As is known, the deciduous tooth buds give rise to the underlying permanent ones (Fig.4 (illustration for the anterior teeth).  Where LR C is missing, most likely the permanent canine (LR 3) is missing (Fig.5,6), whether B is shifted or not. 

In fact, in this case, the lateral incisor (LR 2) is missing (Fig.3, 7). 

The most likely hypothesis is as follows.  What the deciduous tooth bud gives rise to is the ectodermal component of the underlying permanent tooth (the enamel and cementum), but the identity (shape) of the tooth is predetermined by where the tooth bud is during tooth formation (i.e., mesiodistal position of the mesenchyme).

Identity of a Tooth Last Next

Xin Wei, DDS, PhD, MS 1st edition 07/04/2016, last revision 09/15/2019