Comparing the Efficacy of Maxillary Total Arch Distalization Using Zygomatic Mini-screw vs. Palatal Mini-screw: A Randomized Clinical Trial

Evaluation of clinical efficacy of infrazygomatic mini-screws in comparison to palatal mini-screws for maxillary total arch distalization

A controlled, parallel-group, unblinded, randomized, phase 2 clinical trial on 20 patients. Sealedenvelope software was used for randomization.

This study will be conducted in the Orthodontics Department and the Special Clinic of the Faculty of Dentistry at Mashhad University of Medical Sciences. At the beginning of the study, lateral cephalograms and intraoral scans will be taken from the patients. Once a Class I molar relationship and an overjet of 2 to 3 millimeters are achieved, lateral cephalograms and intraoral scans will be taken again to evaluate the changes.

The study includes patients aged 14 to 25 years, presenting an overjet of 4 to 6 mm and classified with Class 2 malocclusion, for whom the treatment plan incorporates the retraction of maxillary teeth. People with systemic diseases or developmental and orthodontic problems affecting bone metabolism and treatment outcomes, as well as smokers and those with poor oral hygiene, were not included in the study.

In the first group, two mini screws are positioned in the crest of the infrazygomatic area on both sides of the maxillary arch to facilitate distalization. In the second group, two palatal mini screws will be applied in the interdental region between the second premolar and the first molar, in conjunction with the palatal arch.

The changes in the arch from the occlusal and sagittal views will be determined using superimposition of pre- and post-treatment scans. Additionally, alterations in the axial inclination of the anterior teeth, occlusal plane changes, anteroposterior changes of the first molar, and its inclination variations will be assessed on cephalograms.

To facilitate randomization of participants into two groups, the Sealed Envelope software will be utilized, employing combined blocks of four and two. In this type of assignment, blocks of four letters long consisting of the letters A and B are used, so that each block contains two letters A and two letters B. Also, blocks of two are used randomly. Therefore, 20 combinations of the letters A and B are generated, which are placed in a matte envelope in the order they are generated by the sealedenvelope software and its number is written on the envelope. The first person takes envelope number 1, the envelope is opened and assigned to the relevant group. Then the second person takes envelope number 2 and so on until envelope number 20.