Hereditary factors that affect the size of the teeth and jaw and the contours of the face are the most common causes of imperfect positioning of teeth with closed jaws (malocclusion).
Disproportions in size between the jaw and the teeth or between the upper and lower jaws is the most common cause of malocclusion. Orthodontic problems result from the interaction of developmental, genetic, and environmental influences.
1. Developmental causes
Developmental anomalies most often accompany major congenital anomalies but can also occur as an isolated finding. Most common ones include:
• Congenitally missing teeth
• Supernumerary (extra) teeth
• Malformed teeth
• Interference with eruption (eg an impaction in which the tooth is blocked from erupting fully into the oral cavity or the tooth is forced to erupt into an abnormal position)
• Ectopic eruption
2. Genetic causes
This occurs when there is discrepancies in the size of the jaw and/or teeth. A child who inherits the mother’s small jaw and a father’s large teeth may have teeth that are too big for the jaw causing overcrowding. Also it’s likely to have a missing tooth if one of your parent or grandparents have the same missing tooth.
3. Environmental causes
1. Trauma during birth, such as an injury to the jaw, may occur during the actual birth, particularly with the use of forceps in delivery
2. Fetal molding occurs when an arm or leg of the foetus is pressed against another part of the body, such as when an arm is pressed against the mandible. This pressure can lead to distortion of rapidly growing areas.
Injury throughout life
1. Damage to permanent tooth buds when injury to the primary tooth occurs
2. Movement of a tooth or teeth as a result of premature loss of a primary teeth
3. Direct injury to permanent teeth