## 4 Discussion  
The aim of this study was to investigate the association between facial typology and gingival biotype in pre-orthodontic patients in order to guarantee a better diagnosis and planning of orthodontic treatment. We tested whether the facial typology measured on two-dimensional cephalograms (SN\({}^{\circ}\)GoGn and CoGoMe\({}^{\circ}\)) or on three-dimensional facial scans (SNMe/NMe) could affect gingival biotype. No association was found between facial typology assessed using the two-dimensional angles SN\({}^{\circ}\)GoGn or CoGoMe\({}^{\circ}\) and maxillary and mandibular gingival biotype of the anterior regions. There is one study that correlates craniofacial morphology using magnetic resonance imaging (MRI) with tooth root exposure and periodontal attachment loss. The study used the ratio of facial width and length (facial index) to describe craniofacial morphology and showed that patients with long narrow faces were associated with higher loss of attachment [37]. A recent study performed by [PERSON] et al. has investigated the relationship between gingival phenotype and craniofacial morphology in the sagittal and vertical directions. In contrast to this research, an endodontic file, namely, transgingival probing, was used to assess gingival phenotype (\(<\)1 mm and \(>\)1 mm, thin and thick phenotype, respectively). These results demonstrated that there is no association between gingival thickness and craniofacial typology [26]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Model** & **Variable** & \(p\)**Value** & **Odds Ratio (OR)** & **95\% IC** \\ \hline Upper biotype (SNMe/NMe) & SNMe/NMe & **0.036 \({}^{*}\)** & 0.843 & 0.719–0.989 \\ Lower biotype (SNMe/NMe) & SNMe/NMe & **0.049 \({}^{*}\)** & 0.904 & 0.818–0.999 \\ \hline Upper biotype (SNMe/NMe \(\times\) Age) & SNMe/NMe & **0.034 \({}^{*}\)** & 0.839 & 0.714–0.987 \\ Age & **0.620** & 0.985 & 0.927–1.046 \\ \hline Lower biotype (SNMe/NMe \(\times\) Age) & SNMe/NMe & **0.048 \({}^{*}\)** & 0.903 & 0.815–0.999 \\ Age & **0.207** & 0.976 & 0.939–1.014 \\ \hline \hline \end{tabular} Data are presented as OR and IQR. \({}^{*}\) and bold text indicate statistically significant values (\(p<\) 0.05).  
\end{table} 
Table 4: Logistic regression model for SNMe/NMe ratio \(\times\) 100 with and without including age as a coviariate. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Facial Typology (N)** & **Upper Gingival Biotype** & & \\ \hline  & Thick & Thin & \(p\) value \\ Brachyfacial (33) & 29 (27.62\%) & 4 (25.00\%) & 0.83 \\ Mesofacial (59) & 50 (47.62\%) & 9 (56.25\%) & \\ Dolichofacial (29) & 26 (24.76\%) & 3 (18.75\%) & \\ Total (121) & 105 (100\%) & 16 (100\%) & \\ \hline  & \multicolumn{3}{c}{**Lower Gingival Biotype**} \\ \hline  & Thick & Thin & \(p\) value \\ Brachyfacial (33) & 16 (25.40\%) & 17 (29.31\%) & 0.75 \\ Mesofacial (59) & 33 (52.38\%) & 26 (44.83\%) & \\ Dolichofacial (29) & 14 (22.22\%) & 15 (25.86\%) & \\ Total (121) & 63 (100\%) & 58 (100\%) & \\ \hline  & \multicolumn{3}{c}{**Gingival Biotype**} \\ \hline  & Thick/Thick & Thick/Thin & Thin/Thin & \(p\) value \\ Brachyfacial (33) & 16 (25.40\%) & 13 (30.95\%) & 4 (25\%) & 0.77 \\ Mesofacial (59) & 33 (52.38\%) & 17 (40.48\%) & 9 (56.25\%) & \\ Dolichofacial (29) & 14 (22.22\%) & 12 (28.57\%) & 3 (18.75\%) & \\ Total (121) & 63 (100\%) & 42 (100\%) & 16 (100\%) & \\ \hline \hline \end{tabular} Data are presented as numbers, percentages, and \(p\) values.  
\end{table} 
Table 3: Classification of gingival biotype in patients with different facial typologies (classified according to SN\({}^{\circ}\)GoGn) using a 15 mm North Carolina probe. In this study, facial typology was also evaluated with three-dimensional facial scans to assess the association between SNMe/NMe and gingival thickness. Our analysis showed that facial proportions have a statistically significant association with gingival biotype.