Under the lens: Critical review of dental caries indices

INTRODUCTION

Dental caries remains one of the most prevalent chronic oral diseases worldwide and continues to pose significant challenges to both clinical practice and public health systems. Despite major advancements in diagnostic technologies, preventive strategies, and restorative techniques, the global burden of dental care persists, particularly in populations with limited access to oral healthcare.^[1] Accurate and standardized measurement of caries is essential for understanding disease burden, monitoring trends, planning interventions, and evaluating the effectiveness of preventive programs. Traditional indices such as the decayed, missing, and filled teeth (DMFT) index have long served as foundational tools in epidemiology due to their simplicity and ease of application. However, they are limited in their ability to detect early, non-cavitated lesions and do not differentiate between stages of disease progression.^[2]

In response to these limitations, modern diagnostic systems – including the International Caries Detection and Assessment System (ICDAS), the pulpal involvement, ulceration, fistula,abscess (PUFA) index, the caries assessment spectrum and treatment (CAST) index, and activity-based systems such as Nyvad’s criteria – have emerged to provide more nuanced and comprehensive assessments. These indices vary widely in complexity, diagnostic sensitivity, and clinical applicability.^[3] Given the diversity of available tools and the absence of a universally optimal index, selecting the most appropriate system depends on the specific purpose— whether clinical diagnosis, epidemiological surveillance, school screenings, or clinical trials. This review aims to provide a clear and comparative evaluation of commonly used dental caries indices to guide their appropriate selection and application in both research and clinical settings.^[4]

DENTAL CARIES INDICES

Russel AL defines Index as a numerical value describing the relative status of the population on a graduated scale with definite upper and lower limits, which is designed to permit and facilitate comparison with other populations classified with the same criteria and the method. The ideal requisites of an index are detailed in Figure 1. Dental caries indices play a central role in understanding disease distribution, monitoring trends, and guiding clinical and public health decision-making. Over the decades, numerous indices have been developed in response to evolving concepts of caries as a dynamic, multifactorial disease rather than a purely cavitated condition [Table 1]. These indices differ in their scope, diagnostic thresholds, complexity, and applicability, ranging from traditional measures of cumulative caries experience to contemporary systems emphasizing early lesion detection, disease activity, and treatment needs. A comprehensive review of dental caries indices is therefore essential to critically evaluate them and to assist clinicians, researchers, and policymakers in selecting the most appropriate index for specific objectives, which is depicted in Table 2.

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Figure 1: Fundamental requisites of an ideal index.

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DISCUSSION

Caries measurement methods vary considerably, making the comparison problematic among different indices. Campus et al.,^[5] conducted a cross-sectional study, where four caries measurement methods, the World Health Organization’s decayed, missing, and filled teeth (WHODMFT), the ICDAS, the CAST, and the Nyvad Criteria were tested among 12-year-old children. The greatest difference among methods was shown by the number of sound teeth. At the level of dentinal distinct/active cavitated lesions, no statistically significant difference was observed, and in the severe caries levels, all methods were partially in agreement, while no accordance was found for the initial (enamel) lesions, concluding that clinicians have to select the caries detection method that best fits with their daily outcome. Table 3 summarizes the strength and limitations and how various indices differ in their applicability in clinical, epidemiological, and public health contexts. Traditional indices such as DMFT/decayed, missing, filled surfaces (DMFS) and def/defs remain indispensable in epidemiological surveillance owing to their operational simplicity, reproducibility, and historical acceptance.^[6,7] Their cumulative scoring enables trend analysis and cross-population comparisons; however, they inherently underestimate disease burden by excluding early non-cavitated lesions and failing to differentiate between lesion severities. By assigning equivalent scores to untreated carious teeth and successfully restored teeth, these indices may misrepresent current disease activity and preventive care outcomes. In addition, in older populations, tooth loss recorded within these systems may reflect periodontal disease or trauma rather than caries, thereby compromising diagnostic specificity.^[8-10]

In contrast, diagnostic systems such as Nyvad’s criteria^[11] and ICDAS^[12,13] represent a shift toward early detection and disease activity assessment. ICDAS provides a standardized visual framework capable of identifying initial enamel changes through advanced cavitation, supporting preventive and minimally invasive approaches. Nyvad’s system further refines diagnosis by distinguishing active from inactive lesions, making it particularly valuable for longitudinal monitoring. Despite these advantages, both systems require extensive examiner training, meticulous calibration, and increased examination time. Their technique-sensitive nature and reliance on examiner expertise limit feasibility in large-scale surveys and resource-limited settings.^[14,15]Indices designed to assess disease severity and consequences, including PUFA^[16] and CAST,^[17] emphasize treatment needs rather than early diagnosis. PUFA is particularly effective in highlighting advanced, untreated care and associated complications, thereby identifying populations with urgent care requirements. However, its focus on severe outcomes excludes early disease stages and may inadvertently include non-caries-related oral pathology. CAST offers a more integrated approach by mapping caries progression from sound teeth to complications and restorations within a single framework, enhancing its utility for community surveys and health service planning. Nevertheless, the absence of lesion activity assessment limits its preventive orientation.^[18]

Several indices address specific analytical objectives. The Significant Caries Index^[19] and Caries Susceptibility Index^[20] high-risk subgroups by focusing on individuals with the highest disease burden, thereby drawing attention to oral health inequalities. While useful for targeted interventions, it lacks diagnostic detail and cannot function independently as a caries assessment tool.^[15] Similarly, indices such as the Specific Caries Index,^[21] Stones Index,^[22] D1-D4 scale,^[23] Root Caries Index,^[24,25] WHO Dentition status^[26] and Moller’s Index^[27] provide qualitative insights into lesion distribution and surface-level involvement but are limited by radiographic dependence, complexity, or reduced sensitivity to proximal lesions.^[28] Across all indices, critical methodological gaps persist. Few systems integrate early lesion detection, activity status, severity grading, and clinical consequences within a single, feasible framework.^[29,30] Inter-examiner variability, inconsistent diagnostic thresholds, and limited adaptability to digital diagnostics further constrain comparability across studies. Moreover, most indices remain static, failing to align with contemporary risk-based and longitudinal models of caries management.

The evolution of dental caries indices reflects the ongoing efforts to enhance diagnostic accuracy, clinical relevance, and epidemiological utility. Traditional indices remain valuable for large-scale studies, while contemporary systems support early detection and activity assessment. However, limitations persist, such as older indices overlooking early lesions, whereas advanced indices require significant training and resources. Across the literature, there is increasing consensus that no single index fully captures lesion initiation, progression, activity, and treatment needs. The findings of this review support a call for a unified diagnostic framework capable of addressing both clinical and public health goals.

CONCLUSION

While each dental caries index fulfills specific functions, none serves as a universal gold standard. Conventional indices such as DMFT/DMFS, def/defs, and the WHO basic methods remain indispensable for population-level surveillance and longitudinal trend analysis, while diagnostic systems, including ICDAS and Nyvad’s criteria, improve sensitivity through early detection of non-cavitated lesions and assessment of lesion activity. Indices such as the CAST provide a comprehensive, continuum-based evaluation by integrating disease severity with treatment needs, while the PUFA index specifically addresses the clinical consequences of untreated advanced caries. Overall, the selection of a caries index should be guided by the study objective, whether epidemiological monitoring, early diagnosis, evaluation of treatment needs, or identification of vulnerable populations. The future of research, practice, and education in cardiology requires the development of an integrated caries assessment framework that simultaneously captures lesion severity, activity, early detectability, and treatment requirements, enabling standardized, comprehensive, and patient-centered caries assessment across clinical and public health settings.