## 3 Results  
A total of 76 specimens underwent radiological imaging with a micro-CT prescan to verify the presence of supernumerary canals (as described in Figure 2). The remaining 66 specimens underwent a full micro-CT scan. By micro-CT, the presence of SNCs in the apical 3 mums of the root could be verified in only 33 teeth, which formed the final study sample. The frequency of SNCs in the entire 188-specimen sample was 17.6%. Broken down by tooth type and referring to the entire 188-specimen sample, 24.6% of the central incisors, 9.6% of the lateral incisors, and 20.7% of the canines contained SNCs. For a summary of the selection procedure, see Table 1.  
The final study sample (N = 33) contained/consisted of 14 central incisors (42.4%), 7 lateral incisors (21.2%), and 12 canines (36.4%). The mean number of SNCs was 1.86 (\(\pm\)0.77) in central incisors, 1.86 (\(\pm\)1.06) in lateral incisors, and 2.90 (\(\pm\)2.30) in canines. The most frequent SNC numbers were one or two (in 23 cases, 69.7%). The highest detected number of supernumerary canals was eight (in one canine, 3%). The 33 teeth had 72 SNCs in all. Descriptive statistics of the study sample are given in Table 2.  
CT scans after the semicircular sections revealed two remaining SNCs in two different teeth altogether. After this, all specimens underwent a corrective (straight-line) section. After the straight-line sectioning, a residual SNC remained within one root only. Interestingly, in this specific sample, the SNC was located exactly at the level of the straight cut, slightly coronally--so that even with the classical straight resection, it persisted. Thus, the semicircular section eliminated all SNCs in 94% of the study samples, and it eliminated 97.3% of the total number of SNCs in all study samples. The success rate of the straight-line cut regarding the total number of SNCs in all study samples was 98.6% and 96.97% for the SNC-containing teeth.  
The changing of the SNC numbers during the process is shown in Table 3, for an easier understanding of our results.  
\begin{table}
\begin{tabular}{c c c c c c} \hline  & **INIT** & **VIS** & **TI** & **PS** & **FS** \\ \hline Teeth (N) & 200 & 188 & 76 & 66 & 33 \\ \hline Percentage (\%) & NA & 100\% & 40.4\% & 35.1\% & 17.6\% \\ \hline \end{tabular}
\end{table}
Table 1: Specim numbers after each step of the progressive selection method. The sequence was to verify the presence of ramifications/lateral canals. INIT: initial specimen count (full sample); VIS: visual screening; TI: transillumination; PS: prescan; FS: full scan (see text).  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c} \hline \multirow{2}{*}{
\begin{tabular}{c} **SNC** \\ **Count** \\ \end{tabular} } & \multicolumn{4}{c}{**Central incisor (N = 14)**} & \multicolumn{4}{c}{**Lateral incisor (N = 7)**} & \multicolumn{4}{c}{**Canine (N = 12)**} & \multicolumn{4}{c}{**Total (N = 33)**} \\ \cline{2-13}  & **N\({}_{\text{TETEH}}\)** & **\%** & **N\({}_{\text{SNC}}\)** & **\%** & **N\({}_{\text{TEH}}\)** & **\%** & **N\({}_{\text{SNC}}\)** & **\%** & **N\({}  
To compare the efficiency of the circular and straight approaches in terms of how many teeth still contained SNCs after their application (regardless of the number of SNCs), the McNemar test was used. After the application of the semicircular trephine, 2 of the 33 teeth contained SNCs, while after the application of the semicircular trephine, 1 of the 33 teeth contained SNCs. The McNemar test yielded a non-significant result (\(\chi^{2}=1.00\), df = 1, and \(p=0.317\)), indicating no significant difference in the occurrence of SNCs between the circular and straight approaches. In other words, had the straight cut not been applied after the semicircular cut, the result would not have been statistically inferior.