Clinical and Radiographic Evaluation of Primary Endodontic Treatment and Non-surgical Endodontic Retreatments

Background: Pulpitis and apical periodontitis are inflammatory conditions of the dental pulp and periapical tissues, primarily caused by microbial invasion. The global prevalence of pulpitis is considered high but underestimated, as up to 40% of cases are asymptomatic. Similarly, the prevalence of apical periodontitis varies widely (16-86%) depending on population characteristics, systemic conditions, and socioeconomic status, and it is reported to be higher in hospital settings. Endodontic therapy aims to disinfect and seal the root canal system, promoting healing of apical periodontitis or maintaining periapical health. Reported success rates for primary and non-surgical retreatment procedures are comparable (75% and 77%, respectively), though outcomes tend to be more favorable in vital teeth compared to those with apical periodontitis (84% vs. 75%). Despite the widespread use of endodontic therapy, few studies have assessed treatment outcomes in a hospital setting. Objectives: The primary aim of this prospective study is to evaluate the success of primary and non-surgical endodontic retreatments performed in a hospital environment. Secondary objectives include assessing (1) the survival of treated teeth, (2) patient-related outcomes (PROs), and (3) the influence of systemic diseases or ongoing therapies on treatment outcomes. Methods: This is a monocentric, prospective, observational, study to be conducted at the Dental Clinic of the A. Gemelli University Hospital, Rome. Adult patients (\>18 years) requiring primary or non-surgical endodontic retreatment due to symptomatic or asymptomatic irreversible pulpitis, apical periodontitis, or acute/chronic abscesses will be enrolled after providing written informed consent in accordance with the Declaration of Helsinki. Exclusion criteria include inability to complete follow-up, vertical root fractures, advanced periodontal disease requiring extraction, pregnancy or breastfeeding, and inability to provide informed consent. Patients will undergo standard endodontic therapy according to the European Society of Endodontology (ESE) guidelines. Clinical and radiographic evaluations will be performed preoperatively, intraoperatively, and postoperatively. Radiographic assessments will be based on the Periapical Index (PAI), and follow-ups will occur at 6 months, 1 year, and annually for up to 4 years, with a final clinical follow-up at 5 years. Patient-related outcomes will be evaluated using the Numerical Rating Scale (NRS-12) for pain and the Oral Health Impact Profile (OHIP-14) questionnaire before treatment and at 1, 3, and 7 days post-treatment. Outcome Measures: The primary endpoint is the rate of endodontic success, defined by the absence of clinical symptoms (pain, swelling, sinus tract, tenderness) and radiographic healing or maintenance of periapical health (Periapical Apex Index, PAI). Secondary endpoints include the incidence of postoperative complications, survival rate of treated teeth, associations between systemic conditions and endodontic outcomes, and patient-reported outcome measures. Statistical Analysis: The sample size was calculated according to Lachin et al., assuming an expected success rate of 85%, a 5% margin of error, and 90% power, resulting in a minimum of 74 patients. Qualitative variables will be expressed as frequencies and percentages, while quantitative variables will be summarized as mean ± SD or median, depending on distribution. Normality will be tested with the Kolmogorov-Smirnov test. Associations between categorical variables will be evaluated using Pearson's χ² or Fisher's exact test, and continuous variables with Student's t-test, Mann-Whitney U, ANOVA, or Kruskal-Wallis tests as appropriate. Repeated measures ANOVA or Friedman tests will be applied to detect longitudinal changes. Mixed-effects models ((G)LMM) will be used to analyze changes in PAI, NRS-12, and OHIP-14 over time while adjusting for confounders. Logistic regression will identify independent predictors of success, and Kaplan-Meier survival curves (log-rank test) will estimate tooth survival over follow-up. Significance will be set at p \< 0.05. Statistical analyses will be performed using IBM SPSS Statistics v25.0 (IBM Corp., Armonk, NY, USA). Expected Results and Conclusions: This study is expected to provide data on the clinical and radiographic success rates of primary and non-surgical endodontic treatments performed in a hospital setting. It will also clarify the impact of systemic diseases and patient-related factors on treatment outcomes. The findings may help optimize clinical protocols and patient management strategies in hospital-based endodontic care, contributing to evidence-based improvement of dental services and patient quality of life.