Tooth and cusp size reduction in second molars.

The present study examined the cusp reduction pattern of molars in two San-Hybrid groups, namely, the Vassekela and Barakwena. Cusp and crownbase area measurements were undertaken on enlarged photographs of maxillary molars and on camera lucida drawings of mandibular molars. The protocone values for the Barakwena were significantly larger than those of the Vassekela and were also the largest of the four maxillary molar cusps (especially in M2). The metacone was the second largest cusp in M1, the paracone the second largest cusp in M2 and M3, while the hypocone was the smallest cusp in all maxillary molars. Maxillary crownbase areas were larger in the Barakwena than in the Vassekela but these differences were not statistically significant. The protoconid, entoconid and metaconid were the largest of the mandibular molar cusps. Generally, the cusp area values in first and third molars were larger in the taller Barakwena than in the shorter Vassekela. These differences were not statistically significant. In second molars, however, an unexpected finding was that crownbase and cusp areas (except the metaconulid) were significantly larger in the Vassekela than in the Barakwena. This study indicates that second molars show more cusp size differences in the two groups than do the other two molars. This may be regarded as a conservative tendency (Korenhof, 1960) in which case it would indicate that some second molar cusps are in a less active phase of evolutionary reduction than the same cusps in first and third molars.