The first maxillary premolars will be extracted with orthodontic purpose. After 3 months of extraction, the orthodontic alignment and dental leveling will be obtained and a 0.016x0.022 stainless steel wire will be placed, as well as orthodontic mini-implants (Morelli, Sorocaba, SP, Brazil).The retraction of the canines will begin using closed nickel-titanium spring (120g).The corticotomy surgery will be performed at the day of begining of canine retraction only in one side of the mouth.A mucoperiosteal flap will be raised from the extraction region to the mesial of the canine.Perforations will be performed using a number 2 spherical drill bit in low speed handpiece under irrigation, only in the cortical none depth.The intraoral digital scans will be performed with 7 and 14 days after the start of retraction, and then 14 in 14 days to a maximum period of 6 months.The patients will be advised to take analgesics (paracetamol or dipyrone) only if necessary.

The first maxillary premolars will be extracted with orthodontic purpose. Fixed orthodontic appliance will be bonded (0.022x0.025 slot with MBT prescription in incisors and Standart in the other teeth) with a power arm welded in the bracks upper canines brackets. After 3 months of extraction, the alignment and dental leveling will be obtained and a 0.016x0.022 stainless steel wire will be placed, as well as orthodontic mini-implants (Morelli®, Sorocaba, SP, Brazil) between the roots of the second premolars and molars. At that time an intra-oral digital scan will be performed. The retraction of the canines will begin using closed nickel-titanium spring (120g of force) from the power arm to the mini-implant. No surgery will be done at this side. The intraoral digital scans will be performed with 7 and 14 days after the start of retraction, and then 14 in 14 days to a maximum period of 6 months.

All micro-osteoperforations will be performed only once time in the experimental group on the same day of the installation of the upper incisors' retraction mechanics. Perforations will be performed with an individualized surgical guide and a 1.6 mm diameter stainless steel surgical drill perpendicular to the alveolar bone, 3 mm deep on the buccal surface, and 5 mm, on the palate. The depth of the perforations will be controlled and standardized by a cursor developed and patented by the research group. Two micro-osteoperforations will be aligned vertically distally from each upper incisor. Due to the proximity of the roots in the cervical third, only the most apical perforation will be performed between the two central incisors. The first perforation will be performed 6 mm away from the gingival margin, and the second, 5 mm from the first, in the vertical direction.

VAS questionnaire will be used after the surgical procedures, as well after TADs placement, separator placement and premolar extraction. Always 7 days after each procedure.

The first molars anchorage loss was assessed on superimposed digital models through the distance of a point on the mesiobuccal cuspid to a coronal reference plan created on the initial CBCT scan.

The initial and final CBCT were superimposed by the "voxel-based method" in the Dolphin Imaging software (Chatsworth, CA, USA), using the cranial base as reference. The inclination of the central incisors was then assessed by means of the angle formed by the long axis of each central incisor in the initial and final CBCT.

The initial and final length of the central incisors were measured by creating a 2D line, passing through the lowest point of the incisal edge and the highest point of the root apex. To perform these measurements, a sagittal cut was used in which the longest length of these teeth was seen.