## 3 Results
### Demographic Information
No differences in post-operative pain distribution were observed at 12 months between the two groups. Differently, teeth with preoperative PAI \(>\) 2 had a higher percentage of healing lesions and a higher percentage of sealer resorption. When comparing the extrusion frequencies in upper or lower jaws, we found a higher percentage of extrusions in maxillary locations, namely 12/18 teeth, when compared to the mandibular sites (6/18 teeth). Sealer resorption occurred in 6/9 maxillary teeth and 3/9 mandibular teeth. Four representative cases included in the study are reported in Figure 2A-D. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Characteristics** & **All** & **Healed** & **Healing** & **Diff. in \%s** & _p-Value** \\  & **(_n = 38_)** & **(_n = 31_)** & **(_n = 7_)** & **(95\% CI)** & _p-Value_ \\ \hline One-day pain & & & & & \\ No & 32 (84\%) & 28 (90\%) & 4 (57\%) & & & \\ Yes \(\dagger\) & 6 (16\%) & 3 (10\%) & 3 (43\%) & \(-\)33 (\(-\)65, \(-\)3) & 0.029 \({}^{*}\) \\ One-week pain & & & & & \\ No & 34 (89\%) & 30 (97\%) & 4 (57\%) & & & \\ Yes \(\dagger\) & 4 (11\%) & 1 (3\%) & 3 (43\%) & \(-\)40 (\(-\)72, \(-\)11) & 0.007 \({}^{*}\) \\ One-month pain & & & & & \\ No & 34 (89\%) & 30 (97\%) & 4 (57\%) & & & \\ Yes \(\dagger\) & 4 (11\%) & 1 (3\%) & 3 (43\%) & \(-\)40 (\(-\)72, \(-\)11) & 0.007 \({}^{*}\) \\ Twelve-month pain & & & & & \\ No & 36 (95\%) & 31 (100\%) & 5 (71\%) & & & \\ Yes \(\dagger\) & 2 (5\%) & 0 (0\%) & 2 (29\%) & \(-\)29 (\(-\)66, \(-\)5) & 0.011 \({}^{*}\) \\ \hline \hline \end{tabular} \({}^{*}\)_p_-value \(\leq\) 0.05. \(\dagger\) Visual analogue scale (VAS) \(\geq\) 1.  
\end{table} 
Table 4: Pain-related parameters of the study sample, overall and by periapical index (PAI) at 12-month follow-up (1–2 [headed] vs. \(\geq\) 3 [still healing]). \begin{table}
\begin{tabular}{l c c c c} \hline \hline  & **No Pain (0)** & **Mild (1–2)** & **Moderate (3–7)** & **Severe (8–10)** \\ \hline One day & 32 (84\%) & 3 (8\%) & 3 (8\%) & 0 (0\%) \\ One week & 34 (89\%) & 4 (11\%) & 0 (0\%) & 0 (0\%) \\ One month & 34 (89\%) & 4 (11\%) & 0 (0\%) & 0 (0\%) \\ Twelve months & 36 (95\%) & 2 (5\%) & 0 (0\%) & 0 (0\%) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Post-operative pain intensity according to VAS at 1 day, 7 days, 28 days and 1 year after root canal obturation. Figure 2: **(A)** Upper incisor with a periapical lesion (PAI = 5). The periapical X-ray at 12 months showed resolution of the periapical pathology (PAI = 2). Note the disappearance of sealer extrusion. (**B**) Upper molar with previous failed root canal treatment (PAI = 4). The meso-buccal root revealed a periapical lesion, a metal post, and an incomplete filling of the apical third. It is interesting to observe the sealer morphology after root canal obturation and after 12 months of follow-up. The extrusion around the meso-buccal root seems to have disappeared, while the one in the palatal root is still present. No post-operative pain was reported (VAS = 0 throughout the entire treatment and follow-up). (**C**) Lower first molar with a deep carious lesion. Slight periapical extrusion was observed in the mesial and distal canals. Uneventful healing was observed at the 12-month follow-up. (**D**) Upper second premolar with a deep carious lesion and no periapical radiolucencies (PAI = 2). Slight modification of the sealer extrusion was observed at the 12-month recall.