DENTIN seminar DENTIN seminar DENTIN seminar

dentin seminar presentation

1. STRUCTURE OF DENTIN Dr . Dipen Majumder

2. DENTINAL TUBULE CONTENT Odontoblastic process- cytoplasmic extensions in dentinal fluid. COURSE Primary curvature- Starting at right angel from the pulpal surface, doubly convex. Secondary Curvature- gradually becomes straighter toward apical and cuspal region, sinusoidal in shape.

3. ARRANGEMENT Tubules wider and closer near pulp. Tubules farther apart and narrower near DEJ or CEJ. BRANCHES Lateral branches all along its course. Terminal branches near DEJ, more in root dentin .

4. (A)-1 μm in diameter at the DEJ. (B)-1.5–2 μm midway through dentin. (C)-1.5–3 μm at the pulp. (D)-Bacterial penetration follows line of least resistance to reach the pulp.

5. PERITUBULAR DENTIN INTERTUBULAR DENTIN Dentin surrounds the dentinal tubule . Dentin present between dentinal tubules. Lacks of collagen fibrils. Type 1 collagen present. PERITUBULAR AND INTERTUBULAR DENTIN

6. PERITUBULAR DENTIN INTERTUBULAR DENTIN D eposite inner wall of the tubules termed as ‘ intratubular dentin’ The main body of dentin is composed of intertubular dentin. I nner organic lining termed as lamina limitans . PERITUBULAR AND INTERTUBULAR DENTIN

7. PREDENTIN The predentin always adjacent to the pulp tissue and is 2–6 µm wide. It is not mineralized Mature dentin- 70 % inorganic and 20% organic material,10% water.

8. ODONTOBLAST Odontoblasts forming layer at the periphery of pulp and processes extending into the dentin. Palisade pattern . Junctions between odontoblasts- Gap junction, Tight junction, Desmosomal junction.

9. The life span of the odontoblasts is equal to the age of the tooth as once differentiated, they cannot undergo further division.

10. PRIMARY DENTIN (formed before root complition ) MANTLE DENTIN (formed along DEJ - seen in crown only) CIRCUMPULPAL DENTIN (all other dentin formed before tooth eruption) SECONDARY DENTIN (formed after root complition without any external stimuli, regular arrangement) TYPES OF DENTIN

11. TERTIARY DENTIN (formed after tooth eruption due to external stimuli , irregular in arrangement) REPARATIVE DENTIN SCLEROTIC DENTIN REACTIONARY DENTIN

12. HISTOLOGY OF DENTIN

13. Thicker dentin seen in boys than girls of similar age group and this increases during puberty. The buccal surfaces of the tooth showed maximum thickness, followed by lingual . CLINICAL CONTENTS Dentinal tubules branches, anastomoses to form canalicular system enhancing carious process.

14. INCREMENTAL GROWTH LINES OF VON EBNER These lines reflect the daily rhythmic, recurrent deposition of dentin matrix as well as a hesitation in the daily formative process. Theses lines situated about 20µm apart . Run at right angle to the tubule. Deposit at 4 µm daily and mineralize in a 12-hour cycle.

15. The contour lines formed from secondary curvatures between neighbouring dentinal tubules due to hypomineralisation known as CONTOUR LINES OF OWEN Prenatal and postnatal dentin are separated by an accentuated contour line known as NEONATAL LINE

16. Between the odontoblastic process and the peritubular dentin, periodontoblastic space is present. This space contains dentinal fluid which is outward from the pulp, having higher K+ and lower Na+ content. PERIODONTOBLASTIC SPACE

17. Hypomineralised dentin wherein globules of dentin fail to coalesce into a homogenous mass , appears dark in transmitted light . INTERGLOBULAR DENTIN Prevalent with vitamin D deficiency or exposure to high levels of fluoride at the time of dentin formation.

18. Tomes’ Granular Layer In transmitted light , a zone adjacent to cementum in root appears granular called as TOMES GRANULAR LAYER ( coalescing and looping of terminal portions of tubules ) This layer has highest concentration of calcium and phosphorus , whereas Interglobular dentin has higher concentration of sulfur.

19. HYALINE HOPEWELL-SMITH LAYER Hyaline layer present outside the granular layer( 15-20 µm wide ) Nontubular and structureless.

20. The processes in tubules may disintegrate or retract, leaving behind an empty tubule, referred as DEAD TRACT . Reparative dentin protect the pulp from infection by sealing off dead tract. Appear black in transmitted light. DEAD TRACT

21. INNERVATION OF DENTIN INTRATUBULAR NERVES- Nerves with close approximation with odontoblastic process. Mostly located in coronal zone( pulp horn ). Synapse like relation seen between the nerve and the odontoblastic process . The subodontoblastic plexus of Raschkow seen in the cell-free zone of Weil .

22. THEORIES OF PAIN TRANSMISSION DIRECT NEURAL STIMULATION HYDRODYNAMIC THEORY TRANSDUCTION THEORY Nerves in the dentine get stimulated . Various stimulus effect fluid movement in dentinal tubules. INWARD MOVEMENT- due to cold stimuli OUTWARD MOVEMENT- due to drying of exposed dentinal surface. The odontoblast process is excited by the stimulus and the impulse is transmitted to the nerve endings in the inner dentin.