The development of the dentition has the general characteristics of a complex adaptive system. Hypodontia is a developmental variation with not only a reduced number of teeth but also the teeth formed are smaller in size, have different crown and root morphology and are delayed in development. We have formed a multicentre, multidisciplinary collaborative study to investigate this complex system from its initiation to its outcome: from genotype with genetic/epigenetic/ environmental interactions to the accurate measurement of the phenotypic outcome. This paper reports an initial study of the root morphology and dental age component of the phenotype of the hypodontia patient compared to controls. The sample consists of orthodontic patients, 30 males and 30 females with hypodontia and 60 controls matched for age, gender and ethnicity. The material studied is the orthopantomographic radiograph of each patient. From these the number and site of each congenitally missing tooth is recorded. The number and shape of roots of each formed tooth are scored. Using the MATLAB computer programming platform, the distance between specific points on the crown and root, their area and hence the crown/ root ratio is computed, and the stages of dental development of each tooth scored; the degree of root development of the second permanent molar is particularly valuable in comparing between hypodontia patients and controls. By combining investigations from different stages of this biological complex adaptive system, we are using dental development, which is an accessible, non-invasive and accurately measurable paradigm to increase understanding of general development.
complex system, developments measures, hypodontia, radiographs
 Brook, A.H. & O’Donnell, M.B., The dentition: a complex system demonstrating self-* principles, 2011 Fifth International Conference on Self Adaptive and Self Organising Systems. C.P.S. Washington IEEE, pp. 208–209, 2011.
 Brook, A., O’Donnell, M.B., Hone, A., Hart, E., Hughes, T., Smith, R. & Townsend, G., General and craniofacial development are complex adaptive processes influenced by diversity. Australian Dental Journal, 59(S1), pp. 13–22, 2014.
 Townsend, G., Harris, E.F., Lesot, H., Clauss, F. & Brook, A.H., Morphogenetic fields within the human dentition: a new clinically relevant synthesis of an old concept. Archives of Oral Biology, 54(S1), 34–44, 2009.
 Brook, A.H., A unifying aetiological explanation for anomalies of human tooth number and size. Archives of Oral Biology, 29, pp. 373–378, 1984. https://doi.org/10.1016/0003-9969(84)90163-8
 Kirkham, J., Kaur, R., Stillman, E.C., Blackwell, P.G., Elcock, C. & Brook A.H., The patterning of hypodontia in a group of young adults in Sheffield. U.K. Archives of Oral Biology, 50, pp. 287–291, 2005.
 Brook, A.H. & Holt, R.D., The relationship of crown length to root length in permanent maxillary central incisors. Proceedings of the British Paedodontic Society, 8, pp. 17–20, 1978.
 Holt, R.D. & Brook, A.H., Taurodontism: a criterion for diagnosis and its prevalence in mandibular first permanent molars in a sample of 1,115 British schoolchildren. Journal of the International Association of Dentistry for Children, 10(2), pp. 41–47, 1979.
 Brook, A.H. & Scheers, M., Variation in tooth root morphology in a Romano-British population. Dental Anthropology, 19(2), pp. 33–38, 2006.
 Falk, D., Book Review of ‘An introduction to human evolutionary anatomy’ by L. Aiello and C. Dean. Man, 27, pp. 410–411. https://doi.org/10.2307/2804064