1. Dentin Dr. Syed Sadatullah Assistant Professor

2. 1. Introduction and Chemical Composition Dentin is a hard bone-like tissue that is present in the crown as well as in the root of teeth. In the crown, dentin is covered by enamel and in the root it is covered by cementum Unlike enamel, dentin is a vital tissue containing the cell processes of odontoblasts and neuron Mature dentin has 20% organic, 70% inorganic and 10% water by weight . Dr.Syed Sadatullah

3. The organic matrix of dentin is collagenous It provides resiliency to the crown which is necessary to withstand the forces of mastication The principle inorganic component of dentin is hydroxyapatite crystals The high mineral content of dentin makes it harder than bone and cementum but softer than enamel The knoop hardness for dentin is approximately 68 Dr.Syed Sadatullah

4. 2. Dentinal structure and classification Dentin is packed with dentinal tubules that traverse its entire thickness Dentinal tubules contain odontoblastic process and nerve fibres The odontoblastic processes have numerous side branches that exist in the lateral branches of the dentinal tubules Dr.Syed Sadatullah

5. Dr.Syed Sadatullah Odontoblasts – peri-tubular and inter-tubular dentin has been removed Dentine tubules – odontoblastic processes removed

6. Dr.Syed Sadatullah Odontoblastic process

7. 3. Histological Features of Dentin Depending on its time of development Dentin is classified as: Primary dentin Secondary dentin Tertiary dentin Dr.Syed Sadatullah

9. Dr.Syed Sadatullah Types of Dentin

10. Tertiary dentin Tertiary dentin is produced in reaction to stimulus, such as attrition , caries or restorative dental procedure Tertiary dentin can be reactionary or reparative Reactionary dentin is that type of tertiary dentin that is deposited by the pre-existing odontoblasts Reparative dentin is deposited by newly differentiated odontoblasts Dr.Syed Sadatullah

11. Dr.Syed Sadatullah Secondary and Tertiary Dentin

12. Dr.Syed Sadatullah Types of Dentin Predentin Mantle Dentin Circumpulpal Dentin Inter-globular Dentin Sclerotic Dentin Intra-tubular Dentin Inter-tubular Dentin Tomes Granular layer

13. Dr.Syed Sadatullah Odontoblast process in dentin tubule

14. Predentin Predentin is the first deposited layer of un-mineralized matrix of dentin Mantle Dentin The outer layer of dentine that mineralizes first is called mantle dentin. It lies near the DEJ Circumpulpal Dentin The bulk of dentin underlying the mantle dentin is called circumpulpal Dr.Syed Sadatullah

15. Dr.Syed Sadatullah Mantle Dentin – Inter-globular Dentin – Circumpulpal Dentin

16. Inter-globular Dentin Dentine separating the mantle dentin and circumpulpal dentin is hypo-mineralized and is called inter-globular dentin Interglobular Dentin Dr.Syed Sadatullah

18. Dr.Syed Sadatullah Intra-tubular Dentin

20. Tomes granular layer In the roots near the cemento-dentinal junction there are hypo-mineralized areas of dentin around the dentinal tubule called the Tomes granular layer Dr.Syed Sadatullah

21. 4. Histological Features of Dentin Incremental growth line The organic matrix of dentine is deposited incrementally at a daily rate of 4µm At the boundary of each daily increment, minute changes in collagen fibre orientation is observed which manifest as incremental lines Incremental lines run perpendicular to the dentinal tubules Dr.Syed Sadatullah

22. Dr.Syed Sadatullah Incremental lines

23. Dr.Syed Sadatullah Incremental lines

24. Incremental lines of von Ebner In ground section the 5-day increment can be seen as incremental or imbrications' lines of von Ebner Counter lines Owen Counter lines of Owen represent normal physiological alterations in the pattern of mineralization Neonatal line represents an exaggerated counter line of Owen. Neonatal lines are seen in all primary teeth and the first permanent molars Dr.Syed Sadatullah

25. Dr.Syed Sadatullah Neonatal Line in Enamel and Dentin Lines of Owen