[Influence of positional relationship between the long axis of the mandibular anterior teeth and the alveolar bone on the treatment design of dental implants].

OBJECTIVE: This study aimed at investigating and measuring the positional relationship between the long axis of the mandibular anterior teeth and the alveolar bone using cone beam computed tomography (CBCT) to provide reference data for implant treatment. METHODS: From the CBCT image database, 150 cases of radiographic data were selected according to the inclusion criteria and then were divided into six groups: males' mandibular central incisors, males' mandibular lateral incisors, males' mandibular canines, females' mandibular central incisors, females' mandibular lateral incisors, and females' mandibular canines. The angle (β) formed by the long axis of the mandibular anterior teeth and the corresponding alveolar bone was measured and recorded. Based on the long axis of alveolar bone, if the teeth incline to the lingual side, the value of the angle (β) was positive; otherwise, the value was negative. The resultant data were analyzed by SPSS 19.0. RESULTS: The β of the mandibular central incisors presented a mean value of 4.77° (range: -8.17°-16.10°) for male subjects and 5.38° (range: -5.63°-12.93°) for female subjects. The β of the mandibular lateral incisors exhibited a mean value of 6.12° (range: -2.87°- 17.57°) for male subjects and 5.81° (range: -7.70°-15.70°) for female subjects. Finally, the β of the mandibular canines presented a mean value of 5.01° (range: -8.13°-17.67°) for male subjects and 6.21° (range: -7.70°-17.87°) for female subjects. The percentages of the β between -10° and 10° of males' mandibular incisors, mandibular lateral incisors, and mandibular canines were 87.34%, 80.67%, and 88.00%, respectively and those of females were 90.67%, 82.66%, and 82.66%, respectively. Whether male or female, the percentages of the β between -10° and 10° of the mandibular anterior teeth were more than 80%. The β that inclined to the lingual was not more than 20° and to the labial did not exceed 10°. CONCLUSIONS: The long axis of the mandibular anterior teeth was almost consistent with the long axis of the alveolar bone. Therefore, the positional relationship could be referred to make reasonable implants treatment plan.