Abstract
The tuberculum accessorium mediale internum (termed by SLENKA in 1898) is situated between the metaconid and entoconid in lower permanent molars and has the appearance of an isolated wrinkle. It is sunk between the two cusps, from each of which it is separated by a deep and narrow furrow which extends over the superior half of the lingual surface.
The authors investigated the frequency of appearance of the tuberculum accessorium medicale internum by the method of making a plaster cast from the crown of the first and second lower permanent molars in 440 Japanese (213 males and 227 females).
The frequencies of appearance of the tuberculum accessorium mediale internum are shown in the table.
Of the 440 individuals, 25 (5.68 per cent) have the tuberculum accessorium mediale internum on the lower permanent first molars. And in 14 (56.0 per cent) individuals from among the 25, an accessory intermediary tubercle was found to be separated from the distal part of the metaconid.
