## 4 Discussion
When diode lasers were irradiated at titanium implants, [PERSON] et al. [12] reported a decrease of 28% at 0.25 W, 61% at 0.5 W, 95% at 0.75 W, and 100% at 1.0 W in _Staphylococcus aureus_. In the present study, the energy density at 1.0-W power was 14, 9, and 10 kJ/cm\({}^{2}\) by K2 mobile, Epic 10 TM, and Saeshin, respectively (Table 1), and the energy density at 1.0-W power in the [PERSON] et al. study was 12 kJ/cm\({}^{2}\)[12]. [PERSON] et al. confirmed a 95% bactericidal effect at 9 kJ/cm\({}^{2}\)[12]. Therefore, 1.0-W output power was selected as a minimum intensity, and it was assumed that diode lasers had a bactericidal effect under all conditions. Further research is needed for the bactericidal effect through laser irradiation in peri-implantitis treatment [17]. An increase in surface temperature was inevitable when a diode laser was irradiated on a titanium disc. A temperature rise of more than 10 \({}^{\circ}\)C has been reported to adversely affect bone tissues due to alkaline phosphatase denaturation [11; 18]. [PERSON] and [PERSON] et al. [19] reported that, with an air flow of 2.5 L/min, irradiating a diode laser at 3.0 W in the continuous mode for 10 s avoided exceeding the threshold temperature. Here, diode lasers were irradiated at Ti disks for 15 s at a maximum output power of 3.0 W to see if titanium surface changes occurred at temperatures slightly above the threshold temperature. The present study was conducted without water cooling and showed a high surface temperature of above 200 \({}^{\circ}\)C at all output powers at the laser irradiation site. In addition, further study is needed to confirm a setting value suitable for more clinical use by lowering the temperature rise of the implant surface by applying less time and power than setting value applied in the present study. Additionally, in clinical practice, open flap treatment is necessary to ensure sufficient cooling of the implant surface. Therefore, additional research is required under water cooling conditions, and the temperature rise must be taken into account when laser irradiation is applied to dental implants in clinical practice. Titanium is a highly reactive element and exists in the form of TiO\({}_{2}\)[20]. Titanium and oxygen signals in the EDS analysis showed that the titanium disc surface consisted of a titanium oxide layer [21]. The thickness of the titanium oxide is known to be 2-6 nm, and EDS analysis provides compositional information averaged over a depth of 1 \(\upmu\)m [22]. The carbon signal in the EDS analysis could be due to surface contamination [21]. The SLA surface has undergone an acid etching process, which washes away any remaining elements on the titanium surface [23]. Thus, it was difficult to find a clear difference in the titanium, oxygen, and carbon element ratios between the laser-irradiated and nonirradiated groups. Therefore, it is suggested that the diode laser does not seem to change the chemical composition of the titanium disc surface. On the other hand, the effects of laser irradiation on the implant surface under salivary conditions have not been evaluated in this work. The chemical composition of the titanium surface can be influenced by microbial pH occurring in vivo. Therefore, further studies are needed under intraoral conditions. In decontaminating the implant surface, an increase in surface roughness can make the osseointegration difficult after treatment [5]. Therefore, it is necessary to irradiate a laser that can remove the contamination and increase the proper surface temperature without increasing the surface roughness of the implant. Further research is needed to confirm these conditions. Finally, the possibility that the beam at the fiber tip has a non-uniform intensity distribution has not been eliminated from the measurements in the present study. Further study is needed the measurement of the beam profile using a charged coupled device camera system.