cariogenic sugar
• fermentable
• easily penetrates plaque

33. Time & Sugar Substrate
There is a direct rela4onship between caries and:
! Frequency of sucrose consump4on
! s4ckiness of the sucrose
Both affects the amount of 4me sugar stays into contact
with the teeth surface

34. Plaque Bacteria

35. Plaque Bacteria
Dental Caries does not occur in vivo if microorganisms in
the form of dental plaque are absent; making it clear that
dental caries is a plaque mediated disease

36. Plaque Bacteria
! Streptococcus mutans
! Lactobacillus species
! Ac4nomyces Species
! Veillonella species

37. Streptococcus species
The term mutans streptococci refers to a group of 7
different species, but two species are most commonly
found in humans
! S. mutans (serotypes c/e/f)
! S. sobrinus (serotypes d/g)

38. Streptococcus species
Factors related to Cariogenicity of S. mutans
! S.mutans counts in saliva and at site of lesion
! Isolated from site before the development of caries
! Efficient sugar metabolism & transport capability
! Acidogenic & acidouric
! Liele effect of pH on growth and metabolism
! Produc4on of EPS & IPS

39. Streptococcus species
S. mutans been implicated in
! Pits & fissure caries (strong evidence)
! Root surface caries
! All forms of caries
! Some strains are more pathogenic than others

40. Streptococcus species
! S. Sobrinus role is uncertain
! Frequently isolated from plaque but in lesser numbers
! Shares the same cariogenic proper4es as S.mutans

41. Lactobacillus species
Lactobacilli can be divided into two groups
! Homofermenta4ve species
! Heterofermenta4ve species

42. Lactobacillus species
Homofermentative species
! L. acidophilus & L. casei
! Mainly produce lac4c acid from glucose fermenta4on
Heterofermentative species
! L. fermentum
! Produce lac4c acid and significant amounts of acetate

43. Lactobacillus species
Most commonly isolated species from oral cavity are
! L. casei
! L. fermentum
! L. acidophilus

44. Lactobacillus species
Factors related to Cariogenicity of Lactobacillus
species
! Increased number in carious cavi4es affec4ng enamel &
root surface
! Number in saliva reflect caries ac4vity
! Acidogenic and acidouric
! Few strains can produce EPS

45. Lactobacillus species
! Have a low affinity for tooth surface
! Low in numbers at healthy site
! Implicated in progression of caries deeper into den4ne
rather than ini4a4on
! Implicated in ae4ology of root surface caries

46. Actinomyces species
Ac8nomyces spp. form a major and complex part of the
oral microflora, par4cularly at the approximal site and
gingival crevice

47. Actinomyces species
! Ac8nomyces odontoly8cus been associated with very
early stages of tooth demineraliza4on
! Ac8nomyces naeslundii been associated with
development of root surface caries

48. CariesVaccination

49. Caries Vaccination
In rats , experimental dental caries have been reduced by
immunizing with cell-­‐wall associated an4gens or
glucosyltransferase from S.mutans

50. Caries Vaccination
The following mechanism have been suggested
! Inhib4on by secretory IgA of bacterial coloniza4on of
teeth
! Interference with bacterial metabolism
! Enhancement of phagocy4c ac4vity in gingival crevices

51. Summary
! Dental Caries is a mul4factorial disease, strongly
associated with the dental plaque
! Ecological Plaque Hypothesis caries forms as a result of
disturbance in the normal balance of Oral Biota
! The main factors involved are suscep4ble tooth surfaces,
4me, sugar substrate and plaque bacteria
! Pits & fissure are the most suscep4ble areas
! Frequency of sugar intake is more decisive than total
consump4on

52. Summary
! Sucrose is the most cariogenic sugar
! Mutans streptococci are implicated in ini4a4on of pits &
fissure and root caries
! Lactobacillus spp are associated with progression of
caries

53. References
! Philip D. Marsh, Michael V Mar4n, Plaque mediated
diseases-­‐ Dental Caries and Periodontal diseases in Oral
Microbiology, 5th Edi4on, Churchil Livingstone, 2009, pp
104-­‐117
! J. Bagg, T. W. Macfarlane, I. R. Poxton and A. J. Smith,
Dental Caries in Essen4als of Microbiology for Dental
Students, 2nd Edi4on, Oxford University Press, 2006
pp238-­‐248