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Development and External Known-Groups Validation of a Severity-Adjusted Caries Index (SACI): An Age-Stratified
Ömer Hatipoğlu1, İremnur Bal2, Esma Nur Güney3
1Corresponding author at Department of Restorative Dentistry, Recep Tayyip Erdoğan University, Turkey.
Background:
Conventional caries indices, such as Decayed, Missing, and Filled Teeth (DMFT) and Decayed, Missing, and Filled Surfaces (DMFS), remain widely used. However, they do not adequately distinguish between lesion severity, restoration extent, and caries-related tooth loss, nor do they account for differences in the available tooth surfaces. This study aimed to develop a Severity-Adjusted Caries Index (SACI), an age-stratified and surface-normalized composite index designed as a structurally differentiated refinement of conventional cumulative caries-burden measures, and to evaluate its external known-groups validity.
Methods:
This two-phase methodological cross-sectional study included a derivation cohort of 223 adults and an independent external validation cohort of 200 adults, including 100 participants with type 1 diabetes mellitus (T1D) and 100 controls without diabetes. The SACI integrates ICDAS-based caries lesion severity, restoration extent, and caries-related tooth loss within a surface-normalized framework. Age-specific weights were derived separately for participants aged <35 and ≥35 years using a deterministic exact constrained search against a composite optimization target incorporating CAMBRA-derived burden measures and conventional caries indices. External known-groups validation assessed the discriminatory performance against T1D status using ROC analysis, logistic regression, and pairwise DeLong comparisons.
Results:
The SACI showed clear age-specific weighting patterns. In the derivation phase, the final age-specific models showed moderate correlations with the composite target (Pearson r=0.641 for <35 years and 0.638 for ≥35 years). Nested 5-fold cross-validation of the complete weight-selection procedure yielded pooled out-of-fold R² values of 0.345 and 0.315, respectively. In the validation cohort, SACI was significantly higher in participants with T1D than in controls (p<0.001) and showed the highest discriminatory performance among the evaluated indices (AUC=0.671), compared with DMFT (AUC=0.606) and DMFS (AUC=0.572).
Conclusions:
SACI provided a more structurally differentiated and age-sensitive representation of cumulative caries burden than conventional unweighted indices and showed greater discrimination of T1D status in an independent adult cohort. These findings support SACI as a potential refinement of conventional caries-burden assessment rather than as a wholly distinct construct. Further validation against direct caries-related outcomes and in broader populations is warranted.
Clinical Significance:
Conventional caries indices may not fully reflect the structural complexity of caries experience in adults because they treat lesions, restorations, and tooth loss as equivalent components. SACI provides a severity-weighted, age-sensitive, and surface-normalized refinement of cumulative caries-burden assessment by incorporating lesion severity, restoration extent, and caries-related tooth loss. It is intended to complement and refine, rather than replace, conventional indices such as DMFT and DMFS.
