Anatomy Mod 10 PDF

Chapter 12‐ Enamel Fehrenbach and Popowics Enamel Characteristics  Hardest mineralized tissue in the human body  Avascular and has no nerve supply  Non‐vital  When lost it is gone forever  Can undergo demineralization and remineralization  Appears radiopaque on x‐ray  Covers the anatomica...

Chapter 12‐ Enamel Fehrenbach and Popowics Enamel Characteristics  Hardest mineralized tissue in the human body  Avascular and has no nerve supply  Non‐vital  When lost it is gone forever  Can undergo demineralization and remineralization  Appears radiopaque on x‐ray  Covers the anatomical crown Enamel Composition Mature enamel by weight: 96% Inorganic material 1% Organic material 3% Water  Calcium hydroxyapetite crystals  Calcium, phosphate, hydroxide  Also contains:  Carbonate, magnesium, potassium, sodium, and fluoride Enamel  Where is enamel thickest?  Near CEJ  In the middle  Near incisal edge/cusps  Where is enamel thinnest?  Near CEJ  In the middle From Anatomy of Orofacial Structures,  Near incisal/cusps 6th ed. by R.W. Brand and D.E. Isselhard, 1998, St. Louis, MO: Mosby. Clinical Significance of Enamel Features  Color  Bluish white  Brittleness  Fairly brittle‐ prone to fracture  Solubility  Acid causes demineralization  Fluoride reduces solubility  Permeability  Ability to be penetrated‐ Fluoride, whitening agents, also stains Enamel Caries‐ Incipient Lesions Microscopic Features of Enamel  Enamel rod  Cylindrical in longitudinal section  Head and tail ends  Longer near cusp tips/ incisal edge  Shorter near CEJ  Interrod enamel  Between enamel rods Appearance of Enamel Rods Enamel Rods Hunter‐Schreger Bands  Crystals in each enamel rod are oriented differently than in other rods  Seen microscopically as light and dark bands in enamel with reflected light Lines of Retzius  Incremental lines formed from daily deposition of enamel matrix  Neo‐natal line  pronounced line of Retzius  found in teeth that are forming at birth Appearance of Enamel  Imbrication lines  Horizontal ridges  Perikymata –  Grooves  Visible on the surface of enamel  Formed by overlapping ends of lines of Retzius Perikymata/ Imbrication lines Enamel Spindles  Blind ends of dentinal tubules  Caused by odontoblasts that lined up on the wrong side of the DEJ Enamel Tufts & Lamellae  Tufts  Located at the DEJ  Form between the groups of enamel rods.  Lamella  Extend from the DEJ to the enamel surface. Fehrenbach and Popowics Properties of Dentin  Bulk of tooth  Yellowish  Less mineralized than enamel  70% inorganic  20% organic  10% water  Slightly elastic  More porous and soluble than enamel  Staining, faster attrition, abrasion and caries spread more quickly Problems with Exposed Dentin Due to gingival recession:  Sensitivity  Staining  Root caries  Maturation of Dentin  2 phases of mineralization  Primary  Initial calcium hydroxyapatite crystal globules form  Produces interglobular dentin  Less mineralized  Secondary  Later, new areas of mineralization occur  Layered on the initial crystals  Produces globular dentin  Complete crystalline fusion‐ highly mineralized (stronger) Components of Dentin  Dentinal tubules  Odontoblast process inside  Contains dentinal fluid  Has an afferent axon  Perceives pain only from different stimuli  Overview: Types of Dentin  In relationship to the  According to the time it dentinal tubules: was formed in the tooth:  Peritubular  Primary dentin  Intertubular  Secondary dentin  Reparative (tertiary)  In relationship to the dentin DEJ:  Sclerotic dentin  Mantle dentin  Circumpulpal Dentin in relation to Dentinal Tubules  Peritubular  Creates the wall of dentinal tubule  Highly mineralized  Intertubular  Found between the dentinal tubules  Less mineralized Dentinal Tubules peritubular intertubular Dentin in Relationship to the DEJ  Mantle dentin (C.)  First predentin that forms in tooth  Highly mineralized  Circumpulpal (B.)  Deep to mantle dentin  Makes up the bulk of the dentin  Lines pulpal wall Dentin based on Time of Development  Primary  Laid down before completion of apical foramen  Secondary  Laid down after completion of apical foramen  Tertiary  Laid down in response to trauma Tertiary Dentin  Causes of injury may include:  Caries  Cavity preparation  Attrition  Recession  Reactive  Made by existing odontoblasts  Reparative  Made by pulpal cells that differentiated into new odontoblasts Sclerotic Dentin  A type of tertiary dentin  Associated with chronic injury  Odontoblasts die leaving dentinal tubules vacant  Tubules fill with minerals  Increases in amount with age  Block caries advance  Permeability to pulp blocked Clinical Considerations‐ Dentinal Tubules  Exposed dentinal tubules can serve as an entryway for bacteria  Leading to caries of the dentin  Rapid expansion, must be restored  Exposed dentinal tubules contribute to sensitivity, triggers for dentinal hypersensitivity include:  Thermal changes  Mechanical irritation  Dehydration  Chemical exposure  Hydrodynamic Theory of Dentinal Sensitivity  Changes in dentinal fluid trigger a pain response in the pulp  Evaporation of fluid  Movement of the fluid  Ionic changes in the fluid Microscopic features of Dentin  Imbrication lines of von Ebner  Look like growth rings on a tree  Show daily deposition of dentin by odontoblasts Microscopic features cont.  Contour lines of Owen  Dark bands of adjoining imbrication lines that show disturbances to odontoblasts Microscopic features cont.  Tomes granular layer  Found beneath cementum in the root  By the DCJ  More interglobular dentin  Less mineralized Aging and Dentin  Diameter of dentinal tubules narrows  Less sensitivity Composition of the Pulp  Innermost part of the tooth  Not mineralized‐ 0% inorganic  Connective tissue proper ‐ soft & gelatinous  Radiolucent on radiographs Functions of the Pulp  Nutritive – blood vessels carry oxygen and nutrition to the tooth  Formative – houses the odontoblast cell bodies that allow for continued formation of dentin  Sensory‐ perceives pain (only)  Protective – WBCs (inflammatory and immune response) Pulp Anatomy  Pulp chamber  Follows the shape of the tooth  Coronal & radicular  In crown  Includes pulp horns  In root  Includes apical foramen & accessory canals Apical Foramen/ Accessory Canals  Apical Foramen  Opening from pulp to PDL  In apex of tooth  Largest opening  Becomes smaller with age  May be at direct apex or off to the side  Accessory Canals  Smaller openings from pulp to PDL  Form when HERS encounters a blood vessel during root formation Apical Foramen/ Accessory Canals  Top arrow – accessory canal  Bottom arrow – main canal of apical foramen Cells of the Pulp  Fibroblasts‐ produce fibers & ground substance  Collagen  Reticular  Most common cell in the pulp  Odontoblasts‐  Cell body only  Mesenchymal cells‐ differentiate to become fibroblasts & odontoblasts Cells of the Pulp Cont.  WBCs‐  Nerves‐  involved in the inflammatory and  Myelinated immune response  Perceive pain only  RBCs‐  Non‐myelinated  Carry oxygen  Extensive vascular supply  Lymphocytes ‐ immune function 4 Microscopic Zones of Pulp  Odontoblastic layer  Cell‐free zone  Cell‐rich zone  Pulpal core 4 Zones of Pulp  Odontoblastic  Next to dentin  Cell bodies of odontoblasts  Secondary or tertiary dentin will encroach on this area  Cell‐free  Fewer cells than odontoblastic layer  Collagen fibers & ground substance (tissue fluid)  Nerve and blood vessel plexus 4 Zones of Pulp  Cell‐rich  fibroblasts, mesenchymal cells, WBCs  collagen fibers & ground substance  larger blood vessels  Central pulp or pulpal core  Many fibroblasts, mesenchymal cells, WBCs  Collagen fibers & ground substance  Large blood vessels & nerves Age Changes in the Pulp  Pulp horns recede  Decrease in cells  Less intercellular substance  fibrosis  Less sensitivity  Obliteration of the apical foramen Comparing Dentin & Pulp from Young to Old Tooth Clinicial Consideration‐ Pulp Stones  True  Mineralized masses of dentin with dentinal tubules and odontoblastic processes  False  Amorphous in structure  Chapter 14 Fehrenbach and Popowics Cementum  Thickest at root apex  Thinnest at the CEJ  Avascular  No nerve supply  Dull yellow in color  Grainy feel with explorer  Easily worn away when exposed in the mouth  Soft‐ gauging of root is possible w/ instruments Composition of Cementum  Inorganic  65%  Water  Calcium hydroxyapatite  12%  Organic  23%  Collagen fibers  Glycoproteins  Proteoglycans Cementum Histology  Mineralized fibrous matrix  Sharpey fibers‐ collagen fibers from the PDL that insert on the cemental surface at a 90 degree angle  Attach root to bone  Intrinsic non‐ periodontal fibers‐ collagen fibers made by cementoblasts Cementum Histology cont.  Cells  Cementocytes‐ entrapped cementoblasts  Lie in a lacuna  With canaliculi  Cementoblasts  Line the PDL space  CEJ Interfaces  3 possible interfaces:  OMG  Overlap, Meet, Gap  M = most common  Consequences of gap Types of Cementum  Acellular  1st layers of cementum  No embedded cementocytes  Width never changes  Cellular  Deposited later  Contains cementocytes  Width can change Cementum Repair  Cementum can be removed from the root resulting in microscopic reversal lines  Arrest lines can be seen microscopically after new secondary cementum is deposited Clinical Consideration‐ Cementicles  Mineralized bodies of cementum  Attached  Free in PDL Alveolar Process  Part of the maxilla or mandible that supports and protects the teeth  60% mineralized/ inorganic  25% organic  15% water  More easily remodeled than teeth  Allows for orthodontic movement Anatomy of the Jaws  2 types of bone  Alveolar process  Contains the roots of the teeth  Basal bone  Apical to the roots of the teeth Alveolar Process Anatomy  Alveolar bone proper  Lining of tooth socket  Compact bone/ lamina dura  Sharpey fibers  Supporting alveolar bone  Cortical plate facial and lingual to the teeth  Trabecular bone between plates and ABP Alveolar Process Anatomy cont.  Interdental septum  ABP (compact bone)  Supporting bone‐ Trabecular bone (cancellous)  Interradicular septum  ABP (compact bone)  Supporting bone‐ Trabecular bone (cancellous) Location of the Alveolar Crest  1‐2 mm apical to the CEJ of the tooth  Creates a scalloped border similar to the gingival margin From Dental Radiography E‐Book, 5th ed. by J.M. Iannucci and L.J. Howerton, 2017, St. Louis, MO: Elsevier. Types of Bone Loss Remodeling of the Alveolar Process  Effect of pressure  Compression zone on one side  PDL crushed  Triggers bone resorption  Tension zone on the other side  PDL stretched  Triggers bone deposition Periodontal Ligament  Appears on radiographs as a radiolucent area  PDL space‐ non‐mineralized  Organized fibrous connective tissue  Allows for a small amount of movement of the tooth  Shock absorber  Sensory function  Can sense more than pain  Pressure, temperature and touch as well  Composition of the PDL  Cells  Fibroblasts  Mesenchymal cells  Epithelial rests  WBCs & lymphocytes  Cementoblasts  Osteoblasts  Osteoclasts  Odontoclasts PDL Principal Fiber Groups  Collagen  Arranged in bundles  Alveolodental ligament  Support tooth  Interdental ligament  Between neighboring teeth  Gingival fiber group  Support free gingiva Alveolodental Ligament Fiber Subgroups  Alveolar crest  Horizontal  Oblique  Apical  Interradicular Interdental Ligament Gingival Fiber Group Changes in the PDL  Hourglass  Wider near apex and CEJ  Narrower in the middle  Excessive function= wider ligament  Lack of function = thinner ligament  Periodontal disease  Disorganization