Abstract: Objective This study aims to analyze the angulation of the maxillary anterior teeth relative to the alveolus to provide reference data for clinicians on the best conditions for implant placement in the esthetic zone. Methods Numerous cone beam computed tomography (CBCT) images were reviewed and screened. A total of 150 maxillary images were selected by strict adherence to the defined inclusive criteria, with 75 images each from male and female patients (between the ages of 19 and 48 years at the time of CBCT scan). The maxillary anterior teeth were gathered into the following three groups for males and females: upper canines, upper lateral incisors, and upper central incisors. Then, the long axis of each qualified tooth and its corresponding alveolar process were drawn, and the angles formed by these structures were measured. The resultant data were analyzed by SPSS 19.0. Results The long axis of the maxillary anterior teeth all inclined to the palatal side of the alveolar process. The internal angle (α) formed by the long axis of the maxillary central incisors and the long axis of the alveolar bone presented a mean value of 16.22° (range:2.50°-28.80°) for male subjects and 15.20° (range:2.20°-27.20°) for female subjects. The internal angle (α) of the maxillary lateral incisors exhibited a mean value of 17.50° (range:3.80°-29.50°) for male subjects and 15.99° (range:4.10°-33.30°) for female subjects. Finally, the internal angle (α) of the maxillary canines presented a mean value of 16.27° (range:1.00°-31.50°) for male subjects and 15.01° (range:3.50°-27.40°) for female subjects. Conclusion The long axis of the maxillary anterior teeth all inclined to the palatal side of the alveolar process. For implant placement, careful preoperative analysis and evaluation with CBCT may be beneficial for avoiding the risk factors and achieving a high probability of success in the esthetic region.

Key words: cone beam computed tomography, the long axis of tooth, the long axis of alveolar bone, esthetic zone, dental implant