2- Dental embryology pdf(2).pdf

DENTAL EMBRYOLOGY Pinelopi Pani DDS, CAGS, MS [email protected] OUTLINE • The periodontium: overview • Embryology Terminology • Why dental embryology? • Dental embryology process WHAT 4 STRUCTURES MAKE UP THE PERIODONTIUM? • Gingiva • Periodontal ligament (PDL) • Root Cementum • Alveolar...

DENTAL EMBRYOLOGY Pinelopi Pani DDS, CAGS, MS [email protected] OUTLINE • The periodontium: overview • Embryology Terminology • Why dental embryology? • Dental embryology process WHAT 4 STRUCTURES MAKE UP THE PERIODONTIUM? • Gingiva • Periodontal ligament (PDL) • Root Cementum • Alveolar Bone Alveolar mucosa Free gingival margin Attached gingiva Mucogingival junction Mucogingival junction Free /marginal gingiva Alveolar mucosa C R O W N ENAMEL DENTIN PULP R O O T CEMENTUM PERIODONTAL LIGAMENT NERVE & BLOOD SUPPLY ALVEOLAR BONE C R O W N ENAMEL DENTIN PULP R O O T Thin layer of mineralized CEMENTUM connective tissue that covers the external root surface PERIODONTAL LIGAMENT NERVE & BLOOD SUPPLY ALVEOLAR BONE C R O W N ENAMEL DENTIN PULP R O O T CEMENTUM PERIODONTAL LIGAMENT Dense collagen fibers connecting the tooth and the bone NERVE & BLOOD SUPPLY ALVEOLAR BONE C R O W N ENAMEL DENTIN PULP R O O T CEMENTUM PERIODONTAL LIGAMENT NERVE & BLOOD SUPPLY ALVEOLAR BONE Bony housing C R O W N ENAMEL DENTIN PULP R O O T CEMENTUM PERIODONTAL LIGAMENT NERVE & BLOOD SUPPLY ALVEOLAR BONE ATTACHMENT APPARATUS EMBRYOLOGY TERMINOLOGY INDUCTION • The interaction at close range between two or more cells or tissues with different histories and properties. • One group of cells, the inducing tissue, directs the development of another group of cells, the responding tissue. COMPETENCE • The ability of a cell or tissue to respond to a specific inductive signal. • Each compartment of cells must be competent to respond to the induction process. DIFFERENTIATION •Differentiate into populations that assume particular functions, shapes and rates of turnover. •All the cells of an individual stem from the zygote are compartmentalized-successive generations of cells in a compartment may remain constant or differentiate, that is, change their characteristics and establish a new population of cells. INDUCTION DIFFERENTIATION WHY EMBRYOLOGY? WHY DO WE CARE? • Periodontal diseases are wide-spread throughout the population • A major cause of tooth loss in adults • Periodontal diseases can be treated fairly predictably • Periodontal tissues that have be damaged in some cases can be repaired or regenerated This has resulted in considerable time, effort and research dollars given to understanding of those cells and molecular signals that result in the formation, maintenance and regeneration of the periodontal tissues CLINICAL EXAMPLE: EMDOGAIN ENAMEL MATRIX DERIVATIVE PROTEIN-BASED GEL DESIGNED TO PROMOTE REGENERATION OF LOST PERIODONTAL TISSUES THOUGHT TO PROMOTE FIBROBLAST PROLIFERATION AND GROWTH ORAL EMBRYOLOGY DEVELOPMENT OF THE FACE 4 weeks of intrauterine life Formation of the STOMODEUM (primitive oral cavity) DEVELOPMENT OF THE PALATE 5 weeks of intrauterine life THE FRONTO-NASAL PROCESS PRODUCES THE MEDIAL AND LATERAL NASAL PROCESSES FAILURE TO FUSE CREATES A CLEFT LIP DEVELOPMENT OF THE PALATE 6 weeks of intrauterine life THE NASAL SEPTUM AND PRIMARY PALATE FORM (TWO PALATAL SHELVES). DEVELOPMENT OF THE PALATE 8 weeks of intrauterine life THE TWO PALATAL SHELVES GET IN CONTACT DEVELOPMENT OF THE MANDIBLE 6 weeks of intrauterine life The mandible appears as a band of dense fibrous tissue known a Meckel’s cartilage; this cartilage provides a framework around which the bone will form. DEVELOPMENT OF THE MANDIBLE 7 weeks of intrauterine life Bone formation starting at mental foramen Formation of the condyle and coronoid process Formation of alveolar process which will surround the developing tooth germ DEVELOPMENT OF THE MAXILLA 8 weeks of intrauterine life Ossification of the maxilla starts at the area of the developing deciduous canines. Growth of the maxilla occurs by remodeling of bone and by sutural growth. Growth carries the maxilla forwards and downwards as it increases in size. TOOTH DEVELOPMENT I: Development of primary epithelial band 6 weeks of intrauterine life • Underneath the oral ectodermal epithelium there is a condensation of mesenchymal cells in areas where teeth will eventually form. • The ectodermal epithelium thickens in these areas and protrudes into the mesenchymal cells forming the primary epithelial band. II: Development of the vestibular band and dental lamina 7 weeks of intrauterine life Primary epithelial band Dental lamina Tooth germ Vestibular band Vestibule III: Development of the tooth germ Enamel organ III: Development of the tooth germ BUD CAP BELL Clumps of mesenchymal cells induce the dental lamina to form swellings known as enamel organs The inner aspect of the enamel organ —> the inner enamel epithelium The outer aspect —> the outer enamel epithelium Beneath it, the condensation of mesenchymal cells —> dental papilla —> pulp Fibrous capsule (Dental follicle) —> PDL Inner enamel epithelium —> enamel Outer + inner epithelium —> cervical enamel loop—> Hertwig’s root sheath—> root THREE PARTS OF THE TOOTH GERM Enamel organ Enamel Dental Papilla Dentin & Pulp Dental Follicle Cementum & PDL & Alveolar bone ENAMEL ORGAN THE ENAMEL ORGAN IS COMPOSED OF: - THE OUTER ENAMEL EPITHELIUM - INNER ENAMEL EPITHELIUM - STELLATE RETICULUM - STRATUM INTERMEDIUM THESE CELLS GIVE RISE TO AMELOBLASTS, WHICH PRODUCE ENAMEL. THE LOCATION WHERE THE OUTER ENAMEL EPITHELIUM AND INNER ENAMEL EPITHELIUM JOIN IS CALLED THE CERVICAL LOOP. THE GROWTH OF CERVICAL LOOP CELLS INTO THE DEEPER TISSUES FORMS HERTWIG'S EPITHELIAL ROOT SHEATH, WHICH DETERMINES THE ROOT SHAPE OF THE TOOTH DENTAL PAPILLA CONTAINS CELLS THAT DEVELOP INTO ODONTOBLASTS, WHICH FORM THE DENTIN OF THE TOOTH THE JUNCTION BETWEEN THE DENTAL PAPILLA AND INNER ENAMEL EPITHELIUM DETERMINES THE SHAPE OF A TOOTH’S CROWN ECTOMESENCHYMAL CELLS WITHIN THE DENTAL PAPILLA ARE RESPONSIBLE FOR THE FORMATION OF THE TOOTH PULP DENTAL FOLLICLE THE DENTAL FOLLICLE GIVES RISE TO THREE IMPORTANT ENTITIES: CEMENTOBLASTS —> THE CEMENTUM OF A TOOTH OSTEOBLASTS —> THE ALVEOLAR BONE AROUND THE ROOTS OF TEETH • FIBROBLASTS —> THE PERIODONTAL LIGAMENT WHICH CONNECT TEETH TO THE ALVEOLAR BONE THROUGH CEMENTUM. • • Dental follicle ORIGINS FORMATION OF THE GINGIVA The connection between the gingiva and the tooth is called the dentogingival junction.This junction has three epithelial types: gingival, sulcular, and junctional epithelium, and forms from a mass of epithelial cells known as the epithelial cuff between the tooth and the mouth. The junctional epithelium forms from reduced enamel epithelium (derived from the enamel organ) and divides rapidly. As the junctional epithelial layer increases in size, the remnants of ameloblasts become isolated from any source of nutrition and degenerate —> forming the sulcus FORMATION OF CEMENTUM - CEMENTOGENESIS The cementoblasts differentiate from follicular cells. They can only reach the surface of the tooth’s root once Hertwig’s epithelial root sheath has begun to deteriorate. Acellular cementum forms first. Cellular cementum develops after most of the tooth formation is complete and after the tooth occludes with a tooth in the opposite arch. The cementoblasts forming the last layer become trapped in the cementum. FORMATION OF CEMENTUM - CEMENTOGENESIS CEMENTOBLASTS SECRETE FINE COLLAGEN FIBRILS ALONG THE ROOT SURFACE AND START MIGRATING AWAY FROM THE TOOTH. AFTER MINERALIZATION, THE CEMENTOBLASTS MOVE AWAY FROM THE CEMENTUM AND JOIN THE FORMING PERIODONTAL LIGAMENT. AS THE CEMENTOBLASTS MOVE, MORE COLLAGEN IS DEPOSITED THICKEN THE BUNDLES OF FIBERS FORMATION OF THE PERIODONTAL LIGAMENT FIBROBLASTS DIFFERENTIATE FROM FOLLICULAR CELLS. FIBROBLASTS SECRETE COLLAGEN, WHICH INTERACTS WITH FIBERS ON THE SURFACES OF ADJACENT BONE AND CEMENTUM LEADING TO AN ATTACHMENT: THE PDL The occlusion continually affects the formation of periodontal ligament. FORMATION OF THE THE ALVEOLAR BONE OSTEOBLASTS DIFFERENTIATE FROM FOLLICULAR CELLS. COLLAGEN FIBERS ARE SECRETED ON THE SURFACE NEAREST THE TOOTH, AND THEY REMAIN THERE UNTIL MINERALIZATION AND ATTACHMENT TO PERIODONTAL LIGAMENT. Alveolar bone is modified throughout life. The ECTOMESENCHYMAL INDUCTION SYSTEM guides the tooth development and formation. CAN IT BE REPRODUCED?