Frequencies of Occurrence of Accessory Tubercles and Other Traits in the Lower Deciduous Second Molar.

Abstract

small irregular cuspules or tubercles are often seen on the occlusal table of the human decidusous molar as well as the permanent molar. These frequencies were investigated semi quantitatively with the use of moire contourography. The protocone and metacone aligned in a horizontal plane parallel to the grating of the moire contourography. Countour interval was set at .2mm. The frequency of occurrence of a tubercle as counted in three grades according to its contour patterns. Materials were Japanese deciduous upper second molars of 23 males and 33 females with negligible attrition. The frequencies of appearance of tubercles were as follows (sexes pooled).... The incidence of the traits was compared with those in the permanent first molars previously studied. the traits (lingual paracone tubercle, metaconule, carabellis, and buccostyle were significantly more frequent in the deciduous molars than in the permanent first molar when tested by chi square test. On the other hand, the traits mesial paracone, mesial accessory tubercle, protoconule and distal accessory tubercle which are located on the mesial and distal marginal ridge did not show significant difference btween both molars. This suggested that there might have been differences of phloygenetical origins beteen traits on the marginal ridge and thsoe in the occlusal table and or on buccal and lingual surfaces.