Repeatability and reproducibility of a new classification for measuring primary stability of dental implants based on progressive insertion torque value: An analytical observational study.

Background: Assessing primary stability is critical to predicting dental implant success, yet existing assessments often rely on subjective judgment. This study presents and validates a classification system based on the progressive insertion torque value (PITV) to provide objective, reproducible parameters for guiding prosthetic loading protocols. Material and Methods: An analytical observational study was conducted on 1,250 implant torque-curve interpretations. Primary stability was classified into three types according to final insertion torque (IT): high (50 Ncm), moderate (30 to <50 Ncm), and low (<30 Ncm). Types I and II included four PITV subtypes (A-D), while Type III included six subtypes (A-F) based on curve trajectory patterns. Twenty-five dentists were trained in curve interpretation, and intra- and inter-examiner agreement was assessed using Cohen's and Fleiss' kappa statistics and prevalence- and bias-adjusted kappa (PABAK). Predictive validity was assessed using receiver operating characteristic (ROC) analysis (area under the curve [AUC] with 95% confidence intervals). Calibration (intercept and slope) and the Brier score were also computed. Results: Intraexaminer agreement was almost perfect in both general dentists and implant specialists (k = 0.82-0.95). Interexaminer agreement was also almost perfect (general dentists: k = 0.81; specialists: k = 0.89). Overall agreement was k = 0.84 (p < 0.001). The classification showed moderate predictive discrimination (AUC = 0.69, 95% CI: 0.56-0.81). Conclusions: The classification of primary stability based on the progressive insertion torque value in edentulous maxillary ridges showed high intraexaminer and interexaminer reliability in interpreting torque-time curves. Its clinical utility, predictive performance, and prosthetic loading thresholds were not assessed in this study and warrant prospective evaluation.