## 4 Discussion
However, to date, we have found no study which ever tested this specific platform to improve the compliance and knowledge of the patients regarding dental hygiene during an orthodontic therapy and this makes our results not directly comparable to those of other analogue studies. A randomized controlled trial considered an intervention with a messaging app (WeChat), consisting of regular reminders and educational messages which caused an improvement in the plaque index and in the gingival index but, as in the present study, the difference was not statistically significant with controls [43]. Conversely, the intervention with the app was effective in decreasing the treatment duration and the bracket bond failure. It would be also interesting to evaluate the variation of these parameters after providing multimedia contents on Instagram. [PERSON] et al. [44] tested a WhatsApp chat room-based competition in a protocol for domestic oral hygiene maintenance where a group of young orthodontic patients enrolled as trials had to monthly share with the other participants self-photographs showing their oral hygiene status. The efficacy of new technologies in the oral health status was demonstrated. Although this result contrasts with that reported in our study, the methodology used is surely different. The active competition among participants, instead of a simple flow of information like in our research, has surely influenced the outcomes with a greater effect. The reason why a major advantage was not assessed for the trial group might be related to a lack of accuracy in visualizing all multimedia contents and for their whole duration time, which represents a limitation of this report. In fact, other research considers information provided in a visual modality effective in improving the attitude of the youngest towards the dental care, however an excessive length of the video might cause a loss of interest and attention [45]. Accordingly, this might justify why a significant improvement in oral hygiene indexes was found in some of the studies previously mentioned in which only text messages reminders were used [31, 37, 38]. These latter are obviously shorter compared to multimedia contents and therefore they are likely to have been read entirely by all participants. Other limitations of our study could be related to the intrinsic limitations of the procedures used to evaluate the clinical indexes such as a different pressure when evaluating the BI, the subjectivity in assessing the MGI, and the rigidity of the PI only distinguishing the presence or absence of plaque with no intermediate distinctions. Moreover, the presence of the oral appliance in the mouth could have made the clinical measurements more difficult resulting in altered results. Finally, the present report tested over time the cooperation of patients after conventional professional oral hygiene (using ultrasonic instruments). Other oral hygiene procedures and protocols (involving ozone, laser, or probiotic treatment) have been reported to be effective [46] so further studies on the topic are needed. The second null hypothesis of this study was rejected: although weekly sharing of information on Instagram did not seem to be able to improve the oral hygiene compliance, it was effective in improving the patients' knowledge on both oral health and correct oral practices as well as on dietary habits. Answers given to the same questionnaire at the beginning (T0) and at the end (T3) of the study were compared: for all the sections of the questionnaire, a significant increase in average scores of correct answers was shown in the intervention group. Instead, patients who obtained information only in a verbal form did not register statistically differences between the two timepoints considered.