# The Impact of Orthodontic Treatment on Pre-Existing Gingival Recessions: A Retrospective Study
## 3 Results
### Gingival Recession Change at Tooth Level
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{5}{c}{**Gingival Recessions at Tooth Level (mm) Median (Q1; Q3)**} \\ \hline
**Pre-Treatment Variable** & **N** & **T0** & **T1** & **Change To–T1** & \(p\) \\ \hline - & 114 & 1.48 (1.02; 2.03) & 0.65 (0; 1.30) & 0.55 (0.12; 0.96) & 0.001 \\ \hline Dental Angle I & 50 & 1.52 (1.02; 2.02) & 0.95 (0.54; 1.13) & 0.59 * (0.19; 1.11) & 0.001 \\ Dental Angle II & 36 & 1.40 (0.98; 2.06) & 1.04 (0.60; 1.35) & 0.66 (0.15; 0.90) & 0.001 \\ Dental Angle III & 28 & 1.36 (0.99; 2.21) & 1.09 (0.92; 1.44) & 0.20 * (-0.08; 0.59) & 0.018 \\ \hline Normal overbite & 77 & 1.36 (1.04; 1.97) & 0.95 (0.54; 1.27) & 0.55 * (0.18; 0.92) & 0.001 \\ Open bite or edge to edge & 19 & 1.16 (0.95; 1.56) & 1.03 (0.95; 1.57) & 0.11 * (-0.12; 0.52) & 0.40 \\ Deep overbite & 18 & 2.08 (1.07; 2.81) & 1.17 (0.60; 1.95) & 0.86 * (0.49; 1.14) & 0.001 \\ \hline Overjet \(<\) 4 mm & 82 & 1.34 (1.05; 1.91) & 1.02 (0.60; 1.31) & 0.51 (0.10; 0.87) & 0.001 \\ Overjet \(\geq\) 4 mm & 32 & 1.86 (0.98; 2.33) & 1.08 (071; 1.53) & 0.76 (0.27; 1.11) & 0.001 \\ \hline Labial tooth position due to crowding & 38 & 1.56 (1.00; 2.32) & 0.99 (0.49; 1.95) & 0.57 (0.09; 0.97) & 0.001 \\ Labial/buccal root inclination & 48 & 1.36 (1.00; 2.02) & 1.01 (0.80; 1.23) & 0.54 (0.14; 1.02) & 0.001 \\ Traumatic contact & 28 & 1.31 (1.05; 2.13) & 1.08 (0.58; 1.55) & 0.52 (0.08; 0.98) & 0.001 \\ \hline Thin biotype & 39 & 1.17 (0.94; 1.64) & 0.95 (0.61; 1.21) & 0.43 * (0; 0.57) & 0.001 \\ Normal/thick biotype & 75 & 1.63 (1.14; 2.12) & 1.05 (0.66; 1.42) & 0.74 * (0.13; 1.08) & 0.001 \\ \hline \hline \end{tabular} \(p\) by Wilcoxon signed ranks test; \(p\) = 0.004 by 1-way ANOVA difference in GR change between three Angle groups and \(p\) = 0.003 by Post Hoc Bonferroni test difference in GR change between Engel III and DTI patients; _*_ = 0.001 by Kruskal-Wallis Test difference in GR change between three overbite groups and \(p\) < 0.01 by Post Hoc Dunn’s test.**_p_ = 0.003 by Student’s t-test.  
\end{table} 
Table 3: Pre-treatment variables and gingival recessions before (T0) and after (T1) orthodontic treatment and recession change T0–T1 at tooth level. Figure 8: Median gingival recession change before and after orthodontic treatment in different groups of teeth. \({}^{\circ}\),*- outliers. A significant difference in GR change was found between three Angle classification (\(p\) = 0.004) and overbite (\(p\) = 0.001) groups. The smallest GR change was found on teeth in Angle III and open bite patients. Teeth with thin gingival biotype were the less prone to GR improvement compared to thick/normal gingival biotype (\(p\) = 0.003). Univariate binary logistic regression analysis revealed a significant association between GR improvement \(\geq\)0.5 mm and overbite group (<1/\(\geq\)1 mm), also GR improvement \(\geq\)0.5 mm and Angle classification group (Angle III and Angle I/II). A reduced trend for GR improvement was observed in open bite (OR 3.89; 95% CI: 1.35, 11.16; \(p\) = 0.008) and Angle's class III participants (OR 2.6; CI: 1.11, 6.0; \(p\) = 0.026). No statistically significant association between GR improvement \(\geq\)0.5 mm and biotype (thin and normal/thick) group was found (\(p\) = 0.12). Analysis showed collinearity between overbite and Angle classification groups (r = 0.25 \(p\) < 0.008) and therefore multivariate regression analysis was not performed.