[A study on effects of immediate bone grafting at mandibular first molar fresh extraction socket on maintaining...

Objective: To investigate the effect of immediate bone grafting at mandibular first molar extraction socket on maintaining alveolar bone height after space closure. Methods: Thirty adult orthodontic patients who need to extract mandibular first molar, totally 38 target teeth, were included. The samples were divided into two groups randomly: graft group and non-graft group. All extraction space was closed orthodontically. Dental models of all patients were taken before extraction (T0), before space closure(T1) and after space closure (T2). The distance, time of the space closure and the velocity of tooth movement were recorded. Probing depth (PD) and clinical attachment level (CAL) at six sites (mesial buccal, buccal, mesial lingual, lingual, distal buccal and distal lingual) on adjacent teeth were measured before extraction (T0) and after space closure (T2). Cone-beam CT (CBCT) was taken at T0 and T2 to compare the changes of alveolar bone height at six sites on adjacent teeth using Invivo Dental 5.0 software. Results: The extraction space in both graft group and non-graft group was closed successfully. However, the space in graft group was closed more slowly than in non-graft group. In graft group, PD and CAL at the six sites on both the second molar and the second premolar did not change significantly after space closure, and CBCT showed that the alveolar bone height of the second premolar had no significant difference after treatment. In non-graft group, alveolar bone height decreased in both adjacent teeth and periodontal attachment loss was found after space closure. On average, alveolar bone height and periodontal attachment of the second premolar decreased (0.75±0.16) mm and (0.64±0.15) mm, respectively. Meanwhile, alveolar bone height and periodontal attachment of the second molar decreased (0.79±0.23) mm and (0.80±0.24) mm, respectively. Conclusions: Bone graft immediately after mandibular first molar extraction could delay alveolar bone resorption and preserve the periodontal attachment of the adjacent teeth during space closure. However, the procedure could slow down tooth movement.