Computer-aided graphical reconstructions of the development of murine dental primordia and surrounding structures from day 12 until birth.

There are studies that discuss spatial impediment as an important co-factor during tooth morphogenesis, especially to the cuspal folding pattern in relation to the space available for the primordium. The aim of this study is to give a description of the 3-dimensional aspect of the dental primordia of the NMRI mouse in relation to their surrounding hard tissue structures, and covering all prenatal stages from lamina to late bell. Serial histological sections were prepared from 31 specimens of NMRI mice from intrauterine days 12-19 (birth), and computer-aided 3D-reconstructions were made from light microscopic traces. During the early stages of days 12-15, the bony structures were too far away to exert a direct mechanical influence. However, from day 16 on (early bell stage in molar primordia), partial bony encapsulations with distances around 100 microm were found. Up to birth, when the folding pattern of the inner enamel epithelium became more prominent, a progressive bony encapsulation, with distances reduced to 40 microm, could be seen. Spatial impediment may be a possible co-factor in bell stages of dental morphogenesis.