Patients with congenitally absent maxillary lateral incisors often exhibit palatal ectopic eruption of the adjacent maxillary permanent canines.1,2 Permanent canines adjacent to absent lateral incisors also erupt mesially. In cases of unilateral absence of a maxillary lateral incisor, the midline is often deviated toward that side (Fig. 2).
Figure 1: Panoramic x-ray shows ectopic canine, absent lower right second premolar, ankylosed primary second molar, ectopic lower left second premolar and absent third molars. Figure 2: Pre-orthodontic anterior view showing missing right lateral incisor, small left lateral incisor and maxillary midline deflected to right side with ectopic palatal upper canine.
Second primary molars without underlying permanent successors show increased frequency of ankylosis and submergence.1 The earlier that ankylosis exists, the more severe are the potential consequences. Progressive infraocclusion can result in compromised alveolar bone height, tipping of adjacent teeth and destruction of bone during the extraction. Because infraocclusion increases as vertical bone development occurs commensurate with facial growth, the earlier the infraocclusion occurs, the more necessary it is to have the primary molar extracted to preserve vertical alveolar bone. The larger mesiodistal width of a retained second primary molar compared to the smaller width of the absent second premolar can compromise molar occlusion.