Temporary anchorage devices (TADs) are orthodontic mini-implants with remarkable characteristics that, once inserted, present mechanical retention (primary stability) without the process of bone osseointegration. However, interaction with the biological environment may cause changes in the morphology of the external surface of dental TADs. In this study, we used 17 TADs made of aluminum–vanadium titanium alloy, produced by two companies, which were analyzed through optical microscopy after being removed from the patients during orthodontic treatment. We evaluated the changes that appeared on the TADs’ surfaces after their use in the biological environment, depending on the morphological area in which they were inserted. In our study, we found changes in the morphology of the implant surface, and especially deposits of biological material in all study groups. On all samples examined after clinical use, regardless of the period of use, corrosion surfaces in different locations were observed. Our obtained results support the idea that the biological environment is aggressive for mini-implant structures, always producing changes to their surface during their clinical use.

Orthodontic mini-implants are well-known anchorage devices and stand out as a particularly effective tool for ensuring maximum anchorage without relying on patient compliance. Therefore, it is necessary to understand what levels of torque strains remain in the physiological limits and can guarantee the stability of these mini-implants. The aim of this study was to investigate and measure the initial and final torque values of orthodontic mini-implants when placed perpendicular to the maxillary and mandibular bone surfaces. In our study, orthodontic mini-implants from different companies were inserted perpendicularly using different insertion torques on the plate of both maxillary and mandibular bones from pig specimens. The torque values were then analyzed. The results of this study highlight the need for continued research to analyze the ideal insertion torque of different types of mini-implants depending on the insertion area, in order to achieve clinical success of mini-implants.