Embryology Of The Oral Tissues GN.pdf

Embryology of oral ,ssues Tutor: Lauren Stockham Module: Biomedical Sciences Year 1 Intended Learning Outcomes By the end of the session, students will be able to: Describe the stages of development of the teeth and oral mucosa Link the structures of the teeth and oral mucosa to their embry...

Embryology of oral ,ssues Tutor: Lauren Stockham Module: Biomedical Sciences Year 1 Intended Learning Outcomes By the end of the session, students will be able to: Describe the stages of development of the teeth and oral mucosa Link the structures of the teeth and oral mucosa to their embryonic origins Link the stages of development to the embryonic ,meline Recognise the clinical signiEcance of oral embryology GDC Learning Outcomes: 1.1.5, 1.1.6  Essential foundation knowledge WHY do we need to learn this? When to expect eruption/ exfoliation Identify healthy Identify abnormal Diagnose Prevent disease Manage disease and Materials and Preventive advice Maintain oral health healing medicaments Upstanding how enamel develops Understand how material bond/adhere If we understand how the oral ,ssues; teeth, gingiva and suppor,ng structures; are formed, then we can support, maintain and restore oral health eDecEvely.  More detail in DiDerent Recap the Oral Tissues DenEEons and Histology lectures in Oral Dental Sciences. The teeth Enamel – surrounds the crown Den,ne – bulk of the crown and root Cementum – surrounds the root Periodontal ligament – connects the root to the alveolar bone Pulp – inside of the tooth Alveolar bone – holds the teeth in place The oral mucosa – the soI Essue lining of This Photo by Unknown Author is licensed under CC BY the oral cavity, lamina propria and the https://philschatz.com/anatomy-book/resources/2409_Tooth.jpg gingiva. Embryonic origins and link to oral structures Ectoderm Neural crest cells Highly specalised Softer structure Highly structure/organised Oral epithelial Ectomesenchyme cells Strong and protect cells Periodontal Ameloblasts Oral mucosa Lamina propria Pulp Cementum Alveolar bone Odontoblasts ligament Connective tissue under oral mucosa Enamel Dentine Comparison of cell Oral epithelial cells are characterisEcs – Ectomesenchymal cells highly organised link to the are soft and jelly-like cells forming a compactly Essues formed. loosely arranged with structured Essue layer. intercellular substance.  Complexity of embryology of oral ,ssues The oral Essues form in the stomadeum of the embryo from a complex set of processes that include: Interac,ons between the epithelial cells (ectoderm) and the Send signals - very complex ectomesenchyme (neural crest cells) >300 genes determine the progress of development Signals between the cells and genes mediate the process The basis of our understanding so far comes from studying animal and human embryos, fetuses and infants. Morphological aspects - 150 years, Image of coding and signals Mechanisms regulaEng development - 50 years representing the complexity of processes in embryogenesis. There remains a lot to be discovered and understood. Research is conEnuing today with stem cells in tooth regeneraEon. Dental Lamina, Bud, Cap and Bell stage Stages and func,ons of oral ,ssue development  Stages of tooth development Ectoderm Seed is planted Ectomesenchyme Stages: Func,ons: Image credit: Thesleff 2014 Stages of tooth development in 3D Video: Watch Urst without sound, a second Eme with sound, repeat as you require. Link to video: hWps://www.youtube.com/watch?v=t3hR2YGdqWk Ini,a,on: The dental lamina, Week 6-7 The oral epithelial cells in the mandibular and maxilla prominences form the primary epithelial band. In week 7 this then divides into: The dental lamina The ves,bular lamina The dental lamina extends to follow the outline of the developing dental arches. Link this back to the development of the face Image adapted: Magreni and May 2015 to visualise the where the dental lamina is Showing site of the dental lamina forming. developing in the future mandibular dental arch. Ini,a,on: The ves,bular lamina, Week 7 The ves,bular lamina forms adjacent to the dental lamina. It will give rise to the vesEbule (space between the teeth and lip) of the oral cavity. The basement membrane separates the two cell layers of oral epithelium and the ectomesenchyme – this membrane is key for facilita,ng messages/interac,ons during the tooth development process. Oral epithelial cells Basement membrane Future lip DL VL Underlying ectomesenchymal cells Image source: UnivNantes VerEcal cross-secEon of the vesEbular lamina (VL) and the dental lamina (DL) – now try and visualise this in your own mouth. Ini,a,on: The dental lamina, Week 8 The dental lamina forms a series of epithelial swellings known as dental placodes that will give rise to each tooth. One placode per tooth - don’t erupt at same time, within in a sequence These placodes are surrounded by ectomesenchyme cells. The interac,ons between the oral epithelial cells of the dental placode and the underlying ectomesenchyme cells via the basement membrane will ini,ate the next stage of tooth development. Showing the dental lamina and dental placode. Image adapted: Theself 2014. The Bud stage, Week 9-10 The oral epithelial cells of the dental placode proliferate to form a bud. The bud presses into the underlying ectomesenchyme forming the enamel organ. The enamel organ will give rise to a tooth with one enamel organ per tooth. Image source: UnivNantes The bud forming in the dental lamina that will eventually give rise to a tooth. The Cap stage, Week 11 Bud changes shape The enamel organ changes shape by hollowing out at the boWom surface to resemble a cap. DF In the hollow, ectomesenchymal cells proliferate rapidly to form the dental papilla (DP). DP Surrounding the dental papilla and enamel organ, ectomesenchymal cells proliferate more to form the dental Image source: UnivNantes follicle (DF). The bud has turned into a cap shape allowing a hollow for the dental papilla (DP). The enamel organ is surrounded by the dental follicle (DF). Morphogenesis: the bud and the cap stage The transiEon between the bud and cap stages is signiUed by morphogenesis – the development of morphological characterisEcs – in this case the tooth crown’s morphology (shape) starts to form. The enamel knot is a key signaling center enabling morphogenesis of the cusp shape and outline. Morphogenesis conEnues up to the bell stage. Image: Theself 2014.  What tooth crown is visible? HINT: the The Bell stage Urst tooth to erupt is B also the Urst tooth to form. The enamel organ changes shape further by hollowing out and extending to map the full size and shape of the tooth crown (A) including the occlusal and cusp details. A The enamel organ separates from the dental lamina (B). The bell stage has 2 parts: Image source: UnivNantes The early bell stage The cap has turned into a bell shape and is separated from the dental lamina (B). The outline of the crown is now The late bell stage visible in verEcal cross-secEon (A). Histo-di_eren,a,on: Bell stage Histodi_eren,a,on (cell diDerenEaEon) takes place in the bell stage where the cells within the enamel organ and the dental papilla di_eren,ate into diDerent cell types ready to form the di_erent ,ssue structures of the tooth. This will be discussed in further detail in Embryology of the Crown. Image: Theself 2014.  Early Bell Stage: cell di_eren,a,on pathway Ectoderm: highly structured Neural crest cells: and organised Enamel organ Dental papilla Specialist cells Outer enamel Stratum Stellate Inner enamel Pre- Pupal cells epithelial cells intermedium reticulum epithelial cells odontoblasts Key points: Pre- Odontoblasts What cells make up the enamel organ and the ameloblasts Form dentine dental papilla? Link their characteris,cs to the structure of the respecEve ,ssues formed. What do you think the role of ameloblasts and Ameloblasts odontoblasts will be? Form enamel HINT: Slide 5  Key cells to remember Early Bell Stage: Enamel organ Image showing a histological verEcal secEon of an enamel organ in the bell stage. Oral epithelial cells in the enamel organ diDerenEate into: Outer enamel epithelium (OEE) - cuboidal cells along the periphery – these will play a key role in the erup,on process Stellate re,culum (SR) - star shape cells on the inside of the outer enamel epithelium – play a key role in facilita,ng amelogenesis OEE SR Stratum intermedium (SI) - haWened cells layer on SI the inside of the inner enamel epithelium – play a key IEE role in facilita,ng amelogenesis Inner enamel epithelium (IEE) - tall columnar cells along the inside – these will eventually di_eren,ate This Photo by Unknown Author is licensed under CC BY-SA into ameloblasts http://www.wikidoc.org/images/6/66/Toothhistology11-17-05.jpg Early Bell Stage: Dental papilla Image showing a histological verEcal secEon of an enamel organ in the bell stage. The ectomesenchyme cells in the dental papilla diDerenEate into: Odontoblasts (O) (from pre-odontoblasts) along the periphery of the dental papilla – these carry out den,nogenesis. Pulpal cells (P) in the centre of the dental papilla that will eventually become the pulp O P of the tooth This Photo by Unknown Author is licensed under CC BY-SA http://www.wikidoc.org/images/6/66/Toothhistology11-17-05.jpg Late bell stage Ameologensis AIer cellular diDerenEaEon the enamel organ is Dentinogenesis ready to undergo crown forma,on (odontogenesis). Crown formaEon includes: Amelogenesis - formaEon of enamel by ameloblasts Den,nogenesis - formaEon of den,ne by odontoblasts Image source: UnivNantes More detail will be discussed in the next The enamel organ in the late bell stage undergoing session ‘Embryology of the Crown’. amelogenesis to form enamel and dentinogenesis to form dentine. Development of the oral mucosa The oral mucosa lines the oral cavity. Oral epithelial cells The oral epithelial cells in the ves,bular lamina (VL) and lingual regions (LR) undergo proliferaEon, migraEon and diDerenEaEon according to the future funcEon of the structure LR of the oral mucosa including: VL masEcatory, lining and Ectomesenchyme specialized mucosa such as gingiva. The underlying ectomesenchymal cells give rise VerEcal cross-secEon of the vesEbular lamina (VL), to the lamina propria (connec,ve ,ssue) and dental lamina and lingual region (LR). submucosa. Development of the Oral Mucosa cross-sec,on Image credit: Michigan Histology and Virtual Microscopic Learning Reources, hWps://histology.medicine.umich.edu/resources/oral-cavity Histological slide showing a verEcal cross-secEon of the developing oral cavity including the lip, tooth, oral mucosa and hard and soI palates. Timeline of erupEon and Developmental anomalies Clinical signiEcance Timeline of primary den,,on development ↑ & Late bell stage Bell stage complete Root starting to form Bell stage for permanent teeth Eruption Starting to erupt 6’s or central incisors can also start formation at birth or around birth Images adapted from: AlQahtani et al (2010)  More to come in Oral Developmental anomalies Dental Science and Year 2. Developmental anomalies may result from interrup,ons (environmental or geneEc) in each stage of tooth development. Supernumerary (extra) teeth – extra bud Missing teeth – no iniEaEon Shape of crown – the cap and early bell stage Quality of the crown – bell stage The impact can range from none to signiUcant, This Photo by Unknown Author is licensed under CC BY https://static-01.hindawi.com/articles/crid/volume-2013/614807/figures/614807.fig.001.jpg therefore addiEonal care may be required. Clinical image showing two permanent teeth Link back to the origami folds – any wrong fold supernumeraries; an anomalie at the iniEaEon or order of folds may aDect the Unal size, shape stage. or quality of the developing tooth/teeth. Links to future learning: Histology of oral ,ssues (enamel, denEne, gingiva etc) – structure and funcEon Histopathology of oral diseases – dental caries, periodontal diseases etc Developmental anomalies  UlEmately links to your day to day work as Clinical image showing a developmental anomaly an e_ec,ve clinician known as enamel hypoplasia – note the appearance of enamel is not smooth. (Patel et al 2019) Summary Bud Overview of the process of the development of teeth and oral mucosa: the stages of tooth development the embryological origins Cap Timings of stages in relaEon to the embryonic Emeline Clinical signiUcance This provides the basis for the next session Bell where we will explore the late bell stage in more detail – the embryology of the crown. Images showing the bud cap and bell reflected in the spring season of flowers forming. Images credit: Lauren Stockham Learning resources: 1. Workbook ac,vi,es 2. Oral embryology reading list and online resources 3. Videos Watch Urst without sound Watch a second Eme with sound https://www.youtube.com/watch?v=WjM3-ymWb3I Watch more as you need and pause along the way Image and video references Colors Paper, 2018. DIY Paper Flowers easy making tutorial (Origami Flower) – paper craI ideas. YouTube. Available online: hWps://youtu.be/nVauFzCx0rg Accessed 02/08/23. AlQahtani S J, Liversidge H M, Hector M P (2010). Atlas of tooth development and erupEon. American Journal of Physical Anthropology 142(3):481-90. ThesleD, I. (2014), Current understanding of the process of tooth formaEon: transfer from the laboratory to the clinic. Aust Dent J, 59: 48-54. hWps://doi.org/10.1111/adj.12102 Patel, A., Aghababaie, S. & Parekh, S. HypomineralisaEon or hypoplasia?. Br Dent J 227, 683–686 (2019). hWps://doi.org/10.1038/s41415-019-0782-9 UniNantes, 2016. Tooth Development – crown formaEon. YouTube. Online: hWps://www.youtube.com/watch?v=t3hR2YGdqWk Accessed 03/08/23. Analogy: Egg to Chick Process of egg to hatchling is complex just like the process for humans. Video link: hWps://www.youtube.com/watch?v=ozMPRSZ8Ykk Thank you! Image credit: Lauren Stockham