ASYMMETRY IN THE OCCLUSAL MORPHOLOGY OF FIRST PERMANENT MOLARS IN 45,X 46,XX MOSAICS/

The genetic control of dental morphology is affected by various chromo somal aberrations, and morphological changes familiar to specific aneu ploidies can be distinguished in many cases. Asymmetry between bilater al teeth in the dental arch in laboratory animals shows increased expr ession after exposure to external stress during development. Bilateral asymmetry in occlusal cuspal morphology has not been widely used as a means of odontometric examination, partly because accurate and reliab le methods are not commonly available. The aim here was to examine lin ear and angular variables of the occlusal morphology of maxillary and mandibular first permanent molars in three dimensions in individuals w ith 45,X/46,XX mosaicism and to find out if this aneuploidism causes d eviations from normal development and increased asymmetry in bilateral variables of the occlusal surface. The participants were five females with 45,X/46,XX chromosome constitution, whose karyotypes were confir med by cytogenetic tests of skin fibroblasts. The controls were 10 fir st-degree female relatives of the mosaic patients with normal 46,XX ch romosome constitution. The method of measuring the three-dimensional m orphology of occlusal surfaces was based on a machine-vision technique using a single video-imaging camera. An apparent increase in asymmetr y of occlusal morphology in first permanent molars in 45,X/46,XX mosai cs was found. As there was evidence of directional asymmetry, it is po ssible that different cell lines regulated by discrete genes cause the directionality. (C) 1998 Elsevier Science Ltd. All rights reserved.