Topic 4: Microscopic Anatomy of the Gingiva & PDL

dentogingival junction

attachment/junction of the gingiva & the tooth

dentogingival unit

functional unit of tissues which provides junction

dentogingival unit provides junction of the:

• junctional epithelium

• dentogingival fibers

significance of dentogingival junction

maintaining the periodontium:

• creates a firm attachment of soft tissue to hard tissue

• forms a seal/protective barrier → separates crown from root environment

three types of epithelium:

• surface

• sulcular

• junctional

surface ET characteristics: 4

• thick

• highly corrugated

• keratinized (cells differentiate)

• many desmosomes, fewer intercellular spaces

sulcular epithelium

epithelium lining of the gingival sulcus

sulcular epithelium characteristics: 5

• not attached to the tooth

• thin

• non-keratinized

• straight interface between ET and the LP of the gingiva

• permeable barrier

in inflamed gingiva, what causes bleeding upon probing?

micro-ulcerations in the sulcular epithelium

sulcular fluid

fluid that flows in the sulcus from the CT

another terms for sulcular fluid

gingival/ crevicular fluid

functions of crevicular fluid: 2

• protective: flushes out the sulcus

• cleans: has antimicrobials (iga proteins, leukocytes) that are delivered to the site

junctional epithelium attaches to where on the tooth?

enamel and cementum

dentogingival fibers attaches to where on the tooth?

cementum

gingival sulcus characteristics:

• shallow groove between the free gingiva & tooth surface

• in health 1-3 mm deep

base of gingival sulcus

junctional epithelium

junctional epithelium

band of epithelium that attaches (the gingiva) to the tooth surface (enamel/cementum) in the cervical area

another term for junctional epithelium

attachment epithelium

structures provided by the junctional epithelium that form the epithelium attachment to the tooth:

• hemidesmosomes

• internal basal lamina

microscopic features of junctional epithelium:

• nonkeratinized ET

• non-distinct rete pegs/CT papillae

• basal layer: cells do not mature as they migrate towards the surface

• thin ET

• more prominent/large intercellular spaces

• fewer # of desmosomes

microscopic features of oral epithelium of the gingiva:

• keratinized ET

• distinct rete pegs/CT papillae

• basal layer: cells mature/differentiate as they migrate towards the surface

• thick ET

• less prominent/small intercellular spaces

• greater # of desmosomes

another term for sulcular epithelium

crevicular epithelium

superior/coronal boundary to the junctional epithelium

gingival sulcus

inferior/apical boundary to the junctional epithelium

dentogingival fibers

external boundary of the junctional epithelium

lamina propria of the gingiva

internal boundary of the junctional epithelium

tooth surface

biological width

width of the dentogingival junction = the natural distance from the base of the sulcus to the alveolar bone

biological width =

1mm junctional epithelium + 1mm dentogingival fibers

the JE is ___ to microorganisms and their products

permeable

the JE migrates ___ when a periodontal pocket forms

apically

the JE is always located ___ to the attachment of the dentogingival fibers to the tooth

coronally

circular/ circumferential fibers attachment location

LP of gingiva; rings around the cervical

circular/ circumferential fibers function

holds the gingiva snugly against the tooth (drawstring bag)

dentogingival fibers attachment location

cementum → free gingiva + attached gingiva

dentogingival fibers function

anchors the gingiva firmly to the cementum & provides stability by resisting gingival displacement

subgroups of dentogingival fibers: 3

1. free gingival fibers

2. attached gingival fibers

3. dentoperiosteal fibers

free gingival fibers

cementum → crest of free gingiva

attached gingival fibers

cementum → outer surface of attached gingiva

dentoperiosteal fibers

cementum → LP of attached gingiva → periosteum of alveolar bone

transseptal fibers

(above the crest) cementum of one tooth → cementum of adjacent tooth (M/D aspect)

transseptal fibers function

maintains adjacent teeth to be in proper alignment by resisting separation by lateral forces

alveologingival fibers attachment location

alveolar crest → LP of gingiva

alveologingival fibers function

resist movement by attachment to alveolar bone

periostogingival fibers

periosteum of alveolar bone → LP of attached gingiva (Bu/Li aspect)

periostogingival fibers function

resist movement by attachment to alveolar bone

what two gingival fibers have the same function?

alveologingival fibers & periostogingival fibers

fibers of the gingiva:

• dentogingival

• alveolargingival

• circular/circumferential

• periostogingival

• transseptal

periodontal ligament

fibrous CT surrounding the root and attaches tooth to the alveolar bone

the PDL is apart of the ___

attachment apparatus

Periodontium components: 4

1. gingiva

2. PDL

3. cementum

4. alveolar bone

attachment apparatus

specialized tissues that act as a attachment unit of the periodontium

components of attachment apparatus: 3

• cementum

• PDL

• alveolar process/bone

PDL additional functions: 5

• absorbs & distributes forces from chewing

• Sensory info: touch & pressure

• allows slight movement of the tooth w/o getting damaged

• proprioception

• supplies nutrients to surrounding periodontal tissues

PDL location

below the crest of the alveolar bone: between the cementum and alveolar bone

PDL characteristics: 2

• ~0.25 mm wide

• hourglass shape

PDL is organized by: 2

• principle fibers

• interstital areas

what type of fiber are the principle fibers in the PDL?

dense CT: Type I collagen fibers in dense bundles → mechanical support

what type of fiber are the interstitial areas in the PDL?

loose CT: Type III collagen, blood vessels, nerves → biologic support

principle fibers groups of the PDL:

• alveolar crest

• horizontal

• oblique

• apical

• interradicular

intrusive force

towards the periodontium ⬇

extrusive force

away from the periodontium ⬆

lateral/horizontal/tilting force

side to side ⬅➡

rotational force

abfraction

alveolar crest fibers

most coronal group of fibers assisting the other fibers in their functions

oblique fibers

main fiber group bearing brunt of instrusive forces during masticatory; function as shock absorbers; bulk of the fibers

horizontal & apical fibers

fibers which prevent a tooth from tilting in its socket by resisting lateral movements

apical fibers: 2

• resist extrusive forces by preventing the tooth from being pulled from its bony socket

• resist lateral movements by preventing the tooth from tilting in its socket

interradicular fibers

unique to multirooted teeth; assist in resisting extrusive & lateral movements

fibers that aid in rotational forces

all principle fibers

sharpey’s fibers

terminal portions of the principle fibers which insert into the cementum on one side and alveolar bone proper on the other side

Type I collagen fibers

• comprise the principle fibers of the PDL

• comprise the gingival fiber groups

Type III collagen fibers

delicate reticulin fibers found in the interstitial areas

elastic fibers

not present in the PDL

oxytalan fibers

• anchor blood vessels in the interstitial areas

• increase the structural integrity of the PDL by supporting the principle fibers

cells of the PDL:

• fibroblasts

• mast cells

• macrophages

• cemento-blasts/clasts

• ostero-blasts/clasts

• wandering/defense cells

• mesenchymal stem cells

• rest of Malassez

fibroblasts

main cell of the PDL, produce & destroys the fibers and ground substance

fibroblasts secrete ___

Matric Metalloproteinases (MMPs)

mast cells

release granules of histamine and other biochemical mediators when injured

macrophages

phagocytize microorganisms and debris

cementoblasts

produce cementum

cementoclasts

destroys cementum given the right stimulus

osteoblasts

produces alveolar bone

osteoclasts

destroys alveolar bone

wandering/defense cells

leukocytes which migrate to areas to defend the tissue when injured

mesenchymal stem cells

undifferentiated “blank” connective tissue cells that can be triggered to specialize when needed

rests of malassez

groups of inactive/latent epithelial cells remaining in the PDL after root development

clinical significance of Rest of Malassez

under certain circumstances can be stimulated → form a cysts/ tumor in the jaw

cementicles

calcified masses composed of cementum that lie free, attach to the tooth surface, or become embedded within the PDL

shape of cementicles

small: spherical or ovoid

anastomosis

natural connection between two blood vessels

proprioception

subconscious ability to sense movement, touch, pressure, position, and forces

supraperiosteal arteries

provide the main blood supply to the gingiva (Bu & Li aspect)

intra-alveolar arteries

• provides the main blood supply to the PDL

• supply the interdental gingiva, sulcus, & col areas

• anastomoses with gingival blood vessels

apical arteries

• anastomoses with gingival blood vessels, supplies the PDL

• through the apical foramen

anastomose with the gingival blood supply

blood vessels from the gingiva overlap to supply the PDL

cell function in PDL

• formative function

• resorptive function (ex: osteoclasts)

Which tissue components can provide biologic support (nutritive & sensory) for the PDL?

• blood vessels

• nerves

Which tissue components can provide mechanical support for the PDL?

• fibers

• ground substance

how does the PDL provide mechanical support?:

1. contains dense CT

2. contains Type I collagen fibers → shock absorbers, resists impact of occlusal forces

3. transmits the occlusal forces to the bone

4. contains loose CT → encases/protects blood vessels & nerves in the in interstitial areas

5. maintenance of the gingival fibers

the tissues the PDL provides nourishment to:

• itself

• gingiva

• cementum

• alveolar bone