Evaluation of the conditions of endodontically treated teeth before and after orthodontic treatment

Objective: This retrospective study aimed to assess the presence and amount of external apical root resorption (EARR) of endodontically treated teeth and contralateral vital teeth following the orthodontic treatment, to research the relationship between resorption and possible risk factors such as orthodontic treatment type, treatment duration, gender and age of the patients. Method: This retrospective study included 503 patients with 620 endodontically treated teeth and 580 contralateral vital teeth. The crown and root length of the teeth were measured on digital panoramic radiographs taken in the beginning and at the end of orthodontic treatment for each patient. By comparing the crown/root ratios pre- and post-orthodontic treatment, the percentage of EARR in the endodontically treated teeth and contralateral vital teeth was calculated. The comparison of one- and two-phase treatment groups according to the extraction decision was performed and the extraction and non-extraction treatment groups were then compared based on the treatment phases. Moreover, endodontically treated teeth and contralateral vital teeth were compared with each other in terms of the percentage of EARR according to the treatment phase and extraction decision. Shapiro-Wilk test was used for the normality of the sample. Mann-Whitney U Test, Independent Samples t Test, Wilcoxon-Signed Rank Test, Paired t Test, Mc Nemar Test and Spearman Correlation Test were applied for comparisons and to test the correlations. Results: A statistically significant difference was observed in all orthodontic treatment groups when endodontically treated teeth and vital teeth were compared in terms of EARR (p<0.05). EARR were positively correlated with orthodontic treatment duration and type (p<0.05), but was not influenced by patient's age and gender. Statistically significant EARR was observed in the two-phase extraction orthodontic treatment group in both endodontically treated teeth and vital teeth (p<0.05). In vital teeth, a statistically significant EARR was found in one phase extraction treatment group compared to non-extraction treatment group, while no significant difference was found in endodontically treated teeth. Conclusion: Endodontically treated teeth showed significantly less EARR than vital teeth. The EARR in endodontically treated teeth might not be a significant factor to take into account when planning orthodontic treatment.