Oral Histology Flashcards
Layers of oral mucosa
California Girls String Bikinis
Corneum
Granulosum
Spinosum
Basale
Basement membrane in oral mucosa
Type IV cartilage
Laminin
Hemidesmosomes mediate epithelial attachment
Specialized epithelial cells of oral mucosa
Melanocytes
Keratinocytes
Langerhans cells (may extend into the stratum Spinosum)
Merkel cells
True or false: all oral mucosa contains stratified squamous epithelium
True
Gingiva
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
False
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
False
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
Dentin
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
Enamel
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
Pulp
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
Cementum
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
Cementogenesis
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
CEJ
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?
Intramembranous
PDL
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?
Cementum
Alveolar bone proper
PDL
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
