U1 And Self-Defined Maxillary Axis In Class Ii Adults

This study investigates the relationship between upper central incisors (U1) and the Self-defined maxillary basal bone (MA1) axis in skeletal Class II adults with varying vertical facial types to establish a reference for U1 positioning in orthodontics. Cephalometric analysis was performed on 100 skeletal Class II adults. The MA1 and alveolar bone (MA2) axes were defined, with MA1 as the perpendicular to the line connecting subspinale A and palatal point P, and MA2 as the line connecting the upper superior prosthesis and subspinale A. Angles between these axes and the anterior cranial base (SN), Frankfort plane (FH), palatal plane (PP), and U1 were measured and analyzed. Significant differences were observed in the angles between MA1 and SN, FH, and PP (P<0.001), following the trend: low angle > average angle > high angle. A similar pattern was observed for MA2 (P<0.001). U1-MA1 and U1-MA2 angles followed the trend: average angle ˃ high angle ˃ low angle but were not statistically significant (P>0.05). U1, MA1, and MA2 exhibit consistent compensatory inclinations across various vertical skeletal patterns. The minimal influence of vertical skeletal patterns on U1-MA1 and U1-MA2 angles suggests their use as references for U1 positioning in orthodontics.