1st lesson

Hertiwig’s Epithelial Root Sheath

• Formation of root dentin

• Grows downward toward the developing jawbone, it stimulates the cells of the dental papilla to differentiate into odontoblasts

• Dentin that forms in the root is called root dentin, and it gradually elongates the root structure as more dentin is deposited

Odontoblasts

HERS grows downward toward the developing jawbone, it stimulates the cells of the dental papilla to differentiate into _______

Epithelial Rests of Malassez (ERM)

• Are small clusters of islands of epithelial cells found in the periodontal ligament surrounding the root of the tooth

• These epithelial cells are remnants of HERS that remain in the periodontal ligament after root development is completed

Louis Charles Malassez

First to describe Epithelial Rests of Malassez, and a French histologists

Radical Cyst Formation

The most common cyst of the jaws originates from the proliferation of epithelial rests of Malassez due to inflammation from a necrotic pulp

Necrotic Pulp

Radicular cyst originates from the proliferation of ERM due to inflammation from a _______

Periodontium

• Attachment Apparatus of the Tooth

• Consists of the tissues that support and anchor the tooth within the jawbone

• “Structures around the tooth”

Formation of Cementum

• Root dentin begins to form, HERS gradually breaks apart

• Dental follicle cells differentiate into cementoblasts, which produces?

Cementum

• Is a calcified tissue that covers the root surface and provides attachment for the periodontal ligament fibers

• Allows the tooth to connect to the surrounding supporting tissues

• Similar to bone but has unique characteristics, unlike bone, it does not have blood vessels, and it grows slowly throughout life

45-50%

• Composition of cementum

• inorganic material (hydroxyapatite)

50-55%

• Composition of cementum

• Organic material and water

Anchoring, Protecting, & Repair

Functions of the Cementum includes:

Acellular Cementum

• Types of cementum

• Located mostly near the cervical portion of the root

• Important for tooth attachment

• Contains no cells

Cellular Cementum

• Types of cementum

• Found near the apical region of the root

• Contains cementocytes

• Helps in repair and adaptation

Periodontal Ligament

• Specialized connective tissue located between the cementum and the alveolar bone

• Acts like a shock absorber, allowing the tooth to withstand forces during chewing

Sharpey’s fibers

It contains bundles of collagen fibers called ______, which insert into both the cementum and the bone

Supportive Function

• Function of the PDL

• Anchors the tooth to the alveolar bone

Shock Absorption

• Function of PDL

• Protects the tooth and bone from excessive chewing forces

Sensory Function

• Function of the PDL

• Contains nerves that detect pressure and pain

Nutritive Function

• Functions of the PDL

• Supplies nutrients to surrounding tissues

Remodeling Function

• Function of the PDL

• Plays a role in tooth movement during orthodontic treatment

Alveolar Crest Fibers

• Principal fiber groups of the PDL

• Resist tooth extrusion

Horizontal Fibers

• Principal fiber groups of the PDL

• Stabilize the tooth against sideways forces

Oblique Fibers

• Principal fiber groups of the PDL

• Most numerous and resist vertical chewing forces

Apical Fibers

• Principal fiber groups of the PDL

• Stabilize the root tip

Interradicular fibers

• Principal fiber groups of the PDL

• Found between roots of multi-rooted teeth

Alveolar Bone

• Forms the tooth socket (alveolus) in which the tooth is embedded

• It supports and protects the teeth and undergoes continuous remodeling in response to mechanical forces such as chewing and orthodontic treatment

Alveolar Bone Proper

• Parts of alveolar bone

• Lines the tooth socket

Lamina Dura

Alveolar bone proper is also called?

Cortical Plate

• Parts of alveolar bone

• Outer dense layer of bone

Cancellous Bone

• Parts of alveolar bone

• Spongy bone between cortical plates

Osteoblasts

Bone forming cells

Osteoclasts

Bone resorbing cells

Gingiva

• Soft tissue that surrounds the teeth and covers the alveolar bone

• It acts as a protective barrier for the deeper supporting structures

• Usually pink, firm, and tightly attached to the teeth

Marginal Gingiva

• Is the unattached portion of the gingiva that surrounds the tooth like a colar

• Acts as a protective barrier around the tooth

• Helps prevent bacterial penetration

Gingival Sulcus

Marginal gingiva creates a small space called the _______

Attached Gingiva

• Is the firm portion of gingiva that is tightly bound to the underlying alveolar bone and cementum

• Provides stability to the gingival tissue

• Helps resist mechanical forces from chewing and brushing

Interdental Papilla

• Is the triangular portion of gingiva located between adjacent teeth

• Prevents food impaction

• Protects the PDL and alveolar bone

Enamel

• The hardest and most highly mineralized tissue in the human body

• It covers the anatomic crown of the tooth

• Protects from mechanical forces, temperature changes, and chemical wear

• Protects underlying dentin and pulp

Ameloblasts

Cells responsible for formation of enamel are called ______

96% inorganic, 1% organic, 3% water

Composition of Enamel

Enamel Hypoplasia

Defective quantity of enamel

Enamel Hypocalcification

Poor mineralization of enamel

Dental Caries

Demineralization due to acids

Fluorosis

Excessive fluoride intake during development

Enamel Rods

• Basic structural unit of enamel

• Extends from dentinoenamel junction to surface

Fish-scale pattern

Enamel rods cross-section, are usually arrange in a what pattern?

Hydroxyapatite Crystals

Enamel rods are made up of tightly packed _____

Interrod Enamel

• Surrounds and fills the spaces between enamel rods

• Helps bind enamel rods together

• Contributes to enamel resistance to fracture

• Plays a role in how enamel responds to acid attack and caries progression

Interprismatic Substance

Other name for interrod enamel

Rod Sheath

• Thin, less mineralized boundary surrounding each enamel rod, marking the junction between rod and interrod enamel

• Contains less mineral content

Incremental Lines (Striae of Retzius)

• Lines in enamel that reflect the rhythmic, peiodic formation of enamel during tooth development

Perikymata

Striae of Retzius are reflected on the surface as _____ (External Groove)

Hunter-Schreger Bands

• Alternating light and dark bands seen in enamel under reflected or polarized light due to changes in the direction of enamel rods

• Helps improve the tooth’s resistance to fracture

Neonatal Line

Distinct growth line formed at birth, marking the boundary between prenatal and postnatal enamel due to physiological stress

Dentin

• Is the hard, yellowish tissue that forms the main bulk of the tooth

• It lies beneath the enamel in the crown and beneath the cementum in the root

• Vital calcified connective tissue produced by odontoblasts

• It is less hard than enamel but harder than bone and cementum

70% inorganic, 20% organic, 10% water

Composition of Dentin

Odontoblasts

• Specialized cells responsible for dentin formation

• These cells are located at the outer surface of the pulp and send specialized processes into the dentinal tubules

Odontoblastic Process (Tomes’ Fiber)

Is a single, hair-like cytoplasmic extension of an odontoblast cell located in the peripheral dental pulp

Dentinal Tubules

• Are tiny channels that run from the pulp to the dentinoenamel junction in the crown or to the cementodentinal junction in the root

• They allow movement of fluid, which is related to the hydrodynamic theory of pain

Hydrodynamic Theory of Dentin

Explains that pain in dentin is caused by movement of fluid inside the dentinal tubules, which stimulates nerve endings in the pulp

Brannstrom

Hydrodynamic Theory of Dentin was proposed by whom and is the most widely accepted explanation for dentin hypersensitivity

Primary Dentin

• Types of dentin

• Formed before tooth eruption

• Makes up the main structure of the tooth

Mantle and Circumpulpal dentin

Primary dentin is composed of ____ and ____, it outlines the pulp chamber and is characterized by a regular tubular structure

Secondary Dentin

• Types of dentin

• Formed after eruption and after root completion

• Deposited slowly throughout life

• Causes the pulp chamber to become smaller with age

Tertiary Dentin

• Type of dentin

• Forms in response to stimuli or injury

• Caries, attrition, abrasion, cavity preparation

Reparative Dentin

Tertiary dentin is also called?

Peritubular dentin

• Parts of dentin

• Found around the dentinal tubules

• More highly mineralized

Intertubular dentin

• Parts of dentin

• Found between the tubule

• Forms the main body of dentin

Predentin

• Parts of dentin

• Newly formed, unmineralized dentin

• Found between odontoblasts and mature dentin

Dentinogenesis Imperfecta

• Genetic disorder

• Opalescent teeth, weak structure

Interglobular Dentin

• Hypomineralized area

• Defective calcification

Sclerotic Dentin

• Tubules filled with minerals

• Seen in aging or mild irritation

Dead Tracts

• Empty dentinal tubules

• Due to odontoblasts death

Dental Pulp

• Is the soft, vital connective tissue located at the center of the tooth

• It contains blood vessels, nerves, and cells essential for tooth vitality

• Located inside, extends into root canals and connected to surrounding tissues via apical foramen

Odontoblastic Layer

• Outer layer adjacent to dentin

• Contains odontoblasts (form dentin)

Cell-Free Zone (Zone of Weil)

• Few cells

• Contains: Capillaries, nerve plexus (Plexus of Raschkow)

Cell-Rich Zone

• High concentration of cells

• Includes: Fibrobalsts and undifferentiated mesenchymal cells

Pulp Core

• Central area

• Contains: Blood vessels, nerves, connective tissue fibers

Formative Function

• Functions of dental pulp

• Produces dentin via odontoblasts

Protective Function

• Functions of dental pulp

• Forms reparative dentin in response to injury

Nutritive Function

• Functions of dental pulp

• Supplies nutrients to dentin via dentinal tubules

Sensory Function

• Functions of dental pulp

• Detects pain, mainly via A-delta fibers and C fibers

Fibroblasts

• Cells of the pulp

• Collagen production

Undifferentiated Mesenchymal Cells

• Cells of the pulp

• Repair

Immune cell

• Cells of the pulp

• Defense

Pulpitis

Inflammation due to caries or trauma

Pulp stones

Calcified masses in pulp

Pulp Necrosis

Death of pulp tissue

Internal Resorption

Destruction of dentin from inside