Oral Bio Final Exam

Salivary Glands

• Exocrine

• Acinar cells are either mucus (thick, viscous), serous (thin, watery), or mixed. Have their own ductal system

• Parenchyma (secretory and epithelial portion) and stroma (outer capsule and inner framework of salivary gland)

• Serous demilune is cap on mucus cells and secretes lysozyme

• With age, acinar cells degenerate, and submandibular gland is more sensitive to metabolic changes (greatly affecting unstimulated salivary flow)

Serous and Mucus Cells

Serous Cells

• Secrete zymogen granules

• Have prominent Golgi and RER

Mucus Cells

• More protein secretion

• Have prominent Golgi but small RER

Ductal System

Intercalated Duct

• Simple squamous epithelium to cuboidal epithelium

• Release HCO3 and absorb Cl from lumen

• Not well-developed in mucus glands

Striated Duct

• Simple cuboidal

• Has infoldings for more mitochondria needed for transport between lumen and cells

• Release K and absorb Na from lumen

• Not well-developed in mucus glands

Excretory Duct

• Simple columnar to stratified cuboidal or pseudostratified columnar

• Do not modify saliva

Myoepithelial Cell

• Actin filaments that support excretory duct

Saliva Functions

• Protection

  • Lubricant

  • Barrier against noxious stimuli

  • Washes debris

  • Forms protective salivary pellicle

• Buffering - Phosphate and bicarbonate ions

• Digestion - Amylase and lipase

• Antimicrobial

  • Lysozyme - Breaks bacterial cell wall

  • Lactoferrin - Deprives bacteria of iron

  • IgA - Agglutinates microorganisms

• Antiviral and antifungals

• Maintain tooth structure - Remineralize with calcium and phosphate ions

• Taste - Solubilized food reaches receptors

Major Salivary Glands

Parotid

• Serous

• Largest salivary gland

• 25% of salivary output

• No serous demilune

• Stenson’s duct opens at opposite 2nd maxillary molar

Submandibular

• Mixed - Mostly serous

• Second largest salivary gland

• 60-65% of salivary output

• Wharton’s duct opens at sublingual caruncle

Sublingual

• Mixed - Mostly mucus

• Smallest major salivary gland

• 10% of salivary output

• Bartholin’s duct opens at sublingual caruncle

Minor Salivary Glands

• Buccal - Mixed (mostly mucus)

• Labial - Mixed (mostly mucus)

• Lingual

  • Anterior - Mixed (mostly mucous)

  • von Ebner’s - Serous

  • Posterior - Mucus

• Palatine (hard and soft palate) - Mucus

• Glossopalatine - Mucus

Autonomic Effects on Salivary Glands

• Parasympathetic

  • CN 9 to parotid gland

  • CN 7 to all other glands

  • Abundant watery saliva

• Sympathetic

  • Superior cervical ganglion

  • Minimal viscous saliva

Conditions Affecting Salivary Output

• Xerostomia

• Sjogren’s Syndrome

  • Autoimmune disorder affecting salivary and lacrimal grands

  • Can have unilateral or bilateral effects

  • 90% of cases in women

  • Usually 50 years of age

  • Primary - Involves exocrine glands only

  • Secondary - Includes other autoimmune diseases like rheumatoid arthiritis

• Sialoliths - Salivary stone

TMD

• Happens most often to pre-menopausal women

• Can have clicking, limited movement, joint degeneration, and pain

• Portion of population have clicking sounds (pain involvement is concerning)

TMJ

• Sliding ginglymoarthroidial joint (ginglymo means hinge)

• Condyle sits against articular eminence in mandibular fossa

• Superior head of lateral pterygoid is attached to disc while inferior head is attached to pterygoid fovea

• It is synovial joint

• Must be able to function and articulate simultaneously

• Both joints function in pairs (effect on one can affect the other)

Embryology of Cartilage and Bone in TMJ

• Primary cartilage - Where 5 zones of hypertrophy occur and form embryonic cartilage of body. Made in first 7 weeks

• Secondary cartilage - Stimulated by muscle or tendon pull

• Normally, cartilage forms bone using endochondral ossification (also, intramembranous ossification uses mesenchyme to make bone). In TMJ, bone comes first and starts developing secondary cartilage

• Meckel’s cartilage serves as scaffold for mandible bone to form around it

• Meckel’s cartilage is initially continuous (called primitive jaw joint from weeks 7-10) but anterior portion gets resorbed into mandible, intermediate becomes sphenomandibular ligament, and posterior becomes malleus and incus bones (separates about week 10)

• Joint does not become functional until 18-20 weeks in utero

• Outer fibrous layer of periosteum (for fibroblasts) and inner osteogenic layer (for bone) become outer articular layer and inner prechondroblastic layer on mandibular condylar cartilage making up the perichondrial articular envelope

Aging Effects on Mandibular Condylar Cartilage

As you age:

• Cellularity of MCC decreases

• Articular layer becomes fibrocartilaginous

• Prechondroblastic layer shrinks

• Bony cap at bone-cartilage is made ceasing growth

• Condyle flattens and disc gets thinner

• Loss of synovial fluid in joints affecting range of motion

• Condyle alters its shape based on forces or load on joint

Immature TMJ layers

• Articular Layer

  • Most superficial layer

  • Continuous with fibrous layer of periosteum

  • Type I collagen

• Prechondroblastic layer

  • Continuous with osteogenic layer

  • Type I collagen

  • Lots of cell division and mitosis occur

  • Has directional orientation

• Chondroblastic layer

  • Filled with chondroblasts

  • Make type II collagen

  • No obvious directional orientation or growth (isotropic)

• Hypertrophic layer

  • Cells are much larger

  • Layer is more mineralized

  • Type II collagen

• Cartilage-bone

  • Cartilage is replaced by new bone formation

TMJ components

• Condyle continues to grow as face grows

• Can be palpated

• Articular eminence - Non-existent at birth but grows until late adolescence (jaw lock occurs). Older people have fibrous CT with chondrocytes

• Mandibular fossa

• Articular Disc - Soft tissue. Has fibroblasts and directional elastic fibers in collagen matrix which becomes fibrocartilagenous as we age. Avascular and aneural (in intermediate zone)

• Retrodiscal pad is loose connective tissue with two layers separated by innervated and vascularized areolar tissue

  • Superior lamina is elastic and attached to mandibular fossa

  • Inferior lamina is collagenous and attached to condylar neck

• Synovial membrane - Covering non-articular surfaces of TMJ that acts as sponge to absorb and release new synovial fluid. Has two layers

  • Intima - Has synoviocytes making synovial fluid and act as macrophages (phagocytosis)

  • Subintima - Has fibroblasts with support cells and vascular collagen

Tooth Eruption and Shedding

• Eruption is continuous (primary teeth are erupting, secondary teeth developing, primary teeth shed, secondary teeth erupt)

• 6 weeks in utero is tooth development beginning

• 6 months old is emergence of primary tooth

• 6 yrs is emergence of permanent teeth

• Tooth eruption - Movement of tooth until it reaches functional position

  • Involves development of tooth and periodontium

  • Resorption of bone in pathway of tooth

  • Removal of connective tissue between crypt and surface

  • Preparation of epithelial pathway

• When tooth develops, bone and PDL develop, and root is formed using HERS in axial direction

Phases of Tooth Eruption

• Preeruptive tooth movement

  • Before tooth emerges into oral cavity

  • No root formation has occurred

  • Teeth are in bony crypt

  • Bodily movement - Entire tooth germ moves. Uses bone resorption (caused by compression) and deposition (caused by tension)

  • Eccentric growth - Only growth of part of tooth germ. Bone resorption only

  • Successional teeth develop lingual to deciduous teeth

• Eruptive tooth movement

  • Crown has completed growth

  • Root formation begins

  • PDL causes tooth eruption, not root formation

  • Until tooth comes into occlusion

  • Bony fundus is apical portion of bony crypt and is resorbed during eruption leaving behind a bone ladder

  • Attachment of collagen bundles and PDL

  • Connective tissue between REE and oral epithelium degenerates and they fuse

  • Gubernacular canal - Made from gubernacular cord. Passageway in bone for tooth to erupt to gum surface made with help of enzymes breaking down epithelia

  • No bleeding because epithelium have no vasculature

• Post-eruptive tooth movement

  • Begins with occlusal contact of teeth

  • Happens throughout teeth lifetime

  • Accommodates for occlusal and interproximal wear

  • Transseptal ligament maintains contact between adjacent teeth

  • Cementum is deposited to allow for continual eruption of teeth for maintaining occlusion

  • Accommodates for growing maxilla, mandible, and remodeling alveolar bone

  • Mesial drift from transseptal ligament contraction and forward direction of occlusal forces to compensate for interproximal wear

  • Anterior crowding can occur causing teeth to move lingually or facially since they have nowhere to go (Billiard ball analogy)

Shedding of Deciduous Teeth

• Loss of root by odontoclasts at sites of pressure and loss of PDL attachment

• Loss of bone by alveolar bone remodeling from growth and shedding of jaw

• Increased masticatory force allows for shedding

• Permanent tooth lingual of primary tooth causes root and PDL loss of developing tooth and decreased primary tooth support. Both dentin and predentin are resorbed

• Resorption is not continuous (switches from active to inactive resorption) causing loosening and tightening of primary teeth

• Anterior teeth shed with portion of root and coronal pulp intact

• Posterior teeth shed when no root remains and coronal pulp is most resorbed

• Odontoclasts, osteoclasts, and cementoclasts are used

• Sometimes, primary teeth remnant can be found that are not fully resorbed. If big enough, they may need to be extracted

Tooth Germ Layers

• Enamel Organ

  • Oral Ectoderm

  • Ameloblasts (enamel)

• Dental Papilla

  • Ectomesenchyme

  • Odontoblasts (dentin) and Pulp

• Dental Follicle/Sac

  • Ectomesenchyme

  • Cementoblasts (cementum), fibroblasts (PDL), and osteoblasts (alveolar bone)

Enamel Organ Layers

• OEE

  • Outer convex layer of enamel organ

  • Provides oxygen and nutrients to capillary plexus

• Stellate Reticulum

  • Between OEE and stratum intermedium

  • Secretes GAGs attracting water. Increases volume of enamel organ

• Stratum Intermedium

  • Spindle-shaped cells perpendicular and adjacent to IEE

  • Contain alkaline phosphatase and participate in enamel formation

• IEE

  • Inner concave layer of enamel organ that is continuous with OEE at cervical loop

  • Induced to become ameloblasts

When are 4 parts formed and distinguished in enamel organ?

• Begin formation - Cap stage

• Distinguishable - Bell stage

Stages of Amelogenesis

Secretory

• Ameloblasts secrete and organize entire thickness of enamel

• Initial secretory ameloblasts - NO tome’s processes, initial enamel secreted is prismless

• Secretory ameloblasts - HAVE Tome’s processes, secrete enamel in prisms or rods

Maturation

• Modulation between two cell subtypes

  • Ruffle-ended ameloblasts - proximal leaky junctions, distal tight junctions (Pump Ca2+ into maturing enamel)

  • Smooth-ended ameloblasts - proximal tight junctions, distal leaky junctions - Remove matrix proteins and water from maturing enamel

Protective

• REE - remnant of enamel organ

  • Protective ameloblasts (outer)

  • Papillary layer (inner)

• REE covers crown of unerupted tooth

• Initial junctional epithelium following tooth eruption

Late bell/apposition stage events

Reciprocal Induction

1. Dental papilla ectomesenchyme cells induce IEE cells to differentiate into preameloblasts

2. Preameloblasts induce dental papilla ectomesenchyme cells to become preodontoblasts which then become odontoblasts

3. Odontoblasts secrete the first predentin, which induces the preameloblasts to further differentiate into secretory ameloblasts

4. Secretory ameloblasts then secrete the proteins of the enamel matrix

Perikymata, Cross striations and Stria of Retzius

• Perikymata - surface impressions of Striae of Retzius found on newly erupted teeth (eventually wear off)

• Cross Striations - perpendicular to long axes of enamel prisms

  • Formed every 24 hours (diurnal)

• Stria of Retzius - Rhythmic variation in mineralization (increased organic content)

  • Longer period (about weekly)

Enamel Tufts, Spindles, and Lamellae

• Enamel Tufts

  • Resemble tufts of grass extending from DEJ → enamel

  • Contain organic enamel proteins - Developmental origin

• Enamel Spindles

  • Elongated odontoblastic processes that extend into the enamel

• Enamel Lamellae

  • Defects resemble cracks

  • Contain organic material

  • Developmental origin or post-eruptive origin

Gnarled Enamel

• Complex twisting of rods nears the DEJ (very hard tissue)

• Extends a short distance into enamel

• Location - cusps and incisal areas

• No collagen

Primary, Secondary, and Tertiary Dentin

Primary Dentin

• Formed prior to and during tooth eruption (before root completion)

• Circumpulpal dentin - Outlines the pulp

• Mantle Dentin - Outermost layer adjacent to enamel and cementum/DEJ and CDJ

Secondary Dentin

• Forms after root formation complete and continues throughout life; pulp recession

• Dentinal tubules continuous with those in primary dentin but not as regular; sharp directional change

• Uneven deposition

Tertiary Dentin

• Produced in reaction to stimuli (defense mechanism) at pulp interface

• Reactionary dentin

  • Stimulus - Mild

  • Cells - preexisting odontoblasts

  • Structure - tubules oriented differently

• Reparative dentin

  • Stimulus - severe

  • Cells - newly differentiated odontoblast-like cells

  • Structure - heterogenous tubules; osteodentin and fibrodentin

Dead Tract and Sclerotic Dentin

Dead Tract

• Empty tubules

• Retraction or degeneration of odontoblastic process

• Sealed off by tertiary dentin

Sclerotic Dentin

• Tubules occluded with mineral

• Most common in apical 1/3 of root and crown halfway between DEJ and pulp

• Form of tertiary dentin

• Increases with age

Peritubular Dentin and Intertubular Dentin

Peritubular Dentin

• Surrounds dentinal tubules

• Most mineralized

Intertubular Dentin

• Between dentinal tubules

• Most prevalent

Incremental Lines of von Ebner and Contour Lines of Owen

Incremental Lines of Von Ebner

• Represents an exaggerated change in collagen fiber orientation

• Comparable to Stria of Retzius in enamel

Contour Lines of Owen

• Accentuated lines due to disturbances in mineralization

Odontoblasts

• Line the pulpal surface

• Cytoplasmic processes - odontoblastic processes (Tome’s fibers)

• Located inside the dentinal tubules

• Thin organic sheath lines the dentinal tubule called the lamina limitans

Pulp Layers

Odontoblastic Zone (Outermost)

• Odontoblasts at pulp dentin border

Cell-free Zone of Weil

• Subodontoblastic plexus of Raschkow (Where most coronal nerves terminate as unmyelinated fibers)

Cell-Rich Zone

• Mainly fibroblasts

Pulp Core (Innermost)

• Network of blood vessels and nerves

What is found in pulp?

Pulp matrix

• Collagen Types I (mainly) and III

Nerves

• Sensory afferents of the Trigeminal n.

• Post-ganglionic sympathetic branches from the superior cervical ganglion

• A delta fibers: myelinated, fast conducting fibers associated with sharp localized pain when dentin is first exposed

• C fibers: non-myelinated, slow conducting fibers associated with dull, diffuse pain

Pulpal blood vessels

Pulp changes with age

• Decreased pulp size

• Increased chances of pulp stones

• Decreased blood vessels and nerves

• Increased dead tracts

Best Theory for Dentin Sensitivity

• Hydrodynamic theory selected over intratubular nerves and odontoblasts as receptors theories

• Hydrodynamic theory involves fluid movement through tubules that stimulates receptors in pulp

Oral Mucosa

Stratified squamous epithelium

• Surface layer

• May be keratinized or non-keratinized

Lamina Propria

• Underlying connective tissue

• Functions as mechanical support to the epithelium and carries blood vessels/ nerves

• Has two layers:

  • Papillary layer: Directly underneath epithelial layer, loose CT, more cells

  • Reticular layer: dense CT fibrous layer located under papillary layer

Submucosa

• NOT a part of the mucosa (deep to it)

• Contains major trunks of blood vessels and nerves

• May contain adipose tissue for padding, glands such as the minor salivary glands

• Absent in mucosa that is tightly bound to bone (mucoperiosteum) - Median raphe of hard palate and attached gingiva

Lining/Masticatory/Specialized Mucosa and Mucogingival Junction

Lining Mucosa

• Lips, cheeks, floor of mouth, ventral tongue, soft palate, alveolar bone

• Non-keratinized stratified squamous

• Provides flexibility and movement

Masticatory Mucosa

• Gingiva and hard palate

• Keratinized stratified squamous

• Provides resistance to abrasion

Specialized Mucosa

• Dorsal tongue

• Usually keratinized stratified squamous

• Sensory-related

Mucogingival Junction

• Marked transition between the epithelium of the attached gingiva (masticatory) and that of the alveolar mucosa (lining)

Different Regions of Submucosa in hard palate

Anterior Region

• Keratinized

• Mucoperiosteum - Lamina attached to bone

• Rugae

• Incisive Papilla

Anterolateral Area

• Keratinized

• Submucosa contains adipose connective tissue

Posterolateral Area

• Keratinized

• Submucosa contains minor salivary glands

Attached Gingiva

Stippled (orange peel) appearance due to prominent rete pegs/papillae

Different Papillae Types

Filiform

• Largest in number

• No taste buds

• Heavily Keratinized tip points towards posterior of tongue to aid in swallowing bolus

Fungiform

• Scattered among filiform papillae in limited numbers

• Contains taste buds (dorsal surface)

Circumvallate

• 8-10 found along sulcus terminalis

• Contain taste buds (lateral surface)

• Surrounded by moat and gutter

• Secretion supplied by von Ebner’s glands in lamina propria and submucosa (serous secretions dissolve food for taste)

Cementum

• Provides attachment sites for PDL fibers

• Derived from cells of dental follicle/sac (gives rise to all components of periodontium)

Primary and Secondary Cementum

Primary Cementum

• No cells (do not get embedded in matrix)

• Covers cervical 1/3 to 1/2 root

• Forms before tooth reaches occlusal plane

• Mainly composed of Sharpey’s fibers (extrinsic)

• Lamellae and Incremental lines of Salter

Secondary Cementum

• Contains cementocytes (trapped cementoblasts)

• Found in bifurcation, trifurcation, and apical regions of the root

• Forms after tooth reaches occlusal plane

• Lamellae and Incremental lines of Salter

• Occlusal forces influence cellular cementum deposition

Purpose of cementum, PDL, and alveolar bone

• Constitute the supporting structures of the teeth

• Maintains teeth in normal function

Alveolar Bone components

• Chemistry - 2/3 inorganic, 1/3 organic

External Cortical Plate

• Compact bone

• Contains Haversian systems

Alveolar Bone Proper

• Forms inner socket wall

• Modified compact bone

• Bundle bone - contains Sharpey’s fibers

• Other modifications - cribriform plate (if spaces present)

• In radiographs - lamina dura

Cancellous Bone

• Located between the 2 layers of compact bone

• Forms interdental septum

• Marrow spaces - blood vessels and nerves

• Source of cells for osteoblastic and osteoclastic activity

Basal Bone

• Apically located

• NOT related to teeth

• NOT part of alveolar process