The disadvantages of the visual/tactile indices described above are overcome by a newly developed assessment instrument termed the “Caries Assessment Spectrum and Treatment” (CAST) instrument [19]. It was introduced for the assessment of dental caries-related conditions and treatment in epidemiological surveys and designed to overcome the shortcomings of the indices/systems described above. It permits the registration of sound teeth, sealants, restorations, enamel, and dentine carious lesions, advanced stages of carious lesions into the pulp and tooth-surrounding tissues, and teeth lost from dental caries (Table 1). The assessment is performed visually, with the naked eye, and does not use compressed air for drying tooth surfaces. CAST consists of 10 codes that are ordered hierarchically. This implies that a sealant (code 1) is less severe than an enamel carious lesion (code 3), and that a dentine carious lesion that can be restored (code 5) is less severe than a tooth with a carious lesion with pulpal involvement (code 6).
Research showed that the CAST instrument has face, content, construct, and external validity for use in children and adults [20, 21] and has a high level of reproducibility [22]. The CAST codes can be converted to dmf/DMF counts so that dmf/DMF scores can be compared with those obtained from using the WHO index [23]. A restoration (code 2) and a tooth lost due to dental caries (code 8) is considered not diseased. With CAST, a caries-diseased tooth is one that has a dentine carious lesion (codes 4, 5) or has pathology (code 6, 7). This affects the determination of the prevalence of dental caries in a population, as discussed in the next section.
The CAST instrument needs to be tested in populations of different ages and backgrounds than those studied so far. CAST has been used or is in use in epidemiological surveys in Brazil [23], India [24], Pakistan [25], Poland [26], Mozambique, Peru, Russia, Surinam, and Turkey.
Reporting Data from Caries Epidemiological Surveys
The manner in which results are reported is important. Documents that describe epidemiological surveys are not restricted to dental professionals. Policy makers, medical practitioners, politicians, and the public have access to such documents, which requires clear reporting and should be straightforward and supported with easily understandable tables and figures. To make caries epidemiological reports easy to read a few typical dental inherited approaches from the past need to be changed, such as the use of the dmf/DMF index, which dates back to 1938 and contains a number of deficiencies.
Table 1. The validated CAST characteristics, codes and descriptions
An inherent deficiency is its use in calculating the prevalence of dental caries. By definition, the presence of carious lesions into dentine, restored dentine lesions, and missing teeth due to dental caries (D3MFT) make up the prevalence of dental caries. If required, the code for enamel carious lesion(s) can be included in the prevalence calculation, but this has to be clearly stated (D1MFT or D2MFT). The present definition covers not only actual disease but also past disease (restored and missing teeth). The advantage of considering teeth restored and teeth lost due to dental caries not diseased anymore is that dental caries prevalence is calculated on the bases of the actual presence of the disease in the individual. This reasoning was one of the cornerstones of the development of CAST. It holds the advantage of depicting the state of the disease and monitoring its changes over time in society more reliably. For example, successful interventions cannot be evidenced by a lower prevalence score [27].
In principle, studies that use CAST do not report the results in dmf/DMF counts but a dmf/DMF count can be calculated using CAST codes [23]. CAST uses frequency distributions per caries code or for maximum CAST code, depending on the aim of the survey (Fig. 1, 2). The severity of caries-related conditions within an individual or group after using CAST is calculated according to a mathematical formula in which the CAST codes have been assigned a weighted coefficient of severity [28]. Those wishing to know more about how to apply CAST and how to report data are referred to the CAST manual [29].
Global Epidemiology of Dental Caries
A recent publication reported on the global epidemiology of dental caries [30]. The paper was based on a systematic review of systematic reviews on the prevalence and incidence of dental caries. As only one systematic review was retrieved covering 1990–2010, and this review had limited background variables [31], the WHO Data Bank at Malmö University Dental School [32] was used to obtain more detailed information. The Data Bank contains dental caries-related data, covers several decades of studies, and is periodically updated. The country dental caries prevalence and the dmf/DMF and d/D-component data from the recommended WHO age groups were used as outcome measures for the period from 2000 to 2016. These data were related to the countries’ gross national income [33], developed by the World Bank, according to high-, upper-middle-, lower-middle-, and low-income countries.
Fig. 1. Maximum CAST score per subject and type of dentition based on hypothetical results. Modified from Leal et al. [57].
Fig. 2. Severity of dental caries based on the maximum CAST score per subject. Modified from Leal et al. [57].
The publication also reported trend studies that had covered a period of at least 20 years, from 1999 to 2016. The caries assessment criterion developed by the WHO (1971) was used most frequently.
Global Burden of Untreated Cavitated Dentine Carious Lesions
The systematic review dealt with the global burden of untreated cavitated dentine carious lesions and covered 187 countries [31].