Repeatability and reproducibility of a new classification for measuring primary stability of dental implants based on...

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.

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.

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).

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.