Trauma to primary incisors occurs during childhood both of the maxilla and mandible. Damage to the primary dentition may possibly be related to the degree of primary root resorption. The finite element method was used in this study to assesss stress and displacement during trauma to the mandibular primary central incisors, alveolar bone, mandibular bone and successive permanent tooth germs for different degrees of root resorption.
The following results were obtained:
1. Trauma to mandibular primary central incisors in the period from no primary root resorption to one-third root resorption was noted to cause luxation of the primary teeth and injury to the crowns of the successive permanent teeth.
2. Trauma in the period from one-third root resorption to full root resorption may possibly cause losed of primary teeth along with alveolar bone fracture, injury to the root and hinder the emergence of the permanent teeth.
The development and emergence of the permanent teeth should be carefully observed following trauma to primary incisors.