Lecture 4 Dentine and Pulp (Part 1) PDF

Dentine and the pulp (Part 1) Dentine structure, histology, function By the end of this lecture, you should be able to: Describe the chemical and structural composition of dentine Identify the major structural and cellular components of dentine Identify and describe the major types of dentine List t...

Dentine and the pulp (Part 1) Dentine structure, histology, function By the end of this lecture, you should be able to: Describe the chemical and structural composition of dentine Identify the major structural and cellular components of dentine Identify and describe the major types of dentine List the roles dentine plays in maintaining a tooth Dentine- the basics Dentin or dentine? Dentine (with an ‘e’) was originally defined by Sir Richard Owen in the 1840’s while working at the Hunterian Museum in London. This is the same man who invented the word “Dinosaur” and founded the Natural History Museum in South Kensington. Found a tubule-rich tissue comprising the bulk of the teeth of all vertebrates, including humans. Sir Richard Owen Before this- ‘os dentale’, ‘tooth bone’, or ‘ivory’. https://en.wikipedia.org/wiki/Richard_Owen Dentine- the basics “The tissue, which forms the chief part or body of the tooth, has, hitherto, received no distinct and specific name in our language … others have treated of it under the name ‘bone of the tooth’ or ‘tooth bone’… I propose to call the substance which forms the main part of all teeth ‘dentine.’” Odontography (1840), pages ii-iii. Owen’s Odontography (1840-1845) Section of a ray tooth Section of a dinosaur tooth Human teeth Dentine- the basics Dentine is the hard tissue component of the pulpdentine complex Mature dentine consists of 70% inorganic material (hydroxyapatite), 20% organic material (mainly type 1 collagen), 10% water. Dentine is softer than overlying enamel, but slightly harder than bone In radiographs, dentine is more radiopaque (lighter) than bone, but more radiolucent (darker) than enamel. Ten Cate’s Oral Histology (8th Edition); Fig. 8-6 Dentine- the basics The histological differences between enamel and dentine affect the bonding strategy during treatments. Enamel: etching of prismatic enamel leaves behind a roughened mineral surface to which materials can bond. Dentine: etching removes the mineral but leaves behind a layer of soft collagen to which materials must bond. Van Merbeek et al. (2003) Operative Dentistry 28: Figs. 2, 4 Dentine- the basics Dentine and the pulp serve several functions for each tooth: Structural support and site of attachment for enamel and cementum Sensitivity (nociception) Mechano-sensory (proprioception) Immune responsive Ten Cate’s Oral Histology (8th Edition); Fig. 8-6 Dentine- the basics Dentine’s most characteristic feature: dentinal tubules. Dentine- the basics Dentine’s most characteristic feature: dentinal tubules. Tubules are the trackways left behind by the dentine-producing cells: the odontoblasts. Ten Cate’s Oral Histology (8th Edition); Fig. 1-4 Dentine- the basics Dentine’s most characteristic feature: dentinal tubules. Tubules are the trackways left behind by the dentine-producing cells: the odontoblasts. Ten Cate’s Oral Histology (8th Edition); Figs. 8-25 Dentine- the basics What’s in the tubules? Odontoblast processes Peritubular fluid** Nerve filaments More dentine (over time) Ten Cate’s Oral Histology (8th Edition); Figs. 8-24, 8-63 Dentine- the basics The pulp and dentine can be considered as a single developmental and functional unit. Unlike enamel, dentine is a living tissue, even after tooth eruption. Ten Cate’s Oral Histology (8th Edition); Figs. 1-1, 8-40 Dentine- the basics Odontoblasts do not become entombed in their matrix à the dentine tubules mark their path as they migrate away from the dentine secretory front. Enamel Dentine Two types of curvatures: Primary (S-bends, longer term) Secondary (undulations, shorter term) Pulp Dentine- the basics Odontoblasts do not become entombed in their matrix à the dentine tubules mark their path as they migrate away from the dentine secretory front. Two types of curvatures: Primary (S-bends, longer term) Secondary (undulations, shorter term) Dentine types Dentine is subdivided into several types based on their topological, histological, and developmental properties: Intertubular dentine More fibrous matrix. Peritubular dentine Deposited gradually by odontoblast processes along the walls of the dentine tubules. Hypermineralized compared to intertubular dentine. NO collagen! Tubule diameter decreases with age. Ten Cate’s Oral Histology (8th Edition); Fig. 8-32 Dentine types- topology There are several types based on their topological, histological, and developmental properties: Coronal dentine Coronal dentine Dentine within the crown Underlies the enamel Radicular dentine Dentine within the root Underlies the cementum Radicular dentine Dentine types- development There are several types based on their topological, histological, and developmental properties: Primary dentine (formed before root completion) a) b) c) Mantle (in the crown) Circumpulpal (crown and root) Root/Radicular Hyaline layer of Hopewell-Smith Granular layer of Tomes Secondary dentine (formed after root completion) Tertiary dentine a) b) Reactionary Reparative Ten Cate’s Oral Histology (8th Edition); Fig. 8-1 Dentine types Primary dentine (dentine that forms prior to completion of the root) Enamel a) Mantle (in the crown) The first dentine layer to form, 20-150 µm of dentine below the EnamelDentine Junction (EDJ) ntle a M ine t n de Circumpulpal dentine Histologically distinct from the underlying circumpulpal dentine (matrix and mineralization patterns are unique). Lots of branching dentine tubules. Ten Cate’s Oral Histology (8th Edition); Fig. 8-1 Dentine types Enamel Primary dentine (dentine that forms prior to completion of the root) a) Mantle (in the crown) The first dentine layer to form, 20-150 µm of dentine below the EDJ Histologically distinct from the underlying circumpulpal dentine (matrix and mineralization patterns are unique). Lots of branching dentine tubules. ntle a M ine t n de Circumpulpal dentine Enamel Mantle dentine Ten Cate’s Oral Histology (8th Edition); Fig. 8-1 Dentine types Primary dentine a) Mantle (in the crown) Collagen fibers of mantle dentine matrix are oriented at right angles to the EDJ à von Korff’s fibers. Alters the optical appearance of mantle dentine under a microscope under crosspolarized light. Ten Cate’s Oral Histology (8th Edition); Fig. 8-15C Dentine types Primary dentine b) Circumpulpal dentine (crown and root) Forms the bulk of the dentine in the crown and the root. Rhythmic deposition of dentine matrix by odontoblasts leads to the formation of different growth lines. Calcospheritic mineralization leaves large circular patterns in the mature dentine. Dentine types Primary dentine b) Circumpulpal dentine (crown and root) Matrix collagen fibers are oriented parallel to the EDJ/secretory front (unlike in mantle dentine). Circadian (daily) variation in odontoblasts’ matrix secretion rates and collagen fiber orientations generate von Ebner lines (~3-4 µm per day). Supra-daily (~5-9 day rhythm) variations that coincide with changes in dentine tubule curvatures manifest as contour lines of Owen. Ten Cate’s Oral Histology (8th Edition); Fig. 8-36 Dentine types Primary dentine b) Circumpulpal dentine (crown and root) Matrix mineralization can occur through formation of calcospherites (globular mineralizations of the collagen matrix). If neighbouring calcospherites fail to merge à globular dentine Ten Cate’s Oral Histology (8th Edition); Figs. 8-20, 8-35, 8-54 sp o c cal es t i r he Dentine types Primary dentine c) Root/radicular dentine Root dentine contains types of “mantle” dentine that receive their own names, which we will classify here. Radicular dentine Dentine types Primary dentine c) Root/radicular dentine Hyaline layer of Hopewell-Smith Thin region (around 10 microns thick) lacking tubules or other features Appears clear in thin section (“hyaline”) and is adjacent to the cementum May contain more enamel-like matrix proteins Serves to bond dentine to cementum? Hyaline layer Cementum Dentine types Primary dentine c) Root/radicular dentine Granular layer of Tomes Hypomineralised regions? Special arrangement of proteins? Looped ends of dentine tubules? Many interpretations, but its appearance along the outermost regions of the root dentine and close to the cementum is very consistent. Granular layer Ten Cate’s Oral Histology (8th Edition); Fig. 8-70 Dentine types Secondary dentine (crown and root) Develops after root formation is complete Same mineral content as primary dentine, but develops more slowly and less regularly Primary Grows continuously throughout life of tooth, but not evenly, resulting in pulp recession (decrease in pulp volume with age) Secondary Boundary between primary and secondary dentine is usually marked by a contour line, due to change in odontoblast/tubule direction. Pulp Dentine types Reactionary dentine Tertiary dentine Deposited as a response to an external stimulus (caries, trauma, attrition etc.). Odontoblasts and resulting dentine matrix will respond differently depending on severity of the stimulus. If mild/slow: odontoblasts may react and deposit reactionary dentine (tubules continuous with those of secondary/primary dentine, mineralization pattern may be different). If strong/fast: odontoblasts die, new odontoblasts deposit reparative dentine (irregular, tubule-poor, sealing tissue). Reparative dentine Ten Cate’s Oral Histology (8th Edition); Figs. 8-7, 8-8 Dentine types Sclerotic/Translucent dentine Forms from occlusion (infilling) of tubules, often with peritubular dentine (sometimes with mineral only). Gives dentine a glassy appearance (hence “translucent dentine”). Occurs naturally with age, reducing the porosity/permeability of dentine. Ten Cate’s Oral Histology (8th Edition); Figs. 8-32, 8-33 By the end of this lecture, you should be able to: Describe the chemical and structural composition of dentine Identify the major structural and cellular components of dentine Identify and describe the major types of dentine List the roles dentine plays in maintaining a tooth