Association, prediction, generalizability: Cross-center validity of predicting tooth loss in periodontitis patients.

OBJECTIVES: To predict patients' tooth loss during supportive periodontal therapy across four German university centers. METHODS: Tooth loss in 897 patients in four centers (Kiel (KI) n = 391; Greifswald (GW) n = 282; Heidelberg (HD) n = 175; Frankfurt/Main (F) n = 49) during supportive periodontal therapy (SPT) was assessed. Our outcome was annualized tooth loss per patient. Multivariable linear regression models were built on data of 75 % of patients from one center and used for predictions on the remaining 25 % of this center and 100 % of data from the other three centers. The prediction error was assessed as root-mean-squared-error (RMSE), i.e., the deviation of predicted from actually lost teeth per patient and year. RESULTS: Annualized tooth loss/patient differed significantly between centers (between median 0.00 (interquartile interval: 0.00, 0.17) in GW and 0.09 (0.00, 0.19) in F, p = 0.001). Age, smoking status and number of teeth before SPT were significantly associated with tooth loss (p < 0.03). Prediction within centers showed RMSE of 0.14-0.30, and cross-center RMSE was 0.15-0.31. Predictions were more accurate in F and KI than in HD and GW, while the center on which the model was trained had a less consistent impact. No model showed useful predictive values. CONCLUSION: While covariates were significantly associated with tooth loss in linear regression models, a clinically useful prediction was not possible with any of the models and generalizability was not given. Predictions were more accurate for certain centers. CLINICAL RELEVANCE: Association should not be confused with predictive value: Despite significant associations of covariates with tooth loss, none of our models was useful for prediction. Usually, model accuracy was even lower when tested across centers, indicating low generalizability.

Long-term tooth retention in periodontitis patients in four German university centres.

OBJECTIVES: In this retrospective study, we compared tooth loss between patients receiving periodontal therapy (PT) in four German university centres, stratified according to periodontal treatment phase. MATERIALS AND METHODS: Overall, 896 patients (Kiel (KI) n = 391; Greifswald (GW) n = 282; Heidelberg (HD) n = 174; Frankfurt a.M. (F) n = 49) were examined initially (T0), after active periodontal therapy (APT, T1) and after supportive periodontal therapy (SPT, T2). Descriptive analyses and multivariable negative binomial regression models were performed. RESULTS: Follow-up periods differed significantly between the centres, ranging between 6.7 ±â€¯3.0 (GW) and 18.2 ±â€¯5.5 (KI) years (p < 0.001). At T0, age, gender, smoking and diabetes showed notable regional distinctions (p < 0.001). However, the number of teeth per patient was similar (between 24.0 ±â€¯4.6 (F) and 24.5 ±â€¯4.1 (HD); p = 0.27). During PT, the number of extracted teeth differed significantly between centres, with greater differences during SPT (0.9 ±â€¯1.8 (GW) to 2.3 ±â€¯2.8 (KI), p < 0.001) compared to APT (0.4 ±â€¯0.9 (F) to 1.0 ±â€¯2.1 (KI), p = 0.02). Annual tooth loss during SPT remained low in all centres (between 0.10 ±â€¯0.14 (F) to 0.15 ±â€¯0.30 (HD), p < 0.001). CONCLUSION: Within the limitation of the study, PT leads to a low risk of tooth loss in all university centres irrespective of patients' baseline characteristics. CLINICAL RELEVANCE: Within the limitations of this retrospective investigation, long-term tooth retention seems to be feasible for most patients, as long as a systematic and structured treatment approach is applied.