Microbiology III

4 Benefits of living in a community of like-minded bacteria

• mutual adhesion

• mutual protection

• mutual metabolism

• ecological niches

Consequences of not brushing your teeth

• most ended up with mod gingivitis

• earlier tooth loss

• edentulism (toothless) was common past 50

Formation of plaque

Acquired pellicle turns into microbial biofilm

Microbes serves as:

Nucleation sites for precipitation of Ca2+ salts—>mineralized plaque—>calculus

Urease effect on calculus formation

Promotes calculus formation by increasing pH

Calculus formation is influenced by: (4)

Salivary flow, diet, and chelators

Mineralized organic material in calculus

70-80% of calculus composition, mostly calcium phosphates ,contains hydroxyapatite and brushite

Principle organic component of calculus

~15% of calculus composition

• most of organic component is protein, then carbs then lipids

Brushite is:

Immature calculus

WHT/HAP are present:

Lower in supragingival calculus

Factors favoring calculus formation (5)

• proximity to salivary glands (max. 1st molars, mand. ling of incisors)

• POH-increased microbes and certain bacteria

• High salivary flow rate

• Calcium and phosphate rich diet that neutralizes acids

• attachment to salivary proteins

Factors to disrupt calculus formation (5)

• Good OH

• regular teeth cleanings

• diet

• antimicrobial mouth rinse

• anticalculus agents: chelating agents, zinc ions, pyrophosphate

Socransky’s microbial complex

Groups of bacteria that are found in dental plaque, and their association with periodontal health/disease

Orange complex

• mature plaque

• gingivitis, inflammation localized at gingival margin

• lots of bacteria

Fusobacterium nucleatum

• gram negative anaerobe

• immediate colonizer

• presence signals increased risk of developing periodontitis, but doesn’t cause

Prevotella intermedia

• gram negative rod

• periodontal diseases

• multiple virulence factors

Red complex

• has porphyromonas gingivalis

• has tannerella forsythia

• has oral spirochetes

Porphyromonas gingivalis

• anaerobic, rod, produces black pigment

• associated with chronic periodontitis and abscesses

• potential link to atheosclerosis

P.g. Endotoxin

• made from gram-negative outer membrane

• Poly saccharide component:

  • highly variable between species

• Lipid component:

  • recognizes toll like receptor (TLR4—>inflammation)

Tennerella forsythia

• anaerobic, rod

• associated with periodontitis bone loss

• invades epithelial cells

Oral spirochetes

• associated with chronic periodontitis and necrotizing periodontal disease

• deeply invades periodontal tissue

Aggressive periodontitis is associated with:

Non-red complex bacteria

Generalize form of periodontitis is associated with:

Immune defects

Aggregatinbacter actinomycetemcomitans

• member of green complex

• aggressive periodontitis (brain/lung abcesses)

• invades epithelium

Epithelium protects by: (5)

• physical barrier

• constantly shedding

• having few desmosomes at the junctional epitheium

• having antimicrobial peptides

• having pathogen sensing

Saliva protects by: (7)

• having antimicrobial peptides

• decoy binding proteins

• buffering capacity

• calcium supersaturation

• chelating agents

• epithelial growth factor

• Salivary IgA

Indicators of good periodontal health (4)

• minimal probing depth

• no bleeding on probing

• no redness

• Stippling (microscopic elevations/depressions on gingiva)

Periodontal health issue indicators in humans: (4)

• minimal sulcus

• some inflammation always present (histological)

• neutrophils at sulcus base

• no Rete pegs in JE

Stage I Gingival inflammation

• subclinical gingivitis

• epithelial and leukocyte cell activation stimulates endothelial cells

• increased vasodilation and blood flow

• collagen changes

• NOT clinically evident

Stage II Gingival inflammation

• early gingivitis

• clinical signs: erythema

• Rete pegs make are JE

Stage III Gingival inflammation

• established, can be a ‘gingival pocket‘

• predominance of lymphocytes (B and plasma cells)

• extensive tissue destruction

• slowed blood flow, engorged capillaries

Stage IV gingival inflammation

• similar microscopic appearance to stage III

• further collagen fiber destruction

• bone loss

• clinical signs: severe inflammation and ‘periodontal pocket‘

In humans, neutrophils are found:

In the marginal tissue and sulcus

When do neutrophils migrate to sulcus?

When there’s plaque

Neutrophils defend the sulcus using: (5)

• respiratory burst (makes peroxide)

• antimicrobial peptides/enzymes

• iron chelators

• phagocytes

• neutrophil extracellular traps

Circumstances where neutrophils can be harmful

• hyperactivity

• chronic inflammation leading to tissue destruction

• lack of or having impaired neutrophils

Celsus’s tetrad of infalmmation

Rubor (redness)

Tumor (swelling)

Dolor (pain)

Calor (temerature rise)

Functio laesa (function loss)

Periodontal disease redness=

gingival erythema, gingival bleeding

Periodontal disease swelling

gingival edema

Periodontal disease heat

elevated gingival temperature

Periodontal loss of function

Attachment loss and sequelae

Redness, swelling, and heat are from:

increased blood flow in inflamed periodontal tissue

Bleeding on probing is important because:

• bleeding=sign of inflammation (healthy gums don’t bleed)

• bleeding sites have worse probing depth, attachment loss, and bone/tooth loss

Smokers and bleeding on probing

Smokers have less bleeding on probing

Periodontal initial response consists of: (5)

• epithelium IL-1

• fibroblasts: IL-1, IL-8

• Endothelium: L-selectin, IL-8, NO

• Mast cells: histamine, prostaglandins

• neutrophils: IL-1, PGE2, TNG-alpha, MMP-9

Vasodilation causes:

• redness

  • increased blood flow to tissue

  • increases capillary diameter

  • stasis of RBCs

• edema

  • leakage of fluid into tissue

  • cells leaving tissue

Gingival bleeding causes: (5)

• increased number of capillaries

• enlarged and leaky capillaries

• tissue fragility

• microulcerations

• +probing=bleeding on probing

Fever and periodontal diseases

• bacterial products stimulate neutrophils

• neutrophils release cytokines (IL-1, TNF-alpha, IL-6)

• PGE2 signal increases body temp

Fever not a sign of periodontal disease EXCEPT when:

• necrotizing ulcerative gingivitis/periodontitis

• severe abscesses of periodontium

Gingival temperature rises as a result of:

• presence of BOP plaque, calculus, crevicular fluid flow

• inc inflammation—>inc flow of warm blood to ginigiva—>inc temp in gingiva

Reasons for tooth loss (4)

Caries, periodontitis, trauma/accidents, dentists

Attachment loss is causes by:

Collagen breakdown

Attachment comes from:

= periodontal and gingival collagen fibers

inserted as Sharpey’s fibers into cementum and bone

anchors teeth and gingiva to bone

Tissue cells that break down ECM (4)

Neutrophils, sulcular epithelium, fibroblasts, macrophages

Periodontal tissue produces:

ECM-destroying enzymes

Inflammation effects ___, then ___, then ___

First crestal bone, then facial and interstitial spaces, then the PDL

BOP (bleeding on probing) is an indicator of:

Future attachment loss

Does all gingivitis progress to periodontitis?

No, unknown when and why it progresses

Image of crestal bone resorption

Bone loss is another form of:

ECM matrix breakdown

To break down organic component of bone you need:

• MMPs and bacterial proteases

• collagen and extracellular matrix proteins

To break down mineral component of bone you need:

• dissolution of hydroxyapatite in low pH env

• Osteoclasts (tipping of RANK/OPG balance)

Under homeostatic conditions:

Favor OPG over RANKL (more bone formation)

Under inflammatory conditions:

Favor RANKL over OPG (more bone breakdown)

Osteoclasts are activated by: (2)

• TNF-alpha and IL-1-beta

• Which are activated by IFN-gamma and IL-17 (from Th1 and Th17 resp)

Osteoclast mediator: LPS

general inflammation

Osteoclast mediator: IL-1

• increases # of mature osteoclasts= more reabsorption

• general inflammation, Th1 response

Osteoclast mediator: TNF-alpha

• increases differentiation, osterclastogenesis, and resorption

• general inflammation, Th1 response

Osteoclast mediator: IL-6

• increases # of osteoclasts

• induces RANKL expression

Osteoclast mediator: IL-8

• promotes PMN infiltration (PMN=leukocyte of innate immunity)

Osteoclast mediator: IL-10

• promotes PMN infiltration

Osteoclast mediator: MCP-1

• stimulates recruitment of precursors

Osteoclast mediator: PTH and PTH related protein

Increases bone resorption

Osteoclast mediator: vitamin D3

increases bone resorption

Osteoclast mediator: RANKL

• induces osteoclast differentiation and bone resorption

Can bone form during periodontitis?

Yes: (bone remodels during bone loss)

• buttressing bone: bone adapts to increases occlusal force by growing more bone

Adaptive immune cells that contribute to periodontal destruction

Th17 and gingival plasma cells

Th17 cells

• chronically activate neutrophils

• favor osteoclast activation (RANKL production)

Gingival plasma cells

• most common cell in periodontally inflamed tissue

• favor osteoclast activation (RANKL production)

Factors influencing bone loss:

• alignment of teeth

• root position, proximity to another root surface

• thickness of facial/lingual bone

• thickness, width and crestal angulation of interdental septa

Systemic conditions that affect/destroy bone:

• osteoporosis

• hyperparathyroidism

• leukemia

• histiocytosis X

Horizontal bone loss

• typical pattern of periodontal bone loss

• bone level parallel to CEJ, but distance increases over time

Vertical bone defects

• result of lack of bone thickness

• usually seen on interproximal area

Image of vertical bone loss

Halitosis is:

bad breath, bad taste

Periodontal disease odor:

• from release of volatile sulfur compounds

• metabolic byproduct and virulence factor

Necrosis

• necrotizing ulcerative periodontal disease mechanism is unknown

Tissue sloughing (peelign)

• severe inflammation

• autoimmune disease (Ab directed against basement membrane)