Surface change of the anodic oxidized orthodontic titanium miniscrew

Abstract

In recent years, various miniscrews based on prosthetic surface treated implants are currently being developed and marketed to improve biological stability. Numerous implant surface modifications have been tried in dental implant, including acid etching, sandblasting, Ti-plasma coating and anodic oxidized. Among these implants, anodic oxidized implants have a surface comprising numerous open pores and possess relatively large surface areas. The aim of this study is to evaluate the structural stability of anodic oxidation treatment on miniscrews under self-drilling implantation procedure and initial loading period by comparing and quantitatively analyzing surface roughness changes of as-received and retrieved miniscrews (machined surface vs. anodic oxidized surface) utilizing both scanning electron microscopy (SEM) and atomic force microscopy (AFM). 8 orthodontic miniscrews with machined surface and anodic oxidized surface were placed into mandible of 2 beagle dogs. In all miniscrews, an orthodontic force was applied immediately after the placement and continued during 12 weeks. After beagle dogs were sacrificed, the miniscrews were carefully removed from decalcified bone fragments. Observation by scanning electron microscopy (SEM) revealed that only a thread edge close to the tip of the retrieved anodic oxidized miniscrew became smooth by smearing, compared to the as-received anodic oxidized miniscrew. No definite changes were observed in the thread valleys of two groups of the miniscrews after placement. Atomic force microscopy (AFM) measurements demonstrated that all surface roughness parameters of thread edges of the retrieved anodic oxidized miniscrews were significantly reduced, compared to as-received miniscrews (p < 0.05). A middle thread edge of the retrieved anodic miniscrew surface was rougher than the as-received and the retrieved machined surface miniscrew (p < 0.05). No definite changes were observed in the thread valleys of two groups of the miniscrews after placement. Surface changes of the anodic oxidized miniscrews after placement were only observed in thread edges and no definite changes were observed in the thread valleys; Anodic oxidation treatment on miniscrew had structural stability and might improve biological stability of the miniscrews, caused by unique surface characteristic. Future research will be needed for biological evaluation of anodic oxidized miniscrews.