Yin-Yu Chang

Analyses of Antibacterial Activity and Cell Compatibility of Titanium Coated with a Zr–C–N Film

Objective The purpose of this study was to verify the antibacterial performance and cell proliferation activity of zirconium (Zr)–carbon (C)–nitride (N) coatings on commercially pure titanium (Ti) with different C contents. Materials and Methods Reactive nitrogen gas (N2) with and without acetylene (C2H2) was activated by Zr plasma in a cathodic-arc evaporation system to deposit either a zirconium nitride (ZrN) or a Zr–C–N coating onto Ti plates. The bacterial activity of the coatings was evaluated against Staphylococcus aureus with the aid of SYTO9 nucleic acid staining and scanning electron microscopy (SEM). Cell compatibility, mRNA expression, and morphology related to human gingival fibroblasts (HGFs) on the coated samples were also determined by using the MTT assay, reverse transcriptase–polymerase chain reaction, and SEM. Results The Zr–C–N coating with the highest C content (21.7 at%) exhibited the lowest bacterial preservation (P<0.001). Biological responses including proliferation, gene expression, and attachment of HGF cells to ZrN and Zr–C–N coatings were comparable to those of the uncoated Ti plate. Conclusions High-C-content Zr–C–N coatings not only provide short-term antibacterial activity against S. aureus but are also biocompatible with HGF cells.

Antibacterial properties and cytocompatibility of tantalum oxide coatings with different silver content

Tantalum (Ta) oxides and their coatings have been proved to increase their applications in the biomedical fields by improving osseointegration and wear resistance. In this study, Ta oxide coatings containing different proportions of Ag are deposited on SS304 materials. A twin-gun magnetron sputtering system is used to deposit the tantalum oxide-Ag coating. In this study, Staphylococcus aureus, which exhibits physiological commensalism on the human skin, nares, and mucosal and oral areas, is chosen as the model for in vitro antibacterial analyses via a fluorescence staining method using Syto9. The cytocompatibility and adhesive morphology of human skin fibroblast cells (CCD-966SK) on the coatings are also determined by using the microculture tetrazolium assay. This study shows that Ta 2O5 and Ta 2O5-Ag coatings with 12.5 at. % of Ag exhibit improved antibacterial effects against S. aureus and have good skin fibroblast cell cellular biocompatibility.

FRICTION OF STAINLESS STEEL, NICKEL-TITANIUM ALLOY, AND BETA-TITANIUM ALLOY ARCHWIRES IN TWO COMMONLY USED ORTHODONTIC BRACKETS

In orthodontic treatment, the efficiency of tooth movement is affected by the frictional force between the archwire and bracket slot. This study evaluated the static and kinetic frictional forces produced in different combinations of orthodontic archwires and brackets. Three types of archwires [stainless steel, nickel-titanium (NiTi) alloy, and beta-titanium (TMA) alloy] and two types of brackets (stainless steel and self-ligating) were tested. Both static and kinetic frictional forces of each archwire–bracket combination were measured 25 times using a custom-designed apparatus. The surface topography and hardness of the archwires were also evaluated. All data were statistically analyzed using two-way analysis of variance and Tukeys test. The experiments indicated that the static frictional force was significantly higher than the kinetic frictional force in all archwire–bracket combinations not involving TMA wire. TMA wire had the highest friction, followed by NiTi wire, and then stainless steel wire when using the stainless steel bracket. However, there was no difference between NiTi and stainless steel archwires when using the self-ligating bracket. For TMA wire, the friction was higher when using the stainless steel bracket than when using the self-ligating bracket. Scanning electron microscopy indicated that stainless steel wire exhibited the smoothest surface topography. The hardness decreased in the order of stainless steel wire > TMA wire > NiTi wire. This study demonstrates that the frictional forces of brackets are influenced by different combinations of bracket and archwire. The reported data will be useful to orthodontists.

Frictional Forces of Conventional and Improved Superelastic NiTi-Alloy Orthodontic Archwires in Stainless Steel and Plastic Brackets

This study evaluated the static and kinetic frictional forces produced between different combination of orthodontic archwires and brackets. Three types of archwires were examined: (1) stainless steel, (2) conventional NiTi alloy, and (3) improved superelastic NiTi alloy. Two types of brackets were tested: (1) stainless steel and (2) plastic. Both static and kinetic frictional forces were measured on a customdesigned apparatus under elastic ligature in the dry state. Each archwire-bracket combination was subjected to 20 independent evaluations. All data were statistically analyzed using two-way analysis of variance and Duncan’s test. The experimental results indicated that the static frictional force was significantly higher than the kinetic frictional force in all archwire-bracket combinations. The frictional force was lower for the stainless steel bracket than for the plastic bracket with stainless steel wire and the improved superelastic NiTi-alloy wire. The frictional force was lower for the improved superelastic NiTi-alloy wire than for NiTi wire with the stainless steel bracket, but higher for NiTi wire with the plastic bracket. The frictional force was lowest for stainless steel wire for both two types of bracket. This study demonstrates that the frictional forces of brackets are influenced by different combinations of bracket and archwire, and that the improved superelastic NiTi-alloy wire does not exhibit “low friction” (as claimed by the manufacturers) in all cases.