**Figure 6.**

*Surface modification with plasma ion-implantation (A) and SLA treated miniscrew (B). (Taken from: Cho et al. [47].)*

*Surface Modification of Titanium Orthodontic Implants DOI: http://dx.doi.org/10.5772/intechopen.100038*

that all the surface treated groups had higher IT values, and the RBM and hybrid groups showed significantly higher surface roughness values [49]. *In vivo* studies on rabbit tibiae have also shown effective results. Gansukh et al. verified previous findings by reporting that after 4 weeks of healing, there was no difference in the IT, RT, and BSC values of machined and RBM treated mini-implants [50]. However, histomorphometric analysis showed an increased bone-area (BA) in the RBM group. In a similar study by Kim et al., the hybrid group consisted of partially RBM treated mini-implants i.e. lower 1/3rd of the cutting edge was left untreated [51]. Out of the four groups, the hybrid group showed the least reduction in bone cutting capacity, highest RT values at 4 and 8 weeks of healing, and the highest amount of tissue remnants on the mini-implant surface. Analysis by EDS showed that calcium and phosphorus were present only on the surface of the hybrid group implants, suggesting that partial RBM surface treatment was perhaps the most clinically effective one. All of these studies conclude that surface treatment of orthodontic mini-implants with RBM may provide good initial stability and has the potential to enhance osseointegration without negatively affecting their bone cutting capacity.

#### **2.6 Nanoscale modifications**

One of the latest techniques for surface modification of dental alloys and implants is their nanoscale modification. This involves the formation of nanotubular arrays mainly by anodization of the surface under specific voltages in various electrochemical solutions (**Figure 7**). Oh et al. combined multiple methods of surface treatment and studied its effect on the stability and osseointegration potential of orthodontic miniscrews in rat tibia [52]. This unique method involved anodization (TiO2 nanotubular arrays) and cyclic pre-calcification (biomimetic Ca-P coating) of miniscrews followed by heat treatment. This method was called APH treatment. Results from mechanical torque testing and histological and SEM/EDS analysis showed that APH treated miniscrews had higher RT and BSC values after both 3 and 6 weeks of healing. Early deposition of densely mineralized bone around APH treated miniscrews was observed, implying good bonding to the treated surface. Jang et al. closely studied the effects of isolated nanoscale modifications on miniscrew biomechanical properties in rabbits [53]. Nanotubular arrays of TiO2 (70 nm diameter, 5 μm length) were produced using a two-step anodization process. When compared to machined miniscrews, the experimental group showed higher BSC and bone-volume-ratio (BVR) values on histomorphometric and micro-CT analysis. Nanotubular arrays have also been used as drug-delivery systems to enhance the biologic potential of miniscrews. In a similar evaluation, Cha et al. used tunnel miniscrews with and without recombinant human bone morphogenetic protein – 2 (rhBMP-2) loaded

#### **Figure 7.**

*SEM images of Ti6Al4V miniscrews: (A) untreated, and (B,C) nanotubes formed on the surface; (B) top and (C) cross-sectional views. (Taken from: Oh et al. [52].)*

onto them and compared them against conventional machined miniscrews [54]. After 8 weeks of healing, BSC, BVR and bone-surface-ratio (BSR) values of tunnel miniscrews with nanotube arrays were considerably higher than machined miniscrews. The rhBMP-2-loaded miniscrews showed a slightly greater osseointegration potential than the non-loaded miniscrews. Jang et al. further studied the effects of drug-loaded nanotube arrays by comparing rhBMP-2-loaded and Ibuprofen-loaded miniscrews along with a machined and non-loaded nanotube array miniscrew group [55]. After 8 weeks of healing, the highest BSC values were recorded for the Ibuprofen-loaded miniscrews followed by the non-loaded, machined and rhBMP-2-loaded groups. In spite of their limited scope, these studies clearly suggest that nanoscale surface modifications of orthodontic miniscrews increase their biologic potential and the same nanotubular structures can also be used as drug-delivery systems to further enhance their osseointegration potential.
