## 4 Discussion  
The oral cavity is one of the most complex ecosystems in the body, affected not only by the overall health condition of the host but also by environmental and behavioral factors including oral hygiene, nutrients, smoking, and mechanical stress [33; 34]. Among the about 700 bacterial species that coexist in the oral cavity, some oral pathogens (e.g., _Aggregatibacter actinomycetemcomitants_, _Prerotella internedia_, _Porphyomonas gingialis_, _Trepurema denticola_, _Fusobacterium nucleatum_, and _Tannerella forysth_) could lead to a dysbiotic biofilm deposition on the teeth surface and in the periodontal pocket [35]. The local inflammatory response seems to be promoted by several inflammatory pathways, and it may lead to microbial products spreading in the systemic circulation and reaching distant organs. Indeed, periodontal diseases have been related to low-grade systemic inflammation driven by several inflammatory mediators [36]. In this scenario, our research group has recently shown that poor oral hygiene might increase the risk of progressive periodontal disease and dental decay in pregnant women and patients affected by chronic diseases [37; 38; 39]. To improve toothbrushes' adaptability and efficiency, several types of manual and powered toothbrushes have been introduced. Both MTB and PTB could lead to optimum oral hygiene through the disorganization, breakdown and removal of bacterial plaque that is adhered to both soft tissue and teeth [40; 41]. The present study aimed at comparing the effects of two different powered toothbrushes on plaque and calculus accumulation, gingival bleeding and inflammation, and the amount of tongue coating. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Group 1 (MTB + OR PTB) T1** & **Group 2 (HFS PTB) T0** & \(p\) **Value** \\ \hline NMPS & 0.18 \(\pm\) 0.32 & 0.27 \(\pm\) 0.37 & 0.043 \\ OHI-S & 0.12 \(\pm\) 0.17 & 0.25 \(\pm\) 0.28 & 0.032 \\ PCR & 5.56 \(\pm\) 9.76 & 7.87 \(\pm\) 9.76 & \textless{}0.001 \\ GBI & 0.58 \(\pm\) 1.10 & 0.72 \(\pm\) 0.74 & 0.080 \\ WTCI & 0.19 \(\pm\) 0.23 & 0.20 \(\pm\) 0.23 & 0.187 \\ \hline \hline \end{tabular}  
* Continuous variables are expressed as means \(\pm\) standard deviations. Wilcoxon rank sum test was performed as statistical analysis. Abbreviations: HFS = high-frequency sonic; MTB = manual toothbrush; OR = oscillating-rotating; PTB = powered toothbrush; NMPS = New Method of plaque Scoring; OHI-S = Oral Hygiene Index Simplified; PCR = Plaque Control Record; GBI = Gingival Bleeding Index; WTCI = Winkel Torque Coating Index.  
\end{table} 
Table 4: Difference in oral hygiene indexes between Group 1 after using the rotating and oscillating powered toothbrush for three months (at T1) and Group 2 at T0. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Group 1 (MTB + OR PTB) T0** & **Group 1 (MTB + OR PTB) T1** & \(p\) **Value** \\ \hline NMPS & 2.17 \(\pm\) 0.85 & 0.18 \(\pm\) 0.32 & \textless{}0.0001 \\ OHI-S & 1.07 \(\pm\) 0.65 & 0.12 \(\pm\) 0.17 & \textless{}0.0001 \\ PCR & 53.84 \(\pm\) 16.47 & 5.56 \(\pm\) 9.76 & \textless{}0.0001 \\ GBI & 3.04 \(\pm\) 3.17 & 0.58 \(\pm\) 1.10 & 0.0002 \\ WTCI & 0.46 \(\pm\) 0.20 & 0.19 \(\pm\) 0.23 & \textless{}0.0001 \\ \hline \hline \end{tabular}  
* Continuous variables are expressed as means \(\pm\) standard deviations. Wilcoxon signed-rank test was performed as statistical analysis. Abbreviations: MTB = manual toothbrush; OR= oscillating-rotating; PTB = powered toothbrush; NMPS = New Method of plaque Scoring; OHI-S = Oral Hygiene Index Simplified; PCR = Plaque Control Record; GBI = Gingival Bleeding Index; WTCI = Winkel Torque Coating Index; T0 = baseline; T1 = 3 months.  
\end{table} 
Table 3: Comparison between oral hygiene status in Group 1 after using the rotating and oscillating powered toothbrush for three months (from T0 to T1). To the best of our knowledge, this is the first study comparing the effectiveness of oscillating-rotating and sonic-powered toothbrushes among dental hygiene students, well-educated and motivated to perform good home oral hygiene.