This document discusses oral microbiology and the microorganisms associated with dental diseases. It begins by introducing the normal oral microflora and then discusses the microflora found in dental caries, root canals, and the periodontal pocket. It explores the importance of studying bacterial pathogenesis and how microbiology relates to dentistry. Key findings are that dental caries and periodontal disease are caused by shifts in the microbial environment that allow pathogenic bacteria like Streptococcus mutans and Porphyromonas gingivalis to dominate. Maintaining a balanced oral microbiome is important for oral health.
Dental & periodontal disease dr . ihsan alsaimary
1. Prof dr. Ihsan Edan Alsaimary
department of microbiology – college of medicine – university of basrah – mobile: 07801410838
e.mail : ihsanalsaimary@gmail.com
Dental and Periodontal Disease
2. Oral Microbiology
Normal Oral Microflora
Microflora of Dental Caries
Microflora of the Root Canal ( endo )
Microflora of the Periodontal Pocket (perio)
3. The Importance of Studying Bacterial
Pathogenesis
• A human body has 1 X 1013 eukaryotic
cells and 1 X 1014 bacterial cells
• Microbial infections are the most epidemic
diseases and the leading cause of death
– Diarrhea and enteric bacteria
– Tuberculosis and Mycobacterium
– Ulcer and Helicobacter infection
– Urinary tract infection
– STD
How microbiology is related to dentistry?
4.
5. The first microbes observed: Anton
Van Leeuwenhoek (1632-1723)
Developed the microscope and was the
first to discover oral bacterial flora:
“I didn’t clean my teeth for three
days and then took the material that
had lodged in small amounts on the
gums above my front teeth…. I
found a few living animalcules..”
6.
7. What causes dental caries?
• Pre-microbiology era
– Dental caries is the death (decay) of a
tissue
• Microbiology period era
– Dental caries is a microbe related disease
10. How to identify bacteria within dental
plaque?
• Culture methods
take saliva or plaque, dilute and plate on appropriate
plates, grow to single colonies,
identify by microscopic and biochemical methods
• 16S DNA/RNA based detection
use 2 oligo-nucleotide primers universal to ALL
bacteria 16S rDNA, PCR amplification of the total
saliva or plaque DNA pool, clone the PCR product
and sequence, phylogenetic analysis using computer
database
12. Supragingival Plaque
Predominant cultivable microflora obtained
from occlusal fissures
Specie Median percentage Range % isolation
S.mutans 25 0-86 70
S. Sanguis 1 0-15 50
S. Oralis 0 0-13 30
S. Anginosus 0 0-3 10
A.Naeslundi 3 0-44 70
L. Casei 0 0-10 10
L. plantarum 0 0-29 10
13. Subgingival plaque
Bacteria Mean percentage Frequency %
Streptococcus 23 100
Actinomyces 42 100
Prevotella 8 93
Veilonella 14 93
S. Sanguis 6 86
A. naeslandii 19 97
14. Current knowledge about bacteria in plaque
• Both culture and DNA/RNA-based techniques
are used for identification and quantification of
oral microorganisms
• Overall, there are ~700 species exist in the oral
cavity
• ~20% of these 700 species have been cultivated
• Both Gram-positive and Gram-negative exist
• Some archaea are found
• Most anaerobic or facultative anaerobic
Who are the bad guys?
15. The first isolation of cariogenic
bacteria by Clark, 1924
Isolation of cariogenic bacteria from
caries lesions
Discovery of Mutans streptococci
16. Keyes and Fitzgerald, 1962’s
Re-isolation of “Mutans streptococci”:
• Streptococcus mutans (human) (same
species Clark isolated in England in 1924)
• Streptococcus sobrinus (human)
• Streptococcus rattus (rats)
• Streptococcus cricetus
• Streptococcus ferus
• Streptococcus macacae
• Streptococcus downeii
17.
18. The “cariogenic bacteria” – bacteria associated with
dental caries
Actinomyces – early colonizers and root caries
• A. odontolyticus
• A. naeslundii genospecies 2
• A. isrealii
• A. gerensceriae
Lactobacilli (L. casei) – caries progression
Mutans streptococci (S. mutans) – caries initiation
19. The virulence factors of
cariogenic bacteria
1. Acid production (acidogenicity)
• Lower the pH to below 5.5, the critical pH, drives
the dissolution of calcium phosphate(hydroxyapatite
of the tooth enamel
• Inhibit the growth of beneficial bacteria, promote
the growth of aciduric bacteria.
• Further lower the pH, promote progression of the
carious lesion
20. 2. Acid tolerance (aciduricity)
Allows the cariogenic bacteria to thrive under acidic
conditions while other beneficial bacteria are
inhibited. This results in dominance of the plaque by
cariogenic bacteria
21. Glucan formation
Allows the cariogenic bacteria to stick onto the teeth
and form a biofilm
Glucan mediated biofilms are more resistant
tomechanical removal
Bacteria in these biofilms are more resistant to
antimicrobial treatments
23. Dental caries is a bacterial infectious
disease
Transmission
• Mother – Child (vertical transmission) -true
for most oral bacteria
• Persons in close contact to the baby
• Horizontal transfer (between spouses) is
rare, only observed in some periodontal
pathogens (i.e. P.gingivalis)
The most common vehicle is
saliva
24. New problem: everybody has S. mutans!
So…….Why not every body who has S.
mutans develop dental caries?
S. mutans is not present in high portions
Acid produced is neutralized by urea or ammonia
produced by other bacteria in the plaque
S. mutans is away from the tooth surface so acid
produced is diffused
25. The ecologic plaque hypothesis
Both pathogenic and commensal (nonharmful)
bacteria exist in a natural plaque. At sound site, the
pathogenic bacteria may exist in low numbers to
cause any clinical effect, or they may exist in higher
numbers, but the acid produced is neutralized by the
action of other bacteria.
Disease is a result of a shift in the balance of the
residence microflora driven by a change in the local
environment (frequent sugar intake etc).
28. Complex
genetic makeup
of man
Human genome
only has
200,000 genes
Each oral bacterium 2000 to 6000 genes.
• With over 1000000 bactrial genes in the oral cavity
32. Dental plaque biofilm infection
Ecological point of view
Ecological community evolved for survival as a whole
Complex community of more than 400 bacterial species
Dynamic equilibrium between bacteria and a
host defense
Adopted survival strategies favoring growth in plaque
“Selection” of “pathogenic” bacteria among microbial community
Selection pressure coupled to environmental changes
Disturbed equilibrium leading to pathology
Opportunistic infection
33. Dental Plaque Hypothesis`
Specific plaque hypothesis
Non-specific plaque hypothesis
Intermediate or ecological plaque hypothesis
Qualitatively distinct bacterial composition:
healthy vs. disease (subjects, sites)
Pathogenic shift; disturbed equilibrium
A small group of bacteria: Gram (-), anaerobic
36. Difficulties in defining Periodontal Pathogens
Classical Koch’s Postulate
designed for monoinfections
Technical difficulties
Conceptual problems
Data analysis
From Socransky et al. J. Clin Periodontol, 14:588-593, 1987
37. 100 Years of Periodontal Microbiology
Specific
Non-specific
Specific
1890
1930
1970
Fusoformis fusiformis (1890)
Streptococci (1906)
Spirochetes (1912)
Amoeba (1915)
Mixed Infection - Fusospirochetal (1930)
Mixed Infection - with Black pigmented
Bacteroides (1955)
Spirochete - ANUG (1965)
A. viscosus (1969)
A. actinomycetemcomitans (1976)
P. gingivalis (1980)
P. intermedia (1980)
C. rectus
B. forsythus1990
41. Microbial complexes in biofilms
Not randomly exist, rather as specific
associations among bacterial species
Socransky et al. (1998) examined over 13,000
subgingival plaque samples from 185 adults, and
identified six specific microbial groups of
bacterial species
42. S. mitus
S. oralis
S. sanguis
Streptococcus sp.
S. gordonii
S. intermedius
S. noxia
A. antino. b
Subgingival Microbial Complex
P. intermedia
P. nigrescens
P. micros
F. nuc. nucleatum
F. nuc. vincentil
F. nuc. polymorphum
F. periodonticum
P. gingivalis
B. forsythus
T. denticola
V. parvula
A. odontolyticus
E. corrodens
C. gingivalis
C. sputigena
C. ochracea
C. concisus
A. actino. a
Actinomyces
species
S. constellatus
C. gracilis
C. rectus
E. nodatum
C. showae
43. Criteria for defining putative
periodontal pathogens
Association with disease
Elimination should result in clinical
improvement
Host response to pathogens
Virulence factors
Animal studies demonstrating tissue destruction
45. Actinobacillus actinomycetemcomitans
First recognized as a possible periodontal pathogen in LJP (Newman et al.,
1976)
Majority of LJP patients have high Ab titers against Aa
Successful therapy lead to elimination or significant decrease of the species
Potential virulence factors; leukotoxin, cytolethal distending toxin, invasion,
apoptosis
Induce disease in experimental animals
Eleveated in “active lesions”, compared with non-progressing sites
Virulent clonal type of Aa
LJP patients exhibit specific RFLP pattern, while healthy pts exhibit other
patterns
Increased leukotoxin production by Aa strains isolated from families of African
origin, a 530 bp deletion in the promoter of the leukotoxin gene operon
22.5 X more likely to convert to LJP than who had Aa strains with the full length
leukotoxin promoter region
Associated with refractory periodontitis in adult patients
46. Porphyromonas gingivalis
Gram (-), anaerobic, asaccharolytic, black-pigmented
bacterium
Suspected periodontopathic microorganism
Association
Elevated in periodontal lesions, rare in health
Elimination or suppression resulted in successful therapy
Immunological correlation
Elevated systemic and local antibody in periodontitis
Animal pathogenicity
Monkey, dog, and rodent models
Putative virulent factors
47. Spirochetes
G (-), anaerobic, spiral, highly motile
ANUG
Increased numbers in deep periodontal pockets
Difficulty in distinguishing individual species
15 subgingival spirochetes described
Obscure classification - Small, medium, or large
T. denticola
More common in diseased, subgingival site
Uncultivated “pathogen-related oral spirochetes
Detected by Ab cross-reactivity to T. pallidum antibody
48. Prevotella intermedia/Prevotella nigrescens
Strains of “P. intermedia” separated into two
species, P. intermedia and P. nigrescins
Hemagglutination activity
Adherence activity
Induce alveolar bone loss
In certain forms of periodontitis
Successful therapy leads to decrease in P.
intermedia
49. G(-), anaerobic, spindle-shaped rod
Has been recognized as part of the subgingival
microbiota for over 100 years
The most common isolate found in cultural studies of
subgingival plaque samples:7-10% of total isolates
Prevalent in subjects with periodontitis and periodontal
abscess
Invasion of epithelial cell
Apoptosis activity
Fusobacterium nucleatum
50. Other species
Campylobacter rectus
Produce leukotoxin
Contains the S-layer
Stimulate gingival fibroblast to produce IL-6 and IL-8
Eikenella corrodens
Peptostreptococcus micros
G(+), anaerobic, small asaccharolytic
Long been associated with mixed anaerobic infections
Selemonas species
Curved shape, tumbling motility
S. noxia found in deep pockets, conversion from healthy to disease site
Eubacterium specues
The “milleri” streptococci
S. anginosus, S. constellatus, S. intermedius
51. Periodontal disease as an infectious disease
Events in all infectious disease:
Encounter
Entry
Spread
Multiplication
Damage
Outcome
52. Virulence factors
Gene products that enhance a
microorganism’s potential to cause disease
Involved in all steps of pathogenicity
Attach to or enter host tissue
Evade host responses
Proliferate
Damage the host
Transmit itself to new hosts
Define “the pathogenic personality”
Virulence genes
53. Expression of virulence factors
Constitutive
Under specific environmental signals
Can be identified by mimicking environmental signals
in the laboratory
Many virulence-associated genes are coordinately
regulated by environmental signals
Only in vivo
Cannot be identified in the laboratory
Anthrax toxin, cholera toxin
54. Identifying virulence factors
Microbiological and biochemical studies
In vitro isolation and characterization
In vivo systems
Genetic studies
Study of genes involved in virulence
Genetic transmission system
Recombinant DNA technology
Isogenic mutants
Molecular form of Koch’s postulates (Falkow)
56. Virulence factors of P. gingivalis
Involved in colonization and attachment
Fimbriae, hemagglutinins, OMPs, and vesicles
Involved in evading (modulating) host responses
Ig and complement proteases, LPS, capsule, other
antiphagocytic products
Involved in multiplying
Proteinases, hemolysins
Involved in damaging host tissues and spreading
Proteinases (Arg-, Lys-gingipains), Collagenase, trypsin-like
activity, fibrinolytic , keratinolytic, and other hydrolytic activities
57. An Example of Studying Microbial Pathogenesis
Hypothesis
S-layer of T. forsythia is a
virulence factor
58. Tannerella forsythia
T. forsythia is a gram-negative, filament-shaped,
non-motile, non-pigmented oral bacterium.
T. forsythia has been associated with advanced and
recurrent periodontitis
Implicated as one of three strong candidates for
etiologic agents of periodontal disease
Actinobacillus actinomycemtemcomitans
Porphyromonas gingivalis
Tannerella forsythia
59. Proving the S-layer as a virulence factor
Studying phenotype of the S-layer
Hemagglutination
Adherence, invasion
Studying the S-layer genes
Cloning the S-layer genes
Construction of the S-layer isogenic mutants
Complementing the mutants with the S-layer genes
60. Proving association of genes with virulence
Molecular form of Koch's Postulates
The phenotype under investigation should be associated
significantly more often with pathogenic organism than
with nonpathogenic member or strain.
Specific inactivation of gene (or genes) associated with
the suspected virulence trait should lead to a
measurable decrease in virulence.
Restoration of full pathogenicity should accompany
replacement of the mutated gene with the wild type
original.
62. Introduction
A chronic bacterial infection that affects the gums and
bone supporting the teeth
Periodontal diseases range from simple gum
inflammation to serious disease that results in major
damage to the soft tissue and bone that support the
teeth.
63.
64. Types
Gingivitis
Early stage of disease
Red, swollen, and
bleeding gums
Usually reversible through
good oral hygiene and
preventive care
Not uncommon in young
adults and even youth
Periodontitis
Advanced stage of disease
Chronic inflammatory
response leading to
irreversible destruction of
tissues and bone that
support the teeth
Treatment requires more
aggressive surgical care
65. What Causes Periodontal Disease
Our mouths are full of bacteria. These bacteria, along
with mucus and other particles, constantly form a
sticky, colorless “plaque” on teeth.
Brushing and flossing help get rid of plaque.
Plaque that is not removed can harden and form
“tartar” that brushing doesn’t clean.
Only a professional cleaning by a dentist or dental
hygienist can remove tartar.
66. Risk Factors
Smoking
Hormonal Changes in
girls/women
Diabetes
Other Illness
Diseases like cancer or AIDS and
their treatments can also negatively
affect the health of gums.
Genetic Susceptibility
Medications
There are hundreds of
prescription and over the
counter medications that
can reduce the flow of
saliva, which has a
protective effect on the
mouth. Without enough
saliva, the mouth is
vulnerable to infections
such as gum disease.
And some medicines can
cause abnormal overgrowth
of the gum tissue; this can
make it difficult to keep
teeth and gums clean.
67. Symptoms of Periodontal Disease
Bad breath that won’t go away
Red or swollen gums
Tender or bleeding gums
Painful chewing
Loose teeth
Sensitive teeth
Receding gums or longer appearing teeth
68.
69.
70. Treatment of Periodontal Disease
Deep Cleaning (Scalling and Root Planning)
Medications
Surgical Treatement
71. Deep Cleaning (Scalling and Root
Planning)
The dentist, periodontist, or dental hygienist
removes the plaque through a deep-cleaning method
called scaling and root planing.
Scaling means scraping off the tartar from above
and below the gum line.
Root planing gets rid of rough spots on the tooth root
where the germs gather, and helps remove bacteria
that contribute to the disease.
In some cases a laser may be used to remove plaque
and tartar. This procedure can result in less bleeding,
swelling, and discomfort compared to traditional
deep cleaning methods.
72. Medications
Prescription antimicrobial mouthrinse
A prescription mouthrinse containing an
antimicrobial called chlorhexidine
To control bacteria when treating gingivitis and after
gum surgery
It’s used like a regular mouthwash.
Antiseptic chip
A tiny piece of gelatin filled with the medicine
chlorhexidine
To control bacteria and reduce the size of periodontal
pockets
73. Medications Cont’d
Antibiotic gel
A gel that contains the antibiotic doxycycline
To control bacteria and reduce the size of periodontal
pockets
The periodontist puts it in the pockets after scaling and root
planing. The antibiotic is released slowly over a period of
about seven days.
Antibiotic microspheres
Tiny, round particles that contain the antibiotic minocycline
To control bacteria and reduce the size of periodontal
pockets
The periodontist puts the microspheres into the pockets after
74. Medications Cont’d
Enzyme suppressant
A low dose of the medication doxycycline that keeps
destructive enzymes in check
To hold back the body’s enzyme response — If not
controlled, certain enzymes can break down gum tissue
This medication is in tablet form. It is used in combination
with scaling and root planing.
Oral antibiotics
Antibiotic tablets or capsules
For the short term treatment of an acute or locally persistent
periodontal infection
These come as tablets or capsules and are taken by mouth.
75. Surgical Treatment
Flap Surgery
A dentist or periodontist may perform flap surgery to
remove tartar deposits in deep pockets or to reduce
the periodontal pocket and make it easier for the
patient, dentist, and hygienist to keep the area clean.
This common surgery involves lifting back the
gums and removing the tartar. The gums are then
sutured back in place so that the tissue fits around
the tooth again.
76. Surgical Treatment Cont’d
Bone and Tissue Graft
In this, Dentist regenerate any bone or gum tissue lost
to periodontitis.
77. Maxillary Central Incisors
Bone loss on radiographs.
A. A. Slight interproximal bone loss.
B. B. Greater bone loss is seen in advanced periodontal disease.
A
B
78. Prevent Periodontal Disease
Practice Good Dental Hygiene
Consistent good dental hygiene can help prevent
gingivitis and periodontitis.
Brush twice daily with a fluoride toothpaste (be sure to replace toothbrushes
every 1 - 3 months).
Clean between the teeth with floss or an interdental cleaner.
Eat a well-balanced diet and limit between meal snacks.
Have regular visits with a dentist for teeth cleaning and oral examinations.
If you smoke, you should quit. Smoking is a major risk factor for gum disease.
79. Summary
Periodontitis is a disease involving pathology of
one or more of the four components of the
periodontium
Periodontal disease is an umbrella term for
several clinically similar types of diseases
