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Flashcards in Oral Histology Deck (78):

Layers of oral mucosa

California Girls String Bikinis



Basement membrane in oral mucosa

Type IV cartilage

Hemidesmosomes mediate epithelial attachment


Specialized epithelial cells of oral mucosa

Langerhans cells (may extend into the stratum Spinosum)
Merkel cells


True or false: all oral mucosa contains stratified squamous epithelium




Fibrous and keratinized
Contains stratified squamous epithelium with rete pegs
Extends from gingival margin to mucogingival junction
MGJ separates gingiva from alveolar mucosa


Chronic mouth breathing can result in pronounced ________ especially in the anterior regions

Gingival erythema


Zones of gingiva

Attached: bound to periosteum and cementum; 40% population has stippling

Free (unattached): coronal to attached gingiva, separated from tooth by gingival sulcus
Interdental papilla
Gingival col (under contact areas, nonkeratinized)


What separates the attached and unattached gingiva?

The free gingival groove

Not to be confused with the mucogingival junction that separates gingiva from alveolar mucosa


3 major types of oral epithelium

Masticatory: gingiva and hard palate; thick, keratinized stratified squamous

Lining: soft palate, alveolar mucosa, FOM, buccal mucosa, lips, ventral tongue; nonkeratinized except for lips

Specialized: dorsal tongue; thick stratified squamous with both keratinized and nonkeratinized


True or false: denture abrasion rarely causes masticatory mucosa (gingiva and hard palate) to become orthokeratinized



What is biologic width?

the length of the dentogingival junction

Average width of epithelial attachment is 0.97mm and connective tissue attachment is 1.07mm = mean biologic width of 2.04mm


Dentogingival junction

Attachment of gingiva to the tooth
Consists of epithelial and connective tissue

Forms as oral epithelium fused with reduced enamel epithelium during eruption


Dentogingival epithelium

Sulcular epithelium: stratified squamous nonkeratinized without rete pegs extending from gingival margin to junctional epithelium

Junctional epithelium: stratified to single layer nonkeratinized epithelium without rete pegs that adheres to tooth at sulcus to provide epithelial attachment to tooth
2 basal laminae (internal and external)
Note: internal does not contain type IV collagen unlike other basal lamina


Dentigingival connective tissue

Type I collagen
Other components are fibroblasts, leukocyte X, mast cells, elastic fibers, proteoglycans, and glycoproteins


Gingival fiber groups - functions

Support gingiva and aid in attachment to alveolar bone and teeth

Continuous with PDL

Resist gingival displacement


Gingival fiber groups - types

Don't confuse with PDL fibers!

Dentogingival: fan laterally from cementum into adjacent CT

Alveologingival: fan coronally from alveolar crest to adjacent CT

Dentoperiosteal: extend from cementum over alveolar crest and turn apically to insert into buccal alveolar bone

Circumferential: surround tooth in circular fashion and help prevent rotational forced


True or false: connective tissue adjacent to Sulcular and junctional epithelia generally contains a decreased inflammatory infiltrate compared to that adjacent to oral epithelium


It is higher

PMNs and other leukocyte migrate between epithelial cells into the sulcus and account for s significant portion of gingival crevicular fluid along with plasma proteins, epithelial cells, and bacteria



Elastic, avascular, 70% mineralized tissue if a yellowish color

Originated from ectomesenchyme cells of dental papilla


Dentinogenesis (mantle dentin formation)

Odontoblasts become elongated and organelles are polarized due to ameloblastic induction

Mantle dentin is formed starting st DEJ progressing in toward pulp (initial 150 micrometers of dentin)
Predentin: type I collagen and ground substance

Odontoblasts continue inward leaving odontoblastic processes (Tomes fibers) in dentinal tubules

Odontoblastic professed release matrix vesicles containing calcium that ruptured to form hydroxyapatite


Dentinogenesis (circumpulpal)

Odontoblasts secrete collagen fibrils perpendicular to odontoblastic processes

Mineralization occurs by globular calcification
Interglobular dentin = failure of fusion

Odontoblastic processes shrink to allow space for hyper mineralized peritubular dentin

Intertubular dentin makes the majority of circumpulpal dentin

Dead tracts: necrotic osteoblastic processes


Reparative dentin formation

Formed only at specific sites of injury

Type I and iii collagen produced by odontoblast-like cells from pulp


What type of shape do coronal dentinal tubules take?

S shaped

Radicular tubules are generally straight

More tubules concentrated near pulp than DEJ


Does mantle dentin or intertubular dentin have larger collagen fibrils?

Mantle dentin has large diameter fibrils


Classification of dentin by time of formation

Mantle: first 150micrometers formed close to CEJ and CDJ

Circumpulpal: dentin formed after until tooth formation is complete

Reparative: formed in response to trauma

Sclerotic: results from calcification of dentinal tubules as one ages


Classification of dentin by root completion

Primary: formed before root complete ion

Secondary: formed after root completion

Tertiary: formed in response to trauma with irregular tubules


Classification of dentin by proximity to dentinal tubules

Peritubular: hypermineralized dentin formed within perimeter of dentinal professed

Intertubular: hypomineralized dentin found between dentinal tubules

Inter globular: hypomineralized dentin between improperly fused HA globules


Dentin classification by location

Coronal: may contain interglobular dentin and dead tracts

Radicular: may contain hypomineralized Tomes granular layer


Cross striations and incremental lines of dentin

Daily imbrication line of von Ebner: daily periodic bands

Contour lines of Owen: wide rings produced by metabolic disturbances in odontogenesis that run perpendicular to dentinal tubules

Neonatal line: pronounced contour line of Owen formed during physiologic trauma at birth


What is the rate that odontoblasts move daily?

4-8 micrometers per day


Effects of aging on dentin

Increased sclerotic dentin
Increased reparative dentin
Increased dead tracts


Dentinal hypersensitivity

Myelinated nerve fibers have been found in dentinal tubules and can be stimulated

Changes in dentinal fluid pressure can affect pulp all nerve fibers directly or cause damage to odontoblasts to release inflammatory mediators in pulp


Dentinogenesis imperfecta

Autosomal dominant defects in dentin formation resulting in opalescent colored teeth with bulb shaped friend and soft dentin

Type 1: often occurs with osteogenesis imperfecta (blue sclera)
Type 2: not associated with osteogenesis imperfecta
Type 3: rare form exhibiting multiple pulp exposures of primary dentin


Dentin dysplasia

Autosomal dominant

Defect in dentin formation and pulp morphology

Normal tooth color

Root dentin affected more - roots can be short, blunt, or absent



Most calcified and brittle substance in body

Yellowish to gray white, translucent

Originated from ectoderm cells of inner enamel epithelium


Amelogenesis - enamel formation

Ameloblasts become elongated and organelles are polarized before odontoblasts

Enamel matrix is produced perpendicular to DEJ and progresses outward
Oldest enamel is located at DEJ under cusp
Ameloblastic activity occurs after mantle dentin formation

As ameloblasts retreat, Tomes professes are formed around which enamel matrix proteins are secreted


Amelogenesis - enamel maturation

Final mineralization occurs with inorganic ion influx and removal of water and protein to form HA crystals

Enamel rods are elongated units extending from width of enamel from DEJ to outer surface

Each keyhole shaped rod is formed by four ameloblasts

At cusp tips, enamel rods appear twisted and intertwined and are called gnarled enamel


What is the main protein in enamel matrix?

Amelogenin (90%)

Other proteins include enamelin and tuftelin


Enamel protection

When enamel maturation is complete, outer enamel epithelium, stratum intermedium, and stellate reticulum collapse onto ameloblastic layer to form reduced enamel epithelium

REE is worn away after tooth eruption and replaced by salivary pellucid


Cross striations and incremental lines of enamel

Daily imbrication lines: daily periodic bands

Striae of Retzius: weekly periodic bands
Perikymata: shallow depressions on enamel surface where these lines reach shreds
Disappear with age

Neonatal line: more apparent stria of Retzius during trauma at birth

Hunter-Schreger bands: light and dark zones produced only as an optical phenomenon during light microscopy of longitudinally ground sections


What is the rate of enamel production per day?

4 micrometers per day


Dentinoenamel junction

DEJ is scalloped, providing more surface area for enamel and dentin adhesion

Enamel tufts: hypocalcified enamel protein projecting a short distance into enamel

Enamel lamellae: hypocalcified enamel defects that can extend all the way to enamel surface

Enamel spindles: trapped odontoblastic processes in enamel


Effects of aging on enamel

Attrition: wear by masticatory forces

Discoloration: darker as dentin becomes more visible

Decreased permeability


Clinical implications regarding enamel

Since it is translucent, color depends on thickness

Tetracycline antibiotics can be incorporated into mineralizing tissues resulting in brownish gray banding within enamel
Drugs from this category should be avoided until age 8


Amelogenesis imperfecta

Autosomal dominant or recessive enamel defects

Hypoplastic: abnormal enamel thickness but normal hardness (defect in matrix formation)

Hypocalcified: normal thickness but soft and chalky (defect in mineralization)

Hypo maturation: normal thickness but abnormal hardness with "snow capped" incisal edged or loss of translucency (defect in maturation)


Enamel hypoplasia

Hard enamel but deficient in amount caused by defective matrix formation

Fluorosis: enamel mottling and brownish pigmentation

Nutritional deficiency: vitamin A, C, and D and calcium can lead to enamel pitting

Infections: febrile diseases at time of mealie edits can halt enamel formation leaving bands of malformed surface enamel


Congenital syphilis affect on enamel

Screwdriver incisors (Hutchinson incisors)

Globular molars (mulberry molars)

Hutchinson's triad: blindness, deafness, dental anomalies



Soft connective tissue supporting dentin

Communicated to periodontal tissues via apical foramen and accessory canals

Originate from ectomesenchyme of dental papilla


Classifications of pulp

Coronal: found in pulp horns

Radicular: found in pulp canals


Functions of pulp

Formative: mesenchymal cells form dentin

Nutritive: nourished avascular dentin

Sensory: free nerve endings

Protective: reparative dentin as needed


Zones of pulp

Odontoblastic zone: single layer of odontoblasts lining pulp chamber

Cell free zone: devoid of cells, contains Raschkows plexus of nerves and blood vessels

Cell rich zone: fibroblasts and undifferentiated mesenchymal cells

Pulp core: fibroblasts, macrophages, leukocytes, blood and lymph vessels, collagen I and iii and ground substance


Why is pulp capping more successful in younger teeth?

Large apical foramen

Highly cellular and vascular

No collateral circulation


Pulp calcifications

Denticles (pulp stones): concentric layers of mineralized tissue
True: surround dentinal tubules
False: surround dead cells or collagen
Free: located unattached to pulp chamber
Attached: attached to pulp chamber
Interstitial: embedded in pulp chamber wall

Dystrophic calcifications: calcifications of collagen bundles or collagen divers surrounding blood vessels and nerves


Affects of aging on pulp

Increase collagen fibers and calcification

Decreased pulp chamber volume, apical foramen size, cellularity, vascularity, and sensitivity



Avascular tissue about 10 micrometers thick covering Radicular dentin

Composition most closely resembles bone

Originated from ectomesenchyme cells of dental follicle


Functions of cementum

Support: provides attachment for teeth (Sharpey's fibers)

Protection: prevents root resorption during tooth movement

Formative: apical deposition accounts for continual tooth eruption and movement



Ectomesenchyme cells of dental follicle migrate through Hertwig's epithelial root sheath and orient along Radicular dentin to differentiate into cementoblasts

Resting lines: layers formed by calcification of cementum matrix

Cementoblasts become trapped in matrix and are called cementocytes in lacunae
Receive nutrients via canaliculi connected to PDL

Cementum is constantly produced at apical root
Hypercementosis: deposition of excessive cementum


Classification of cementum by formation

Primary: first formed; covers coronal cementum, is acellular, and consists of extrinsic collagen fibers

Secondary: overlies primary cementum to cover apical cementum, consists of mixed collagen fibers, can be cellular or acellular


Classification of cementum by cellularity

Cellular: contains cementocytes, cementoblasts, and cementoclasts; found in apical areas

Acellular: no cells; found in coronal areas


Classification of cementum by collagen fibers

Intrinsic fibers: produced by cementoblasts arranged parallel to tooth surface

Extrinsic fibers: produced by PDL arranged perpendicular to tooth surface
Called Sharpey's fibers when trapped in cementum

Mixed fibers: combination



5-10% of people the cementum does not reach enamel

30% of people the cementum meets enamel

60-65% of people the cementum overlaps enamel


Effects of aging on cementum

Increased cementum deposition


Clinical implications of cementum

Cementum enables orthodontic tooth movement because it is more resistant to resorption than alveolar bone


Alveolar bone

General term to describe bone that houses teeth

Interalveolar septum: bone separating 2 alveoli

Interradicular: alveolar bone btweeb roots of multi rooted teeth

Originated from ectomesenchyme cells of dental follicle


Function of alveolar bone

Support teeth


Components of alveolar bone

Alveolar bone proper: cortical bond immediately surrounding teeth into which Sharpey's fibers insert
AKA bundle bone, lamina dura, cribriform plate

Supporting alveolar bone: surrounds alveolar bone proper
Cortical and cancellous bone


Clinical implications of alveolar bone

Radio graphic appearance of lamina dura is determined by integrity and angulation of X Ray beam
Radiographic presence or absence of crested lamina has no correlation with periodontal attachment loss


What type of bone is deposited during orthodontic treatment?




Soft connective tissue between tooth and alveolar bone

0.2mm wide usually but varies with tooth function and age

Originated from ectomesenchyme cells of dental follicle


What are the components of periodontium?

Alveolar bone proper

And gingiva


Functions of PDL

Support: attachment of tooth to alveolar bone
Formative: cells responsible for formation of periodontium
Nutritive: contains vascular network for nutrients
Sensory: contains afferent nerve fibers responsible for pain, pressure, and proprioception
Remodeling: cells responsible for remodeling the periodontium


Cells of PDL

Fibroblasts: most common cell
Cementoblasts and cementoclasts
Osteoblasts and osteoclasts
Macrophages, mast cells, and eosinophils
Mesenchymal cells

Ground substance
Epithelial tests of malassez: remnants of Hertwig's epithelial root sheath
Cementicles: calcified masses


Fibers of PDL

Transseptal fibers: interproximally over alveolar crest between teeth (resist medial distal forces)

Alveolar crest: from cementum to alveolar crest (resist vertical forces)

Horizontal: cementum to alveolar bone (resist tipping and rotation)

Oblique: cementum to alveolar bone obliquely - most abundant fiber type (resistant to masticatory forces)

Apical: cementum to bone at root (resist extrusive forces)

Interradicular: extend from radicular cementum to interrradicular alveolar bone in multirooted teeth (resist vertical and tipping forces)

Oxytalan fibers: not principle fibers of collagen, but are elastic like and are associated with blood vessels


Vasculature of PDL

Arises from maxillary artery

Periosteal vessels: branches from periosteum - primary source

Apical vessels: branches of dental vessels

Transalveolar vessels: branches of transseptal vessels perforating alveolar bone proper

Anastomosing vessels of gingiva


Nerves of PDL

Arise from trigeminal nerve

Free nerve endings: most abundant, transmit pain

Ruffini corpuscles: mechanoreception

Coiled endings

Spindle endings


What are the fibers that insert into cementum or alveolar bone proper?

Sharpey's fibers

Thicker on alveolar side


Lymphatics of PDL

Drain to submandibular lymph nodes

Except mandibular incisors (drain to submental)


Effects of aging on PDL

Decreased PDL width

Decreased cellularity and fiber content


Clinical implications of PDL

Teeth in hypofunction have decreased PDL width

Teeth in hyperfunction have increased PDL width

Orthodontic tooth movement is possible due to PDL actively responding to externally applied forces