Fig. 4

Landmarks and linear measurement parameters used to evaluate changes in the alveolar bone height and width in this study (A, immediately after surgery; B, 6 months after ARP). Line A was the line passing through points a and b, where points a and b were defined as the most superior point of the lingual and buccal alveolar bone, respectively. Point c was the point that bisects line A, and point d was the apex of the extraction socket. The line passing through points c and d was defined as line B. Line C was set as the line perpendicular to line B and passing through point d. The height of the alveolar bone immediately after surgery was measured as the distance from point c to point d. The width of the alveolar bone was measured at the points where the alveolar bone height was divided into quarters. To measure the changes of the alveolar ridge 12 weeks after surgery, the reference lines B and C, reference lines for 25%, 50%, and 75% ESL, and point d were transferred to the CT images taken 12 weeks after surgery. Point a’ and b’ were marked as the most superior point of the lingual and buccal alveolar bone, and line A’ was defined as the line passing through points a’ and b’. Point c’ was the intersection of line A’ and line B. By measuring the distance from point c’ to point d, the alveolar bone height at 12 weeks after surgery was measured. The width of the alveolar bone was measured at the points where the alveolar bone height was divided into quarters