# A Novel Method to Measure the Powder Consumption of Dental Air-Polishing Devices
## 4 Discussion  
This study aimed to precisely determine the powder consumption of dental air-polishing systems in their standard working mode. As stipulated, the precise measurement of powder consumption enables air polisher quality assessment. Considering a fraction of a second, slight variations are normal for most types of powder chambers, but large powder consumption variations can have detrimental effects on prophylactic treatments, both for the user and for the patient's dental tissue. Unpredictable device behaviors causing powder consumption fluctuations lead to variability in efficiency. For dental tissue (e.g., dentine), consumption peaks lead to abrupt and uncontrolled abrasiveness increases [12]. This becomes detrimental when critical regions, such as exposed dentine, are treated. In fact, a user usually adapts his hand movement according to the cleaning speed. Furthermore, in order to avoid overtreatment, the usage of a disclosing agent is also a tool to better guide his movement. Unfortunately, here, the use of a disclosing agent [11] to avoid overtreatment is of no help, as the variability of the flowrate occurs over a very short period of time (<0.1 s), which is shorter than any possible user's reaction time. These variations in powder consumption also have two additional effects. First, it generates different dust amounts during the treatment time, which also makes it more difficult to remove properly. Second, the powder overconsumption is also powder wastage, which increases the treatment cost. Therefore, the most optimized device is the device with the most constant powder consumption during one pedal press. The use of six different devices highlighted the impact of different technologies on general powder behavior. For example, whereas Table-top E1 used a'venturi' powder chamber principle [13], in which the powder is taken out of the chamber from the bottom of the chamber, the other Table-tops (i.e., N2 and M3) and the Handies used a standard'swirling' generation with a picking-up mechanism above the powder level. This latter mechanism is less predictable than the first. This difference is underlined by the variations observed within the ten repetitions, which were significantly higher for the latter two Table-tops or the Handies. N2 and M3, as well as the Handies, were found to be powder-volume dependent, as we observed a decrease in powder consumption as a function of time. This was due to the decreasing powder volume in the powder chamber. With regard to the stability of the powder delivery, it can be concluded that Table-top E1, the most predictable device, ensures the highest repeatability between two patients with minimal invasiveness. It has also the least instantaneous powder consumption variability, which also makes it the easiest to use, because the required treatment movement and dust removal are the most predictable. It is, consequently, more ergonomic than the two other Table-tops or Handies. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Device**} & **Mean Powder** & \multicolumn{2}{c}{_p Values on Mean_} & \multicolumn{2}{c}{_p Values for_} \\  & **Consumption** & **(Mann–Whitney) vs.** & **Deviation (F-Test) vs.** \\  & **[g/min]** & **E1** & **E1** \\ \hline Table-top E1 & 1.2 \(\pm\) 0.3 & - & - \\ Table-top N2 & 1.6 \(\pm\) 0.8 & \textless{}0.001 & \textless{}0.001 \\ Table-top M3 & 4.2 \(\pm\) 0.7 & \textless{}0.001 & \textless{}0.001 \\ Handy E1 & 1.5 \(\pm\) 0.3 & - & - \\ Handy N2 & 2.9 \(\pm\) 1.1 & \textless{}0.001 & \textless{}0.001 \\ Handy M3 & 1.3 \(\pm\) 0.6 & 0.23 & \textless{}0.001 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Powder consumption and the standard deviation during one single pedal press: the statistical difference is compared between Table-Top E1 for Table-tops and Handy E1 for Handies. Considering the mean powder consumption of the Table-top, it should be highlighted that one device had an extremely high mean consumption (Table-top M3). This elevated consumption was mainly due to two factors:  
1.