The Histology of Dentin Pauline Hayes Garrett D

The Histology of Dentin Pauline Hayes Garrett, D. D. S. Department of Endodontics, Prosthodontics, and Operative Dentistry University of Maryland, Baltimore Histology 2007

This material was taken from: • Essentials of Oral Histology and Embryology, third edition, Leslie P Gartner, 1999, Jen House Publishing Co. Chapter 3 • Ten Cate’s Oral Histology Development, Structure, and Function, Antonio Nanci, sixth edition, 2003, Mosby, Chapter 8 • Oral Anatomy, Histology and Embryology, Third edition, B. K. B. Berkovitz, G. R. Holland, B. J. Moxham, pg. Histology 2007

Objectives: To recognize and apply the following concepts to clinical dentistry: • • • Physical Properties of Dentinal Tubules – Peritubular Dentin – Intertubular Dentinal Types of Dentin – Peritubular – Intertubular – Primary Dentin – Secondary Dentin – Tertiary Dentin – Dead Tracks – Sclerotic Dentin – Globular Dentin – Interglobular Dentin • • • Histology 2007 Markings on Dental Tubules – Daily imbrication lines of von Ebner – Contour Lines of Owen – Neonatal line Dentin Intervention – Granular layer of Tomes – Hyline layer of Hopewell. Smith Root Dentin – Nerve Fiber Theory – Odontoblastic process Theory – Hydrodynamic Theory

Physical Properties of Dentin • Dentin, located in both the crown and root. Second hardest surface of the body. It is harder than cementum and bone; and softer than enamel. • It is composed of 65 -70% mineralized substances and 20 -25% organic material and 10% bound water. – The mineralized substance is calcium hydroxyapatite. – The organic material is collagen and ground substance. • The color of dentin is yellow. • Dentin is highly elastic. It is the support substance for Enamel which is extremely brittle. Dentin is living tissue. The odontoblasts reside in the pulp and continue to be active throughout the life of the tooth. Histology 2007 Illustration reprinted and modified from: Oral Histology and Embryology, second edition, Gartner, 1999 pg. 46. with permission from Dr. Leslie P. Gartner

Dentinal Tubules • Dentinal tubules are enclosed spaces, surrounded by peritubular dentin, which connects the pulp to the DCJ and DEJ. A scanning electron microscope specimen of dentinal tubules. Reproduced with permission from Mathias Nordve, IOB, Ui. O, University of Oslo. Histology 2007

Dentinal Tubules • Primary Curvature is: S-shaped • Secondary Curvature: jagged or wrinkled texture • Curvatures result from movement of odontoblasts during development Histology 2007

• In the coronal portion of the tooth, dentin has a “S”shaped curvature. Vs. • In the root portion of the tooth, dentin has a more Straight path. Histology 2007 Illustration Reprinted from Ten Cate’s Oral Histology, Developme nt, Structure, and Function, Antonio Nanci, 6 th edition, Mosby 2003, with permission from Elsevier

Dentinal Tubules • Note the “S” shape primary curvatures of Dentinal Tubules in the ground section of coronal dentin on the right. • Photomicrograph of decalcified dentin and illustration below, show the second degree curves in dentin Histological slides prepared and provided by the Department of Biomedical Sciences, University of Maryland, Dental School. Histology 2007

Peritubular dentin and Intertubular dentin • Dentinal tubules contain fluid = extracellular fluid (ECF) - Comes from pulp and provides nutrients - Extends from the pulp to the DCJ or DEJ - Important for pain sensation Histology 2007

Dentinal Tubules, Peritubular dentin and Intertubular dentin A scanning electron microscope specimen of dentinal tubules. Reproduced with permission from Mathias Nordve, IOB, Ui. O, University of Oslo. Histology 2007

Types of Dentin • - Primary Dentin: all dentin formed prior to root formation or completion. • - Secondary Dentin: all dentin produced after root formation or completion. (NOT due to trauma) • - Tertiary Dentin: all reparative dentin (all regular and irregular)* Histology 2007

Types of Dentin: Primary Dentin • Two Types: All collagen in Dentin is produced by Odontoblasts. – Mantle Dentin (M) is the area of initial dentin matrix formation and is the first formed dentin. It is located in the crown and underlying the DEJ. • It is ~20 micrometers thick. • The fibers are perpendicular to the DEJ. • Contains von Korff’s fibers – Large coarse bundles of type I collagen. – Circumpulpal dentin forms the remaining and the Mantle Dentin (M arrow) is the initial layer of Dentin formed in the bulk of primary dentin. crown portion of the tooth. • The collagen fibers are much narrower Ameloblasts (A), Odontoblasts (O). (~0. 05 micrometers thick) than mantle dentin. . Histological slide prepared and provided by the Department of Biomedical Sciences, • It is more mineralized than mantle dentin. University of Maryland, Dental School. • It is more compactly arranged collagen fibers than mantle dentin. . Histology 2007

Types of Dentin: Secondary Dentin • • • Secondary Dentin is a narrow band of dentin around the pulp chamber and is formed subsequent to root completion. It is not formed as a response to trauma. It is formed at a slower rate than primary dentin. It contains fewer tubules than primary dentin. It is formed in an unequal fashion and more secondary dentin produced on the roof and floor of the pulp than on the walls. There is usually a bend in the direction of of the tubules where primary and secondary meet. Image reprinted from the Leeds University: The Virtual Oral Histology Laboratory Histology 2007

Types of Dentin: Tertiary Dentin • Reparative Dentin: Once a carious lesion or fracture reaches dentin, the pulp will try to protect itself by making new dentin (Reparative dentin) to seal off the open tubules on the pulp side – 2 kinds: • If lesion is due to chronic trauma (slow process), dentin is regular • If lesion is due to acute trauma (fast process), dentin is irregular – Chronic reparations made by odontoblasts (more recovery) – Acute reparations made by fibroblasts (because the cell died) Histology 2007 Histological slide prepared and provided by the Department of Biomedical Sciences, University of Maryland, Dental School.

Types of Dentin: Dead Tracks If the carious demineralization of enamel reaches dentin, the carious lesion allows bacteria to enter the dentinal tubules – Odontoblasts can then be either damaged or killed, as well as their processes. • If killed, then there will be areas of dentin w/ no odontoblasts: • Called Dead Tracts (empty dentinal tubules that lead directly to pulp) Histology 2007

Types of Dentin: Sclerotic • • Sclerosis of dentin is the naturally occurring deposition of minerals within tubules that results in a thicker layer of peritubular dentin. It is highly mineralized Deposited inside the periphery of the tubules. The tubules become smaller in diameter and less permeable and so transmit stimuli to a lesser degree. Image reprinted from the Leeds University: The Virtual Oral Histology Laboratory Histology 2007

Types of Dentin: Globular vs. Interglobular Dentin • Arrows indicate regions of hypocalcified dentin called interglobular dentin. • Interspersed among regions of normally calcified dentin which is occasionally called Globular dentin. Histology 2007 Histological slide prepared and provided by the Department of Biomedical Sciences, University of Maryland, Dental School.

Markings on Dentin Tubules: • Length of the Dentin tubule – Has striations called Daily Imbrication Lines of Von Ebner – In between the lines is the amount of dentin that you make in 1 day (4 -8μm) – Segments of dentin are called Contour Lines of Owen • Result from metabolic disturbances during development • Indicative of health of person during dentin formation • Neonatal Line is An exaggerated Line of Owen – Just like in enamel, a Neonatal line in dentin: • Demarcates trauma experienced during birth Lengthwise section of a Dentin tubule Histology 2007

Dentin: Granular layer of Tomes/ Hyaline layer of Hopewell-Smith • Granular layer of Tomes: A granular appearing layer of dentin underlying the cementum that covers the root. Viewed under transmitted light in ground sections. – Located in the peripheral most layer of radicular dentin. – Increases slightly in width, proceeding from the CEJ to the root apex. – Possibly a coalescing and looping of the terminal portions of the dentinal tubules. Seen only because of light refraction in thick ground sections. – Also, suggested to be a special arrangement of collagen and noncollagenous matrix proteins at the interface between dentin and cementum. • The clear layer between the granular layer of Tomes and cementum is known as the Hyaline layer of Hopewell-Smith. – Facilitates the adherence of cementum and dentin. Histology 2007 Histological slides prepared and provided by the Department of Biomedical Sciences, University of Maryland, Dental School.

Root Dentin • • • This is a cross section of a decalcified root. The root canal is not evident in this photo The parallel semicircular lines within dentin are the lines of Owen. (O arrows) The radiating lines represent dentinal tubules (T arrows) The light semicircular line is called the hyaline layer of Hopewell-Smith (H) The thin dark line is the dentinocemental juntion. The cementum (C) is a relatively thin layer and is surrounded by the periodontal liga Histology 2007

Clinical Significance: Natural Desensitization • Sclerosis of dentin and deposition of secondary, and tertiary dentin. are several naturally occurring processes that can improve hypersensitivity over time. Histology 2007

Clinical Significance: Tetracycline staining and Bleaching • During the 1950’s Tetracycline was the drug of choice for pneumonia. If a young child receives this antibiotic during tooth development, it can be incorporated into tooth structure. Depending on the stage and level within the tooth when the tetracycline was incorporated, clinical bleaching of the stained teeth can be compromised. Generally, tetracycline stained teeth have a decreased prognosis for success and in many cases the preferred treatment are veneers. Figure 23 -16, Reprinted from Oral Anatomy, Histology and Embryology, 3 rd edition, B. K. B. Berkovitz, G. R. Holland, B. J. Histology 2007 Moxham, Mosby 2002, with permission from Elsevier

Figure 22 -31 above is reprinted from: Oral Anatomy, Histology and Embryology, 3 rd edition, B. K. B. Berkovitz, G. R. Holland, B. J. Moxham, Mosby, 2002, pg. 318, with permission from Elsevier Histology 2007

Question #1 [Click mouse for answer. ] • Dentin which is produced as a result of decay or trauma is known as: A. B. C. D. E. Primary Dentin Secondary Dentin Tertiary Dentin Intertubular Dentin Peritubular Dentin Histology 2007

Question #2 [Click mouse for answer. ] • Mantle dentin is the first dentin and located: A. B. C. D. E. At the cementoenamel junction (CEJ) Adjacent to predentin and pulpal area Only in the intercuspal areas In ridiculer dentin At the dentinoenamel junction (DEJ) Histology 2007

Question #3 [Click mouse for answer. ] • The neonatal line in dentin is: A. B. C. D. An exaggerated Striae of Retzius. An exaggerated line of Owen. Exaggerated Imbrication line of Von Ebner. A dead track. Histology 2007

Question #4 [Click mouse for answer. ] • The structure located at the tip of the arrow is known as: A. B. C. D. Histological slide prepared and provided by the Department of Biomedical Sciences, University of Maryland, Dental School. Intertubular Dentin Interglobular Dentin Globular Dentin Pre-Dentin Histology 2007

Question #5 [Click mouse for answer. ] • The whitish structure located at the tip of the arrow is known as: A. B. C. D. Intertubular dentin Peritubular dentin Mantle dentin Sclorotic dentin Histological slide prepared and provided by the Department of Biomedical Sciences, University of Maryland, Dental School. Histology 2007

Question #6 [Click mouse for answer. ] • The structure located at the tip of the white arrow is known as: A. B. C. D. E. Primary curvature of Dentin Secondary curvature of Dentin “S” curve of Dentinal Spindles Reparative Dentin Histology 2007 Histological slide prepared and provided by the Department of Biomedical Sciences, University of Maryland, Dental School.

Question #7 [Click mouse for answer. ] • A 55 year old recently widowed female presents to your office complaining of gray teeth. Her medical history reveals that she had a history of pneumonia as a one year old. What is her probable diagnosis, and prognosis of successful clinical bleaching. A. B. C. D. E. Tetracycline staining, poor to fair. Enamel Hypoplasia, poor to fair. Physical Trauma, fair Fluorosis, poor High fever, fair to good. Histology 2007

THE END Histology 2007