## 4 Discussion
Anyway, current literature points to a positive correlation between ATP levels and Total Viable Count (TVC) values, which estimate the microorganisms present on the evaluated surface, defining it as a suitable method for measuring the microbial count [34,35]. The choice to analyze the sciatic lamp, the control button panel and the spit bowl of the dental chair was dictated by the fact that these are easily accessible surfaces, resistant to heat, and representative of the surfaces that are most exposed to contamination during AGDPs. The sciatic lamp is one of the most exposed surfaces to aerosol, the control button panel is one of the surfaces most touched by the operator, and the spit bowl is the most exposed to the patient's saliva. Data on the contamination of the evaluated surfaces showed a significant decrease of ATP on all the tested surfaces at T1 in comparison to T0, both in terms of RLU values (T1 median value = 28 versus T0 median value = 255; cut-off = 150) and of categorical data (56 \"approved\" evaluations at T1 out of the 60 performed). With respect to the four \"not approved\" evaluations at T1, the high cellular ATP amount detected on these surfaces by the luminometer (RLU mean value = 550, which is more than three times the cut-off) after the steam application, might be related to the incomplete removal of residual water or saliva on the tested surfaces. The fact that these surfaces were found to be clean after 30 additional seconds of steam disinfection (RLU mean value = 69) suggests that 60 s steam disinfection may be required in the case of high contamination. In addition, it should be considered that in this study, the _Polti lpMED_ detergent [37] was not used in order to evaluate the efficacy of the steam alone. It may be hypothesized that using the detergent in combination with the steam might help remove the residual contaminants on the surface, improving the disinfecting power of this procedure. Significant findings were also observed when stratifying the data by type of surface. Median RLU values calculated for the sciatic lamp, the control button panel and the spit bowl decreased, in fact, from 175, 201.5 and 417.5, respectively, at T0 to 20, 26.5 and 48, respectively, at T1. In relation to the categorical data at T1, of the 20 evaluations performed for each surface, 19 evaluations of the sciatic lamp' surface, 17 of the control button panel surface and 20 of the spit bowl surface out were \"approved,\" showing that the use of the overhead dry-saturated steam disinfection after the performing of AGDPs was effective in reducing the contamination on the evaluated surfaces. The primary hypothesis tested was thus accepted. On the other hand, considering the different surfaces evaluated at T0, the spit bowl showed the highest RLU value (417.5), while the sciatic lamp showed the lowest (175). However, differences in terms of superficial contamination among the evaluated surfaces were not statistically significant, which demonstrates that all surfaces of the dental chair were equally contaminated after performing AGDPs. Based on this study's findings, overheated dry-saturated steam effectively reduced the superficial contamination of selected surfaces of the dental chair. Decreasing the microbial contamination on frequently touched surfaces means reducing the risk of indirect infections for patients and DHCPs and, consequently, the care burden. Overheated dry-saturated steam has several advantages: it is an easy-to-use and rapid method able to inactivate heat-sensitive pathogens in a few seconds at the temperature of 180\({}^{\circ}\)C without leaving any residues and without the need to ventilate the environment after its use, unlike chemical disinfectants; it does not require the use of individual protective devices for users; and the risk of burns is very low since the temperature of the steam jet considerably decreases at a few centimeters distance from the emission nozzle.