## 1 Introduction  
Dentin hypersensitivity is a dental condition which is defined as a condition with sharp pain caused by extrinsic stimuli on the abnormally exposed dentin surface [1, 2]. The etiology of dentin hypersensitivity includes dental caries, gingival recession, chronic trauma from improper brushing, and damage to the gingival tissue after periodontal treatment [3, 4, 5]. Dentin hypersensitivity reportedly occurs in 8-35% of individuals, mainly in adolescents and adults, and is predominantly more common in women than in men [6]. According to the hydrodynamic theory, which is the most widely accepted explanation for dentin hypersensitivity, pain results from liquid moving through dentinal tubules as a result of external stimulation of exposed dentin [7, 8]. The number and diameter of the dentinal tubules are known to be the most important factors affecting dentin hypersensitivity [9, 10, 11, 12]. In addition, the number of dentinal tubules per area is reportedly higher in teeth with hypersensitivity and the diameter is twice that of normal teeth [13]. One study also reported that the diameter of the dentinal tubule has a tremendous effect on permeability, as the latter increases 16-fold when the diameter of the dentinal tubule is increased by approximately 2-fold [14]. Therefore, it is important to increase the concentration of potassium ions that induce nerve depolarization to block sensory nerve excitation in the pulp, reduce permeability of the dentinal tubule, and occlude the exposed dentinal tubule for the treatment of dentin hypersensitivity [15]. Inhibiting flow within dentin by physically closing the dentinal tubules is a widely used method for treating dentin hypersensitivity. [PERSON] et al. reported the effect of sodium fluoride (NaF) on hypersensitivity; NaF-containing toothpaste and high-concentration NaF solutions are mainly used to relieve dentin hypersensitivity [16]. Because F\({}^{-}\) has an affinity for Ca, it creates a barrier via the formation of calcium fluoride (CaF\({}_{2}\)) crystals on the tooth surface, conferring resistance to external stimuli. However, since CaF\({}_{2}\) crystals are extremely small (about 0.05 \(\upmu\)m) and easily soluble in saliva, F\({}^{-}\) undergoes rapid dissipation in the oral cavity, limiting its therapeutic effect for dentin hypersensitivity [17]. In addition, topical application of high concentrations of F\({}^{-}\) evinces a temporary effect within a short period of time; however, it may be toxic to odontblasts [18]. Hydroxapatite (HA) is another widely used material for occluding the dentinal tubules. The chemical formula of HA is Ca\({}_{10}\)(PO\({}_{4}\))\({}_{6}\)(OH)\({}_{2}\), which accounts for 97% of the tooth enamel component [19]. HA, a representative biomaterial, has widespread application as a coating material for titanium implants and as a bone graft material, owing to its bone conduction properties in vivo and promotion of bone formation without toxicity [20]. According to [PERSON] et al. [21], postoperative hypersensitivity was reduced when sub-gingival calculus removal was performed using an ultrasonic device containing polishing fluid with HA granules. Toothpastes containing nano-HA can yield a considerably higher re-mineralization effect than amine fluoride-based toothpastes [22]. However, HA can be distributed to any location in the body, such as the lungs and liver, via blood circulation when it is not properly attached to the dentinal tubules in the teeth [23]. There is a need for a treatment that can overcome the shortcomings of the existing agents, reduce their side effects, and act synergistically when used in conjunction with other agents. Therefore, this study investigated the utility of plasma for the effective treatment of dentin hypersensitivity. Plasma is a fourth-phase material generated when additional energy is applied to a gas, which is the third phase of the material, and refers to an ionized gas state.