Dentin nbde part 1 sample by DENTIN

dentin™

NBDE I

COPYRIGHT ©2015. DENTIN, LLC. ALL RIGHTS RESERVED. No part of this book may be produced, stored in a retrieval system, or transmitted in any form, or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission from the publisher. Produced by DENTIN, LLC dentin.co Printed in the United States

dentinâ&#x201E;˘

NBDE I

TABLE OF CONTENTS CHAPTER 1 ANATOMICAL SCIENCES Muscles ................................................................................................................................................ 7 Joints & TMJ ....................................................................................................................................... 16 Bone (Hard Tissue) ............................................................................................................................. 19 Tissues ................................................................................................................................................ 27 PDL & Gingiva ..................................................................................................................................... 35 Tooth Histology & Life Cycle .............................................................................................................. 37 Tooth Tissues ..................................................................................................................................... 40 Enamel Structures .............................................................................................................................. 44 Reproductive System ......................................................................................................................... 47 Gastrointestinal System ...................................................................................................................... 50 Respiratory System ............................................................................................................................ 55 Endocrine System ............................................................................................................................... 58 Urinary System ................................................................................................................................... 68 Lymphatic System .............................................................................................................................. 70 Nervous System ................................................................................................................................. 73 Cranial Nerves .................................................................................................................................... 80 Foramen .............................................................................................................................................. 90 Heart ................................................................................................................................................... 92 Arteries................................................................................................................................................ 98 Veins ................................................................................................................................................. 106 Blood ................................................................................................................................................ 111 Embryology ....................................................................................................................................... 113

dentinâ&#x201E;˘

NBDE I

CHAPTER 2 BIOCHEMISTRY & PHYSIOLOGY The Cell & Cell Division ..................................................................................................................... 117 Cell Membrane ................................................................................................................................. 119 Central Nervous System (CNS) ........................................................................................................ 124 PNS & ANS ....................................................................................................................................... 130 Nerve Transmision ............................................................................................................................ 131 Hormones ......................................................................................................................................... 135 Gastrointestinal Hormones ............................................................................................................... 142 Blood ................................................................................................................................................ 145 Heart Physiology............................................................................................................................... 151 Vitamins, Minerals, & Deficiencies .................................................................................................... 159 Physiologic Disorders ....................................................................................................................... 164 Metabolism ....................................................................................................................................... 168 Oral Cavity Physiology ...................................................................................................................... 171 Muscle .............................................................................................................................................. 173 Respiration ........................................................................................................................................ 177 Reproduction .................................................................................................................................... 180 Sensory Organs ................................................................................................................................ 182 Renal (Kidney) ................................................................................................................................... 185 Liver .................................................................................................................................................. 189 Gastrointestinal System .................................................................................................................... 191 DNA & RNA ....................................................................................................................................... 193 Compounds & Substances ............................................................................................................... 197 Chemistry.......................................................................................................................................... 199 Carbohydrates .................................................................................................................................. 203 Lipids ................................................................................................................................................ 206 Proteins & Amino Acids .................................................................................................................... 211 Enzymes ........................................................................................................................................... 217

dentinâ&#x201E;˘

NBDE I

CHAPTER 3 MICROBIOLOGY & PATHOLOGY Bone Disorders ................................................................................................................................. 225 Hormonal Disorders .......................................................................................................................... 229 Gastrointestinal Disorders ................................................................................................................ 232 Endocrine Disorders ......................................................................................................................... 234 Skin Disorders .................................................................................................................................. 236 Neurological Disorders ..................................................................................................................... 238 Cardiac & Cerebral Disorders ........................................................................................................... 239 Renal Disorders ................................................................................................................................ 244 Eye Disorders ................................................................................................................................... 247 Autoimmune Disorders ..................................................................................................................... 248 Immunology ...................................................................................................................................... 250 Cellular Disorders ............................................................................................................................. 259 Genetic Disorders & Mutations ......................................................................................................... 260 Respiratory Disorders ....................................................................................................................... 262 Blood & Hemodynamic Disorders .................................................................................................... 265 Liver Disorders .................................................................................................................................. 272 Inflammation & Necrosis ................................................................................................................... 275 Neoplasms (Tumors) ......................................................................................................................... 278 Infections .......................................................................................................................................... 289 Plaque, Caries, Calculus ................................................................................................................... 293 Cells & Organelles............................................................................................................................. 296 Pathogen Sterilization & Disinfection ................................................................................................ 299 Wound Healing, Grafts, & Teratology ............................................................................................... 302 Bacteria............................................................................................................................................. 305 Antibiotics ......................................................................................................................................... 317 Viruses .............................................................................................................................................. 321 Vaccines ........................................................................................................................................... 332 Fungi ................................................................................................................................................. 334 Parasites ........................................................................................................................................... 337

dentinâ&#x201E;˘

NBDE I

CHAPTER 4 DENTAL ANATOMY & OCCLUSION Tooth Anatomy ................................................................................................................................. 340 Eruption Sequence ........................................................................................................................... 343 Deciduous (Primary) Teeth ............................................................................................................... 346 Succedaneous Anterior Teeth .......................................................................................................... 350 Succedaneous Posterior Teeth ........................................................................................................ 357 Periodontium Anatomy ..................................................................................................................... 368 Tooth Histology & Development ....................................................................................................... 374 Enamel, Dentin, Cementum, Pulp..................................................................................................... 376 Parafunction & Erosion ..................................................................................................................... 381 Muscles & TMJ ................................................................................................................................. 382 Mandibular Movements & Positions ................................................................................................. 387 Posterior Contacts in Ideal MICP ..................................................................................................... 389 Anterior Contacts in Ideal MICP ....................................................................................................... 391 Curves of Spee & Wilson .................................................................................................................. 392 Centric Occlusion, Centric Relation, & Rest ..................................................................................... 393 Articulation, Occlusal Balance & VDO .............................................................................................. 396

CHAPTER 5 NBDE I TEST PEARLS Anatomy & Physiology ...................................................................................................................... 405 Biochemistry & Physiology ............................................................................................................... 409 Microbiology & Pathology................................................................................................................. 414 Dental Anatomy & Occlusion ............................................................................................................ 418

dentinâ&#x201E;˘

NBDE I

dentin™

NBDE I

MUSCLES SOFT PALATE-mobile fold attached to the hard palate that separates the oral cavity from the nasopharynx. Attached laterally to the tongue by glossopalatine arches, and to the lateral wall of the pharynx by pharyngopalatine arches. • Palate salivary glands are in the posterolateral zone, derived from ectoderm and are separated by C.T. septa. Two arches formed by the anterior & posterior pillars of the Fauces: 1. glossopalatine arch (palatoglossal arch)-formed by anterior pillars. Palatoglossus muscle is below this arch and elevates the tongue and narrows the fauces. It’s the posterior boundary of the oral cavity, and anterior boundary of the fauces. 2. pharyngopalatine arch (palatopharyngeus arch)-formed by posterior pillars. • Palatopharyngeus muscle-located below this arch, it elevates the pharynx, shuts the nasopharynx, narrows the fauces, and aids in swallowing. During swallowing, muscular contraction causes movements that seal off the oropharynx from the nasopharynx. Palatopharyngeus muscle CAUSES MOVEMENTS THAT FORM A FOLD IN THE POSTERIOR WALL OF THE PHARYNX. PALATINE TONSILS-consist mostly of lymphoid tissue, found between the two arches in the “fauces area”= passageway from the oral cavity to the oral pharynx. Soft Palate-consists of 5 paired skeletal muscles: 1. Tensor veli palatini-tenses soft palate & opens mouth of auditory tube during swallowing/yawning. It curves around pterygoid hamulus, so if hamulus fractures, it affects tensor veli palatini. Its tendon loops around pterygoid hamulus. 2. Levator veli palatini-elevates soft palate. 3. Palatoglossus-draws soft palate down to the tongue, closing the oropharyngeal isthmus. 4. Palatopharyngeus-elevates pharynx, pulls palatopharyngeal arches toward midline, & closes nasopharynx. 5. Muscularis uvulae-elevates uvula.

Pharyngeal plexus INNERVATES all soft palate muscles EXCEPT Tensor veli palatini (innervated by nerve to the medial pterygoid) = branch of mandibular division of trigeminal nerve (V3). Soft Palate receives blood supply from: 1. greater and lesser palatine arteries (descending palatine artery branches of maxillary artery) 2. ascending palatine artery (facial artery branch) 3. palatine artery (ascending pharyngeal artery branch) Anterior zone of the palatal submucosa contains fat, and posterior zone contains mucous glands. Soft palate ends posteriorly in the midline as a conical projection = UVULA • Bifid uvula-results from failure of complete fusion of the palatine shelves.

dentin™

NBDE I

TONGUE-all tongue muscles (intrinsic & extrinsic) are innervated by Hypoglossal nerve (CN XII) EXCEPT palatoglossus muscle (innervated by pharyngeal plexus of CNX). •

Paired Extrinsic Tongue Muscles: originate on structures away from the tongue and insert onto it causing tongue movements during speaking, food manipulation, cleaning teeth, and swallowing: 1. Genioglossus-protrudes tongue apex through mouth (sticks out tongue). Origin is superior genial spine of mandible. Insertion is dorsum of tongue. Innervation: hypoglossal nerve. 2. Hyoglossus-depresses side of tongue. Origin is hyoid bone. Inserts on side of tongue. CN XII. 3. Styloglossus-elevates and retracts tongue. Origin is styloid process of temporal bone. Insertion: lateral side and dorsum of tongue. Innervation: hypoglossal nerve. 4. Palatoglossus-pulls tongue root up and back (elevates the tongue). Origin: palatine aponeurosis. Insertion: side of tongue. Innervation: PHARYNGEAL PLEXUS of Vagus.

•

Intrinsic Tongue Muscles: longitudinal, transverse, and vertical muscles alter tongue shape, and are confined to the tongue and NOT attached to bone. All are innervated by HYPOGLOSSAL NERVE. Intrinsic muscles are named based on the 3 spatial planes that they run.

•

Tongue develops from: copula, tuberculum impar, 2nd & 3rd brachial arches, & lateral lingual swellings.

Tongue Blood Supply: 1. lingual artery (from tonsilar branch of facial artery) 2. ascending pharyngeal artery 3. veins drain into the internal jugular vein. Tongue Lymph Drainage: 1. tip of tongue-drains into submental lymph nodes. 2. remaining anterior 2/3-drains into submandibular and deep cervical lymph nodes on both sides. 3. posterior 1/3-drains into deep cervical lymph nodes on both sides. CARDIAC MUSCLE FIBERS-make up the myocardium (thick, middle layer of the heart). It is striated muscle that contains transverse tubules, a slow rate of calcium sequestration, and is inhibited by acetylcholine. • Have MORE mitochondria b/t myofibrils and richer in myoglobin than most skeletal muscle. • Like skeletal muscle, contain mylofilaments (contractile units) and are STRIATED with actin & myosin. • Have LARGER t-tubules and LESS DEVELOPED sarcoplasmic reticulums than skeletal muscle fibers. • Cardiac muscle fibers are short, branched, and single or binucleated in contrast to skeletal muscle fibers. • Contain large, oval centrally placed nuclei, and strong, thin unions b/t fibers = INTERCALATED DISCS. o Intercalated discs-junctions b/t cardiac muscle cells that provide low resistance to current flow. Contains desmosomes which are within the discs to attach cells, and gap junctions to communicate electrical impulse from cell-to-cell. •

Cardiac muscle fibers CONTRACT SPONTANEOUSLY WITHOUT NERVE SUPPLY. Cardiac fibers respond to increased demand by increasing its fiber size = Compensatory hypertrophy.

dentin™ •

NBDE I

Cardiac and skeletal muscle fibers cannot mitotically divide. Certain smooth muscle fibers can under hormonal influences (e.g. during pregnancy myometrium smooth muscle fibers of the uterus increase in length and form new cells).

SKELETAL MUSCLE FIBERS-attaches to the skeleton responsible for voluntary body movement. Consists of BUNDLES of very long, narrow, cylindric, multinucleated cells with regularly ordered myofibrils = STRIATED (distinct transverse striations) that span a joint attached at either end by a tendon. Comprises ~40% of a person’s body weight. • slender ovoid or elongated nuclei, and are situated peripherally. • CONTAIN transverse tubules (t-tubules) & WELL-DEVELOPED sarcoplasmic reticulum. • FAST, FORCEFUL VOLUNTARY CONSCIOUS CONTRACTION caused by myofibrils (ACTIN & MYOSIN) = contractile element proteins of skeletal muscle that reduces sarcomere length. Actin Filaments (thin myofilaments 5-8nm diameter) is composed of: 1. Actin-globular actin (G-actin) molecules arranged in double spherical chains = fibrous actin (F-actin). 2. Tropomyosin-long threadlike molecules that lie on the surface of F-actin strands and physically cover actin binding sites during the resting state. 3. Troponin-small oval molecule attached to each tropomyosin. Myosin Filaments (thick myofilaments 12-18nm diameter) composed of myosin which has two components: 1. light meromyosin (LMM)-makes up the rod-like backbone of myosin filaments. 2. heavy meromyosin (HMM)-forms shorter globular lateral cross-bridges that link to actin binding sites during contraction. Skeletal muscle contracts when a stimuli from the nervous system excites individual muscle fibers. This starts as a series of events leading to interactions b/t myosin (thick filaments) and actin (thin filaments) of the sarcomeres of the fibers. • Skeletal muscle fiber origin is the stationary attachment, and their insertion is the movable attachment. • Skeletal muscle fibers are classified by their fiber arrangement (parallel, convergent, circular, or pinnate). • Each skeletal muscle fiber is innervated by an axon of a motor neuron terminal at a motor end plate (a large complex terminal formation by which an axon of a motor neuron establishes synaptic contact with a skeletal muscle). • The axon of a motor neuron is highly branched, thus one motor neuron innervates many muscle fibers. When a motor neuron transmits an impulse, ALL fibers it innervates contract simultaneously. Skeletal muscle fibers are enclosed/covered by sheets of fibrous C.T. (fascia): 1. Endomysium-fine C.T. sheath surrounding an individual skeletal muscle fiber. 2. Perimysium-fibrous sheath surrounding a bundle of muscle fibers. 3. Epimysium-external C.T. sheath surrounding an entire muscle. Sarcoplasmic reticulum-the organelle that releases & stores calcium ions during contraction and relaxation of skeletal muscle. It’s a network membranous channels of tubules and sacs in skeletal muscles that extends throughout the sarcoplasm. Similar to the endoplasmic reticulum of other cells.

dentin™

NBDE I

TOOTH TISSUES PULP FUNCTIONS: MAIN FUNCTION of dental pulp is to FORM DENTIN (FORMATIVE). 1. Formative (main function)-peripheral layer of pulp cells gives rise to the odontoblasts that form dentin. 2. Nutritive-pulp keeps organic components of the surrounding mineralized tissue supplied with moisture and nutrients. Very rich blood supply that surrounds the odontoblasts. 3. Sensory-free nerve endings that contact the odontoblasts to sense extremes in temp, pressure, or trauma to dentin or pulp which are perceived as pain. 4. Protective- Responds to external stimuli that may trigger formation of reparative or secondary dentin. PULP CAPPING is more successful in YOUNG TEETH because the apical foramen is larger AND young pulp contains more odontoblastic cells, is very vascular, less fibrous, and has more tissue fluid than adult pulp. YOUNG PULP LACKS COLLATERAL CIRCULATION. As pulp ages, PULP SIZE & NUMBER OF RETICULIN FIBERS DECREASES. • As pulp ages reticulin fibers decrease (the pulp becomes less cellular and more fibrous). The size of the pulp also decreases because of continued deposition of dentin. •

As pulp ages, the number of collagen fibers and calcification (pulp stones or denticles) within the pulp increases.

PULP contains MYELINATED & UNMEYLINATED NERVE FIBERS (afferent and sympathetic). Sympathetic and afferent fibers are the primary nerves in dental pulp. 1. myelinated fibers are sensory 2. unmyelinated fibers are motor and regulate lumen size of blood vessels. 3. free nerve ending-the only type of nerve ending found in pulp. It’s a specific pain receptor. Regardless of the source of stimulation (heat, cold, pressure) the only response is PAIN. 4. Proprioceptors-respond to stimuli regarding movement (found in gingiva, skeletal muscle, PDL, TMJ) BUT NOT FOUND IN PULP! Anatomically, PULP is divided into two portions (CORONAL & RADICULAR PULP): 1. Coronal Pulp-located in the pulp chamber and pulp horns (CROWN portion of tooth). 2. Radicular Pulp-located in pulp canals (ROOT portion of tooth). • Accessory Canals extend from pulp canals through the root dentin to the PDL. CENTRAL ZONE (PULP PROPER)-area that contains large nerves and blood vessels, lined peripherally by a specialized odontogenic area that has 3 layers: 1. Cell-rich zone-contains fibroblasts = the most numerous cell type found in dental pulp. 2. Cell-free zone (zone of Weil)-rich in capillaries and nerve networks. 3. Odontoblastic layer-contains odontoblasts and lies next to predentin and mature dentin. Odontoblasts are derived from ectomesenchyme. DENTAL PULP CELLS: fibroblasts, odontoblasts, histiocytes (macrophages), and lymphocytes. • Diseased pulp contains: plasma cells, PMN’s, monocytes, and eosinophils.

dentin™

NBDE I

PERIKYMATA-tiny valleys on the TOOTH (CROWN) SURFACE created by the termination of the lines of Retzius, and travel circumferentially around the crown. MATURATION OF ENAMEL is characterized by a percentage INCREASE in inorganic content and a percentage DECREASE in water and organic content. COMPARISON OF TOOTH TISSUES

Mineral Content Color Formative cells Embryology Repair Aging Sensitivity Cells in mature tissues

ENAMEL 96% (highest)

DENTIN 70%

CEMENTUM 50%

Translucent yellow Ameloblast Epithelial No replacement, some remineralization Wear, staining, caries

Light yellow Odontoblast Ectomesenchyme Physiological, reparative, secondary dentin Increase in secondary and sclerotic dentin Yes-only as pain Cytoplasmic extensions from odontoblasts

Light yellow Cementoblast Ectomesenchyme New cementum deposition

None None

Increased amount with age (apex) No Cementocytes

PULP 0% (except denticles/pulp stones) Blood red Dental Papilla Ectomesenchyme Can recover if mild inflammation but severe = death Reduced size and may be obliterated. Yes Odontoblasts and other cell types

ORTHODONTIC MOVEMENT OF TEETH: always causes remodeling of alveolar bone proper to accommodate teeth movement. • If a tooth is tilted MESIALLY during orthodontics, the CORONAL HALF of the mesial wall shows resorption due to osteoclastic activity, while the CORONAL HALF of the distal wall shows deposition due to osteoblastic activity. • A similar situation is the alternate loosening and tightening of a deciduous tooth before it is lost caused by the alternate resorption (cementoclasts, osteoclasts) and apposition (cementoblasts, osteoblasts) of cementum and bone. • During active tooth eruption, there is apposition of bone on all alveolar crest surfaces and on all walls of the bony socket. Permanent teeth move OCCLUSALLY & BUCALLY when erupting. • In a newly erupted tooth, the junction between tooth surface and the crevicular epithelium consists of a basal lamina-like structure between enamel and epithelium. Apical abscesses of MANDIBULAR SECOND & THIRD MOLARS have a marked tendency to produce cervical spread of infection MOST RAPIDLY. Attachment of muscles may determine the direction/route that an infection will take, channeling the infection into certain tissue spaces. •

INFECTIONS OF MANDIBULAR TEETH (Especially 2nd & 3rd molars) perforate the bone below the buccinator causing swelling of the lower half of the face. The infection spreads medially from the mandible into the submandibular and masticatory spaces. It pushes the tongue forward and upward. Further spread cervically may involve the visceral space and lead to edema of the vocal cords and airway obstruction.

dentin™

NBDE I

MAJOR SALIVARY GLANDS (parotid, submandibular, & sublingual) are compound tubuloalveolar glands that deliver salivary secretions into the mouth by way of large excretory ducts (Stenson’s, Wharton’s, and numerous small Rivian ducts). • Parasympathetic innervation controlling salivation originates in cranial nerves VII and IX. Major Salivary Glands: Parotid (purely serous), Submandibular (submaxillary-mixed with serous demilunes), & Sublingual Glands (mixed with serous demilunes). • All major salivary glands are compound tubuloalveolar glands (their ducts branch repeatedly (compound) and their secretory portions are tubular and composed of small sacs (alveoli or acini). •

Salivary gland EPITHELIUM.

striated

ducts

are

composed

SIMPLE

LOW

COLUMNAR

PAROTID GLANDS-LARGEST salivary gland, and is PURELY SEROUS. The parotid glands are below and just anterior to the ear. It divides into deep and superficial lobes with the stylomandibular tunnel (encloses facial nerve) being the dividing line. Thus, part of the parotid lies superficial to the mandibular ramus, and another portion lies deep. • STENSON’S DUCT-drains the parotid gland. Stenson’s duct pierces the buccinator muscle and crosses the masseter muscle where it drains into the vestibule of the mouth opposite the maxillary second molar. •

Innervation: receives parasympathetic secretomotor innervation from glossopharyngeal nerve (via lesser petrosal nerve), otic ganglion, and auriculotemporal nerve (V3 branch).

•

Facial nerve (CN7), retromandibular vein, & external carotid artery LIE INSIDE the parotid gland. EXTERNAL CAROTID ARTERY and its terminal branches (superficial temporal and maxillary arteries) within the parotid, supply the parotid.

•

If a needle is advanced to far posteriorly during an inferior alveolar block injection, anesthesia of the mandibular teeth will NOT OCCUR because the needle has entered the PAROTID GLAND.

•

As a result of a mandibular block injection, a patient can develop paralysis of the muscles of facial expression due to depositing anesthetic solution into the parotid gland.

dentin™

NBDE I

PANCREAS-a triangular organ that lies across the posterior abdominal wall. It’s a retroperitoneal organ (except a small part of its tail which lies in the lienorenal ligament). The pancreas head and neck rests in the curve of the duodenum, and its body stretches horizontally behind the stomach, and its tail extends to the spleen. PANCREAS IS BOTH AN ENDOCRINE & EXOCRINE GLAND with groups of special cell scattered among glandular alveoli. 1. Islets of Langerhans (Endocrine Portion)-3 types: • Alpha cells-secrete glucagon which counters the action of insulin. Increase blood sugar. • Beta cells-secrete insulin that helps carbohydrate metabolism. Decrease blood sugar. • Delta cells-secrete somatostatin which inhibits growth hormone. • *degeneration of the Islets of Langerhans cells lead to DIABETES MELLITUS. 2.

Acinar Cells (Exocrine Portion)-produce pancreatic juice that contains trypsinogen and other digestive enzymes. Trypsinogen is then converted to trypsin in the small intestine.

The primary histologic characterstic of the pancreas is groups of special cell scattered among glandular alveoli.

PANCREAS DUCTS (2): 1. Duct of Wirsung-MAIN EXCRETORY DUCT OF PANCREAS that begins at the tail, joins the common bile duct from the gallbladder to form the hepatopancreatic ampulla (ampulla of Vater) before opening into the duodenum. Ampulla of Vater discharges bile and pancreatic enzymes into the duodenum. 2.

Santorini’s duct-an accessory pancreatic duct that begins in the lower portion of the pancreas head and opens into the duodenum.

THYROID GLAND-located in the neck, just below the larynx (Adam’s apple). Its two lateral lobes (one on each side of the trachea) join with the isthmus-a narrow tissue bridge that contracts the trachea to give the gland its butterfly shape. • Thyroid gland is a very vascular organ that receives its blood supply from superior and inferior thyroid arteries. It is innervated from glandular branches of the three cervical ganglia of the sympathetic trunk. Lymph from the thyroid gland drains laterally into the deep cervical lymph nodes.

dentinâ&#x201E;˘

116

NBDE I

dentin™

NBDE I

THE CELL PROTOPLASM-a viscous, translucent, watery material that is the primary component of plant and animal cells. It contains a large percentage of water, inorganic ions (potassium, calcium, magnesium, and sodium), and naturally occurring organic compounds (proteins, lipids, and carbohydrates). Types of protoplasms: 1. Nucleoplasm-the protoplasm of the cell nucleus that plays a role in reproduction. 2. Cytoplasm-the protoplasm of the cell body that surrounds the nucleus, converts raw materials into energy. A clear, thin film of protoplasm (cell membrane) always surrounds the cytoplasm. Ectoplasm-the outer part of the cytoplasm. 3. Cytoplasm is the site of most synthesizing activities and contains: • Cytosol-viscous, semitransparent fluid that is 70-90% water. •

Organelles (mitochondria, peroxisomes)

ribosomes,

vacuoles,

lysosomes,

centrosomes,

•

Metaplasm (cytoplasmic inclusions)-lifeless substances (yolk, fat, starch) that may be stored in various parts of the cytoplasm. Examples: glycogen (carbohydrate deposits in liver cells), fat deposits, pigment granules (deposits of colored substances). Two types of pigment granules: 1. Lipofuscin-yelllowish-brown substance that increases in quantity as cells age. 2. Melanin-abundant in epidermis of the skin and retina.

ORGANELLES: 1. Centrosomes-organelle that contains centrioles (short cylinders adjacent to the nucleus that take part in cell division). 2. Peroxisomes-contain oxidases, enzymes capable of reducing oxygen to hydrogen peroxide and hydrogen peroxide to water. Beta-oxidation of very long chain fatty acids begins in peroxisomes. 3. Ribosomes-sites of most protein synthesis. 4. Mitochondria-threadlike structures within the cytoplasm that provide most of body’s ATP (fuels cellular activities). 5. Vacuoles-store and excrete various substances within the cytoplasm. 6. Lysosomes-digestive bodies formed in the golgi apparatus that break down foreign or damaged materials in cells. Contain hydrolytic enzymes. 7. Cytoskeletal elements-form a network of protein structures. 8. Endoplasmic Reticulum (ER)-organelle & extensive network of membrane-enclosed tubules in the cell cytoplasm involved in protein and lipid synthesis, and transport these metabolites within the cell. • granular (rough surfaced ER)-has ribosomes attached to the membrane surface. • agranular (smooth surfaced ER)-no ribosomes, but enzymes that synthesize lipids. CELLULAR COMPONENTS: 1. Golgi Apparatus-synthesizes COMPLEX CARBOHYDRATES that combine with protein produced by RER to form secretory products (e.g. lipoproteins). Procollagen filaments are produced by the golgi apparatus. 2. Endoplasmic Reticulum-extensive network of internal membrane-enclosed tubules. RER is covered with ribosomes and produces certain proteins. Smooth ER contains enzymes that synthesize lipids. Involved in coordinating protein synthesis. Two types of ER:

117

dentinâ&#x201E;˘

NBDE I

Plasma Mast Schwann Sertoli Leydig Fibroblast Osteoblast Odontoblast Ameloblast T-lymphocytes B-lymphocytes Alpha cells Beta cells

CELLS & THEIR PRIMARY FUNCTION PRIMARY FUNCTION Antibody Synthesis Mediators of inflammation on contact with antigen Form myelin sheath around axons of the PNS Produces testicular fluid Produces testosterone Produces collagen and reticular fibers Forms bone matrix, gives rise to osteocytes Forms dentin Forms enamel Cell-mediated immunity Differentiate into plasma cells Produce glucagon (in pancreas) Produces insulin (in pancreas)

CELL Sustentacular Pyramidal Endothelial Ependymal Clara Ganglionic Globular Prickle Fibroblast Chromaffin Purkinje Goblet Interstitial Islet Juxtaglomerular Mesenchymal

CELLS & THEIR PRIMARY FUNCTION PRIMARY FUNCTION Internal ear (organ of Corti), taste buds, olfactory epithelium Cerebral cortex (cerebrum) Lining blood and lymph vessels, endocardium (inner layer) Lining the brain ventricles and spinal cord Terminal bronchioles In a ganglion peripheral to the CNS Transitional epithelium (kidney, ureter, bladder) Stratum spinosum of epidermis Most common cell of connective tissue Adrenal medulla and paraganglia of SNS Cerebellar cortex (cerebellum) Mucous membranes of respiratory and intestinal tracts C.T. of ovary and testis Pancreas Renal corpuscle of kidney Found between ectoderm and endoderm of embryos

CELL

123

dentin™

NBDE I

CENTRAL NERVOUS SYSTEM (CNS) CEREBRUM-divided into right and left hemispheres connected by nerve fibers = CORPUS CALLOSUM. Each hemisphere has 4 lobes: 1. Frontal Lobes-control skilled motor behavior (speech, mood, thought, and planning for the future). In most people, the control of language is situated predominantly in the left frontal lobe. 2. Parietal Lobes-interpret sensory input for the rest of the body and control body movement. 3. Occipital Lobes-interpret vision. 4. Temporal Lobes-generate memory and emotions (contains the limbic system). CEREBELLUM-functions to maintain muscle tone, coordinate voluntary muscle movement, and control balance. Cerebellum lies below and posterior to the cerebrum just above the brainstem (pons, midbrain, & medulla). It is morphologically divided into two lateral hemispheres and a middle portion. Its function is to coordinate voluntary muscular activity, maintaining equilibrium, and coordination. BRAINSTEM-lies immediately inferior to the cerebrum, just anterior to the cerebellum. Brainstem consists of: 1. Midbrain-connects dorsally with cerebellum, and contains large voluntary motor nerve tracts. 2. Pons-connects the cerebellum with the cerebrum, and links the midbrain to the medulla oblongata; serves as the exit point for cranial nerves V, VI, and VII. Pons is the primary link between the nervous and endocrine systems. 3. Medulla Oblongata-is the lowermost portion of the vertebrate brain, continuous with the spinal cord. It joins the spinal cord at the level of the foramen magnum. It contains the cardiac, vasomotor, and respiratory centers of the brain, serving as an autonomic reflex center to maintain homeostasis, regulating respiratory, vasomotor, and cardiac functions. Mediates reflexes like blinking, coughing, vomiting, swallowing. It’s the origin of the VAGUS NERVE. LIMIBIC SYSTEM-the PRIMITIVE BRAIN area deep within the TEMPORAL LOBE of the brain. Limbic system initiates basic drives: hunger, aggression, EMOTIONAL feelings, sexual arousal, and screens all sensory messages traveling to the cerebral cortex. HYPOTHALAMUS-a collection of nerve cells at the base of the cerebrum (CNS) that regulates or affects body temperature, water balance, appetite, sleep, pituitary secretions, emotions, carbohydrate metabolism & autonomic nervous system functions (e.g. sleep and wakeful cycles). Hypothalamus is a collating center for information concerned with good body health and in turn, much of this information controls secretions by the pituitary gland. • hypothalamus controls many vital processes associated with the autonomic nervous system (ANS). Hypothalamus is involved in regulating body temperature, water balance, appetite, GI activity, sexual activity, sleep, and emotions of fear and rage. Hypothalamus also regulates the release of pituitary gland hormones, thus, it greatly affects the ENDOCRINE SYSTEM. •

Hypophyseal Portal Vessels-carry hypothalamic releasing factors to anterior lobe of pituitary gland (adenohypophysis).

THALAMUS-a large ovoid mass of gray matter that RELAYS ALL SENSORY STIMULI (except olfactory) as they ascend to the cerebral cortex. Thalamus is a collection of nerve cells at the base of the cerebrum.

124

dentin™

NBDE I

SENSORY ORGANS EAR-consists of three major parts: 1. External Ear-consists of the external part (pinna) and ear canal. It receives sound waves. • Auricle (pinna)-directs sound waves. • External auditory canal (meatus)-contains hair and cerumen (brown earwax); serves as a resonator. 2. Middle Ear (tympanic cavity)-an air-filled cavity in the temporal bone that communicates anteriorly with the nasopharynx via the Eustachian (Auditory) tube (pharyngotympanic tube). Middle ear communicates posteriorly with the mastoid air cells and the mastoid antrum through the aditus ad antrum. Eustachian tube serves to equalize air pressure in the tympanic cavity and nasopharynx. • Auditory tube-regulates pressure. •

Ossicles (malleus (hammer), incus (anvil), stapes (stirrup)-three small bones linked together to transmit sounds.

•

Stapedius muscle (smallest skeletal muscle in the body) and tensor tympani muscle.

•

Middle ear infections (otitis media) are quite prevalent and may become extensive due to connection to both the mastoid air cells and the nasopharynx by way of the Eustachian tube.

3. Inner Ear-formed by a bony labyrinth and a membranous labyrinth. Consists of the acoustic apparatus, vestibular apparatus, semicircular canals, and a bony and membranous laryrinth: • Vestibule apparatus (saccule and utricle)-associated with sense of balance. • Semicircular canals-concerned with equilibrium. • Cochlea (contains two membranes: vestibular and basilar)-portion of inner ear responsible for hearing. • Organ of Corti-a spiral organ that contains hair cell receptors for hearing and is responsible for sound perception.

182

dentinâ&#x201E;˘

224

NBDE I

dentin™

NBDE I

BONE DISORDERS FRACTURE-the most common bone lesion. Healing of fractures involves 3 phases: 1. Inflammatory phase-characterized by formation of a blood clot. 2. Reparative phase-characterized by formation of a callus of cartilage, replaced by a bony callus (compact bone). 3. Remodeling phase-the cortex is revitalized. Reasons Fractures Fail to Heal (non-union): 1. Ischemia-the navicular bone of the wrist, femoral neck, and lower third of the tibia are all poorly vascularized and thus, subject to coagulation necrosis after a fracture. 2. Excessive mobility-pseudoarthrosis or a pseudojoint may occur. 3. Interposition of soft tissue-between the fractured ends. 4. Infection-most likely with compound fractures. Fat embolism-is most often a sequela of fractured bones due to the mechanical disruption of bone marrow fat and by alterations in plasma lipids. Osteochondroma-a benign tumor made of bone and cartilage, found most frequently near the ends of long bones. Most common in patients 10-25 years old. OSTEOCHONDROSES-a group of diseases that affects the growth plate during childhood, resulting in abnormal bone growth and deformity. Their cause unknown. Different diseases affect different bones, characterized initially by degeneration and aseptic necrosis followed by regeneration and reossification. Types of Osteochondroses: 1. Osgood-Schlatter Disease-inflammation of bone and cartilage at the top of the SHINBONE. Usually develops between ages 10-15 more common in athletic boys. Major symptoms: pain, swelling, and tenderness at the top of the shin. It usually involves the tibial tubercle of the knee. 2. Legg-Calve-Perthes Disease-destruction of the growth plate in the neck of the thighbone. Develops between ages 5-10, more common in boys. Caused by poor blood supply to the neck of the thighbone. Main symptoms are hip pain and problems walking. 3. Scheuermann’s Disease-relatively common condition in which backache and humpback (kyphosis) are caused by changes in vertebrae. Usually begins in adolescence, affecting mostly boys. Symptoms are rounded shoulders and persistent mild backache. 4. Kohler’s bone Disease-a rare form of inflammation of bone and cartilage (osteochondritis) affecting one of the small bones (navicular bone) in the foot. Usually affects children (boys 3-5 years). Symptoms are swollen foot with limping. OSTEOMALACIA-caused by VITAMIN D DEFICIENCY in adults. Characterized by a gradual softening and bending of the bones with varying severity of pain. This softening of the bones occurs b/c the bones contain osteoid tissue that failed to calcify due to lack of vitamin D. •

All bones are effected, specifically their epiphyseal growth plates. It is identified radiographically by diffuse radiolucency that can mimic osteoporosis. Bone biopsy is often the only way to differentiate between osteoporosis and osteomalacia.

•

Osteomalacia is the ADULT FORM OF RICKETS, appearing more in women. It may be asymptomatic until fracture occurs.

225

dentin™

NBDE I

TYPE III Hypersensitivity Reactions: 1. SERUM SICKNESS-an acute, self-limited disease that occurs 6-8 days after injecting a foreign protein (bovine albumin), characterized by fever, arthralgias, vasculitis, & an acute glomerulonephritis. Serum sickness is an example of a systemic Arthus reaction. • Serum sickness is a reaction that is a type of immune complex disorder (Type 3 hypersensitivity) that results when patients are given large doses of foreign serum (most often horse serum). The antigens in these serums stimulate an immune response. Immune complexes form between the residual antigens and circulating antibody. These antigen-antibody complexes are then deposited at certain body sites (joints, kidneys, and vessel walls). 2. ARTHUS REACTION-another type of immune complex disorder that involves severe local sensitivity at the site of injection of antigen. This reaction requires prior sensitization. When an antigen-antibody complex initiates such a reaction in alveoli, symptoms include fever, cough, and difficulty breathing. Symptoms typically develop over 4-6 hour period. The attack subsides within a few days. 3. SYSTEMIC LUPUS ERYTHEMATOSUS (Lupus)-an autoimmune disease that results in episodes of inflammation of joints, tendons, and other C.T. and organs. HISTAMINE DOES NOT PLAY A ROLE IN ABOVE TYPE 3 HYPERSENSITIVITY REACTIONS.

HYPERSENSITIVITY REACTION COMPARISON Reaction Type I

III

Alternate Name Allergy (immediate)

Disorders

Mediator

Description

Atopy, anaphylaxis, asthma, hay fever

IgE

Fast response (minutes); involves mast cells and basophils

Immune complex disease Cell-mediated immune memory response, antibodyindependent

Thrombocytopenia Rheumatic Heart Goodpasture’s Syndrome Erythroblastosis fetalis Grave’s Disease Myasthenia Gravis Serum sickness Rheumatoid Arthritis Lupus Contact dermatitis Multiple Sclerosis Mantoux test TB Sarcoidosis Transplant Rejection

Autoimmune disease

Graves’ Disease Myasthenia Gravis

Cytotoxic, antibodydependent

249

IgM or IgG Complement MAC

Cellular destruction via MAC

IgG Complement Neutrophils

Circulating immune complex deposited in vessel walls of joints and kidney

Helper T-cells

Th1 cells activate macrophages to cause an inflammatory response and tissue damage

IgM or IgG Complement

Testing with Coombs Test

dentin™

NBDE I

IMMUNOLOGY MAIN FUNCTION of the IMMUNE SYSTEM is to prevent or limit infections by microorganisms (bacteria, viruses, fungi, and parasites). Protection is provided by cell-mediated and antibodymediated (humoral) arms of the immune system: 1. CELLULAR IMMUNITY-a specific acquired immunity involving T cells. It acts to resist most intracellular pathogens (bacteria and viruses). It involves soluble factors from Tlymphocytes (lymphokines) and macrophages (monokines). • Cell mediated immunity (arm) consists primarily of T-lymphocytes (e.g. helper T cells and cytotoxic T cells). 2. HUMORAL IMMUNITY (antibody-mediated immunity)-immunity produced by the activation of the B-lymphocyte population which produces immunoglobulins (IgA, IgD, IgM). Circulating antibodies are produced by plasma cells (are differentiated B cells) within lymphatic tissue. The key to humoral immunity is the ability of antibodies to react specifically with antigens. This type of immunity provides PROTECTIONS AGAINST ENCAPSULATED BACTERIA. • Antibody-mediated immunity (humoral immunity) involves B-lymphocytes & plasma cells. Complement & Phagocytes are two other MAJOR IMMUNE SYSTEM COMPONENTS. NATURAL (INNATE) IMMUNITY-immunity that occurs naturally as a result of a person’s genetic constitution or physiology, and does not arise from a previous infection or vaccination. It is nonspecific, does not improve after exposure to the organism, and its processes have no memory. • Natural immunity (innate) is resistance not acquired through contact with an antigen. ACQUIRED IMMUNITY-occurs AFTER EXPOSURE to an agent, improves upon repeated exposure, and is specific. It is mediated by antibody and T-lymphocytes (T helper and cytotoxic T cells). The cells responsible for acquired immunity have long-term memory for a specific antigen. Acquired immunity is specific, improves after repeated exposure, and has “long-term” memory for an antigen. ACQUIRED IMMUNITY-occurs naturally and artificially. It can be ACTIVE or PASSIVE. • Naturally (innate) Active immunity-person is exposed to an antigen and the body produces antibodies. • Naturally (innate) Passive immunity-antibodies (IgG) passed from mother to fetus during pregnancy and IgA passed from mother to newborn during breast-feeding. • •

Artificially Active immunity-vaccination with killed, inactivated, or attenuated bacteria or toxoid. Artificially Passive immunity-injection of immune serum or gamma-globulin.

ACTIVE IMMUNITY-the host actively produces an immune response consisting of antibodies and activated helper and cytotoxic T lymphocytes. The main advantage of active immunity is RESISTANCE IS LONG TERM (years). The major disadvantage is its SLOW ONSET. PASSIVE IMMUNITY-antibodies are preformed in another host. It is not as permanent and does not last as long as active immunity. Main advantage is IMMEDIATE AVAILABILITY OF ANTIBODIES; the major disadvantage is the SHORT DURATION (months).

250

dentin™

NBDE I

HYPERSENSITIVITY-an exaggerated immunological response upon re-exposure to a specific antigen (positive skin test after having a disease). HYPERSENSITIVITY REACTIONS: 1. TYPE I (anaphylactic type) immediate hypersensitivity: a specific cytotropic antibody (IgE) binds to receptors on basophils and mast cells and reacts with a specific antigen. IgE antibody mediatedmast cell activation and degranulation. Ex: “Hay fever”, asthma, anaphylaxis. • During a Type I hypersensitivity reaction, leukotrienes and prostaglandins D2 are generated from Arachidonic acid. Also causes atopic allergies. 2. TYPE II (cytotoxic type) cytotoxic antibodies: cytotoxic (IgG, IgM) antibodies form against cell surface antigens. Complement is usually involved. Ex: Autoimmune hemolytic anemias, antibody-dependent cellular toxicity (ADCC), Goopasture disease. 3. TYPE III (immune complex type) immune complex disease: Antibodies (IgG, IgM, IgA) formed against exogenous or endogenous antigens. Complement and leukocytes (neutrophils, macrophages) are often involved. Ex: Autoimmune disease (SLE, rheumatoid arthritis), most types of glomerulonephritis. 4. TYPE IV (cell-mediated type)-delayed type hypersensitivity: Mononuclear cells (T lymphocytes, macrophages are the cellular infiltrates) with interleukin and lymphokine production. Ex: Granulomatous diseases (tuberculosis, sarcoidosis). 5. TYPE V (auto-immune Disease)-reaction that occurs when IgG antibodies directed toward cell surface antigens have a stimulating effect on their target. Ex: Graves Disease (antigen-antibody complex on the follicular cell surface causes excess secretion of thyroid hormone as if were TSH). HYPERSENSITIVITY REACTION COMPARISON Reaction Type I

III

Alternate Name Allergy (immediate)

Disorders

Mediator

Description

Atopy, anaphylaxis, asthma, hay fever

IgE

Fast response (minutes); involves mast cells and basophils

Immune complex disease Cell-mediated immune memory response, antibodyindependent

Autoimmune disease

Graves’ Disease Myasthenia Gravis

Cytotoxic, antibodydependent

251

IgM or IgG Complement MAC

Cellular destruction via MAC

IgG Complement Neutrophils

Circulating immune complex deposited in vessel walls of joints and kidney

Helper T-cells

Th1 cells activate macrophages to cause an inflammatory response and tissue damage

IgM or IgG Complement

Testing with Coombs Test

dentinâ&#x201E;˘

339

NBDE I

dentin™

NBDE I

TOOTH ANATOMY OCCLUSAL SURFACE-chewing surface of POSTERIOR teeth that consists of cusps, ridges, and grooves. The occlusal surface is bounded mesiodistally by the marginal ridges and buccolingually by the cusp ridges. • Anterior teeth DO NOT HAVE an occlusal surface. OCCLUSAL TABLE-that area of a tooth bordered facially and lingually by the crests of the cuspal ridges of facial and lingual cusps, and mesially and distally by the crests of the marginal ridges. INCISAL EDGE-the cutting edge or biting surface of ANTERIOR teeth. ANATOMIC CROWN-the part of the tooth covered by enamel. CLINICAL CROWN-the part of the tooth visible in the oral cavity. It may be larger or smaller than the anatomic crown. The anatomic crown is shorter than the clinical crown of a tooth during gingival recession. INTERPROXIMAL SPACE-triangular space between adjacent teeth cervical to the contact area. The sides of the triangle are the proximal surfaces of the adjacent teeth, the apex of the triangle is the area of contact of two teeth, and the base of the triangle is the alveolar bone. • Interproximal space is normally occupied by the interdental papilla. EMBRASURES-triangularly shaped spaces between the proximal surfaces of adjacent teeth. Embrasures diverge buccally, cervically, lingually, and occlusally from the area of contact. • Pronounced developmental grooves are usually associated with embrasures between permanent maxillary canines and first premolars; and between permanent mandibular canines and first premolars. •

LARGEST incisal/occlusal embrasure is between the maxillary lateral incisor & canine.

•

Each contact area has 4 Embrasures: BUCCAL, LINGUAL (larger than buccal), OCCLUSAL/INCISAL, & CERVICAL.

•

Embrasure Functions: spillways to direct food away from the gingiva, make teeth more selfcleansing, protect gingival tissue from undue frictional trauma, while providing the proper degree of tissue stimulation.

EMBRASURES DO NOT CONTRIBUTE TO ARCH STABILITY. § Embrasures also make the natural hygienic factors in the mouth more effective by exposing tooth surfaces to oral fluids and the mechanical cleansing action of the tounge, lips, and cheeks. PROXIMAL CONTACTS-areas where mesial & distal surfaces of adjacent teeth in the same arch make contact. • Support neighboring teeth to stabilize the dental arches. • Prevent food particles from entering interproximal spaces. • Protect interdental papillae of the gingiva by shunting food toward the buccal and lingual areas. • Form embrasures. • Loss of proximal contact may result in periodontal disease, malocclusion, food impaction, or drifting of teeth.

340

dentin™

NBDE I

PRIMARY MAXILLARY SECOND MOLAR strikingly resembles the PERMANENT MAXILLARY FIRST MOLAR (but they are smaller). Primary second molars are larger than primary first molars, and resemble the form of the permanent first molars. • Crown is greater F-L > M-D. • May have a FIFTH CUSP (Cusp of Carabelli). • Has a prominent M-B cervical ridge and oblique ridge. • MB cusp is EQUAL in size or slightly larger than the M-L cusp. • MB pulp horn is the largest and longest.

•

PRIMARY FIRST MOLAR is the primary tooth with the most noticeable morphologic deviations from permanent teeth.

•

PRIMARY SECOND MOLAR has the greatest F-L diameter of all primary teeth.

PERMANENT MANDIUBLAR FIRST MOLAR morphology closely resembles the PRIMARY MANDIBULAR SECOND MOLAR. However, some differences include: 1. Relative size of the distal cusp. The primary second molar’s M-B, D-B, and distal cusp are almost equal in size. The distal cusp of the permanent molar, however, is smaller than the other two cusps. 2. From the buccal aspect, the primary mandibular second molar has a narrow M-D calibration at the cervical portion of the crown compared with the calibration mesiodistally on the crown at contact level. The mandibular first permanent molar, accordingly, is wider at the cervical portion. 3. Groove patterns are different on the occlusal surface. 4. Primary tooth has more divergent roots to allow for eruption of the second premolar. 5. Primary tooth has a more prominent facial crest of contour. PERMANENT MANDIBULAR 1st MOLAR

348

dentin™

NBDE I

PERIODONTIUM ANATOMY

1. Soft uncalcified tissues are dental pulp, gingiva, and PDL. 2. Cementoenamel junction does not contribute to stabilization and protection of the dental arches. Facial embrasures, occlusal embrasures, proximal contact areas, and horizontal and vertical overlap do contribute to stabilize and protect the dental arches. 3. Opening of the nasopalatine canal is located at the anterior midline of the palate.

PERIODONTAL LIGAMENT (PDL) & GINGIVA PERIODONTIUM (“attachment apparatus”)-tissues that invest and support the teeth. Periodontium consists of the gingiva, PDL, cementum, alveolar and supporting bone. 3 Features of the Human Dentition that directly affect PDL heath and its hard tissue anchorage in terms of resisting occlusal forces: 1. Anterior teeth have slight or no contact in the intercuspal position. 2. occlusal table is less than 60% of the overall faciolingual width of the tooth and is generally at right angles to the long axis of the tooth. 3. mandibular molar crowns are inclined 15-20° toward the lingual, while the root apices are positioned more facially. PDL PRINCIPAL FIBERS (collagen fibers)-a connective tissue that consists of bundles of collagen fibers grouped according to the direction they extend from the cementum of the root to the alveolar bone. PDL principal fibers connect the root cementum to alveolar bone and are distinguished by their location and direction. Principal fibers are sometimes classified as belonging to the general group of alveolodental fibers. 1. Alveolar Crest Fibers-extend from the cervical cementum of the tooth to the alveolar crest that function to counterbalance the occlusal forces on the more apical fibers and resist lateral movements.

368

dentinâ&#x201E;˘

404

NBDE I