Fig. 2

Data measurement. a The long axis of the tooth was determined by connecting the apex of the mesial root (point A) and the midpoint of a line drawn from the abrupt point of the buccal counterpart (point B) to the lingual counterpart (point C). b The long axis of the alveolar process (line 2) was marked by bisecting the buccal line of the alveolar process (line Le) and lingual line of the alveolar process (line Lf). The upper internal angle a was formed by L1 and L2. The width GH was between the buccal and lingual alveolar plates at the lowest point of the alveolar bone and perpendicular to L2. KL was between the midpoint of EF and GH. c The long axis of the basal bone (line 3) was marked by bisecting the buccal basal bone surface (line Lg) and lingual basal bone surface (line Lh). The upper internal angle b was formed by L2 and L3. The width IJ was between the buccal and lingual basal plates at the highest point of the basal bone and perpendicular to L3.Distance EF was between the buccal and lingual alveolar crest