The piezocision surgery was performed two weeks after orthodontic appliance placement. The patients received local anesthesia in mandibular arch and vertical interproximal incisions were made below the interdental papillae in the midline, from the mesial aspect of each canine and in between each of the posterior lower teeth. The periostium was then released in order to create two subperiotal envelopes connecting the vertical incisions together. Thereafter, corticotomies were performed in the region of the incisions with a piezotome (Acteon, Merignac, France) and the envelopes were filled with a beta tricalcium phosphate, a resorbable biomaterial in order to thicken the buccal bone plate. Resorbable 5-0 sutures were used to close the flaps. Careful tooth brushing and the use of a mouthwash (chlorhexidine 0.2% Perio-Aid, Dentaid Benelux, Houten, Netherlands) were recommended for 7 days.

The patients underwent baseline and post treatment CBCT scans (Somaton® Emotion; Siemens, Munich, Germany). Measurements of the alveolar bone changes in the lower front region on pre- and post- treatment CT volumes were done by reformatting the orthogonal slices, along the sagittal, coronal and axial length axes of each individual tooth. A strict vestibular bone level measurement (sagittal slice) and three alveolar bone width measurements at crestal level, 3mm from the crest and 6mm from the crest (axial slices) were performed per individual tooth. In addition, CT images were analyzed in using a dedicated platform in an image processing software (MeVisLab, MeVis Medical Solutions AG, Bremen,Germany) where pre- and post-treatment volumes were superposed using rigid image registration. Semi-automatically segmentation using region growing with same seed-point and threshold value for both scans, was followed with a hole-filling algorithm to obtain segmented volumes of the cropped image in

The following clinical parameters were measured at baseline and after the orthodontic treatments: recession depths (RDs), pocket depth, plaque index (PI) and papilla bleeding index (PBI). A recession score was calculated by summing the recession depths. Next, the presence of gingival scars due to the overall treatment of each patient was categorized as an absence of scars, point-shape scars or linear-shape scars. Full periodontal charting (probing in four sites per tooth) was performed in all patients before and after the treatment; the results were expressed as score per sextant.