Survival study on teeth after successful endodontic surgical retreatment: influence of crown height, root length, crown-to-root ratio and tooth type

Aim: To assess the influence of the crown height, root length, crown-to-root ratio, and tooth type on the survival of teeth subjected to surgical endodontic retreatment and classified as periapically healed. Methodology: A single operator performed endodontic microsurgery interventions between 2008 and 2018 on teeth with refractory apical periodontitis. The present analysis selected the teeth classified as ‘‘complete periapical healing’’ according to the scale suggested by Molven. The postoperative periapical radiographs and those taken at the last recall visit were analysed by two independent calibrated examiners, who measured crown height and root length in a blind manner. The crown-to-root ratio was calculated as the ratio of the two variables. The level of inter- and intra-operator agreement was tested with Bland—Altman plots with 95% limits of agreement. An independent statistician conducted a survival analysis using Kaplan—Meier plots and a log-rank test (a = 0.05) to assess the significance of the differences among the subgroups defined by the following criteria: (a) crown height <median vs. >median; (b) root length <median vs. >median; (c) crown-to-root ratio <1 vs. >1; (d) crown-to-root ratio <median vs. >median; (e) single-rooted teeth vs. multi-rooted teeth. Results: At the end of the analysis, 42 patients were evaluated, each one contributing to the study with a single tooth. The mean follow-up period was 4.2  2.4 years. Survival estimates were significantly improved for the teeth with roots longer than 8 mm, in comparison with that with shorter roots ( p < 0.05). There were no statistically significant differences among the remaining considered subgroups. Conclusions: Under the conditions of this retrospective study, teeth with longer residual roots after apical surgery exhibited better chances of survival when compared to teeth with roots shorter than 8 mm. The other considered variables did not seem to affect the survival of apically resected teeth.