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Abstract

Comparison of Direct and Indirect Mini-implant Anchorage in Adults with Maxillary Protrusion: A Randomized Controlled Trial

Author(s): L. Zhang1, Y. Lin2, R. Guo, Y. Huang, B. Xu, W. Li and W. Li*
Department of Orthodontics, Peking University School and Hospital of Stomatology, 1Dental Medical Center, China-Japan Friendship Hospital, Beijing 100081, 2Faculty of Dentistry, The University of Hong Kong, Hong Kong 999077, China

Correspondence Address:
Department of Orthodontics, Peking University School and Hospital of Stomatology, China

The purpose of this randomized controlled trial was to investigate the effects of direct and indirect mini-implant anchorage on tooth movement, skeletal and soft-tissue changes following sliding en masse retraction in adult patients with maxillary protrusion. A total of 30 patients (6 male, 24 female, mean age 23.5±6.29 years) were randomly assigned to group A with direct mini-implant anchorage or group B with indirect mini-implant anchorage. Lateral cephalograms taken before and after retraction were used to evaluate the changes during space closure. Independent sample t tests were performed to compare the baseline cephalometric data and treatment changes between the two groups. Paired sample t tests were performed to examine the changes within each group. The Results showed that no significant difference in anteroposterior skeletal changes was found between the two groups. The occlusal plane rotated clockwise 4.11° (p<0.001) in group A and remained stable in group B. Regarding dental changes, the maxillary molars mesialized by 0.83 mm in group B and showed non-significantly anteroposterior movement in group A. In group A the molars showed significant distal inclination (6.97°, p<0.001) and intrusion (2.74 mm, p<0.001) compared with group B (p<0.001). There was no significant difference in the anteroposterior or vertical movement of the incisors between the two groups. The soft-tissue parameters were significantly improved in both groups (p<0.001) while no differences were found between the groups. In conclusions, both directly and indirectly loaded mini-implants can provide successful anchorage. Indirect mini-implant anchorage enabled better sliding mechanics compared to direct anchorage.

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