Injuries to primary teeth occur mostly at:

Trauma to primary dentition is common, many times unnoticed as they are minor and a child who is involved in busy play or other activity may not remember minor injuries and report to parents. Most usual age of occurrence is 1 to 2 years as they try to stand up and walk because of lack of control on motor movements. 28% of 5-year olds would have experienced some kind of injury to the teeth and supporting structures. Most injuries are luxation type as bone is resilient in primary dentition (injury is primarily to the supporting structures). For injuries of permanent dentition, school age is the common age. 20% of 12-year-olds had experienced some kind of trauma. More of crown fractures compared to root fractures. Boys to girls ratio is said to be 2:1 but not many studies supporting this fact are available. The prevalence may be more in boys because of their physical activity. Prevalence of injuries is more in maxillary central incisors followed by maxillary laterals, mandibular centrals and laterals. Reference: Pediatric Dentistry Principles and Practice SECOND EDITION, MS Muthu; pdf no 859