Integumentary System - Tooth Development
The tooth is an extrordinary integumentary system specialization providing insights into epitheilal/mesenchymal (ectoderm of the first pharyngeal arch and neural crest, ectomesenchymal cells) interactions in development and develops with a major contribution from the neural crest. (More? Neural Crest Development)
There are 4 morphological stages describing the early tooth development: bud, cap, bell, and terminal differentiation.
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Some Recent Findings
- Human Embryology (2nd ed.) Larson Chapter 14 p443-455
- The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Chapter 20: P513-529
- Before We Are Born (5th ed.) Moore and Persaud Chapter 21: P481-496
- Essentials of Human Embryology Larson Chapter 14: P303-315
- Human Embryology, Fitzgerald and Fitzgerald
- Color Atlas of Clinical Embryology Moore Persaud and Shiota Chapter 15: p231-236
- ectoderm, mesoderm and neural crest ectomesenchyme contribute
- inductive influence of neural crest with overlying ectoderm
- neural crest-derived mesenchymal cells
- differentiate under the influence of the enamel epithelium
- form predentin
- calcifies to form dentin
- produce enamal
- tooth growth occurs in ossifying jaws
- periodontal ligament holds tooth in bone socket
|Stage||Human (weeks)||Mouse (days)|
Human 2 Sets of Teeth
- 20 deciduous teeth
- Differential rates of growth, shed at different times over 20 year period
- 32 permanent teeth
- Incisors - sharp cutting edge, adapted for biting the food.
- Canines - are larger and stronger than the incisors. The upper canines have also been called the "eye teeth", while the lower canines "stomach teeth".
- Premolars - or Bicuspid teeth are smaller and shorter than the canines.
- Molars - are the largest teeth adapted for grinding and pounding food.
Epithelial Mesenchymal Interaction
local ectodermal thickening expresses several signaling molecules these in turn signal to the underlying mesenchyme triggering mesenchymal condensation (epithelially expressed Bmp4 induces Msx1 and Lef1 as well as itself in the underlying mesenchyme)
Four epithelial signaling molecules, Bmp2, Shh, Wnt10a, and Wnt10b, in the early inductive cascade, each signal has a distinct molecular action on the jaw mesenchyme.
Mouse (E11.0 and E12.0) - all four genes are specifically expressed in the epithelium.
Shh and Wnt10b induce general Hedgehog and Wnt targets, Ptc and Gli for Shh and Lef1 for Wnt10b,
Bmp2 is able to induce tooth-specific expression of Msx1.
(Text above modified from: Hélène R. Dassule and Andrew P. McMahon Developmental Biology, v 202, n 2, October 15, 1998, p215-227)
(More? Developmental Mechanism - Epithelial Mesenchymal Interaction)
The tooth is not anchored directly onto its bony socket (alveolar bone) but held in place by the periodontal ligament (PDL), a specialized connective tissue structure that surrounds the tooth root coating of cementum.
The additional roles of the PDL are to also act as; a shock absorber, transmitter of chewing forces (from tooth to bone), sensory information (heat, cold, pressure and pain).
The collagen fiber bundles within the ligament are called "Sharpey’s fibres".
Cementum (from investing layer of the dental follicle) is contiguous layer with the periodontal ligament on one surface and firmly adherent to dentine on the other surface.
Molecular Tooth Development
More than 300 genes have been associated with tooth development including: BMP4, FGF8, MSX1, MSX2, PAX9, PITX2, SHOX2, Delta/Notch, Hox-8, Runx2
Most recent review in Developmental Dynamics by Lin D, Huang Y, He F, Gu S, Zhang G, Chen Y, Zhang Y. Expression survey of genes critical for tooth development in the human embryonic tooth germ. Dev Dyn. 2007 Mar 29.
Amelogenin - abundant protein secreted by ameloblasts which is a major component of tooth enamel.
The papers below are from UNSW Embryology (version 3), information requires updating.
Bone Morphogenic Protein (BMP) / Fibroblast Growth Factor (FGF)
Growth factors in the BMP- and FGF-families are expressed in dental epithelium during initiation of tooth development and their effects on the underlying mesenchyme mimic those of the epithelium. They upregulate the expression of many genes, including the homeobox-containing Msx-1 and Msx-2, and stimulate cell proliferation suggesting that they may act as epithelial signals transmitting epithelial-mesenchymal interactions. During subsequent morphogenesis, when the characteristic shapes of individual teeth develop as a result from folding of the dental epithelium, several signal molecules including Sonic hedgehog, Bmps-2, 4, 7 and Fgf-4 are expressed specifically in restricted and transient epithelial cell clusters, called enamel knots.
(Text: Irma Thesleff and Carin Sahlberg Seminars in Cell & Developmental Biology, v 7, n 2, April, 1996, p185-193)
The expression pattern of Delta 1 in ameloblasts and odontoblasts is complementary to Notch1, Notch2, and Notch3 expression in adjacent epithelial and mesenchymal cells. Notch1 and Notch2 are upregulated in explants of dental mesenchyme adjacent to implanted cells expressing Delta1, suggesting that feedback regulation by Delta-Notch signaling ensures the spatial segregation of Notch receptors and ligands. TGF1 and BMPs induce Delta1 expression in dental mesenchyme explants at the stage at which Delta1 is upregulated in vivo, but not at earlier stages. In contrast to the Notch family receptors and their ligand Jagged1, expression of Delta1 in the tooth germ is not affected by epithelial-mesenchymal interactions, showing that the Notch receptors and their two ligands Jagged1 and Delta1 are subject to different regulations.
Text: Mitsiadis etal Developmental Biology,v 204, n 2, December 15, 1998, p420-431
A total lack of tooth development.
The teeth are translucent and often roughened with severe amber discolouration. Discoloured teeth with an opalescent sheen, dentin does not support enamel (dentin sialophosphoprotein mutation)
The primary teeth are translucent and amber in colour whereas the erupting secondary central incisors are of normal appearance.
Abnormal tooth enamel formation (AMELX, ENAM, KLK4, MMP20).
Dental anomaly mainly affecting premolars in people of Mongolian origin.
Lack of development of one or more teeth.
Hypohidrotic Ectodermal Dysplasia
Maldevelopment of one or more ectodermal-derived tissues.
- ↑ Xiaofeng Huang, Pablo Bringas, Harold C Slavkin, Yang Chai Fate of HERS during tooth root development. Dev. Biol.: 2009, 334(1);22-30 PMID:19576204
- ↑ Dahe Lin, Yide Huang, Fenglei He, Shuping Gu, Guozhong Zhang, YiPing Chen, Yanding Zhang Expression survey of genes critical for tooth development in the human embryonic tooth germ. Dev. Dyn.: 2007, 236(5);1307-12 PMID:17394220
- ↑ Takuya Ogawa, Hitesh Kapadia, Jian Q Feng, Rajendra Raghow, Heiko Peters, Rena N D'Souza Functional consequences of interactions between Pax9 and Msx1 genes in normal and abnormal tooth development. J. Biol. Chem.: 2006, 281(27);18363-9 PMID:16651263
- ↑ 4.0 4.1 Despina S Koussoulakou, Lukas H Margaritis, Stauros L Koussoulakos A curriculum vitae of teeth: evolution, generation, regeneration. Int. J. Biol. Sci.: 2009, 5(3);226-43 PMID:19266065 | PMCID: PMC2651620
- ↑ Martin J Barron, Sinead T McDonnell, Iain Mackie, Michael J Dixon Hereditary dentine disorders: dentinogenesis imperfecta and dentine dysplasia. Orphanet J Rare Dis: 2008, 3();31 PMID:19021896
Marianna Bei Molecular genetics of tooth development. Curr. Opin. Genet. Dev.: 2009, 19(5);504-10 PMID:19875280
Maisa Seppala, Maria Zoupa, Obinna Onyekwelu, Martyn T Cobourne Tooth development: 1. Generating teeth in the embryo. Dent Update: 2006, 33(10);582-4, 586-8, 590-1 PMID:17209531
Irma Thesleff The genetic basis of tooth development and dental defects. Am. J. Med. Genet. A: 2006, 140(23);2530-5 PMID:16838332
Kevin Tompkins Molecular mechanisms of cytodifferentiation in mammalian tooth development. Connect. Tissue Res.: 2006, 47(3);111-8 PMID:16753804
Martyn T Cobourne, Paul T Sharpe Tooth and jaw: molecular mechanisms of patterning in the first branchial arch. Arch. Oral Biol.: 2003, 48(1);1-14 PMID:12615136
P T Sharpe Neural crest and tooth morphogenesis. Adv. Dent. Res.: 2001, 15();4-7 PMID:12640730
Dahe Lin, Yide Huang, Fenglei He, Shuping Gu, Guozhong Zhang, YiPing Chen, Yanding Zhang Expression survey of genes critical for tooth development in the human embryonic tooth germ. Dev. Dyn.: 2007, 236(5);1307-12 PMID:17394220
M Nakatomi, I Morita, K Eto, M S Ota Sonic hedgehog signaling is important in tooth root development. J. Dent. Res.: 2006, 85(5);427-31 PMID:16632755
Takuya Ogawa, Hitesh Kapadia, Jian Q Feng, Rajendra Raghow, Heiko Peters, Rena N D'Souza Functional consequences of interactions between Pax9 and Msx1 genes in normal and abnormal tooth development. J. Biol. Chem.: 2006, 281(27);18363-9 PMID:16651263
P Kettunen, I Thesleff Expression and function of FGFs-4, -8, and -9 suggest functional redundancy and repetitive use as epithelial signals during tooth morphogenesis. Dev. Dyn.: 1998, 211(3);256-68 PMID:9520113
External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name.
- StemBook - Tooth organogenesis and regeneration
- University of Helsinki Gene Expression in Tooth
- American Dental Association Overview - Tooth
- Columbia University Medical Centre Illustrations: How a Tooth Decays
- Merck Tooth disorders
- Nemours Foundation Teething Tots
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