## 4 Discussion  
This study investigated the possibility of increasing the efficacy of APF or HA using NCP technology developed to safely deliver low-temperature plasma to the oral cavity, which is located in close proximity to the respiratory system. The dentin is exposed to various stimuli, resulting in hypersensitivity [32; 33]. Although dentin hypersensitivity is frequently encountered in clinical practice, no effective and reliable treatment method is available. The treatment methods used so far are divided into self-administered methods, such as toothpaste or rinses, and professional treatment methods that entail application of high-concentration fluoride to the tooth surface or resin restorations [34]. To date, preparations composed of various ingredients have been developed; conoctions containing biocompatible ingredients such as F\({}^{-}\), HA, and carbonate apatite have found widespread application owing to the ease of use. Several materials have been developed to reduce or eliminate the pain caused by hypersensitivity to dentin, which generally act by blocking the dental tubule or interfering with nerve impulse transmission. F\({}^{-}\), which is commonly used in clinical practice, forms a protective film by the formation and deposition of CaF\({}_{2}\) on the exposed tooth surface. APF used in the experiment is known to induce a higher CaF\({}_{2}\) concentration in dentin than in enamel, releasing a greater amount of Ca [18]. However, it does not remain permanently on the tooth surface and  
Figure 5: Dentinal Tubule Occlusion: SEM Analysis: (**a**) Observation of the dentinal tubule surface using SEM analysis after NCP treatment (1000\(\times\)); (**b**) Measurement of the dentinal tubule occlusion rate after NCP treatment (* \(p<0.05\)); (**c**) Effect of NCP on dental tubule re-mineralization (* \(p<0.05\)) NCP: no-ozone cold plasma, SEM: scanning electron microscopy. is easily washed off by the presence of saliva or food, making long-term retention in the oral cavity difficult. In this study, we examined the utility of low-temperature plasma to increase the efficacy of APF and HA, which are the most frequently used conventional materials for the treatment of hypersensitivity. We found that the F\({}^{-}\) content on the tooth surface was higher in the experimental group treated with APF after NCP treatment than that in the group treated with APF alone (Figure 4a). Our previous research found that the plasma jet generated using helium dramatically increased the F\({}^{-}\) content of extracted teeth [25]. The results of this study are consistent with those of previous studies using a helium plasma jet: the F\({}^{-}\) coating effect of APF is maintained with NCP pre-treatment, and the amount of ozone generated is negligible [29] and the plasma plume does not directly contact the teeth. Two types of meshes that can be mounted on the NCP device were fabricated and the change in the F\({}^{-}\) coating effect by NCP was examined in order to determine the most important working element of NCP (which is little influenced by ozone and heat) responsible for dental F\({}^{-}\) coating. According to this experiment, a higher amount of F\({}^{-}\) was detected in the group treated with APF after pre-treatment with NCP than the group treated with only AFP. When a grounded metal mesh was installed for NCP treatment, the value decreased from 0.41 to 0.06, indicating a drastic reduction in the amount of F\({}^{-}\) (Figure 4b). This result is akin to the phenomenon where low-temperature argon plasma-mediated E-cadherin protein inhibition in HaCaT cells completely disappears when an EG mesh is applied between the cell and plasma device [35]. In the sample pre-treated with the DE mesh-equipped NCP, the amount of F\({}^{-}\) was similar to that of the sample pre-treated with NCP.