A four-rooted primary upper second molar.

Both primary upper second molars were extracted from a young male patient. The left had a normal root pattern but the right had four well-defined roots. The accessory root appeared to be the mesiopalatal which had a distinctly rounded cross-sectional profile. The other roots had the typical form characteristic of primary molar roots. Some degree of bifurcation can occur in the mesiobuccal roots of upper molars and the accessory root described in this report may represent an extreme example of such bifurcation.