Mirror image supplemental primary incisor teeth in twins: case report and review.

During a survey in a rural area of northern Namibia (South West Africa) in 1988,4-year-old twin boys were seen (Fig 1). One child had a supplemental primary maxillary lateral incisor on the right side; the other had a supplemental primary maxillary incisor on the left side (Figs 2 and 3, see next page). Root length occlusal and panoral radiographs were taken which showed that each child had a supplemental permanent incisor that replaced the primary supplemental incisor (Fig 4, see next page). The primary supplemental teeth were mirror images, and subsequent caries patterns which occurred also involved the maxillary teeth in a mirror-image fashion (Figs 2 and 3). The existence of transposed viscera could not be investigated. It was not possible to obtain birth records for this rural village community of Herero people, or to obtain blood samples to confirm the monozygotic relationship. Traditionally, in Southern African tribes, twins are not welcomed, and the second twin commonly is not allowed to survive. It is unusual to find acceptance of these children within the community. Because of this tradition, it was not possible to seek out other family members who were twins and could have had similar dental conditions.