Histology of Pulp PDF

Histology of Pulp 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 the pulp Describe how the structure of pulp relates to its function​​ Apply this knowledg...

Histology of Pulp 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 the pulp Describe how the structure of pulp relates to its function​​ Apply this knowledge to interpret the clinical implications of the pulp in health and disease GDC Learning outcomes: 1.1.5, 1.1.6 Histology of the tissues of the teeth and supporting structures Enamel Dentine Pulp Cementum Bone (alveolar) Periodontal ligament Gingiva Refresh the memory Tooth morphology - location of the pulp within a tooth Embryonic origin – ectomesenchyme of the dental papilla Refer back to Lectures on: - Tooth Morphology - Oral Embryology Why do we need to know this…? The dental pulp is like the heart of a tooth - without it, a tooth cannot survive except with lengthy and costly treatment. Anatomy and composition Structure and composition Anatomy of the pulp The pulpal anatomy is consistent with the type of tooth, it is encased in the pulp cavity surrounded by the mineralised tissues where the: - Coronal pulp is located in the pulp chamber Floor of the pulp chamber - Root pulp is located in the root canal/s The pulpal anatomy of an upper molar tooth. Composition The pulp is a highly vascular, soft connective tissue made up of 75-80% water and 20-25% organic material (by weight) that consists of: 1. Cells: 2. Extracellular matrix: Odontoblasts Fibres Fibroblasts Ground substance Undifferentiated cells Blood vessels Defense cells Lymph vessels Nerves Structural composition The structure of the pulp visible under a microscope includes 4 different zones: Odontoblast zone – lines the periphery of the pulp Cell free zone – space between zones with only a few fibres Cell rich zone – contains all the cells except odontoblasts Pulp core – contains the blood vessles, nerves and some cells Diagram showing the 4 zones of the pulp. Composition – Cells, odontoblasts Odontoblasts: the most distinct cells of the pulp that line the periphery in the odontogenic zone They have a process extending into dentine Functions: Perform dentinogenesis Sensory transduction Composition – cells, Fibroblasts Fibroblasts: the most prevalent cells in the pulp in the cell rich zone Functions: Form and maintain the extracellular matrix of collagen and ground substance They are very active in young pulps and over time this reduces as the pulp shrinks Image of the zones of the pulp showing the fibroblast cells Composition – cells, undifferentiated Undifferentiated cells found in the cell rich zone and pulp core include: Ectomesenchymal cells that can differentiate into odontoblasts and fibroblasts Mesenchymal stem cells (MSC) that have shown potential to differentiate into various cells, research is ongoing to understand their regenerative ability Showing the differentiation potential of mesenchymal stem cells from the dental pulp (Image sourced from Nuti et al 2016) Composition – cells, defense Numerous defense cells are located in the pulp core: Macrophages T-lymphocytes B lymphocytes are scarce Some leukocytes that increase during infection Dendritic cells beneath the odontoblast The defense cells of the pulp (Image sourced from Lee 2015) zone function in immunosurveillance and thus increase in carious teeth Composition – Extracellular Matrix The extracellular matrix consists of: Fibers of collagen, principally type I and III, that increase in content with age. The apical pulp contains the greatest concentration Ground substance, a loose connective tissue, that supports the cells and consists of glycosaminoglycogens, glycoproteins and water Composition – vascular and lymph supply The vascular and lymph vessels supply the circulation to the pulp and can be found in the pulp core. They enter and exit through the apical foramen along with the nerve supply and some through accessory foramina. The largest vessels are arterioles and venules that branch into an extensive capillary network in the coronal portion. Showing the vascular supply through the apical foramen (image source Niklas et al 2013) Composition – nerve supply 1 The pulp is richly supplied with nerves that enter through the apical foramen along with the vascular and lymph supply following the same course to the pulp core. The nerve supply enables the pulp to recognise stimuli, perceived as pain and trigger defense responses. Composition – nerve supply 2 In the coronal portion the Nerve Plexus of Raschkow can be found just beneath the cell free zone. While most nerve bundles end as free nerve endings in the plexus, some continue to end between the odontoblasts and into the dentinal tubules. Showing the nerve plexus of Raschkov and a nerve extending into the odontoblasts. Composition – nerve supply 3 Two types of nerves can be found: Predominantly sensory afferent nerves of the trigeminal nerve – enable perception of pain Sympathetic nerve branches from the superior cervical ganglion – help to regulate blood flow in the smooth muscles of the vascular vessels The nerve bundles are both myelinated and unmyleinated. Clinical relevance in health and disease Functions Functions of the pulp Formative Circulation Protective = vital, healthy tooth The pulp over the life-course Over time, the deposition of secondary dentine reduces the size of the pulp tissue and the diameter of the apical foramen. This has a number of impacts: Reduced circulation Reduced innervation Fewer odontoblasts Increased fibers and collagen These impacts reduce the ability to Ground section showing reducing size of pulp over the life-course. respond and repair.  Refer to lectures on: Clinical significance of the pulp - Inflammation - Pulpitis In response to stimuli or injury, the pulp experiences inflammation either reversible pulpitis or irreversible pulpitis (painful!). While the pulp has some ability to repair itself, the response is limited to the size of the apical foramen and can lead to necrosis of the pulp. Think about this in relation to the 5 signs of inflammation. Structural anomalies – pulp stones Pulp stones are small calcified areas of tissue (similar to dentine) frequently found in pulp tissue. They are either free or attached to the dentine. Clinical significance: reduce the cell content in the pulp pose challenge for endodontic treatment. Bitewing radiograph showing radiopacities in the pulp chamber. Image sourced from (Ranjitkar et al 2002) Structural anomalies – accessory canals Disruptions during development of the root may lead to a break in the continuity of Hertwig’s epithelial root sheath. This leads to a disruption in odontogenesis of the root forming accessory root canals. These may have implications for the ingress of bacteria to the pulp if become exposed leading to periodontal and endodontic problems. Clinical application and links to other sessions Pulpitis - Pain Differential Dental Perio-endo Health acute and history diagnosis abscess lesions chronic Summary of the pulp Composition Clinical Structure relevance Functions References for images Nuti, N., Corallo, C., Chan, B., Ferrari, M., & Gerami-Naini, B. (2016). Multipotent Differentiation of Human Dental Pulp Stem Cells: a Literature Review. Stem Cell Reviews and Reports, 12, 511- 523. Lee SM. (2015) Role of NLRP3 Inflammasome in Pathogenesis of Pulpal Disease. Dental Thesis. University of Pensylvania. http://repository.upenn.edu/dental_theses/6. A. Niklas, P. Proff, M. Gosau, P. Römer, (2013) ‘The Role of Hypoxia in Orthodontic Tooth Movement’, International Journal of Dentistry, vol. 2013, Article ID 841840, 7 pages, 2013. https://doi.org/10.1155/2013/841840 S Ranjitkar, JA Taylor &GC Townsend. (2002) ‘A radiographic assessment of the prevalence of pulp stones in Australians.’ Australian Dental Journal. 47(1). 36-40. https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1834-7819.2002.tb00301.x Reading List Useful overview with histological sections of the dental pulp in the oral histology virtual laboratory: http://www.uky.edu/~brmacp/oralhist/module4/lecture/oh4lect.htm Useful article with details on the dental pulp functions and responses Yu C, Abbott PV. An overview of the dental pulp: its functions and responses to injury. Aust Dent J. 2007 Mar;52(1 Suppl):S4-16. doi: 10.1111/j.1834- 7819.2007.tb00525.x. PMID: 17546858. More detailed information available in Ten Cate’s Oral Histology 9th Edition: Chapter 8 Dentine-Pulp Complex.