1. Maxillo-Facial Surgery, School of Medicine, University of Ferrara, Corso Giovecca 203, 44100 Ferrara, Italy.
2. Department of Morphology and Embryology, Section of Histology and Embryology, University of Ferrara, Via Fossato di Mortara 64/B, 44100 Ferrara, Italy.
3. Institute of Histology and General Embryology, School of Medicine, University of Bologna, Via Belmeloro 8, 40126 Bologna, Italy.