We carried out structure analysis by using the three dimensional finite element method for the mandibular primary anterior teeth and mandibule of children in order to research the damage mode during trauma. The results were as follws;
1. For the load of the labial on mandibular primary central and lateral incisor, the tendency in which the tooth causes the luxation, mobility and shedding by the external force is strong, but the tendency which causes the fracture of tooth is weak.
2. For the load of the labial on mandibular primary canine, the tendency in which the tooth causes the luxation, mobility and shedding by the external force is weak, and the tendency which causes the fracture of tooth also is weak. The tendency of the opposite side of neck of the mandibule and the opposite side of head of the temporomandibular joint to cause bone fracture is strong.
3. For the load of the bone surface on chin, the tendency in which the neck of mandibule and the head of temporomandibular joint causes bone fracture is strong, but the tendency in which the chin causes bone fracture is weak.
4. For the load of the bone surface on mandibular first and second primary molar, the tendency in which the distal of the second primary molar, the oppsite side of the neck of mandibule and the oppsite side of the head of temporomandibular joint causes bone fracture is strong.
5. For the load of the bone surface on mandibular first molar, the tendency in which the neck of mandibule and the head of temporomandibular joint causes bone fracture is weak, but the tendency in which the lower first molar portion causes bone fracture is strong.
6. For the load of the bone surface on the angle of the mandibule, the tendency in which the angle of mandibule, the same side of the neck of mandibule and the same side of the head of temporomandibular joint to cause bone fracture is strong.
We believe which this structure analysis is useful for the clinical research of the trauma of lower primary anterior teeth and mandibule in childhood.