Microscopic Anatomy of the Periodontium PDF

CHAPTER 2 Microscopic Anatomy of the Periodontium Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com. Microscopic Anatomy of Tissue  Histology  Study of microscopic features of tissues  Tissue  Group of interconnected cells that perform similar function...

CHAPTER 2 Microscopic Anatomy of the Periodontium Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com. Microscopic Anatomy of Tissue  Histology  Study of microscopic features of tissues  Tissue  Group of interconnected cells that perform similar function Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Tissues and organs composed of several different types of cells and extracellular elements Cells  Smallest structural unit capable of functioning independently  Group together to form tissue Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Four basic types of tissue:  Epithelial, connective, nerve, and muscle Extracellular Matrix  Mesh-like network surrounding cells  Physically supports cells within tissue Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Provides biomechanical framework for cell migration and interaction © Wolters Kluwer Extracellular Matrix (cont.)  Composed mainly of ground substance and fibrous proteins  Sparse in epithelial tissue  Consists mainly of a thin matt (basal lamina) Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  More plentiful in connective tissue Microscopic Anatomy of Epithelial Tissue  Makes up the outer surface of the body  Lines body cavities (mouth, stomach, and intestinal mucosa) Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Skin and oral mucosa composed of stratified squamous epithelium (flat cells in layers) Composition of Epithelial Tissue  Plentiful cells closely packed, bound together  Basal lamina  Thin mat of extracellular Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com matrix secreted by epithelial cells supports overlying epithelium © Wolters Kluwer Keratinization  Process by which surface epithelial cells become stronger and waterproof  Keratinized epithelial cells  Have no nuclei and form tough, resistant layer on skin Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Nonkeratinized epithelial cells  Have nuclei and act as cushion Blood Supply of Epithelial Cells  Epithelial cells are avascular  Completely lack blood vessels Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Receive oxygen and nourishment from vessels in underlying connective tissue through diffusion Microscopic Anatomy of Connective Tissue  Fills spaces between tissues and organs in body  Supports or binds other tissues  Consists of sparse cells (fibroblasts, phagocytes, and Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com lymphocytes) and abundant extracellular substance  Dental Connective Tissue: cementum, dentin, alveolar bone, pulp  Enamel is the exception: classified as epithelial tissue. Epithelial-Connective Tissue Interface  Site where epithelial and connective tissues meet  Basal lamina not visible under light microscope  Aids attachment of epithelial cells to adjacent structures Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Basement membrane  Thin layer visible with light microscope beneath epithelium  Combination of basal lamina and reticular lamina Morphologic Patterns of the Epithelial- Connective Tissue Interface Most common is tight interdigitation pattern in which tissues interdigitate like Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com fingers of clasped hands © Wolters Kluwer Morphologic Patterns of the Epithelial- Connective Tissue Interface (cont.)  Epithelial ridges or rete pegs  Epithelial extensions reaching down into connective tissue  Connective tissue papillae Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Finger-like extensions projecting up into epithelium  Gingival stippling in periodontally healthy individuals  Correlated to the presence of rete pegs Morphologic Patterns of the Epithelial-Connective Tissue Interface (cont.) Smooth non-interdigitizing interface No epithelial ridges or connective tissue papillae Histologically seen in healthy sulcular epithelium and healthy junctional Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com epithelium Function of the Epithelial-Connective Tissue Interface  Enhances adhesion of epithelium to connective tissue by increasing surface area  Allows skin to resist mechanical forces  Provides larger area to receive nourishment from Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com underlying connective tissue Epithelial Cell Junctions  Cellular structures that mechanically “lock” cell and its cytoskeleton to its neighbor or basal lamina  Binding cells form structurally strong unit Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Tissues such as epithelium of skin have most abundant number of cell junctions  Can withstand severe mechanical stresses Desmosomes  Create cell-to-cell connections  Important form of cell junction found in gingival Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com epithelium Modified with permission from Rubin R, Strayer DS. Rubin’s Pathology: Clinicopathologic Foundations of Medicine. 5th ed. Lippincott Williams & Wilkins; 2008. © Wolters Kluwer. Hemidesmosomes  Create cell-to-basal lamina connection  Important form of cell junction found in gingival Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com epithelium © Wolters Kluwer Microscopic Anatomy of Gingival Epithelium  Specialized stratified squamous epithelium that functions well in a wet oral cavity Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Three anatomical areas:  Oral epithelium  Sulcular epithelium  Junctional epithelium © Wolters Kluwer Oral Epithelium  Covers outer surface of free gingiva and attached gingiva from crest of gingival margin to mucogingival junction Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Covered by keratin  Stratified squamous epithelium that can be divided into cell layers Cell Layers of the Oral Epithelium  Basal cell layer  Stratum basale  Prickle cell layer  Stratum spinosum Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Granular cell layer  Stratum granulosum  Keratinized cell layer © Wolters Kluwer  Stratum corneum Sulcular Epithelium  Epithelial lining of gingival sulcus continuous with oral epithelium, extending from crest of gingival margin to coronal edge of junctional epithelium  Thin, nonkeratinized, and has three layers: Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Basal cell layer  Prickle cell layer  Superficial cell layer Sulcular Epithelium (cont.)  Permeable, allowing gingival crevicular fluid to flow from gingival connective tissue into the sulcus  Flow slight in health and increased in disease Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Joins connective tissue at a smooth, flush interface with no epithelial ridges  No interdigitation junction Junctional Epithelium  Forms base of sulcus and joins gingiva to tooth  In health, attaches to tooth slightly coronal to cementoenamel junction (CEJ) Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Thin, nonkeratinized, and semipermeable  Easiest entry point for bacteria into connective tissue  Has only basal cell and prickle cell layers Junctional Epithelium (cont.)  0.71 to 1.35 mm in length  15 to 30 cells thick at the coronal zone  Tapers from 4 to 5 cells thick at Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com the apical zone  In health, has a smooth, flush interface with connective tissue Why the Teeth Need a Junctional Epithelium  Teeth create break in epithelial protective covering  Protective epithelial sheet covers body  Teeth erupt and puncture protective epithelial sheet  Body attempts to seal opening by attaching epithelium Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com to tooth Functions of the Junctional Epithelium  Attachment  Barrier  Host defense Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com © Wolters Kluwer Attachment of the Cells of the Junctional Epithelium  Components of junctional epithelium:  Closely packed epithelial cells  Desmosomes and hemidesmosomes  Sparse extracellular matrix with internal basal lamina and Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com external basal lamina Attachment of Junctional Epithelium  Attach to tooth surface via hemidesmosomes and internal basal lamina  Attach to underlying Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com gingival connective tissue via hemidesmosomes and external basal lamina © Wolters Kluwer Microscopic Anatomy of Gingival Connective Tissue of the Free and Attached Gingiva  Function  Provides solidity to gingiva  Attaches gingiva to cementum of root and alveolar bone  Also known as lamina propria (gingival connective tissue) Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Has an abundance of extracellular matrix and few cells  Cells comprise about 5% of gingival connective tissue Cells of the Gingival Connective Tissue  Three types of cells:  Fibroblasts (secrete collagen)  Mast cells  Immune cells, such as macrophages, neutrophils, and Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com lymphocytes  Fibers of connective tissue produced by fibroblasts Extracellular Matrix of the Gingival Connective Tissue  Collagen fibers, fibroblasts, vessels, and nerves embedded in extracellular matrix Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  55% to 65% protein fibers  30% to 35% gel-like material © Wolters Kluwer The Supragingival Fiber Bundles of the Gingival Connective Tissue Network of rope-like collagen fiber bundles located coronal to crest of alveolar bone Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com © Wolters Kluwer Features of the Supragingival Fiber Bundles  Embedded in gel-like extracellular matrix  Strengthen attachment of junctional epithelium to tooth by bracing gingiva against tooth Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com surface  Dentogingival unit  Composed of junctional epithelium and supragingival fibers  Provides structural support to gingival tissue Functions of the Supragingival Fiber Bundles  Brace gingiva firmly against tooth and reinforce attachment of junctional epithelium to tooth  Provide gingiva with rigidity to withstand mastication forces Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Connect gingiva to cementum and alveolar bone  Stabilize adjacent teeth to one another Classification of Supragingival Fiber Groups  C: Circular  Encircle the tooth coronal to the bone  AG: Alveologingival  Alveolar crest into the gingiva Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  DG: Dentogingival  Cementum into gingiva  PG: Periosteogingival  Extend laterally from bone to gingiva © Wolters Kluwer Classification of Supragingival Fiber Groups (cont.)  C: circular  IG: intergingival  IC: intercircular Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  IP: interpapillary  DG: dentogingival  TG: transgingival  TS: transseptal © Wolters Kluwer The Periodontal Ligament Fibers of the Gingival Connective Tissue  Thin sheet of fibrous connective tissue that surrounds roots of teeth and joints root cementum to socket wall Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  0.05 to 0.25 mm thick depending on patient’s age and function of tooth  Consists of connective tissue fibers, cells, and extracellular matrix Functions of the Periodontal Ligament Fibers  Supportive: Anchors tooth to the socket and separates it from the socket wall  Sensory: Transmit tactile pressure and pain sensation  Nutritive: Blood vessels provide nutrients to the cementum Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com and bone  Formative: Cells to form collagen (fibroblasts), cementum (cementoblasts), and bone (Osteoblasts)  Resorptive: Resorption of bone and sometimes cementum in response to pressure Principal Fiber Groups of the Periodontal Ligament  Alveolar crest fibers  Horizontal fibers  Oblique fibers Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Apical fibers  Interradicular fibers  Only in the furcation area of multirooted teeth. © Wolters Kluwer Sharpey’s Fibers of the Periodontal Ligament  Calcified terminal ends of periodontal ligament fibers embedded in cementum and alveolar Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com bone  Attach when cementum and bone are forming © Wolters Kluwer Microscopic Anatomy of Cementum  Mineralized tissue covering tooth roots (hydroxyapatite: calcium & phosphate)  Attaches tooth to the bone via periodontal ligament collagen fibers Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Maintains integrity of root, helps maintain tooth, and is involved in tooth repair and regeneration  May influence activities of periodontal cells(possible periodontal ligament regeneration) Components of Mature Cementum  Organic portion composed of densely packed collagen fibers and groups of proteins  Mineralized portion made of hydroxyapatite crystals Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  No blood vessels or nerves  Biologic components include growth factor molecules produced during formation and stored in matrix Conservation of Cementum During Periodontal Instrumentation  Historical perspective  Bacterial products penetrate cementum, so aggressive cementum removal is necessary to obtain a treated root surface Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Current research  Bacterial products not located in cementum, and we must preserve cementum for new attachment and growth factors Types of Cementum Page 43  Intermediate (located at CEJ)  Acellular (primary) Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Cellular (secondary) © Wolters Kluwer Three Possible Arrangements of Enamel at the Cementum  Arrangements:  Overlap the enamel  Meet the enamel  Gap Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Often abbreviated OMG  All three may be present © Wolters Kluwer Microscopic Anatomy of Alveolar Bone  Part of maxilla and mandible that forms and supports sockets  Anatomy Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com 1. Alveolar bone proper 2. Trabecular bone 3. Cortical (compact) bone © Wolters Kluwer Microscopic Anatomy of Alveolar Bone (cont.)  Function  Protects roots of teeth  Responds to mechanical forces and inflammation  Characteristics Copyright © 2024 by Jones & Bartlett Learning, LLC. www.jblearning.com  Major cell types: osteoblasts and osteoclasts  Rigid extracellular matrix due to mineralization  Has blood vessels and nerve innervation