*Article* **Fabrication of a Potential Electrodeposited Nanocomposite for Dental Applications**

**Chun-Wei Chang 1,†, Chen-Han Tsou 2,†, Bai-Hung Huang 3,4, Kuo-Sheng Hung 5,6, Yung-Chieh Cho <sup>7</sup> , Takashi Saito <sup>8</sup> , Chi-Hsun Tsai <sup>8</sup> , Chia-Chien Hsieh <sup>9</sup> , Chung-Ming Liu 3,\* and Wen-Chien Lan 10,\***


**Abstract:** In the present study, a nanocrystalline Ni-Fe matrix with reinforced TiO<sup>2</sup> nanoparticles as a functional nanocomposite material was fabricated by pulsed current electroforming in UV-LIGA (lithography, electroplating, and molding). The influences of TiO<sup>2</sup> nanoparticles on the Ni-Fe nanocomposite deposition were also investigated using scanning electron microscopy, transmission electron microscopy, and in vitro cytotoxicity assay. It was found that the Ni-Fe nanocomposite with 5 wt.% TiO<sup>2</sup> nanoparticles showed a smooth surface and better dispersion property. When the Ni-Fe nanocomposite is combined with 20 wt.% TiO<sup>2</sup> , it resulted in congeries of TiO<sup>2</sup> nanoparticles. In addition, TiO<sup>2</sup> nanoparticles possessed better dispersion properties as performed in pulse current electrodeposition. The microstructure of the electrodeposited Ni-Fe-TiO<sup>2</sup> nanocomposite was a FeNi3 phase containing anatase nano-TiO<sup>2</sup> . Moreover, the electrodeposited Ni-Fe-5 wt.% TiO<sup>2</sup> nanocomposite exhibited a smooth surface and structural integrity. Cytotoxicity assay results also proved that the Ni-Fe nanocomposite with different concentrations of TiO<sup>2</sup> nanoparticles had good biocompatibility. Therefore, the optimization of pulse current electroforming parameters was successfully applied to fabricate the Ni-Fe-TiO<sup>2</sup> nanocomposite, and thus could be used as an endodontic file material for dental applications.

**Keywords:** Ni-Fe-TiO<sup>2</sup> nanocomposite; microstructure; biocompatibility; endodontic file

## **1. Introduction**

Nickel-based alloys have been extensively used as endodontic files for root canal treatment in dental fields because of their unique advantages such as high strength and toughness, superior flexibility, good shape-memory ability, excellent corrosion resistance, and acceptable biocompatibility [1–5]. Despite the advantages of nickel-based alloys, nickelbased endodontic files fracture caused by torsional and cyclic fatigue in root canal treatment still is the main issue in clinical applications [6–8]. It is well known that metallic material with a nanocrystalline structure improves mechanical properties [9–12]. Accordingly, it

**Citation:** Chang, C.-W.; Tsou, C.-H.; Huang, B.-H.; Hung, K.-S.; Cho, Y.-C.; Saito, T.; Tsai, C.-H.; Hsieh, C.-C.; Liu, C.-M.; Lan, W.-C. Fabrication of a Potential Electrodeposited Nanocomposite for Dental Applications. *Inorganics* **2022**, *10*, 165. https://doi.org/10.3390/ inorganics10100165

Academic Editor: Roberto Nisticò

Received: 12 July 2022 Accepted: 15 September 2022 Published: 3 October 2022

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would be desirable if the traditional nickel-based alloy could be developed as a nanocomposite with high torsional and cyclic fatigue resistance using potential fabrication methods or by adding reinforced nanostructured materials to avoid fracture formation in root canal without sacrificing desirable physicochemical and biological properties.

There are extensive studies on methods to produce nanocrystalline materials such as current electroplating, electroless plating, co-deposition processes, pulse plating, etc. [9,12–18]. In general, electrodeposition produced porosity-free products and no consolidation was required. In contrast, nanocrystalline precursor powders were considered a vital raw material in other processing methods. Many pure metals such as Pd, Co, Ni, Ni–Mo Ni–Zn, Ni–Fe, binary alloys, and Ni–Fe–Cr ternary alloys have been fabricated by the above-mentioned methods [19–24]. Electrodeposition can produce nanostructured materials with selected treatment parameters such as pH value, overpotential, bath composition, temperature, etc. [25–27], while electrocrystallization occurs through two competing processes (existing crystals buildup and new materials formation) and can be affected by several factors. The ratio of the two processes was determined by the diffusion status of anions on the surface of crystal and charge transfer rate on the surface of the electrode [28]. Low over potential and high surface diffusion rates could cause grain growth, while high over potential and low diffusion rates of surface promote the new nuclei formation. The current density allowed by pulse plating is much higher than the limited direct current density, which can improve the new nuclei formation [29]. As stated above, the goal of the present study aimed to fabricate the Ni-Fe with reinforced Ti dioxide (Ni-Fe-TiO2) nanocomposite (nanocrystalline Ni-Fe matrix and TiO<sup>2</sup> nanoparticles) as a potential endodontic instrument by the co-deposition approach with pulse electroplating for dental applications. Properties of the Ni-Fe-TiO<sup>2</sup> nanocomposites were evaluated through material analyses and biocompatibility assays.

#### **2. Results**

## *2.1. Electrodeposition of the Ni-Fe-TiO<sup>2</sup> Nanocomposites*

According to the used parameters of pulse plating, it was found that the deposited nanocomposites exhibited extremely shiny and smooth surface features. Moreover, the TiO<sup>2</sup> concentration of the samples changed from 0.1 ± 0.1 wt.% (minimum) to a concentration of 2.9 ± 0.1 wt.% (maximum) for the plating solution. Different parameters such as TiO<sup>2</sup> concentration in the plating solution, duty cycle, current density, and solution agitation affected the TiO<sup>2</sup> concentration in the electrodeposits. The TiO<sup>2</sup> concentration in the plating solution was affected most at peak current density. Enhancing the TiO<sup>2</sup> concentration of the solution could increase the TiO<sup>2</sup> amount in the electrodeposition. However, the amount of electrodeposited TiO<sup>2</sup> reduced as the peak current density increased.
