Panoramic X-ray shows underdevelopment of #20 and 29 tooth buds (Fig.6), which is related to K and T being retained (Fig.3).  There is no root formation at #20 or 29, as compared to that in the maxilla.

Space & Underdeveloped Tooth Buds

Xin Wei, DDS, PhD, MS 1st edition 10/12/2016, last revision 10/12/2016