Molecular characterisation of odontoblast during primary, secondary ...

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1.2.3 Dentinal tubules - a means of communication. 1.2.3.1 The tubular structure Introduction The tubular density of dentine is high (~30,000/mm² on average), and these tubules are approximately 1 to 3 micrometers in diameter on average in humans depending on the intratubular dentine thickness; their distribution is unequal throughout the dentine and their density increases near the pulp cavity reflecting the crowding of odontoblasts as they move pulpally during dentinogenesis (Figure 4). Figure 4 : The density of the dentinal tubules varies according to the depth of the dentine and the proximity to the pulp. Surface area occupied by tubules is 2/3% near the Enamel, but 20- 25% near the pulp. (Pashley 1996) (according to (Olgart and Bergenholtz 2003) – D=Dentine, P=Pulp, B=Bone. Bar=500µm The tubules course in a sinusoidal manner in the crown rather than a rectilinear way, due to a change in the radius of curvature from the outer to the inner aspect of the dentine and each has numerous lateral extensions, which provide a means of communication between them. Thus, much of the area of the dentine matrix is in direct communication with the odontoblasts on its formative surface through their processes contained within the tubules. This has significant clinical implications in 24
Introduction terms of the communication between the inner and outer regions of the tooth and how disease or surgical intervention can impact. The tubular density differs significantly at outer and inner areas of the dentine. It is estimated that the surface occupied by these tubules represents 1% of the dentinal surface in the periphery of the dentine (under the enamel) and 22% near the pulp (Fosse, Saele et al. 1992). This variable distribution underlines the importance of location when drilling a cavity or making a coronal preparation, due to the opening of a diffusion pathway into the pulp tissue and potentially allowing the ingress of bacteria, toxins, and other adverse agents. The entire length of the tubules will contain dentinal fluid, which probably represents a cellular transudate from the pulp parenchyma together with any local odontoblast secretions. Two different phenomena are encountered from the moment when open tubules are exposed: Diffusion (Figure 5): When two biological environments (i.e., the pulp and the external environment of the oral cavity) are separated by a filter (i.e., the tubular dentine), a concentration gradient is established for agents within these two environments. Diffusion occurs from the most concentrated to the least concentrated milieu in order to equilibrate the concentrations. In the case of teeth, the presence of bacteria at high concentration in the saliva will lead to their passive diffusion to the sterile pulp parenchyma if the permeability barrier of the enamel is absent from the outside of the tooth. Nevertheless, the relatively large diameter of bacteria relative to the diameters of tubules is an obstacle to their movement through the tubules, although toxins and other molecules can still readily pass through. The phenomenon of intra-pulpal pressure, is greater than that external to the tooth: physiologically, the pressure in the pulp relative to that external to the tooth is such that there tends to be an outward flow of fluid if open tubules are exposed, 25
Page 1 and 2: ECOLE DOCTORALE : Génétique, Cell
Page 3 and 4: ACKNOWLEDGEMENTS I wish to express
Page 5 and 6: Abstract : This research aimed to i
Page 7 and 8: CONTENTS List of Figures ………
Page 9 and 10: 4.5.2 MSX2 and pulp repair ........
Page 11 and 12: Figure 11 : Dentine bridge formatio
Page 13 and 14: minutes. (DMP = dentine matrix prot
Page 15 and 16: lipofectamin ® vector only (MDPC v
Page 17 and 18: List of Tables: Table 1: Primer det
Page 19 and 20: 1.1 Towards a biological approach I
Page 21 and 22: Introduction odontoblast processes
Page 23 and 24: Introduction Secondary dentine: thi
Page 25: Introduction Understanding the dist
Page 29 and 30: Figure 5 : There is a differential
Page 31 and 32: Introduction Movement of the dentin
Page 33 and 34: 1.2.3.3 Consequences of new technol
Page 35 and 36: Introduction an apical nucleus, whe
Page 37 and 38: Introduction creates a physical bar
Page 39 and 40: Introduction polarisation and the d
Page 41 and 42: Introduction variations in pressure
Page 43 and 44: Introduction also express neurogeni
Page 45 and 46: 1.4.1 Reactionary dentinogenesis In
Page 47 and 48: Introduction responses, including a
Page 49 and 50: Introduction superficial cells move
Page 51 and 52: Introduction induce dentine bridge
Page 53 and 54: Introduction Because of its highly
Page 55 and 56: Introduction (Hayashi 1982). At 11
Page 57 and 58: Introduction To date, involvement o
Page 59 and 60: Introduction In deeper cavities, wh
Page 61 and 62: Introduction dental papilla cells.
Page 63 and 64: 2 Materials and Methods Material an
Page 65 and 66: Material and methods containing; 12
Page 67 and 68: 2.1.2.3 Microarray analysis Materia
Page 69 and 70: Material and methods 2.2 Part Two:
Page 71 and 72: Material and methods a Modulyo free
Page 73 and 74: Material and methods Figure 16: Pri
Page 75 and 76: Material and methods To date, sever
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Material and methods (pH=6.8) with
Page 79 and 80:
Material and methods (P), and calci
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Material and methods (Sigma, la Ver
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Material and methods visualized by
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2.4.2.6 MSX2 over-expression in imm
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Material and methods channel. Data
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Results Amelogenin, IBSP, DCN, Alka
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Results data previously reported fo
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91 MAPK PATHWAY probe set GENE ID b
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Results Alkaline phosphatase and am
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Figure 24: Mouse upper incisor (A)
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Figure 25: Phosphorylated p38 prote
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3.3 MSX2 proteins and dentinogenesi
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Figure 29: First upper molar in +/+
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3.3.1.3 At 21days post natal : Resu
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Results expression, obtained using
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Figure 37: Immunohistochemical anal
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3.3.4 BrdU IHC Results BrdU was inj
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3.3.6 Quantitative RT-PCR (Q-RT-PCR
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Results 3.4 Design and use of a new
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Results Figure 46: Histology at 2 w
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Results cells is also characteristi
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4 Discussion Discussion 4.1 Regulat
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Discussion odontoblast secretory be
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Discussion 4.2 Molecular characteri
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Discussion al. 2004; Magloire, Coub
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Discussion differences. Bone cells
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Discussion we can conclude that the
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Discussion pathway is complex and i
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Discussion odontoblast physiologica
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Discussion dentinogenesis. By perfo
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Discussion cellular and molecular s
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Discussion Notably, our results are
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Discussion contribute to reparative
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Discussion other species (Abedi, To
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Discussion dentinogenesis, some cel
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Discussion morphology. It was not p
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5 Conclusion Discussion Research on
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Discussion Figure 50: 14 months pos
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References during normal and in vit
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References Faraco, I. M., Jr. and R
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References Kidd, E. A., A. Banerjee
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References antigen-expressing cells
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References Smith, A. J. and H. Leso
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References Yamashiro, T., M. Tummer
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References Appendix 1: Full list of
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probe set GENE ID baseline mean (LS
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Appendix 3: Molecular characterizat
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Appendix 5: Evaluation of a new lab
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