Effect of agenesis on the crown-size profile pattern.

Abstract

Agenesis and hypodontia are associated with crown-size reduction in the remaining teeth (S. M. GARN ET AL, J Dent Res 41:717, 1962, Nature 200:488-489, 1963; J Dent Res 42:13441363, 1963; H. J. KEENE, Amer J Orth 50: 445-451, 1964; and K. HANIHARA ET AL, J Anthrop Soc Nippon 73:72-81, 1965). The question arises as to whether crown-size reduction associated with tooth number reduction is uniform throughout the remaining teeth or whether there is differential reduction in tooth material that results in a distinctly different crown-size profile pattern. In order to answer this question we measured the mesiodistal crown diameters of 658 subjects, including 82 with third molar agenesis and 19 with radiographically verified agenesis of multiple teeth. The original measurements were converted into sex-specific t-scores using a computer program (C. R. BLACK, Ann NY Acad Sci 134:538-540, 1966). The crown-size profile patterns were then compared using the statistic rT as previously described (S. M. GARN ET AL, J Dent Res 47:1190, 1968: Arch Oral Biol 13:1235-1242, 1968: Amer Anthrop 71: 79-84, 1969). As shown in the table, the crown-size profile pattern of individuals lacking one or more mandibular third molars is distinctly different from that of the total group (r=-0.34). Sim-