Figure 3.

The model system of the un-opposed molar – the focus of Sicher and Weinmann’s interest in the evolution of the dentition during the last years of their distinguished exile careers at the University of Illinois. Fig. 3A. An un-opposed occlusal situation in the lower jaw is created by extraction of the antagonistic upper molar teeth (asterisk). Mouse dentitions feature three upper and three lower molars on each side of the jaw. Four continuously erupting incisors protrude into the anterior portion of the oral cavity, one in each quadrant. The anterior aspect of a tooth is called mesial while the posterior aspect is called distal. Three regions of a fully erupted tooth are distinguished: The coronal portion, which describes the area of the tooth crown, the apical portion, which is directed toward the tip of the root of the tooth (apex), and the cervical portion, which is located at the interface between tooth crown and tooth root. Fig. 3B. As a consequence, molars of the lower jaw super-erupt beyond the plane of occlusion (asterisk). Tooth elevation during a period of 12 days amounts to 0.13mm.