The tooth #4 has special canal morphology (Fig.6).  In addition to the middle main canal (Fig.7 *), there are 2 lateral finer curved canals (arrowheads).  The tooth #13 has the same canal patterns.

Possible Bifurcation

Xin Wei, DDS, PhD, MS 1st edition 12/21/2014, last revision 01/19/2018