1. Department of Dental Sciences, Faculty of Medicine, University of Liège, 4000 Liège, Belgium
2. Unit of Ultrastructural Morphology, Laboratory of Evolutive and Functional Morphology, University of Liège, 4000 Liège, Belgium
3. L'Unité de Morphologie Expérimrntale, Université Catholique de Louvain, 1200 Bruxelles, Belgium