Dentinogenesis and dentin permeability

Transcription

1 Dentinogenesis and dentin permeability Dr. Gábor Varga February, 2016 Department of Oral Biology Faculty of Dentistry, Semmelweis University

2 Radiograph of teeth dentin is the major component

3 Molar longitudinal section Pulp Horn Dentin is the major component of the pulp

4 Section of the tooth types of dentin mantle dentin tertiary dentin primary dentin secundary dentin predentin

5 Constituents of dentin Water, Inorganic, Organic W W I O I O Wet weight Volume

6 Tooth development details 1

7 Tooth development details 2

8 Section of tooth pulp is inside

9 Gene activation during tooth development Epithelium Mesenchyme

10 Differentiation of odontoblasts

11 Formation of mantle dentin during the early phase of mineralization

12 Section of the developing tooth

13 Dentin is produced by odontoblasts dentin Mineralization front Predentin Odontoblasts Mesenchyme

14 Cross section of a rat insicor illustrating mature secretory odontoblasts

15 Odontoblast structure

16 Mature secretory odontoblast

17 Involvement of hard tissue proteins in mineral formation

18 Interaction of odontoblast secretory products in predentin, dentin and the mineralization front

19 Light microscopic autoradiographs of the utilization of tritiated proline by odontoblasts at various time periods after intravenous injection

20 Collagen fibers are visible after dissolution of the mineral phase - dentine tubules are visible

21 Collagen fibers around tubules

22 (A) Primary, (B) secondary and (C) tertiary or reparative dentin

23 Dentinogenesis Imperfecta

24 Dentin phosphoprotein (DPP), a highly acidic protein, is the major noncollagenous component of dentin, being solely expressed by the ectomesenchymal derived odontoblast cells of the tooth. Takagi and Sasaki (1988) suggested that a deficiency of this protein is a causative factor factor in dentinogenesis imperfecta (DGI1; ). MacDougall et al. (1997) demonstrated that 2 major noncollagenous dentin matrix proteins, dentin sialoprotein (DSP) and dentin phosphoprotein (also known as phosphophoryn) are encoded by a single gene termed dentin sialophosphoprotein (DSPP).

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26 Dentinogenesis Imperfecta Characteristics autosomal dominant (1:8000) Opalescent teeth Irregular structure and hypomineralized dentin, grey or dark yellow/brown

27 Dentinogenesis Imperfecta Radiology Onion- or tulip-like tooth crown large pulp chamber, narrow dentin matrix

28 Dentin permeability, dentin sensitivity

29 Dentin tubules, inter tubular and intratubular dentin

30 Components of dentin

31 Permeability: the number and the diameter change depending on the dentin tubules 20000/mm 2 0,2-1,0 μm 45000/mm 2 Number Diameter

32 Entrance of a dentine tubule

33 The empty dentin tubules provide the basis for permeability - longitudinal section

34 Mineral deposits narrow down dentin tubules

35 Debris closing the entrance of dentin tubules

36 Components of dentin tubules besides extracellular fluid

37 Electron micrographs of the odontoblastic process and nerve ending in dentin

38 Neuronal network of pulp/dentin

39 Nerve endings in dentin

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41 Diffusion - Fick s 2nd law J s =D s A s / ( C s x) J s : diffusion rate D s : diffusion coefficient A s : size of cross sectional surface C s : concentration gradient x: length

42 Hagen Poiseuielle equation - fluid movement - basis of the hydrodynamic theory V=π Pr 4 / 8ηL V: fluid movement P: pressure difference r: radius η: viscosity L: length

43 Dentine sensitivity Dentinal tubules pass from pulp to dentine surface Contain dentinal fluid Pulpal one third of dentine contains odontoblast processes and some nerve fibres Problem: how can dentine transmit stimuli?

44 Dentine sensitivity Hydrodynamic theory of dentine sensitivity - fluid movement and pressure changes Is sensitivity due to nerve fibers in tubules? or movement of odontoblasts? Could odontoblasts be sensory endorgans? Are nerve fibers in the subodontoblastic plexus the actual sensors?

45 Dentine sensitivity Great variation between subjects secondary dentine and sclerosis of dentine

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47 In a caries lesion, cariogenic bacteria invade the dentinal tubules, demineralizing sclerotic and peritubular dentin in the process

48 Current concepts of the generation of dentinal pain

49 General position of afferent nerve endings in the odontoblastic layer, the predentin, and the dentin Od: odontoblastic layer, SP: substance P, CGRP: calcitonin gene- releated peptide, BV: blood vessels, PAN: primary afferent nociceptor, SPGN: sympathetic postganglionic nerves

50 Substance P- immunreactive nerve fibers (Nf) and nerve endings ( ) of the odontoblastic plexus beneath a pulp horn. D: dentin

51 Potential mechanisms that lead to the sensitization of primary afferent nociceptors (PAN)

52 Sensitization of primary afferent nociceptors (PAN) by arachidonic acid (AA) cascade and phospholipase A- aktivating protein (PALP)

53 The rate of pain also depends on the level of heat exposure

54 Pain development: gate control theory A: stimulator effect, SG: spinal ganglion, B: interneuron, T: transmitting neurons

55 Dentine hypersensivity Treatment To obliterate tubules by deposition of calcium salts To block tubules by protein precipitation To hyperpolarize or depolarize nerve fibers by altering ionic environment