The Outcome of Old-School Indirect Pulp Capping over 40 Years: A Practice-Based Retrospective Evaluation

(1) <b>Background:</b> The aim of this in vitro study was to evaluate the success of indirect pulp capping (IPC) procedures over a period of 40 years. (2) <b>Methods:</b> The investigation of 1412 dental records included 159 patients with 366 IPC teeth having been treated from 1969 to 1980. The teeth revealed caries within the inner third of dentin, were symptom-free, and showed no pulp exposure. The caries were excavated thoroughly and teeth with accidentally exposed pulp were excluded. Zinc-oxide-eugenol was used for the IPC procedures. The posterior teeth were restored with amalgam, and the anterior teeth received direct resin composite fillings. The gathered parameters with possible influences on survival rates were age, gender, tooth locations/positions, dates of vital therapy, the number of filled surfaces, types of primary restoration material, successional treatments on each tooth, and the last dates of surveillance. Data collection and statistical analysis were performed using Excel sheets and DataTab. Significant differences among groups were computed by cox regression analysis and the significance level was set at <i>p</i> = 0.05. Kaplan-Meier curves were utilized to illustrate the survival rates. (3) <b>Results:</b> Treatment success was measured by the maintenance of vitality beyond 365 days. The loss of vitality within 365 days was determined as treatment failure. Treatment outcomes were assessed after different time periods (1 and 6 months; 1, 2, 5, 10, 20, and 40 years). Pulp vitality dropped from 95% after 3 months to 32% after 40 years. Cavity size had a significant influence on the survival of pulp, but tooth position did not; however, third molars at least initially showed a better outcome. Beyond the 1-year recall, no differences for the evaluated parameters were present. (4) <b>Conclusions:</b> IPC showed excellent long-term success rates, revealing a 1.7% annual failure rate after 40 years of clinical service. Larger defects suffer more pulp damage in the long run.