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Background and objectives Orthodontic relapse is a physiologic process that involves remodelling of the alveolar bone and principle periodontal ligament fibres. Raloxifene is an Food and Drug Administration (FDA)-approved selective oestrogen receptor modulator that inhibits systemic bone loss. In our study, we examined the effects of Raloxifene on alveolar bone modelling and orthodontic relapse in a rodent model. Materials and methods The efficacy of raloxifene was evaluated in 15-week-old male Wistar rats, 8 in each group (Control, Raloxifene, Raloxifene + 7-day relapse, Raloxifene + 14-day relapse) for a total of 42 days. All animals had 14 days of orthodontic tooth movement with a closed nickel–titanium coil spring tied from incisors to right first molar applying 5–8 gm of force. On the day of appliance removal, impression was taken with silicon material and the distance between first molar and second molar was filled with light-cured adhesive resin cement for retention phase. Raloxifene Retention, Raloxifene Retention + 7D, Raloxifene Retention + 14D groups received 14 daily doses of raloxifene (2.0 mg/kg/day) subcutaneously after orthodontic tooth movement during retention. After 14 days of retention, the retainer was removed and right first molar was allowed to relapse for a period of 14 days. Raloxifene injection continued for the Raloxifene + 14-day relapse group during relapse phase too. Control group received saline injections during retention. Animals were euthanized by CO2 inhalation. The outcome measure included percentage of relapse, bone volume fraction, tissue density, and histology analysis using tartrate-resistant acid phosphatase staining and determining receptor activator of nuclear factor-кB-ligand (RANKL) and osteoprotegerin expression. Results Raloxifene Retention + 14D group had significantly less (P < 0.05) orthodontic relapse when compared with other groups. There was a significant increase (P < 0.05) in bone volume fraction and tissue density in the Raloxifene Retention + 14D group when compared with other groups. Similarly, there was significant decrease in number of osteoclasts and RANKL expression in Raloxifene Retention + 14D group when compared with Raloxifene Retention + 7D group (P < 0.05). Conclusion Raloxifene could decrease post-orthodontic treatment relapse by decreasing bone resorption and indirectly enhancing bone formation.

Structured AbstractObjectives: To evaluate the amount of external apical root resorption (EARR) secondary to orthodontic treatment in patients with Short Root Anomaly (SRA) compared to patients with average root lengths using Cone Beam Computed Tomography (CBCT). Settings and Sample Population:Cone beam computed tomography scans of 23 SRA and 26 control patients were selected from 232 pretreatment scans from a single private practice. Materials and Methods:Cone beam computed tomography scans before (T1) and after orthodontic treatment (T2) were evaluated for differences in the change in tooth and root length of the maxillary incisors between both groups. Gender, treatment duration and age were examined as covariates. Results:The mean values for root and tooth length of the maxillary incisors decreased by a range of 0.6 to 1.3 mm after orthodontic treatment. There was no significant difference between the groups for the majority of the measurements although there was a trend for less EARR in the SRA group. The maxillary left central incisor had significantly less proportional and non-proportional loss in tooth length in the SRA group. Age, gender and treatment duration were not associated with change in the proportional and non-proportional lengths for both groups. Conclusion:Patients with SRA did not exhibit a significant difference in the proportional and non-proportional change of length after orthodontic treatment when compared to the controls for most measurements. Only tooth length for the maxillary left central incisor had significantly less reduction after orthodontic treatment for both the proportional and non-proportional measurements in the SRA group compared to the control group. K E Y W O R D Sapical root resorption, cone beam computed tomography, Short Root Anomaly | 33 CUTRERA ET Al.

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