Maxillary lateral incisor agenesis (MLIA) is a medical term referring to the absence (agenesis) of a certain tooth: the upper (maxillary, meaning upper jaw), outer (lateral, as opposed to central) incisor. In normal human dentition, this would be the second tooth on either side from the center of your top row of teeth. The condition is bilateral if the incisor is absent on both sides. It appears to have a genetic component.