Tissue response to selective alveolar corticotomy after speedy orthodontics in uprighting lower molars in adult patients

The aim of this study was to analize and describe histological findings of bone remodeling at the time of surgery and 90 days later, at corticotomized and non-corticotomized sites. This randomized split mouth study included 8 adult patients, with bilaterally inclined mandibular molars, regardless their malocclusion type. A one-stage intervention was performed to corticotomize the test site, and harvest bone in both mandibular hemi-arches. Bone blocks were harvested using a trephine bur in a low speed hand piece. The specimens of aproximatelly 6 mm were stored in 10% buffered formalin at room temperature, until dispatch to Forsyth Institute lab (Boston, USA). After surgery, cantilevers were activated to upright inclined mandibular molars on both sides. Approximately 90 days post-surgery, new bone blocks were harvested from test and control sites located in the mandible. Histological analysis were performed in the control and test group at two time points: baseline (T0) and, ninety days post-surgery (T90). Bone blocks were stained with Hematoxylin & Eosin for descriptive analysis. Masson's trichrome staining protocol was used to identify new bone formation and collagen in mineralized and non-mineralized connective tissue. The following items were investigated to describe bone turnover: (1) ratio between secondary and primary bone, (2) ratio between inorganic and organic bone, (3) quantity of osteocytes and, (4) reversal lines of bone remodeling.The histologic analysis results were compared using clustered Generalized Estimating Equations (GEE) model, adjusted by baseline measures. The test group at T90 presented: increase of 0.16% in ratio of primary bone (p<0.001), increase of 6.54 in the quantity of osteocytes (p=0.039), and increase of 4.06 in the quantity of reversal lines (p=0.924). Both groups presented decay in inorganic proportions, with a decrease of 0.02% and 0.03% in test and control group, respectively (p=0.105). Data suggest that bone turnover provoked by corticotomy, might be partially reverted in 90 days, through bone formation and deposition. The intentional bone injury performed in adult patients undergoing orthodontic treatment, can be considered temporary and reversible, there is evidence to indicate baseline bone characteristics are restored.