## 3 Results  
The penetration by _E. faecalis_ from the side of the root canal into the dental tubules of the specimens was verified with CLSM. A homogeneous infection, with a minimum depth of 300 \(\upmu\)m, was reached in all of the specimens. The negative control group showed no bacterial contamination. The mean depth of action and the red fluorescence ratios for each group and sub-group are reported in Table 1 and Figure 2. The 3-MIX and 3-MIXC antibiotic pastes exhibited similar depths of action, which were slightly higher than that of 2-MIX, but the differences were not statistically significant (\(p>0.05\)). Moreover, the HA or MG vehicles did not significantly influence the depth of action in any tested group (\(p>0.05\)). The mean ratios of red fluorescence to green-and-red fluorescence were similar between the 3-MIX and 3-MIXC groups, and both were statistically higher than those of the 2-MIX group (\(p=0.014\)). Each antibiotic mixture demonstrated a higher bactericidal efficacy if conveyed with HA compared to MG (3-MIX, \(p=0.019\); 3-MIXC, \(p=0.013\) and 2-MIX, \(p=0.0125\)). The images from the control groups are reported in Figure 3.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Mean Depth of Action (\(\upmu\)m)** &
\begin{tabular}{c} **Mean Proportion of Dead Cells** \\ **Volume (Red Fluorescence Ratio)** \\ \end{tabular} \\ \hline
**3-MIX hyaluronic acid (HA) (N = 10)** & \(290\pm 58.5\) \\
**3-MIX macrogol gel (MG) (N = 10)** & \(230.7\pm 39.1\)[FOOTNOTE:]Footnote : Superscript letters: the different letters show the statistically significant differences among the groups (\(p<0.05\)). The first superscript letter refers to the comparison between the antibiotic pastes, while the second one refers to the type of vehicle tested. Nd: data not determined.[ENDFOOTNOTE]** \\
**3-MIX** CHA (N = 10)** & \(268.2\pm 30.2\)** \\
**3-MIX** MG (N = 10)** & \(246\pm 48.1\)[FOOTNOTE:]Footnote : Superscript letters: the different letters show the statistically significant differences among the groups (\(p<0.05\)). The first superscript letter refers to the comparison between the antibiotic pastes, while the second one refers to the type of vehicle tested. Nd: data not determined.[ENDFOOTNOTE]** \\
**2-MIX** HA (N = 10)** & \(202.3\pm 38.5\)[FOOTNOTE:]Footnote : Superscript letters: the different letters show the statistically significant differences among the groups (\(p<0.05\)). The first superscript letter refers to the comparison between the antibiotic pastes, while the second one refers to the type of vehicle tested. Nd: data not determined.[ENDFOOTNOTE]** \\
**2-MIX** MG (N = 10)** & \(168.8\pm 31\)[FOOTNOTE:]Footnote : Superscript letters: the different letters show the statistically significant differences among the groups (\(p<0.05\)). The first superscript letter refers to the comparison between the antibiotic pastes, while the second one refers to the type of vehicle tested. Nd: data not determined.[ENDFOOTNOTE]** \\
**Positive controls HA (N = 3)** & \(0.5\pm 0\)** \\
**Negative controls (N = 6)** & Nd & Nd \\ \hline \hline \end{tabular}
\end{table}
Table 1: The mean depth of action and the mean proportion of dead cell volume for each tested group and sub-group (3-MIX (ciprofloxacin, metronidazolezole and minocycline); 3-MIXC (ciprofloxacin, metronidazolezole and clarithromycin); 2-MIX (ciprofloxacin and metronidazolezole); hyaluronic acid (HA) and macrogol (MG)). The different superscript letters indicate the statistically significant differences between the groups (\(p<0.05\)). Among the mean proportion of dead cell volume, 2-MIX groups showed different results when compared with the other groups and the presence of HA significantly influenced all of the groups.