BDS1075 Tooth Development Histology PDF

NEWGIZA UNIVERSITY BDS1075 Tooth Development Histology Date: 8/12/21  NEWGIZA UNIVERSITY Objectives At the end of this lecture students should understand the basic stages of tooth development and the features of each stage. Describe the shape an...

NEWGIZA UNIVERSITY BDS1075 Tooth Development Histology Date: 8/12/21  NEWGIZA UNIVERSITY Objectives At the end of this lecture students should understand the basic stages of tooth development and the features of each stage. Describe the shape and functions of the basic stages of tooth development.  Frontal Coronal NEWGIZA UNIVERSITY view section Sagittal Side view section Head Ectodermaly- lined stomodeum Stomodeum Heart (6 weeks embryo) (At a later phase of development)  At 5-6 w.i.u. Embryo NEWGIZA UNIVERSITY ECTODERM Ectoderm Mesoderm MESODERM Basement Basement membrane membrane Basal cell layer At 5 – 6 w.i.u. the primitive oral cavity or stomatodeum (stomodeum) is lined by ectoderm of two or three layers. The basal layer is columnar and the superficial layer is flattened cells. The ectoderm is separated from mesoderm (ectomesenchymal cells) by basement membrane.  Stages of Tooth Development NEWGIZA UNIVERSITY Developmental stages of teeth are classified into :: Morphological stages Histophysiological stages 1- Dental lamina 1- Initiation 2- Bud stage 2- Proliferation 3- Cap stage 3- Histodifferentiation 4- Bell stage: - early bell 4- Morphodifferentiation - late bell 5- Apposition I- Morphological stages NEWGIZA UNIVERSITY Tooth Development Initiation Stage (Dental Lamina) Bud Stage Cap Stage Crown Stage Early Bell Stage Late Bell Stage  NEWGIZA UNIVERSITY Bud. Cap. Early bell. Late bell.  NEWGIZA UNIVERSITY Tooth development starts at about 5-6 W.I.U. The development of the deciduous teeth is followed by development of the permanent teeth. Stages of tooth development for both deciduous and permanent teeth are classified according to morphology into: 1- Dental lamina. 2- Bud stage. 3- Cap stage. 4- Bell stage A- Early bell stage. B- Late bell stage.  NEWGIZA UNIVERSITY Tooth development starts at about 5-6 W.I.U. The development of the deciduous teeth is followed by development of the permanent teeth. Stages of tooth development for both deciduous and permanent teeth are classified according to morphology into: 1- Dental lamina. 2- Bud stage. 3- Cap stage. 4- Bell stage A- Early bell stage. B- Late bell stage.  NEWGIZA UNIVERSITY Tooth development starts at about 5-6 W.I.U. The development of the deciduous teeth is followed by development of the permanent teeth. Stages of tooth development for both deciduous and permanent teeth are classified according to morphology into: 1- Dental lamina. 2- Bud stage. 3- Cap stage. 4- Bell stage A- Early bell stage. B- Late bell stage.  NEWGIZA UNIVERSITY Tooth development starts at about 5-6 W.I.U. The development of the deciduous teeth is followed by development of the permanent teeth. Stages of tooth development for both deciduous and permanent teeth are classified according to morphology into: 1- Dental lamina. 2- Bud stage. 3- Cap stage. 4- Bell stage A- Early bell stage. B- Late bell stage.  NEWGIZA UNIVERSITY Tooth development starts at about 5-6 W.I.U. The development of the deciduous teeth is followed by development of the permanent teeth. Stages of tooth development for both deciduous and permanent teeth are classified according to morphology into: 1- Dental lamina. 2- Bud stage. 3- Cap stage. 4- Bell stage A- Early bell stage. B- Late bell stage.  NEWGIZA UNIVERSITY Tooth development starts at about 5-6 W.I.U. The development of the deciduous teeth is followed by development of the permanent teeth. Stages of tooth development for both deciduous and permanent teeth are classified according to morphology into: 1- Dental lamina. 2- Bud stage. 3- Cap stage. 4- Bell stage A- Early bell stage. B- Late bell stage.  1- Dental Lamina NEWGIZA UNIVERSITY The neural crest cells (NCC, ectodermal in origin) migrate to the mesoderm of the stomodeum forming ectomesenchymal cells  Dental Lamina NEWGIZA UNIVERSITY By the influence of the Flat cells ectomesenchymal cells, the basal columnar cells of ectoderm will proliferate to ECTODERM Columnar cells form an arch shaped ( S.SQ.E. ) primary epithelial band Basement membrane MESODERM (Ectomesench- ymal cells)  NEWGIZA UNIVERSITY *Development of Dental and vestibular laminae Vestibular Lamina Become the vestibule between cheek, lip and the teeth bearing Primary Epithelial area. Band Dental Lamina The life span of the dental lamina is about 5 years. Earliest signs of embryonic tooth formation  NEWGIZA UNIVERSITY Primary Epithelial Band Maxillary Process Mandibular Process  Primary epithelial band NEWGIZA UNIVERSITY Coronal section of Embryo’s head Primary epithelial band extending along the free margin of both jaws Coronal section of primary epithelial band  NEWGIZA UNIVERSITY Histology of Primary epithelial band Oral ectoderm Primary epithelial band Dental lamina Vestibular lamina Condensed Ecto- mesenchyme  Sagittal section in mandible NEWGIZA UNIVERSITY during teeth development Primary epithelial band which in turn divides to form two parallel laminae; vestibular lamina and dental lamina which extend along the free margin of the jaws.  NEWGIZA UNIVERSITY FUNCTIONS OF THE DENTAL LAMINA 1- Initiation of the entire Deciduous Dentition. 2- Initiation of the Permanent Successors. 3- Initiation of the Permanent Molars.  2.BUD STAGE (at 8 WIU) NEWGIZA UNIVERSITY Epithelium of the dental lamina begins to form a ‘bud’ extending into the underlying mesenchyme The dental lamina has labial and lingual sides. On the labial side 1-Dental organ there are 10 swellings for the development of the deciduous teeth for each jaw. 2-Dental papilla 3-Dental sac 1 + 2 + 3 = Tooth germ  NEWGIZA UNIVERSITY Bud stage These swellings having the bud shape which is called the enamel (Dental) organ. Dental organ (Bud shaped) I.e. Ectoderm Dental sac (Condensed Ectomesenchyme) I.e. More fibrous Dental papilla Dental papilla (Condensed Ecto- (Condensed Ecto- mesenchyme) mesenchyme) 3-CAP STAGE NEWGIZA UNIVERSITY Enamel cord Stellate R. Outer D. E. Enamel knot Inner D. E. Cell free Dental Papilla. zone Dental Sac  Enamel Ķnot and Enamel cord NEWGIZA UNIVERSITY condensation of the (I.E.E.) cells and is called enamel knob or knot. Enamel cord extends as Enamel Cord polyhedral cells from the enamel knot to the (O.E.E.). Enamel Ķnot  Cap stage Broad connection NEWGIZA UNIVERSITY bet. Dental organ & Unequal growth in Dental lamina Oral Ectoderm different parts of tooth bud, leading to Vestibular Outer Dental change of its shape to lamina Epithelium a cap shape attached Enamel cord to the dental lamina. Dental sac Enamel knot This is characterized by: Stellate reticulum Cell-Free zone a) Outer convex and inner concave surfaces which face the dental papilla. Inner Dental b) The enamel organ has Epithelium short and broad Dental connection to the dental papilla lamina.  4-CROWN STAGE NEWGIZA UNIVERSITY Differential growth of enamel organ will lead to more deepening of the concave surface to give the enamel organ the shape of a bell. Earlybell The bell stage is divided into: stage a) Early bell stage No hard dental tissue Late bell b) Late bell stage stage Hard dental tissue is present (It started by the formation of first layer of dentine)  4-CROWN STAGE (Early Bell Stage) NEWGIZA UNIVERSITY DENTAL LAMINA DENTAL LAMINA PROPER SR SI LDL Cervical ODE loop The connection of dental IDE organ to the dental lamina is elongated forming a lateral dental lamina  NEWGIZA UNIVERSITY Dental lamina will be divided by the invasion of mesenchymal tissue into lateral dental lamina carrying the enamel organ of the deciduous tooth and the main dental lamina which will grow deeper to give rise to the permanent tooth germ. Lingual extension of the dental lamina is called the successional lamina. It gives the permanent successors  NEWGIZA UNIVERSITY Hallmark: Lateral dental lamina (Thin Early Bell stage Formation of Cervical loop connection) Dental lamina Oral Ectoderm Successional dental lamina Lateral dental lamina Outer Dental Epithelium Stratum Intermedium Ameloblasts Dental papilla Odontoblasts Cervical loop Cervical loop NEWGIZA UNIVERSITY Elongation of Inner Enamel Induction NEWGIZA UNIVERSITY Epithelium Favour and Influence return of Pre- peripheral On the Ameloblast cells of Dental Favour expense of the cell-free papilla zone Proximal end (Cell free zone) Distal end Centriol Odontoblasts Golgi apparatus (Cell free zone) Nucleus Mitochondria 4-CROWN STAGE ( late Bell Stage ) N E W G I Z A UNIVERSITY Deposition of first layer of dentine changes the early bell stage into late bell stage. So, the epithelial enamel organ (free of blood vessels) will not depend only on dental papilla for nutrition so, these changes will take place to gain other source of nutrition: 1) Dental lamina: degenerated ____ERS 2) Enamel organ: O.E.E: folded , capillary loops I.E.E : reciprocal induction Stellate reticulum : shrunken Stratum intermedium __ Alkaline phosphatase Reciprocal Induction NEWGIZA UNIVERSITY Ameloblast Enamel matrix Under the influence of the Mineralized first dentin layer formed dentin Predentin Note: (Dentin Basement matrix) membrane degenerated by Ameloblasts’ Odontoblast enzymes  NEWGIZA UNIVERSITY Tooth germ ? Tooth germ Dental organ Ameloblasts Enamel Odontoblasts Dentin Dental papilla Mesenchyme (Connective tissue) Pulp Cementoblasts Cementum Dental sac/Follicle Fibroblasts PDL Osteoblasts Bone  NEWGIZA UNIVERSITY FUNCTIONS OF THE ENAMEL ORGAN 1- OUTER ENAMEL EPITHELIUM. a -Active transport of materials specially, after hard dental tissues formation. b- protective barrier for the rest of the enamel organ during enamel formation.  FUNCTIONS NEWGIZA UNIVERSITY OF THE ENAMEL ORGAN 2- STELLATE RETICULUM. a-Act as a buffer against physical forces that may distort the configurations of the developing amelodentinal junction giving rise to gross morphological changes. b- It acts as a store house for the nutritive materials. c- It keeps room for the developing enamel.  FUNCTIONS NEWGIZA UNIVERSITY OF THE ENAMEL ORGAN. 3- STRATUM INTERMEDIUM a- It control fluid diffusion into and out of the ameloblasts. b- It provides the enamel organ with alkaline phosphatase enzyme needed for mineralization. c- These cells plus the IDE form a single functional unit responsible for enamel formation FUNCTIONS OF THE ENAMEL ORGAN (cont.) NEWGIZA UNIVERSITY 4- INNER ENAMEL EPITHELIUM. Morphology Organizing Nutritive Root formation. Enamel matrix Reduced enamel Primary epithelium. enamel cuticle  NEWGIZA UNIVERSITY FUNCTIONS OF INNER ENAMEL EPITHELIUM. a- It exerts an organizing influence on the undifferentiated cells of the dental papilla to differentiate into odontoblasts. b- Transport of the nutritive materials from the dental papilla to the enamel organ before dental hard tissues formation. c- Arranged in a pattern to determine the future morphology of the amelodentinal junction and the crown. d- It lays down enamel matrix and helps in its mineralization. e- It shares in the root formation. f- It secretes primary enamel cuticle, after the full thickness of enamel is deposited, to protect the enamel of the unerupted tooth against resorption and preventing precipitation of cementum. g- It shares in the formation of the reduced enamel epithelium.  NEWGIZA UNIVERSITY Functions of the Dental (Enamel) Organ 1- Differentiation of odontoblasts to form dentin. 2- Formation of the future tooth shape. 3- Formation of enamel. 4- It will end as reduced enamel epithelium which will form primary dento-gingival junction.  NEWGIZA UNIVERSITY FUNCTIONS OF THE DENTAL PAPILLA AND DENTAL SAC Function of dental papilla: Formation of 1- Dentine 2- Pulp. Function of dental sac: Formation of the following supporting structures; 1- Cementum 2- Periodontal ligament 3- Alveolar bone proper. FUNCTIONS OF THE TOOTH GERM (DENTAL NEWGIZA UNIVERSITY ORGAN, DENTAL PAPILLA AND DENTAL SAC) The Dental Organ Enamel Dentin The Dental Papilla PULP Cementum, The Dental Sac Periodontal Ligament Alveolar Bone Proper  NEWGIZA UNIVERSITY Reading Material Master Dentistry, Vol 3, 3rd or 4th edition Barry Berkovich et al Ten Cate’s Oral Histology; Development, Structure, and Function, 6th Ed., Antonio Nanci  NEWGIZA UNIVERSITY Objectives At the end of this lecture students should understand the basic stages of tooth development and the features of each stage. Describe the shape and functions of the basic stages of tooth development.  NEWGIZA UNIVERSITY Towards unbounded thinking. Thank You