## 4 Discussion  
We have previously discussed the developmental theoretical framework and usability of the OSCA [10]. Objectives of this study were (1) to investigate the effectiveness of the OSCA intervention in improving OHS and facilitating change in OHBs and (2) to identify the factors that influence OHS improvement. The findings indicate that the effectiveness of the OSCA intervention is substantial. OHS improvement was evaluated by the difference in PCR scores at baseline and re-evaluation. The participants in the intervention group demonstrated slightly better OHS improvement compared with the participants in the control group, and the low-frequency users in the intervention group demonstrated much less OHS improvement compared with the moderate- and high-frequency users (Figure 3). From the result, we can conclude that the intervention effectiveness was significant and positively correlated with the frequency of OSCA use. That is, participants could effectively improve their OHS by adhering to the OHIs with the OSCA and that frequency of app use affected the effectiveness of the OSCA intervention. It may be the case that frequent use of OSCA brought sufficient opportunities for impact on improving oral hygiene. Similar findings that adherence to OHIs is the main factor affecting OHS improvement for patients with periodontitis [9; 10] and that higher frequency of app use increases its effectiveness [16] have been reported. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Variable** & **Coefficient (Standard Error)** & \(t\) & \(p\)**-Value** \\ \hline Change of OHBs & 7.250 (2.477) & 2.927 & 0.006 \\ Smoking & \(-14.770\) (5.928) & \(-2.491\) & 0.017 \\ Level of OSCA use frequency & 8.211 (3.764) & 2.181 & 0.035 \\ Gender & \(-5.594\) (4.981) & \(-1.123\) & 0.268 \\ Age & \(-5.526\) (3.523) & \(-1.568\) & 0.124 \\ Education & 0.184 (3.072) & 0.060 & 0.952 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Multiple regression of the improvement in OHS. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \(n\) & **Likeability** & **Capability** & **Opportunity** & **Motivation** \\  & **(Mean \(\pm\) SD)** & **(Mean \(\pm\) SD)** & **(Mean \(\pm\) SD)** & **(Mean \(\pm\) SD)** \\ \hline Total & 49 & 5.85 \(\pm\) 0.76 & 6.00 \(\pm\) 0.71 & 5.77 \(\pm\) 0.70 & 5.71 \(\pm\) 0.73 \\ \hline \hline \multicolumn{5}{c}{_Frequency of OSCA use_} \\ High-level & 15 & 6.36 \(\pm\) 0.43 & 6.42 \(\pm\) 0.28 & 6.00 \(\pm\) 0.57 & 6.13 \(\pm\) 0.42 \\ Moderate-level & 20 & 6.14 \(\pm\) 0.47 & 6.31 \(\pm\) 0.49 & 6.09 \(\pm\) 0.50 & 6.03 \(\pm\) 0.39 \\ Low-level & 14 & 4.89 \(\pm\) 0.43 & 5.11 \(\pm\) 0.46 & 5.07 \(\pm\) 0.60 & 4.81 \(\pm\) 0.58 \\ \hline \hline \multicolumn{5}{c}{_p_-value} \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Overall likeability and functional preferences of the OSCA for participants in the intervention group. Furthermore, the effectiveness of the OSCA intervention was significantly affected not only by the frequency of its use but also by change in OHBs and smoking. Change in OHBs toward the target behavior of oral self-care had a positive impact on the improvement in the level of plaque control, indicating that better OHBs resulted in improved OHS, which is consistent with the findings of previous studies [10; 28; 29]. Research has found that good oral care plays an important role in maintaining oral health [4; 5; 6; 7] and is the foundation for the long-term success of periodontal treatment [28; 29; 30]. Therefore, changing OHBs toward well performing daily oral self-care can improve OHS and enhance the treatment effect for periodontitis. Moreover, studies have shown that apps designed based on behavioral change theories are more effective at eliciting behavioral change in users [13; 20; 31; 32; 33; 34] and that personal information as well as evidence-based interventions can significantly help patients manage their conditions better [34; 35].