## 4 Discussion
The results of our study showed that oral hygiene status was better in the group using HFS PTB than in the group using MTB at baseline. Indeed, all the investigated parameters (NMPS, OHI-S, PCR, GBI, and WTCI) revealed a significantly healthier oral status in Group 2 (\(p<0.0001\)). Our results are in line with [PERSON] et al. [42], who compared the efficacy of sonic versus manual tooth brushing in terms of plaque reduction after a session of professional mechanical plaque removal. In this randomized controlled trial, the authors showed that sonic brushing was significantly more effective than manual, both at the statistical and clinical level, for Plaque Index, Bleeding on Probing, and Gingival Index. After 3 months of using the OR PTB, Group 1 showed a significant improvement in all the investigated indexes (NMPS, OHI-S, PCR, GBI, and WTCI). These results are in line with the scientific literature [2; 9; 19; 21; 43]; indeed, different authors showed that powered toothbrushes were more effective than manual ones. Moreover, Cochrane systematic reviews showed that oscillating-powered toothbrushes could remove plaque and reduce gingivitis more than manual brushes in both the long and short term [2; 21], reporting minor and transient injuries to the gums. Moreover, it is interesting to note that although Group 1 subjects reported a higher number of smokers and shorter tooth brushing timing before the study began, at T1 the Group 1 subjects improved their periodontal indexes compared to Group 2 subjects at T0. These results could be related to the positive influence of the information and instructions on oral hygiene provided to Group 1 subjects. In this context, in 2022, [PERSON] et al. [43] showed the efficacy of both brief motivational interviewing and hygiene instruction in improving periodontal health, showing better periodontal outcomes in terms of plaque score, bleeding on probing, and gingival index over a 12-month period. After 3 months of OR PTB, the main oral hygiene indexes (NMPS, OHI-S, and PCR) improved so much that they resulted in being significantly better than those detected at T0 in Group 2, albeit from a clinical point of view, this statistically significant difference was not relevant. In the scientific literature, there is still no agreement on this topic, considering that a meta-analysis performed by [PERSON] et al. [44] showed a small but significant difference between the oscillating-rotating power toothbrush and high-frequency sonic toothbrush, confirming a clinically more relevant advantage of oscillating-rotating than using HFS PTB. Moreover, a review of randomized clinical trials by [PERSON] et al. [27], taking into account the quality assessment, resulted in being in favor of sonic toothbrushes, reporting greater long-term results for both the gingival and bleeding indices. [PERSON] and [PERSON] [45] conducted a meta-analysis of RCTs to analyze the efficacy of OR PTB compared with other PTB (specifically HFS), assessing plaque removal and gingival inflammation indexes. The authors showed that OR PTB reported statistically significant improvement for the full-mouth plaque reduction (\(p<0.01\)) and the number of bleeding sites (\(p<0.001\)), but not for the modified gingival index (\(p>0.05\)). The study had several limitations: first, the inclusion of students attending the 2 nd and 3 rd year of the Dental Hygiene Degree Course that should be more observant in performing adequate oral hygiene, thus precluding an external validity; second, the small number of study participants, albeit it should be considered the proof-of-concept study design; third, there is a lack of a complete periodontal chart (with full-mouth plaque and full-mouth bleeding values) and the periodontal phenotype assessment, which might have provided additional information for this study. The findings from the present study might suggest clinical recommendations to transit from MTB to PTB and provide oral hygiene instructions, aimed to improve plaque removal and achieve better periodontal indexes.