Titanium-Silver Alloy Miniplates for Mandibular Fixation: In Vitro and In Vivo Study.

PURPOSE: Titanium (Ti) alloys have received considerable attention as materials for oral and maxillofacial surgery, which require high mechanical strength, osteosynthesis, and biocompatibility. The objective was to implant miniplates fabricated from commercially pure Ti (CP Ti) and newly developed Ti-silver (Ag) alloy in fractured mandibles of adult dogs after preliminary mechanical and biological characterization. MATERIALS AND METHODS: The surface characteristics, biocompatibility, and pre-osteoblast adhesion and proliferation of CP Ti (grade 3) and Ti-Ag (2 at% Ag) alloys were evaluated. Next, the bending strength of 6- and 8-hole miniplates fabricated from CP Ti and Ti-Ag was compared according to ISO (International Organization for Standardization) 9585. Six-hole miniplates were implanted for 12 weeks in fractured mandibles of adult dogs. The Ag ion concentration in each alloy and implanted bone block with soft tissue was measured by inductively coupled plasma mass spectroscopy after euthanasia according to ISO 10993-12. RESULTS: Precipitated Ag was detected in Ti-Ag by alpha- and beta-phase Ti in x-ray powder diffraction. The biocompatibility with pre-osteoblasts of Ti-Ag and CP Ti was comparable in terms of cytotoxicity, cell adhesion, and proliferation (P > .05). Ti-Ag miniplates had up to 3-fold greater bending strength than CP Ti miniplates (P < .05). An in vivo study showed that CP Ti and Ti-Ag miniplates had comparable soft and hard tissue regeneration ability (P > .05). Ag ions were detected in Ti-Ag alloys and applied mandible blocks. CONCLUSIONS: The results of this study suggest that Ti-Ag alloys can be used to produce miniplates with high mechanical properties, as well as considerable biocompatibility, osteosynthesis ability, and Ag ion-release properties. Further studies, including preclinical investigations, are required to enable clinical use of Ti-Ag bone plates.

Effect of silver addition on the properties of nickel-titanium alloys for dental application.

Equiatomic and near-equiatomic nickel-titanium alloys exhibit a shape-memory effect and superelasticity. However, the properties of such alloys are extremely sensitive to the precise nickel-titanium ratio and the addition of alloying elements. High corrosion resistance is necessary for biomedical applications, especially orthodontic. The purpose of this study was to investigate the effect of silver addition to nickel-titanium alloys for dental and medical application. Arc melting, homogenization, hot rolling, and solution heat treatment were performed to prepare the nickel-titanium-silver (NiTi-Ag) specimens. The properties of the ternary NiTi-Ag alloys such as phase-transformation temperature, microstructure, microhardness, corrosion resistance, and cytotoxicity were investigated. The NiTi-Ag alloys showed low silver recovery rate for the cast alloy, due to silver's low evaporation temperature, and low silver solubility in nickel-titanium. Silver addition to nickel-titanium increased the transition temperature range to 100 degrees C and stabilized the martensitic phase (monoclinic structure) at room temperature, because the martensitic transformation starting temperature (Ms) was above room temperature. Martensitic and austenitic phases existed in X-ray diffraction patterns of solution-annealed NiTi-Ag alloys. The silver addition was considered to improve the corrosion resistance and form a stable passive film. Significantly, the mechanical properties of the silver-added alloys were dependent upon the amount of alloying addition. There was no toxicity in the NiTi-Ag alloys, as the response index showed none or mild levels.

Surface changes of anodic oxidized orthodontic titanium miniscrew.

OBJECTIVE: To evaluate the structural stability of anodic oxidation treatment of miniscrews during a self-drilling procedure and an initial loading period. MATERIALS AND METHODS: 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). RESULTS: 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). CONCLUSION: 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.