Embryology of Oral Tissues Revision PDF

Embryology; Oral tissues Embryonic origins and oral structures Neural crest cells Ectomesenchymal cells Ectoderm...

Embryology; Oral tissues Embryonic origins and oral structures Neural crest cells Ectomesenchymal cells Ectoderm are loosely arranged and highly specalised. Oral epithelial cells Ectomesenchyme cells Ameloblasts Oral mucosa Lamina propria Pulp Cementum Periodontal Alveolar bone Odontoblasts ligament Enamel Dentine Oral epithelial cells are highly organised and structured and provide strength and protection. Stages of tooth development Oral tissues form in Week 6–7: Initiation: Dental and vestibular lamina: the stomadeum of Mandibular and maxillary prominences form the primary epithelial band. the embryo. Week 7, primary epithelial band divides into: dental lamina (where dental placodes rise) and vestibular lamina (gives rise to vestibules). Basement membrane (facilitates messages/interactions) separates oral epithelium and ectomesenchyme. Week 8: Initiation: Dental lamina: Dental lamina forms epithelial swellings: dental placodes (one swelling per tooth and surrounded by ectomesenchyme cells). Interactions between dental placode oral epithelial cells and Week 6: Primary epithelial band ectomesenchyme via basement memebrane initiate next stage of tooth development. Oral epithelial Cells DL X Basement Week 9–10: Bud stage: membrane Dental placode oral epithelial cells proliferate to form a bud. VL < Ectomesenchymal Cells Bud grows/presses into ectomesenchyme cells to form enamel organ (one enamel organ per tooth). Week 7: Dental & vestibular lamina Week 9-10: Bud Week 11: Cap Week 11: Cap stage: Bottom of the enamel organ hollows out. Dental Ectomesenchyme cells proliferate to form the dental papilla and follicle dental follicle. I Dental placode Dental Enamel knot serves as key signalling centre for tooth L Buch morphogenesis (cusp and outline). Bell stage: Histo/cell differentiation = Morphogenesis = Enamel organ hollows out more to map out full size and Cells within enamel organ and Development of tooth shape of tooth crown. dental papilla differentiate into crowns morphology - Enamel organ separates from dental lamina. different cells to form different transition between bud tooth tissue structures (Bell Ectoderm — enamel organ, highly separated > and cap stages. from stage). structured and organised (OEE, SR, SI, IEE, dental (Week 10) lamina ameloblasts). Neural crest cells — dental papilla, specialist cells (odontoblasts, pupal cells). Early bell stage Early bell stage: Week 14 Oral epithelial cells in the enamel organ differentiate into: Dental lamina Enamel organ Outer enamel Stellate reticulum — epithelium — peripheral star shape cells inside, cuboidal cells, key role in key role in facilitating eruption process. amelogenesis. Stratum intermedium — Inner enamel flattened cells inside of IEE, epithelium — columnar key role in facilitating cells along the inside of amelogenesis. OEE, eventually differentiate into ameloblasts. Dental papilla Ectomesenchyme cells in the dental papilla differentiate into: Dental lamina Enamel organ Odontoblasts — peripheral of dental papilla from pre- Pupal cells — odontoblasts, carry out centre of dental dentinogenesis. papilla, becomes the pulp of tooth. Dental papilla Late bell stage: Week 18 Amelogenesis Enamel organ can undergo odontogenesis (crown formation) after Dentinogenesis cellular differentiation. Odontogenesis includes; o Amelogenesis = formation of enamel by ameloblasts. o Dentinogenesis = formation of dentine by odontoblasts. Development of oral mucosa: Week 7?8? Oral epithelial cells in vestibular lamina and lingual regions give rise Late bell stage to oral mucosa. oral epithelial cells Undergo; proliferation, migration and differentiation dependent on LR future function; masticatory, lining and specialised such as gingiva. VL Ectomesenchyme cells give rise to lamina propria (connective tissue) and submucosa. Stomesenchymal als Stratified squamous epithelium. Developmental anomalies Can result from interruptions (environmental or genetic) in each stage of development. Impact can range from none to significant, additional care may be required. Supernumerary — Shape of crown — Missing teeth — Quality of crown — Extra tooth/teeth due Cap and early bell No initiation Bell stage. to extra bud/s. stage. At birth — Bell stage complete for deciduous central incisors. Birth - 4.5 months — Bell stage for permanent teeth starts (central incisors and 6’s). 4.5 months — Eruption of deciduous central incisors.