Most commonly missing primary teeth are:
Maxillary central incisors
Mandibular central incisors
Maxillary lateral incisors
Maxillary canines
Developmental agenesis of primary teeth is relatively rare. When several primary teeth fail to develop, other ectodermal deficiencies are usually evident. Most commonly missing primary teeth are maxillary canines.
Reference: McDONALD AND AVERY’S DENTISTRY for the CHILD and ADOLESCENT, 10th ed page no 64