In hereditary cases, evidence of dental germ developing after surrounding tissues have closed the space required for development may be a large contributing factor, as well as such genetic disorders as Down syndrome, ectodermal dysplasia, cleidocranial dysplasia, and cleft lip and cleft palate. MSX1
MSX1 (muscle segment homeobox 1) is involved in condensation of ectomesenchyme in the tooth germ. Among the members of homeobox genes, MSX1 and MSX2 are crucial in mediating direct epithelial-mesenchymal interactions during tooth development by expressing in regions of condensing ectomesenchyme in the tooth germ. MSX1 mutations have been identified as a contributing factor in missing second premolars, third molars, and a small percentage of first molars. MSX1 is less likely to cause anterior agenesis.Heterozygous mutations in PAX9 (paired box gene 9) could arrest tooth morphogenesis as it plays a role of transcription the gene expressed in tooth mesenchyme at the bud stage during tooth development. A study showed that single nucleotide polymorphisms in PAX9 were highly associated with missing upper lateral incisors. AXIN2
The AXIN2 (AXIS inhibition protein 2) gene is a negative regulator of the Wnt signalling pathway, which is important in regulating cell fate, proliferation, differentiation and apoptosis. Its polymorphic variant may be associated with hypodontia such as missing lower incisors or in a more severe form of agenesis like oligontia (lack of six or more permanent teeth). EDA
EDA provides instructions for making a protein called ectodysplasin A. It encodes transmembrane protein that is part of TNF (tumour necrosis factor) family of ligands.
Anti-inflammatory eicosanoids include lipoxins, epi-lipoxins, and resolvins, which cause release of growth hormones. See also
Scar free healing
Health

References
External links
How wounds heal and tumors form With this simple Flash demonstration, Harvard professor Donald Ingber explains how wounds heal, why scars form, and how tumors develop. Presented by Childrens Hospital Boston. Wound Healing and Repair
Lorenz H.P. and Longaker M.T. Wounds: Biology, Pathology, and Management. Stanford University Medical Center. Romo T. and McLaughlin L.A. 2003. Wound Healing, Skin. Emedicine.com. Rosenberg L. and de la Torre J. 2003. Wound Healing, Growth Factors. Emedicine.com. After the Injury- Childrens Hospital Of Philadelphia