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

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.