Figure 2.

The values of microbial loads were converted into log10 × to compare the results over the years using box-and-whisker plots. A box-and-whisker plot shows a ‘box’ with a low edge at lower quartile, the high edge at upper quartile, the ‘middle’ of the box at the median and the maximum and minimum as ‘whiskers’. The dotted line in the figure corresponds to lg500 colony-forming units (CFUs)/mL. DUWLs, dental unit waterlines.