This study aimed to evaluate the precision of the guided endodontic technique applied to calcified canals in anterior teeth in relation to demographic and dental variables. The present observational study was conducted during the period 2020–2021. The patients were consecutive referrals at the Department of Endodontics and Conservative Dentistry of the University Hospital of Siena. The guided endodontics protocol was applied using 0.75 mm diameter burs for the lower teeth and 0.90 mm for the upper teeth. The inclusion criteria were as follows: (i) teeth with pulp canal obliteration (PCO) associated with a periapical lesion (periapical index (PAI) ≥ 2); (ii) teeth with PCO that require the placement of a root canal post for the execution of a prosthetic treatment; (iii) teeth in which surgical treatment was not justified. Socio-demographic characteristics of the patients were recorded and related to the drill path accuracy through the guide in the calcified endodontic canal, evaluated through a radiographic analysis, and classified as optimal (in the center of the root canal) and acceptable (deviated peripherally/tangentially). A logistic regression model was built to predict the factors that influence the poor precision of the technique. Seventeen patients (mean age 48 years) with eighteen calcified single-rooted teeth were enrolled. All teeth were associated with periapical lesions with PAI scores from 2 to 5 (mean PAI: 3.055). From the model, it is evident that the presence of a calcification affecting the apical area of the root increases the probability of being off-center with the bur by about 15 times. In addition, a previous attempt at endodontic treatment and the position in the lower arch increases the probability of non-centrality of the drill, although in a non-statistically significant way. In any of the analyzed cases, the guided endodontic technique applied to PCO did not determine the presence of iatrogenic errors, such as perforations. However, the apical localization of the obliteration increases the probability of being off-center with the drill during the instrumentation phase by about 15 times.

Background/Aim: Third molar impaction with the consequent root resorption of second molars often creates complexities in treatment planning and execution. In the past, the root canal treatment (RCT) of second molars was required in these cases to avoid pulp necrosis and infection. The aim of this paper is to report a surgical/retrograde approach for the maintenance of pulp vitality, proposed as retrograde vital pulp treatment (rVPT), in cases of asymptomatic or reversibly affected teeth with root resorptions caused by impacted adjacent teeth. Methods: A case report on the rVPT of two upper second molars with root resorption due to third molar impaction is presented. The chief complaint of the patient was a slight pain during bite involving the upper second molars. Heat and cold sensitivity tests were performed, suggesting a healthy pulp status. A cone beam computed tomography (CBCT) scan was performed to aid the diagnosis and treatment planning, showing bilateral upper third molar impaction and both distal roots of the upper second molars affected by external root resorption (ERR). In both cases, the third molar was surgically extracted, the surface of the root with ERR was smoothened and rVPT was carried out by performing a 3 mm retrograde preparation of the root canal and its retrograde sealing using a hydraulic calcium silicate-based cement (hCSCs). Results: Heat and cold sensitivity tests were performed 1 month, 3 months, 6 months and 1 year after the treatment. The patient reported no pain, and the pulp sensitivity was maintained in all follow-up periods. A CBCT scan was performed 24 months after the treatment, reporting a complete perirradicular endogenous bone apposition. Conclusions: Based on the successful clinical and radiographic outcomes observed in the present case after two years of follow-up, rVPT is proposed for the maintenance of pulp vitality in cases of asymptomatic or reversibly affected teeth with ERR caused by impacted adjacent teeth.