Prediction of bone recovery after iatrogenic dehiscences/fenestrations caused by lingual bonded retainers: a clinical report.

The "periodontal ligament-periosteum (PDL-PS) sandwich hypothesis" has been proposed to explain the mechanism of bone recovery around roots moved outside their bony housing. This hypothesis suggests that the presence of the periosteum and periodontal ligament facilitates bone recovery in such cases. This retrospective case series examines three adult patients who developed iatrogenic dehiscences and fenestrations of the anterior teeth due to the placement of fixed lingual retainers after orthodontic treatment. Each patient then underwent orthodontic retreatment aimed at repositioning the roots back into the alveolar housing. Cone-beam computed tomography (CBCT) scans and intraoral photographs taken before (T2) and after (T3) retreatment were used to evaluate bone recovery. To test the PDL-PS sandwich hypothesis, predictions of bone recovery were made based on T2 parameters and the root movements achieved during retreatment. The observed bony recovery at T3 was then compared with these predictions. Roots that were partially or fully repositioned into the original alveolar housing exhibited partial to complete bony recovery. In contrast, teeth with minimal root movement back into bone showed limited or no recovery. In cases with pre-existing gingival recession, bone recovery occurred only apical to the areas of recession, even with favorable root movements. Additionally, the dimensions of the alveolar housing remained stable as roots moved through the alveolar bone, supporting the theory that roots move through alveolar bone, rather than with bone, in adults. These findings highlight the need for evidence-based clinical strategies to guide the management of inadvertent tooth movement caused by orthodontic appliances or retainers, with particular attention to the potential for bone recovery when repositioning teeth into their original alveolar housing.