Surface changes of anodic oxidized orthodontic titanium miniscrew

To evaluate the structural stability of anodic oxidation treatment of miniscrews during a self-drilling procedure and an initial loading period. Eight orthodontic miniscrews with a machined surface and an anodic oxidized surface were placed in the mandible of two beagle dogs. With all miniscrews, an orthodontic force was applied immediately after placement and was continued for 12 weeks. After beagle dogs were sacrificed, the miniscrews were carefully removed from decalcified bone fragments. Miniscrews were evaluated by comparing and quantitatively analyzing changes in surface roughness of unused and used miniscrews (machined surface vs anodic oxidized surface) utilizing both scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM revealed that only a thread edge close to the tip of the used anodic oxidized miniscrew became smooth by smearing, compared with the unused anodic oxidized miniscrew. No definite changes were observed in the thread valleys of the two groups after placement. AFM measurements demonstrated that all surface roughness parameters of thread edges of the used anodic oxidized miniscrews were significantly reduced compared with the unused anodic oxidized miniscrew (P < .05). A middle thread edge of the used anodic miniscrew surface was rougher than the unused and used machined surface miniscrews (P < .05). Anodic oxidized miniscrews had improved surface characteristics compared with machined surface miniscrews, even if the surface texture was changed by the self-drilling procedure and during the initial loading period.