Accuracy of surrogate outcomes in predicting true endpoints of surgical periodontal therapy. A narrative review with a 20‐year longitudinal analysis

Abstract Background Periodontal clinical trials commonly use surrogate end points (e.g., probing pocket depth PPD, clinical attachment level CAL, bleeding on probing BoP, and composite scores such as the Periodontal Risk Score PRS) for efficiency, yet tooth loss, treatment burden/cost, and re‐treatment are the definitive patient‐relevant measures of long‐term success. Methods This mixed‐methods study evaluated the predictive performance of three surrogate definitions and contextualized the findings with a 50‐year narrative review of longitudinal evidence linking PPD, CAL, and BoP to tooth retention. Additionally, a retrospective cohort (2001–2024) of 160 patients (919 teeth) treated at the University of Michigan was studied. Each participant had baseline PPD ≥6 mm after initial therapy (sites nonresponsive to initial nonsurgical therapy) and received up to 20 years of supportive periodontal therapy (SPT) following active periodontal therapy (APT). Three surrogate definitions: TEP A (no pockets ≥6 mm), TEP B (pockets ≤4 mm without BoP), and the PRS were compared against two true end points: tooth loss due to periodontitis (TLP) and need for additional therapy (re‐treatment). Logistic regression with generalized estimating equations was used to estimate sensitivity, specificity, positive/negative predictive values, and area under the curve (AUC). Results Overall, tooth loss was 28.4%, with 18.9% due to periodontitis. Additional treatment was required by 91.5% of patients. For TLP, TEP‐B provided the highest sensitivity, whereas PRS = 3 provided the highest specificity and positive predictive value (AUC = 0.556, p = 0.021). PRS ≥2 showed the best overall discrimination/accuracy for TLP (AUC = 0.637, p < 0.001). TEP‐A and TEP‐B demonstrated modest discrimination (AUC = 0.567, p < 0.007 and AUC = 0.549, p = 0.047, respectively). For re‐treatment, TEP‐B yielded 82.2% sensitivity, and PRS = 3 demonstrated 96.6% specificity (PPV = 96.8%); PRS ≥2 alone achieved AUC = 0.625 ( p = 0.033), while no significant differences were observed among the remaining models. Conclusions For practical application, baseline risk stratification can be performed using PRS ≥2 to support early screening for periodontitis‐related tooth loss, while PRS = 3 can be reserved for high‐confidence confirmation when minimizing false positives is critical. During postsurgical follow‐up after APT and throughout SPT, TEP‐B (PPD ≤4 mm with no BoP) can be used as the primary monitoring target to flag likely instability and identify teeth likely to require re‐treatment, whereas PRS = 3 can be applied to guide final treatment decisions or resource‐intensive interventions.