抄録
The dwarfed or peg-shaped upper lateral incisor frequently noted in human dentitions has been accepted as a manifestation of evolutionary phenomena as well as the diminished teeth of ten found in the third molars and the second premolars without correlation to jaw and quadrant. On the contrary, some uncertainty still exists concerning the phylogenetical behavior of the lower anterior teeth since only a few cases have been reported concerning their dwarfism. It is noted in the reports of many authors that the lower central incisors are more frequently diminished in their shape and size than the laterals. This supposition, however, is acceptable in the light of two facts: first, the width of the crown of the central incisors usually is smaller than that of the laterals and, second, central incisors are more frequently congenitally absent than laterals. Thus, the lower central incisor forms an exception to the general theory of dental phylogeny in which it is widely accepted that teeth are reduced in size and shape mostly from the distal aspect of each tooth group, namely, the third molars and the second premolars and upper laterals. If evidence exists of many dwarfed or peg-shaped teeth particularly in the location of the lower incisor, we could term them a "missing link" which fills up the gap between normal variation of the morphology and congenital absence. It would be informative that the lower incisor is an exception to the general rule of teeth reduction. The following report of seven cases of the lower dwarfed incisors may help to elucidate the problem.
