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Questions and Answers

What is the primary characteristic of the oral epithelium?

It is covered by keratin and stratified squamous. (correct)

It has a smooth, flush interface with connective tissue.

It consists only of a single cell layer.

It is nonkeratinized and permeable.

Which of the following layers is NOT present in the sulcular epithelium?

Basal cell layer

Superficial cell layer

Prickle cell layer

Granular cell layer (correct)

Which anatomical area forms the base of the gingival sulcus?

Sulcular epithelium

Junctional epithelium (correct)

Connective tissue

Oral epithelium

What feature differentiates junctional epithelium from oral epithelium?

It is semipermeable and thinner. Signup and view all the answers

How thick is the junctional epithelium at the coronal zone?

15 to 30 cells thick Signup and view all the answers

What is the flow condition of gingival crevicular fluid in health?

Flow is slight. Signup and view all the answers

What type of epithelium lines the gingival sulcus?

Nonkeratinized epithelium Signup and view all the answers

Which cell layers are found in both oral and junctional epithelium?

Basal cell layer and prickle cell layer Signup and view all the answers

What is the primary focus of histology?

Study of microscopic features of tissues Signup and view all the answers

Which type of tissue is characterized by closely packed cells bound together?

Epithelial tissue Signup and view all the answers

What primarily composes the extracellular matrix?

Ground substance and fibrous proteins Signup and view all the answers

Which of the following tissues has a sparse extracellular matrix?

Epithelial tissue Signup and view all the answers

What type of epithelial tissue is primarily found on the outer surface of the body?

Stratified squamous epithelium Signup and view all the answers

Which of the following is NOT a basic type of tissue?

Ciliated Signup and view all the answers

The extracellular matrix primarily serves what purpose?

Support and framework for cells Signup and view all the answers

What type of epithelial tissue is found lining body cavities such as the mouth and stomach?

Stratified squamous epithelium Signup and view all the answers

What is the primary supportive function of the periodontal ligament fibers?

To anchor the tooth to the socket Signup and view all the answers

What is the thickness range of the periodontal ligament fibers?

0.05 to 0.25 mm Signup and view all the answers

Which component of the periodontal ligament is responsible for forming bone?

Osteoblasts Signup and view all the answers

What unique characteristic do interradicular fibers have in the periodontal ligament?

They exist in the furcation area of multirooted teeth. Signup and view all the answers

Which fiber group of the periodontal ligament is primarily responsible for anchoring the tooth at the alveolar crest?

Alveolar crest fibers Signup and view all the answers

What role do Sharpey’s fibers play in the periodontal ligament?

They attach the tooth to the bone. Signup and view all the answers

What type of tissue covers the roots of teeth and is formed during the attachment process?

Cementum Signup and view all the answers

What is the main nutritive function of the periodontal ligament?

Providing nutrients to the cementum Signup and view all the answers

What is the primary function of cementum in relation to teeth?

Maintains the integrity of the root and aids in tooth repair Signup and view all the answers

Which portion of mature cementum consists of hydroxyapatite crystals?

Mineralized portion Signup and view all the answers

What is the primary function of the junctional epithelium in relation to teeth?

To provide a barrier and host defense Signup and view all the answers

What has current research indicated about the presence of bacterial products in cementum?

They are not located in cementum and should be preserved Signup and view all the answers

Which structure is involved in the attachment of the junctional epithelium to the tooth surface?

Hemidesmosomes Signup and view all the answers

What are the three possible arrangements of enamel at the cementum?

Overlap, meet, or gap Signup and view all the answers

Which component of alveolar bone primarily protects the roots of teeth?

Alveolar bone proper Signup and view all the answers

What type of connective tissue is responsible for attaching gingiva to the tooth cementum and alveolar bone?

Lamina propria Signup and view all the answers

What characteristic of alveolar bone allows it to respond to mechanical forces?

Trabecular structure Signup and view all the answers

What is a characteristic feature of the cells within gingival connective tissue?

They are sparse and make up about 5% of the tissue Signup and view all the answers

Which component of the junctional epithelium helps to form a seal around the teeth?

Internal basal lamina Signup and view all the answers

Which type of cementum is primarily classified as acellular?

Primary cementum Signup and view all the answers

Which growth factor molecules are associated with cementum during its formation?

Molecules stored in the matrix Signup and view all the answers

Which type of cells in the gingival connective tissue are primarily responsible for collagen secretion?

Fibroblasts Signup and view all the answers

What occurs when teeth erupt through the protective epithelial covering?

The body attempts to attach epithelium to the tooth Signup and view all the answers

What is the composition of the extracellular matrix in gingival connective tissue?

Low cell density and high matrix Signup and view all the answers

What is the primary composition of the extracellular matrix of the gingival connective tissue?

55% to 65% protein fibers and 30% to 35% gel-like material Signup and view all the answers

Which function do the supragingival fiber bundles NOT perform?

Assist with blood supply to the gingiva Signup and view all the answers

Which of the following classifications of supragingival fiber groups is responsible for encircling the tooth?

Circular Signup and view all the answers

The dentogingival unit is primarily composed of which two components?

Junctional epithelium and supragingival fibers Signup and view all the answers

What is one of the functions of supragingival fiber bundles in relation to mastication?

To provide rigidity to withstand forces from mastication Signup and view all the answers

Which of the following fibers extends laterally from the alveolar bone to the gingiva?

Periosteogingival fibers Signup and view all the answers

Which component is NOT typically found embedded in the extracellular matrix of gingival connective tissue?

Lymphocytes Signup and view all the answers

The supragingival fibers primarily help in which of the following aspects?

Reinforcing the attachment of junctional epithelium to the tooth Signup and view all the answers

Study Notes

Microscopic Anatomy of the Periodontium

This chapter focuses on the microscopic structures of the periodontium.
The foundational aspects of histology, tissue, cells, and extracellular matrix are critical for understanding the complex structures of the periodontium.
The periodontium is composed of multiple tissues: epithelial, connective, nerve, and muscle, crucial in its overall function.

Microscopic Anatomy of Tissue

Histology: The study of microscopic features of tissues.
Tissue: A group of interconnected cells performing similar functions.
Tissues and organs: Composed of various cell types and extracellular elements.

Cells

Cells are the smallest structural units capable of independent functioning.
Cells group together to form tissues.
There are four basic tissue types: epithelial, connective, nerve, and muscle.

Extracellular Matrix

A mesh-like network surrounding cells.
Physically supports cells within tissue.
Provides a biomechanical framework for cell migration and interaction.
Primarily composed of ground substance and fibrous proteins.
Sparse in epithelial tissue (primarily basal lamina).
Plentiful in connective tissue.

Microscopic Anatomy of Epithelial Tissue

Forms the outer surface of the body and lines body cavities (mouth, stomach, and intestines).
Skin and oral mucosa are composed of stratified squamous epithelium (layers of flat cells).
Epithelial cells are tightly packed and bound together.
Basal lamina is a thin mat of extracellular matrix secreted by epithelial cells supporting overlying epithelium.

Keratinization

A process by which surface epithelial cells become stronger and waterproof.
Keratinized epithelial cells lack nuclei, forming a tough, resistant layer (e.g., skin).
Nonkeratinized epithelial cells have nuclei and act as a protective cushion.

Blood Supply of Epithelial Cells

Epithelial cells are avascular (lack blood vessels).
They receive oxygen and nutrients from blood vessels in underlying connective tissue via diffusion.

Microscopic Anatomy of Connective Tissue

Fills spaces between tissues and organs in the body.
Supports or binds other tissues.
Composed of sparse cells (fibroblasts, phagocytes, lymphocytes) and abundant extracellular substance.
Dental connective tissues include cementum, dentin, alveolar bone, and pulp.
Enamel is the exception, classified as epithelial tissue.

Epithelial-Connective Tissue Interface

The site where epithelial and connective tissues meet.
Basal lamina is not visible under a light microscope.
Aids in the attachment of epithelial cells to adjacent structures.
A basement membrane is visible with a light microscope beneath the epithelium.
A combination of basal lamina and reticular lamina.
The most common pattern is tight interdigitation, where tissues interlock like clasped fingers.
Also composed of epithelial ridges or rete pegs.
Finger-like extensions of connective tissue projecting into the epithelium.

Morphologic Patterns of the Epithelial-Connective Tissue Interface (cont.)

Seen in healthy sulcular epithelium and healthy junctional epithelium.
A smooth non-interdigitizing interface without epithelial or connective tissue papillae.

Function of the Epithelial-Connective Tissue Interface

Enhances adhesion of epithelium to connective tissue by increasing the surface area.
Allows skin to resist mechanical forces.
Provides a large area to receive nourishment from underlying connective tissue.

Epithelial Cell Junctions

Cellular structures that mechanically 'lock' a cell and its cytoskeleton to its neighbor or basal lamina, forming a structurally strong unit.
Tissues like the epithelium of the skin have the most abundant number of cell junctions.
They can withstand severe mechanical stresses.

Desmosomes and Hemidesmosomes

Create cell-to-cell or cell-to-basal lamina connections.
Important junctions found in gingival epithelium.

Microscopic Anatomy of Gingival Epithelium

Specialized stratified squamous epithelium enabling optimal function in a wet oral cavity.
Three anatomical areas: oral epithelium, sulcular epithelium, and junctional epithelium.

Oral Epithelium

Covers the outer surface of free and attached gingiva, extending from the crest of the gingival margin to the mucogingival junction.
Keratinized stratified squamous epithelium.
Divided into cell layers (e.g., stratum basale, stratum spinosum, stratum corneum).

Cell Layers of the Oral Epithelium

Includes basal cell layer (stratum basale), prickle cell layer (stratum spinosum), granular cell layer (stratum granulosum), and keratinized cell layer (stratum corneum).

Sulcular Epithelium

Epithelial lining of the gingival sulcus, continuous with oral epithelium.
Extends from the crest of the gingival margin to the coronal edge of junctional epithelium.
Thin, non-keratinized with three distinct layers: basal cell layer, prickle cell layer, and superficial cell layer.
Permits gingival crevicular fluid flow from gingival connective tissue to the sulcus.

Sulcular Epithelium (cont.)

Permeable, allowing gingival crevicular fluid to flow into the gingival sulcus.
The flow increases in cases of disease.
Joins connective tissue at a smooth interface without epithelial ridges. No interdigitation.

Junctional Epithelium

Forms the base of the sulcus and joins gingiva to tooth.
Attaches to the tooth slightly coronal to the cementoenamel junction (CEJ).
Thin, nonkeratinized, semipermeable.
The easiest entry point for bacteria into connective tissue.
Contains only basal and prickle cell layers.
Approximately 0.71 to 1.35 mm in length and tapers from 15 to 30 cells thick to 4 to 5 cells thick in the apical zone.
Exhibits a smooth, flush interface with connective tissue in healthy cases.

Functions of Junctional Epithelium

Attachment.
Barrier.
Host defense.

Attachment of the Cells of the Junctional Epithelium

Components include closely packed epithelial cells, desmosomes, hemidesmosomes, and sparse extracellular matrix with internal and external basal lamina.

Attachment of Junctional Epithelium

Attaches to the tooth surface through hemidesmosomes.
Interacts with underlying connective tissue through hemidesmosomes and external basal lamina.

Microscopic Anatomy of Gingival Connective Tissue of the Free and Attached Gingiva

Function: Provides support to gingiva, attaches gingiva to the cementum of the tooth root and the alveolar bone.
Also known as lamina propria.
Abundant extracellular matrix with few cells (around 5%).

Cells of the Gingival Connective Tissue

Three cell types: fibroblasts (secrete collagen), mast cells, and immune cells (macrophages, neutrophils, lymphocytes).
Fibers of connective tissue are produced by fibroblasts.

Extracellular Matrix of the Gingival Connective Tissue

Collagen fibers, fibroblasts, vessels, and nerves are embedded in the extracellular matrix.
55% to 65% of the matrix comprises protein fibers.
30% to 35% of the matrix is gel-like material.

The Supragingival Fiber Bundles of the Gingival Connective Tissue

Network of rope-like collagen fiber bundles located coronally to the crest of the alveolar bone.
Support gingival tissue.

Features of the Supragingival Fiber Bundles

Embedded in a gel-like extracellular matrix.
Strengthens attachment of junctional epithelium to the tooth.
Provides structural support to gingival tissue.

Functions of the Supragingival Fiber Bundles

Braces the gingiva against the teeth and reinforces junctional epithelium attachment.
Provides rigidity to withstand mastication forces.
Connects gingiva to the cementum and alveolar bone.
Stabilizes adjacent teeth.

Classification of Supragingival Fiber Groups

Categories include: Circular (C), Alveologingival (AG), Dentogingival (DG), Periosteogingival (PG), Intergingival (IG), Intercircular (IC), Interpapillary (IP), Transgingival (TG), and Transeptal (TS).

The Periodontal Ligament Fibers of the Gingival Connective Tissue

Thin sheet of fibrous connective tissue surrounding the roots of teeth.
Connects root cementum to the socket wall.
Vary in thickness (0.05 to 0.25 mm).
Composed of connective tissue fibers, cells, and extracellular matrix.

Functions of the Periodontal Ligament Fibers

Supportive: anchors the tooth to the socket and separates it from the socket wall.
Sensory: transmits tactile pressure and pain sensations.
Nutritive: blood vessels nourish the cementum and bone.
Formative: responsible for collagen formation (fibroblasts), cementum formation (cementoblasts), and bone formation (osteoblasts).
Resorptive: resorption of bone or cementum in response to pressure.

Principal Fiber Groups of the Periodontal Ligament

Include: Alveolar crest fibers, Horizontal fibers, Oblique fibers, Apical fibers, and interradicular fibers.

Sharpey's Fibers of the Periodontal Ligament

Calcified terminal ends of periodontal ligament fibers embedded within cementum and alveolar bone.
Attachment occurs during cementum and bone formation.

Microscopic Anatomy of Cementum

Mineralized tissue covering tooth roots.
Composed mainly of hydroxyapatite (calcium and phosphate).
Attaches the tooth to the bone via periodontal ligament collagen fibers.
Maintains root integrity, supports tooth maintenance, aids in repair, and possibly influences periodontal ligament regeneration.

Components of Mature Cementum

Organic portion: Densely packed collagen fibers and groups of proteins.
Mineralized portion: Made of hydroxyapatite crystals.
Blood vessels and nerves absent.
Biological components: Growth factors produced during formation stored in the matrix.

Conservation of Cementum During Periodontal Instrumentation

Historically, aggressive removal of cementum was necessary to treat bacterial products.
Research now demonstrates that bacterial products are not located within the cementum, thus highlighting the importance of preserving the cementum for new attachments.

Types of Cementum

Categories include: Intermediate (found at the CEJ), Acellular (primary), and Cellular (secondary).

Three Possible Arrangements of Enamel at the Cementum

Possible arrangements of enamel at the cementum include: Overlap the enamel, meet the enamel, or a gap.
Often abbreviated as OMG.

Microscopic Anatomy of Alveolar Bone

Part of the maxilla and mandible forming and supporting tooth sockets.
Anatomical components include: Alveolar bone proper, Trabecular bone, and Cortical (compact) bone.

Microscopic Anatomy of Alveolar Bone (cont.)

Function: Protects tooth roots, resists mechanical forces and inflammation.
Characteristics: Major cell types include osteoblasts and osteoclasts. Rigid extracellular matrix due to mineralization. Blood vessels and nerve innervation.

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