**Application of Solution Plasma Surface Modification Technology to the Formation of Thin Hydroxyapatite Film on Titanium Implants**

**Akashlynn Badruddoza Dithi 1,2,\*, Takashi Nezu 1, Futami Nagano-Takebe 1, Md Riasat Hasan 2, Takashi Saito <sup>2</sup> and Kazuhiko Endo <sup>1</sup>**


Received: 21 September 2018; Accepted: 13 December 2018; Published: 21 December 2018

**Abstract:** Hydroxyapatite (HA) coatings on titanium implants enhance rapid bone formation around the implant due to their osteoconductive property. The present study aimed to achieve a thin and uniform HA film coating on titanium implants by solution plasma treatment (SPT). Commercially pure titanium and porous titanium disks were employed. A pulse plasma generator was used on the disks for 30 min. Morphologic and crystallographic features of the deposited films were examined by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). To evaluate the wettability of the disks, water droplet (20 μL) surfaces were measured using a contact angle analyzer. The initial attachment of osteoblast-like cells (MC3T3E1) on the titanium substrates before and after solution plasma treatment was evaluated by counting the number of attached cells after incubation for 4 h. After immersion in the mineralizing solution for up to seven days, no crystals were observed on the polished-Ti surface. A more uniform and dense precipitation of round and grown crystals with diameters of approximately 1–5 μm was observed on Ti-SPT. XRD clearly showed that the precipitated crystals on titanium disks were HA. The contact angle of the polished-Ti increased with time (θ = 37◦–51◦). The surface of the Ti-SPT remained hydrophilic (θ < 5◦) after up to 30 days of aging. The number of attached cells on the Ti-SPT after aging for 30 days remained above 85% of that on the Ti-SPT without aging. SPT in a mineralizing solution can be used to acquire a homogenous precipitation of HA on porous-surfaced titanium implants.

**Keywords:** hydroxyapatite; titanium implants; mineralizing solution; solution plasma treatment
