## 4 Discussion  
Due to the working conditions in close contact with the patient and the performing of aerosol-generating dental procedures [6; 7; 8], dentists are reported to be among the healthcare professionals with a high risk of contagion and have been considered particularly exposed during the COVID-19 pandemic [8; 9]. Adopting proper disinfection protocols in dental work environments is fundamental to reduce the risk of cross-infections for patients and dental healthcare professionals [8; 12; 18; 19; 20]. Among the physical so-called \"No-Touch\" Disinfection (NTD) systems, the overheated dry-saturated steam is reported to be effective inactivating heat-sensitive bacteria, fungi and viruses, including the HCO-OC43 virus, a surrogate for SARS-CoV-2 [21; 22; 23; 24; 25; 26; 27; 28; 29]. However, the literature to date is lacking in studies evaluating the efficacy of overheated dry-saturated steam in the disinfection of surfaces in dental offices [21]. Given the limited available data, the present pilot in vitro study aimed to deepen the knowledge on the use of an overheated dry-saturated steam disinfection procedure in the dental practice and, in particular, its efficacy in reducing the superficial contamination of selected dental surfaces of the dental chair after performing aerosol-generating dental procedures. The rationale of this study was that the overheated dry-saturated steam might decrease the superficial microbial contamination of the evaluated surfaces thanks to its bactericidal, virucidal and fungicidal activity [22; 23; 24; 25; 26; 27; 28], consequently reducing the risk of cross-infections for both patients and professionals. In order to evaluate the cleanliness of the surfaces under study, an ATP bioluminescence analysis was used. This easy-to-use and handy tool is helpful in evaluating the effectiveness of disinfection procedures by providing an immediate result of the ATP amount present on the tested surfaces. The main limitation of this method, however, is linked to the fact that it measures the total organic contamination \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Surface**} & \multicolumn{3}{c}{**T0**} \\ \cline{2-4}  & \multicolumn{1}{c}{_“Not approved”_ (n = 40)} & _“Approved”_ (n = 20) & **Chi-square \(p\)-value** \\ \hline _Scialytic lamp_ & 11 (27.5) & 9 (45.0) & \\ \hline _Control panel_ & 14 (35.0) & 6 (30.0) & 0.38 \\ \hline _Spit bowl_ & 15 (37.5) & 5 (25.0) & \\ \hline \multirow{2}{*}{**Surface**} & \multicolumn{3}{c}{**T1**} \\ \cline{2-4}  & \multicolumn{1}{c}{_“Not approved”_ (n = 4)} & _“Approved”_ (n = 56) & \\ \hline _Scialytic lamp_ & 1 (25.0) & 19 (33.9) & \\ \hline _Control panel_ & 0 (0.0) & 20 (35.7) & 0.31 \\ \hline _Spit bowl_ & 3 (75.0) & 17 (30.4) & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Associations between the surface type and categorical disinfection results; (\(p<0.05\)). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Time**} & \multirow{2}{*}{**Surface**} & \multirow{2}{*}{**N**} & \multirow{2}{*}{**Min**} & \multicolumn{2}{c}{**25 th**} & \multirow{2}{*}{**Median**} & \multicolumn{2}{c}{**75 th**} & \multirow{2}{*}{**Max**} & \multicolumn{2}{c}{**Kruskal**} \\  & & & & & **Percentile** & & & \(p\)**-Value** \\ \hline \multirow{4}{*}{T0} & _Scialytic lamp_ & 20 & 15 & 70 & 175 & 441.5 & 4846 & \\ \cline{2-8}  & _Control panel_ & 20 & 42.5 & 126.5 & 201.5 & 596 & 32,097 & \\ \cline{2-8}  & _Spit bowl_ & 20 & 36 & 175 & 417.5 & 1070 & 3739 & \\ \hline \multirow{4}{*}{T1} & _Scialytic lamp_ & 20 & 4 & 9 & 20 & 28 & 645 & \\ \cline{2-8}  & _Control panel_ & 20 & 7 & 17 & 26.5 & 69 & 94.5 & \\ \cline{1-1} \cline{2-8}  & _Spit bowl_ & 20 & 7 & 23 & 48 & 90.5 & 410 & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Distributions of the RLU values for each evaluated surface at T0 and T1; (\(p<0.05\)). A cut-off of 150 RLU was set to consider a surface clean. on the surface and not the microbial count alone.