Histology of Cementum - Oral Dental Sciences, Year 1 PDF

Histology of Cementum Tutor: Lauren Stockham Module: Oral Dental Sciences Year 1 Intended learning outcomes By the end of the session students should be able to: Describe the composition and structure of cementum Distinguish between the 2 main types of cementum and their distribution Desc...

Histology of Cementum Tutor: Lauren Stockham Module: Oral Dental Sciences Year 1 Intended learning outcomes By the end of the session students should be able to: Describe the composition and structure of cementum Distinguish between the 2 main types of cementum and their distribution Describe how the structure of cementum relates to its function Apply this knowledge to interpret the clinical significance of cementum in health and disease GDC Learning Outcomes; 1.1.5, 1.1.6 Analogy for location of cementum An ice-cream cone filled with ice-cream demonstrating an analogy of a tooth and cementum as the cone. Cementum in relation to the Periodontium Part of tooth root and periodontium structures. Tooth root: Periodontium: Dentine Alveolar bone Pulp canals Periodontal ligament Cementum Cementum Cementum supports the junction between the tooth root and the alveolar bone forming a key part of the periodontium and thus attachment. Why do we need to know about Cementum? Prevention and In health Periodontal Disease treatment Root Caries Images: Stock images Acellular and Cellular Cementum Composition and Structure Composition How does this compare to enamel, dentine and bone? Inorganic content: 45-50% hydroxyapatite crystal critical pH=6.7 The point the crystals can start to disolve Organic content: 50-55% Collagen fibers mainly type I and minor quantities of other types III, V, VI, XII and XIV Non-collagenous matrix proteins Water Overview of structural features Structural features: Types of Cementum Cell presence Acellular Cellular Extrinsic Intrinsic Fibre type (Sharpey's Fibres) Afibrilar (no fibres) Mixed (intrinsic and extrinsic) (formed by cementoblasts) Time of formation Primary Cementum Secondary Cementum First cementum that’s formed Can continue forming through the lifecycle of cementum Acellular cementum Also known as primary cementum: It covers the cervical and middle third of the root (40-70% of root surface) As the first formed cementum, it is adjacent to the dentine creating the dento-cementum junction (CDJ) It forms slowly as the tooth erupts and continues post-eruption It contains collagen fibers (extrinsic) and non-collagenous matrix proteins Cross-section of the root surface of a tooth No cells are present at the CDJ showing the structural layers. Acellular cementum distribution Acellular afibrillar cementum (AAC) Found only in the cervical region covering enamel and dentine AAC Contains no collagen fibers No known functional significance AECF Acellular extrinsic fibers cementum (AEFC) The main type of acellular cementum Key function in support and anchorage Lower molar tooth showing distribution of acellular cementum - the AAC and AECF Acellular cementum functions Support and anchorage: As part of the periodontium, Alveolar Cementum cementum supports the tooth’s bone position within the alveolar socket PDL The extrinsic fibers form the attachment with the periodontal ligament fiber bundles known as Sharpey’s fibers (formed by fibroblasts) and the alveolar bone Sharpey’s fibres (extrinsic) are embedded into These fibers are oriented cementum and the alveolar perpendicular to root surface bone Cellular cementum Alveolar bone Cementum Cementoid Cementoblasts Also known as secondary cementum: Contains cemetocytes PDL Forms quickly compared to primary cementum A layer of cementoid (unmineralized matrix or pre-cementum) can found at the periphery of cellular cementum Contains intrinsic fibers that are parallel to the root surface Extrinsic fibers Over time, also contains extrinsic fibers Intrinsic fibers within cementum Cementocytes Cellular Cementum Cells Cementoblasts form cementum via cementogenesis The picture can’t be displayed. originate from the dental sac Cementocytes found in cellular cementum originate from cementoblasts trapped in the matrix as a result of the speed of deposition The cementocyte cell body (B) with its cytoplasmic processes (C) embedded within cellular cementum and the lines of rest in cementogenesis (A). (Image sourced from the University of Kentuky Digital Lab, link in resources.) Cellular cementum distribution Cellular intrinsic fiber cementum (CIFC) Is found in the apical third of the roots and inter-radicular regions of posterior teeth Often absent in single-rooted teeth Cellular mixed stratified cementum (CMSC) Is a subcategory of CIFC containing both intrinsic and extrinsic fibers Lower molar tooth showing distribution of Over time this makes up the bulk of cellular cementum - the CMSC, and CIFC cellular cementum Cellular cementum functions Adaption is a key function of cellular Occlusal cementum that enables: wear reducing Reshaping of the root to adjust for the height movement of the tooth such as drifting of the when a tooth has been extracted enamel cusps over Deposition of cementum at the apex to time maintain occlusion and compensate for occlusal wear – thicker in posteriors teeth (post-eruptive movement) Lower molar tooth showing thickening of cementum at the apex to compensate for the occlusal wear that happens over time Cellular cementum functions 2 The picture can’t be displayed. Cellular cementum has the ability to repair itself in two ways: Anatomical repair - Able to repair resorbed or fractured root surfaces to some degree Functional repair - Plays in a role in periodontal disease healing maintaining the width of the PDL (see image) Histological stained sample of the root surface showing an area of functional repair at C. D is the dentine. Image sourced from Ghanbarzadeh et al (2017) Distribution of cementum Ground section of teeth showing the distribution of cementum – acellular cementum (AEFC) towards the cervical of the roots the cellular cementum (CMSC) towards the apical region note the difference between the thickness on the molar tooth compared to the incisor. This is because molar teeth undergo heavier occlusal loads. (Image sourced from Yamamoto et al 2016). Clinical significance Functions Cementum over the lifecourse Cementogenesis takes place continuously throughout life The thickness, hardness and mineral content increases with age. Representative graphs of cementum width vs. anatomical location show a two-step increase in cementum thickness when measured from the cementum enamel junction (CEJ) to the root apex regions, that is, along the length of the root. Graph sourced from Jang et al (2014) Cemento-Enamel Junction (CEJ) The relationship of the CEJ (where to cementum and enamel meet) varies among teeth and within the same tooth. A = Overlap 60-65%, B = GAP 10%, C = Meet 25-30% Structural abnormalities Hypercementosis is where there is excessive deposition of cementum towards the apex resulting in thicker roots. The aetiology includes: Local factors such as trauma or inflammation Systemic factors such as Paget's disease, or Idiopathic (unknown) Clinical implications: It may affect single or multiple teeth. Often asymptomatic Periapical radiograph showing hypercementosis of the lower left 6 distal May cause problems for extractions root. (Image sourced from Pinto et al 2017) Summary Inorganic and organic Composition Cellular and cellular Fibre types Functions Cementum Types Anchorage Support Adaption Repair Clinical implications Continues to grow, deposit Increase in thickness, hardness and mineral content CEJ relationship variations References for images: Yamamoto, T., Hasegawa, T., Yamamoto, T., Hongo, H., & Amizuka, N. (2016). Histology of human cementum: Its structure, function, and development. The Japanese dental science review, 52(3), 63–74. Available at: https://doi.org/10.1016/j.jdsr.2016.04.002 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5390338/#bib0380 Accessed date: 25 March 2021 Ghanbarzadeh, M., Heravi, F., Abrishamchi, R., Shafaee, H., Ghazi, N., Heravi, P., & Ghanbarzadeh, H. (2017). Cementum and dentin repair following root damage caused by the insertion of self-tapping and self-drilling miniscrews. Journal of Orthodontic Science, 6, 91 - 96. Jang, A. T., Lin, J. D., Choi, R. M., Choi, E. M., Seto, M. L., Ryder, M. I., Gansky, S. A., Curtis, D. A., & Ho, S. P. (2014). Adaptive properties of human cementum and cementum dentin junction with age. Journal of the mechanical behavior of biomedical materials, 39, 184–196. Available at: https://doi.org/10.1016/j.jmbbm.2014.07.015 Accessed date: 25 March 2021 Matalová, Lungová, &Sharpe, Chapter 26 - Development of Tooth and Associated Structures, Editor(s): Ajaykumar Vishwakarma, Paul Sharpe, Songtao Shi, Murugan Ramalingam, Stem Cell Biology and Tissue Engineering in Dental Sciences, Academic Press, (2015), Pages 335-346, ISBN 9780123971579. Available at: https://doi.org/10.1016/B978-0-12-397157-9.00030-8. Accessed date: 25 March 2021 Pinto AS, Carvalho MS, de Farias AL, da Silva Firmino B, da Silva Dias LP, Neto JM, da Silva AM, Castro FA, Costa AL, De Castro Lopes SL. Hypercementosis: Diagnostic imaging by radiograph, cone-beam computed tomography, and magnetic resonance imaging. J Oral Maxillofac Radiol [serial online] 2017 [cited 2021 Mar 24];5:90-3. Available at: https://www.joomr.org/text.asp?2017/5/3/90/221078 Accessed date: 25 March 2021 Vandana, K. L., & Haneet, R. K. (2014). Cementoenamel junction: An insight. Journal of Indian Society of Periodontology, 18(5), 549–554. Available at: https://doi.org/10.4103/0972-124X.142437 Accessed date: 25 March 2021