The Caries Assessment Spectrum and Treatment (CAST) index: rational and development

Abstract

Serious difficulties in reporting results were encountered when using ICDAS II and PUFA separately in an epidemiological survey in a child population in Brazil. That necessitated the development of a comprehensive but pragmatic caries assessment index. This publication describes the rationale, development and content of a novel caries assessment index. Strengths and weaknesses of ICDAS II, PUFA and other indices were analysed. The novel caries index developed for use in epidemiological surveys is termed ‘Caries Assessment Spectrum and Treatment’ (CAST). ‘Spectrum’ indicates what is considered the main strength of the new index – its usefulness in describing the complete range of stages of carious lesion progression: from no carious lesion, through caries protection (sealant) and caries cure (restoration) to lesions in enamel and dentine, and the advanced stages of carious lesion progression in pulpal and tooth-surrounding tissue. CAST combines elements of the ICDAS II and PUFA indices, and the M- and F-components of the DMF index. A DMF score can easily be calculated from the CAST score, thereby enabling retention of the use of existing DMF scores. The CAST index for use in epidemiological surveys is very promising. It should be validated and its reliability and usefulness be tested in different age groups in different countries and cultures.

INTRODUCTION

Dental caries is a dynamic disease that manifests as lesions of different sizes in enamel and dentine. The rate of carious lesion progression can be controlled through various caries- control measures; such as restricted ingestion of refined sugars, disorganisation of the biofilm, application of fluoride-containing vehicles and restoration of the cavitated carious lesion. It is widely accepted that carious lesions in enamel and dentine can be arrested and that their progression can recommence if caries-controlling measures are not effectively applied. Eventually, the caries process may decay large parts of the tooth, leading to ulceration, abscesses and infection of the alveolar bone and surrounding tissue¹.

For patients and dental practitioners to apply appropriate caries-control measures, and for policy makers to have a reliable picture of the caries situation in a specific population, the dynamics of dental caries should be reflected in carious lesion assessment systems. Many such systems have been developed since the late 19th century². They vary in their methods of assessing the various stages of carious lesion progression. Some have concentrated on assessing obvious cavities only³. Others have included the assessment of carious lesions in enamel4., 5., 6..

The most widely used carious lesion assessment system is the DMF proposed by WHO3., 7.. Its purpose was to allow meaningful comparison of the caries situation in various populations. For this to be achieved with an acceptable level of precision, the data collected should be of a similar quality. This implies that assessment of carious lesions which are expected to cause large variation amongst examiners from all over the world, such as lesions in enamel, would not be scored separately. That lead to a clearly marked cut-off point, a cavitated dentine lesion of sizable size, and a substantial underscoring of the total load of dental caries in individuals and subsequently, in populations.

In 2001 a group of dental researchers took the initiative to develop a caries assessment system termed ICDAS, based on visual/tactile inspection⁸. This system includes three codes for recording stages of carious lesions in enamel and in dentine, each in ascending order of severity. ICDAS is the result of an attempt to find a common caries assessment system based on the many available such systems and of the perceived need to move from assessing dental caries at the so-called ‘decayed’ status only, as the ‘understanding of dental caries had progressed’ over the years⁹. The ‘decayed’ status relates to the WHO caries index.

Inclusion of enamel carious lesions in a caries assessment index is essential, as shown in the fluoridated drinking water, Tiel-Culemborg study⁴. If enamel carious lesions had not been assessed, the study outcome would have been a 50% reduction in dental caries between test and control group only. However, assessing enamel carious lesions led to a second important finding: that fluoride retards carious lesion progression¹⁰. Assessing enamel carious lesions has become essential, particularly in communities that have experienced a large decline in cavitated dentine lesions during the last three to four decades¹¹. Assessing various stages of carious lesions in enamel would allow the patient and dental practitioner to manage lesion progression through using caries-control measures. However, data available in the WHO Oral Health Data Base for 12-year-olds indicates that caries experience (DMF) in middle- and low-income countries has been on the increase since the beginning of the 1990s¹². The caries situation in these countries is characterised by a very high proportion of untreated cavitated dentine lesions in this age group¹³. In certain countries like The Philippines, many carious lesions had progressed into the pulp, leading to infection of surrounding structures seen as ulcerations, abscesses and fistulae¹⁴. Because the conventional dental caries indices did not record such lesions, an index, termed Pulpal involvement Ulceration Fistula Abscess (PUFA), was developed to score these very advanced stages of carious lesion progression¹⁴.

In the middle of 2010, the dental community had a validated caries index that assesses carious lesions visually and tactically, excluding those involving the pulp and those at advanced stages (ICDAS II), and a caries index that assesses the advanced stages of dental caries (PUFA). The ICDAS Coordinating Committee (ICDAS CC) is very aware that a newly-developed international caries index will continue to evolve¹⁵. In the early documents, a cavity reaching the pulp was included in code 69., 15., which was excluded in recently published documents16., 17..

In May 2009, an epidemiological survey was carried out in an area of Brasilia. Both the ICDAS II and the PUFA indices were used to assess the caries situation among children. In the course of reporting study results, difficulties were encountered that needed immediate attention. As PUFA is considered an extension to classical caries indices¹⁴, there are reasons for combining the ICDAS II and PUFA indices into one index for recording the continuum in stages of carious lesion progression from the early demineralised area in enamel to infection of pulp and its surrounding tissue and severe destruction of the tooth. This would make the presentation of results of epidemiological surveys, using both indices, easy to report, clearly structured and would also provide a link to the existing DMF index. The proposed new index is termed: Caries Assessment Spectrum and Treatment (CAST) and covers assessment of stages of carious lesions progression in Enamel, Dentine and the Pulp, together with teeth Sealed, teeth Lost due to dental caries and teeth with a cavity Restored because of dental caries.

The aim of this paper is to describe and provide the rational for a comprehensive caries index – Caries Assessment Spectrum and Treatment.

MATERIALS AND METHOD

The caries indices

International Caries Detection and Assessment System (ICDAS II)

The originators of ICDAS have performed a remarkable piece of work. In a relatively short time span the index has been validated, its reliability tested, a training module constructed, a monograph published¹⁸ and conferences organized; and the index has been regularly discussed and updated by the ICDAS CC. The ICDAS II index has been described for coronal and root surface caries, and for caries assessment associated with restorations and sealants (CARS). Its codes for coronal caries range from 0 to 6, indicating the severity of the lesion (Table 1). The codes range from sound surfaces (code 0), through primary carious lesions in enamel (codes 1–3), to primary carious lesions in dentine (codes 4–6). Carious lesions involving the pulp are not being scored16., 17.. In addition, the ICDAS CC has developed a classification for conditions related to sealants and various types of restorations. As a result ICDAS II became a two-digit coding method. More information about ICDAS is available from the website: http://www.icdas.org

Table 1.

The ICDAS II index codes and descriptions for primary carious lesions in coronal surfaces (2nd row of digits)

Code	Description
0	Sound
1	First visual change in enamel (seen only after prolonged air drying or restricted to within the confines of a pit or fissure)
2	Distinct visual change in enamel
3	Localized enamel breakdown (without clinical visual signs of dentinal involvement)
4	Underlying dark shadow from dentin
5	Distinct cavity with visible dentin
6	Extensive distinct cavity with visible dentin

Pulpal involvement, Ulceration, Fistula and Abscess (PUFA) index

This newly developed index emerged because of the lack of an index that could describe the burden of untreated cavitated carious lesions at the tooth and surrounding tissue stages¹⁴. In many low- and middle-income countries, cavitated teeth are not being treated for various reasons¹³. The commonly used DMF index does not address the consequences of untreated advanced stages of carious lesion progression beyond dentine, which PUFA does. PUFA is, therefore, an index used for assessing the presence of oral conditions resulting from untreated advance stages of cavitated carious lesions¹⁴. It is described in Table 2. The uppercase letters refer to permanent teeth and the lowercase letters to primary teeth.

Table 2.

The codes and descriptions of the PUFA index

Code	Description
P/p:	Pulpal involvement: the opening of the pulp chamber is visible or the coronal tooth structures have been destroyed by the carious process and only roots or root fragments are left
U/u:	Ulceration due to trauma: sharp edges of a dislocated tooth with pulpal involvement or root fragments have caused traumatic ulceration of the surrounding soft tissues, e.g., tongue or buccal mucosa
F/f:	Fistula: a pus releasing sinus tract related to a tooth with pulpal involvement is present
A/a:	Abscess: a pus containing swelling related to a tooth with pulpal involvement is present

THE SHORTCOMINGS OF ICDAS II AND PUFA

ICDAS II index

The ICDAS II index was developed among others, as a result of the decline in the relevant proportion of cavitated carious lesions in population groups in high-income countries, the many different criteria in use for scoring dental caries worldwide and the absence of scoring of enamel carious lesion progression in the most commonly used DMF index⁸. Scoring primary carious lesions in enamel became important in low-caries-prevalence populations, as these types of lesions had become more prevalent than cavitated carious lesions. Hence the inclusion of three codes for stages of carious lesions progression in enamel.

The ICDAS II index, being a primary caries detection and assessment system, does not correlate well with the detection and assessment of the condition of sealants and various types of restorations. Indices exist for assessing the condition of restorations19., 20.. To relate stages of carious lesion progression to sealants and restorations (CARS) implies that the onset of these lesions is considered to be different from the onset of those that are unrelated to sealants and restorations which, in essence, is incorrect²¹. Incorporating these non-primary carious lesion-related conditions makes the use of the ICDAS II index complicated. A wealth of information is collected but can this information be presented in a meaningful and pragmatic way for easy use by researchers, dental practitioners and policy makers in all countries of the world?

This aspect seems to have been insufficiently explored by the ICDAS CC. It is not mentioned in the various manuals that they have produced and the few studies that have presented results after having used ICDAS II have not succeeded in reporting these results in an easy, straightforward, understandable way. Some have combined the individually collected caries codes22., 23., 24., 25.. Others have presented long lists of conditions that appear to be unpragmatic, non-cohesive and difficult to read, particularly by policy makers²⁴. Obvious questions related to ICDAS are:

• •Why does the index contain a score for three stages of carious lesion progression, both in enamel and in dentine, when these stages are combined in the reported results?
• •Why are these stages not presented separately?
• •Why are epidemiologists requested to collect data when they appear not to be used in reports and publications?
• •Why make an epidemiological survey a long-time event and perhaps unnecessarily expensive, when the collected data are not being used for their specific purpose?

Using the ICDAS II index may lead to an overestimation of the seriousness of dental caries experience as shown in the study from Brasilia²⁶. The prevalence of dental caries in the primary and permanent dentitions of the 6–7-year-olds surveyed was 95.6% and 63.7%, respectively. ICDAS II code 1 was the code most scored. This code reflects the very early clinically visible sign of the caries process. It may require no other treatment than regular maintenance using fluoride toothpaste and a tooth brush. When using ICDAS II in epidemiological surveys, the chance that every person in the world is affected by dental caries becomes very high, showing the low discriminating power of the index. Such an outcome makes it very difficult for oral health professionals and researchers to communicate seriously and meaningful with health authorities and medical colleagues.

The advantages of the ICDAS II index are that it includes stages of carious lesion progression in the enamel, that carious lesion assessment can be carried out through visual/tactile inspection and that the index has been validated2., 9. and appears to be reliable in permanent teeth in vivo²⁷ and in vitro²⁸ and acceptable in primary teeth in vitro²⁹. ICDAS II could be very suitable for use in clinical trials assessing the efficacy and/or effectiveness of caries control agents. However, its two-digit system does not make primary carious lesion assessment the focus of the index, as is suggested in its name. Its reporting is not pragmatic: no distinction has been made for comparative recording of conditions in primary versus permanent teeth and the results are difficult to compare against the widely-used DMF index. As the DMF index has been used extensively by many for decades, the results obtained from the ICDAS II index should be convertible to the DMF index, thus allowing the use of the latter index for comparison purposes. Furthermore, ICDAS II does not assess the very advanced stages of carious lesion progression; those that cause infection of the pulp and destruction of surrounding tissue.

PUFA index

This index is restricted to scoring consequences of infection in teeth and surrounding tissue as a result of the carious process. The presentation of results is straightforward, using prevalence and mean scores for the individual index components and for the combined components. It can be used for primary and permanent teeth. Results are reported in line with the presentation of results according to the DMF index¹⁴. They are presented alongside results for carious lesions without pulpal infection, excluding those in enamel, using the DMF index.

Different to the high prevalence of pufa scores (85%) and the high severity score (mean number of teeth affected was 3.5), reported for 6-year-olds in The Philippines, the survey in Brasilia resulted in a prevalence of pufa scores of 24% and a mean number of teeth affected by pufa of 0.4 amongst 6–7-year-olds (M.J Figueiredo, R.G. de Amorim, S.C. Leal et al., data in preparation). Only one tooth received a score ‘u’. The Brasilia survey challenged the pufa index and concluded that the assessment of abscess and fistula be combined in one code and that code ‘u’ be dropped.

RESULTS

A new comprehensive index: Caries Assessment Spectrum and Treatment (CAST)

This index was developed because of the need to find a reliable, pragmatic, cohesive and easy-to-read reporting system for presenting results obtained from using both ICDAS II and PUFA indices in a child population in Brazil. The indices were chosen to test their applicability in an epidemiological survey. However, the authors faced a big challenge during the reporting phase of the study. The results from use of both indices were difficult to present in words, figures and tables in a simple and easy-to-read manner. This situation necessitated the search for a pragmatic and an easy way of reporting the results and led to the creation of a new caries index. The newly proposed index is more than a combination of the two previously mentioned indices, as it also aggregates the M- and F-component of the DMF-index. As mentioned previously, PUFA complements ICDAS II, as there is no overlap between them. The fusion of the three indices resulted in the development of the new Caries Assessment Spectrum and Treatment (CAST) index. It covers the total dental caries spectrum, from no carious lesion, through caries protection (sealant) and caries cure (restoration) to carious lesions in enamel and dentine, and the advanced stages of carious lesion progression in pulpal and tooth-surrounding tissue. It comprises assessing stages of primary and, so-called, secondary carious lesion progression in Enamel, Dentine and the Pulp, as well as Lost and Restored teeth resulting from dental caries. Furthermore, CAST has been developed such that the severity of the consequences of the dental caries process increases with increase in codes. Different to common caries indices, a restored tooth is considered a sound, well functioning tooth, and is therefore positioned at the beginning of the list of codes.

Clearly, only the primary carious lesion assessment criteria from the two-digit ICDAS II index are needed and their Caries-Associated with Restorations and Sealants (CARS) criteria are not scored separately but are included in the primary carious lesion assessment criteria. This is because the so-called secondary carious lesions do not differ in their onset from primary carious lesions, so separate scoring would be superfluous. The CAST index follows the scoring instructions accompanying the use of the ICDAS II, save code 1 and combines codes 2 and 3, and 5 and 6; that of PUFA, save code ‘u’ and combines codes ‘f’ and ‘a’; that of the DMF-index (for the M- and F- component); and includes sealant. The decision to delete code 1 and combine codes 2 and 3 of ICDAS II echoes the decision made by Marthaler⁵ who, having first described carious lesions in detail, then had to reverse this decision after using the index in practice. He subsequently introduced the ‘reduced count method’ that, amongst others, deleted the first of the two caries codes: ‘first detectable changes’ and ‘distinct changes without loss of surface continuity’³⁰. Excluding ICDAS II code 1 from the CAST index eliminates the need to dry the tooth surface with an air spray before assessing the enamel: this dental aid is often not available in field situations in many countries. Combining ICDAS II codes 5 and 6 reflect obvious cavities without pulpal involvement. The latter situation is reported in PUFA code ‘p’ and taken up in the CAST index as code 6. As the difference between an abscessed tooth and a tooth with a fistula is minimal, these situations are combined as CAST index code 7. The exclusion of ICDAS II code 1 and the combinations of codes will most probably result in shorter, easier to complete, training and calibration exercises and increased index acceptance and eventually increase the reliability and usefulness of the collected data. These expectations need to be tested. The codes and description of the CAST index are presented in Table 3.

Table 3.

The codes and descriptions of the Caries Assessment Spectrum and Treatment (CAST) index

Characteristic	Code	Description
	0	Sound. No visible evidence of a distinct carious lesion is present
Sealed	1	Sealed. Pits and fissures have been at least partially sealed with a sealant material
Restored	2	A cavity has been restored with an (in)direct restorative material currently without a dentine carious lesion and no fistula/abscess present
Enamel	3	Distinct visual change in enamel. A clear carious related discolouration (white or brown in colour) is visible, including localized enamel breakdown without clinical visual signs of dentine involvement
Dentine	4	Internal caries-related discolouration in dentine. The lesion appears as shadows of discoloured dentine visible through enamel which may or may not exhibit a visible localized breakdown
	5	Distinct cavitation into dentine. No (expected) pulpal involvement is present
Pulp	6	Involvement of pulp chamber. Distinct cavitation reaching the pulp chamber or only root fragments are present
	7	Abscess/Fistula. A pus containing swelling or a pus releasing sinus tract related to a tooth with pulpal involvement due to dental caries is present
Lost	8	The tooth has been removed because of dental caries
Other	9	Does not match with any of the other categories

DISCUSSION

The CAST index

A new caries assessment index has been presented. It is based on the strengths of the ICDAS II and PUFA indices and provides a link to the widely used DMF index. The DMF is considered important because researchers using only the ICDAS II index are unable to compare results with those obtained when the DMF index is used and this disadvantage could hinder full implementation of the ICDAS II index in future caries epidemiological studies. The link in the CAST index with the DMF index also seems to work well for the PUFA index. In its only publication so far, caries outcomes from use of the DMF index were presented alongside those that had been obtained from use of the PUFA index ¹⁴. Consequently, stages of carious lesion progression in enamel are not being assessed when PUFA and DMF indices are used independently.

Therefore, the CAST index is not proposed as just another caries assessment index. The word ‘spectrum’ means: a complete range of situations, going from one extreme to its opposite (Longman dictionary). This definition is applicable to the main strength of the new index: its usefulness for analysis of the dental caries situation in the public oral health setting. Not only can the CAST index provide information regarding the number of non-cavitated and cavitated lesions; it can also report the consequences of the untreated ones, by recording pulp involvement and the presence of fistula and abscess due to the caries process. In addition, the incorporation of the ‘lost’ and ‘restored’ component makes the outcomes obtained through CAST easily comparable to those derived from surveys in which the DMF index was used. In this way, the CAST index can become an important dental epidemiological tool. The quantity and the quality of information that can be gathered from a whole population through the adoption of this new index clarify the extent of dental caries and facilitate easy communication between the dental community and policy makers. Being able to inform others about the severity and consequences of dental caries is as relevant as reporting the number of carious lesions. Through having all these data assessed in one index, the whole spectrum of the dental caries situation is defined and strategies to deal with a specific spectrum can be better developed.

Active and inactive stages of enamel carious lesions have not been taken up in the CAST index. We think that detecting inactive and active carious lesions in enamel should be part of an index used in clinical studies but not for use in caries epidemiological surveys. This thought is supported by the outcome of a three-year clinical study amongst children that evaluated the effectiveness of fluoride mouth rinsing and fluoride tooth brushing. No difference was reported in Relative Risk between tooth surfaces with inactive and active carious lesions in enamel at baseline and their transition into a cavity, filling or extraction in both the fluoride and control group after three years³¹. Whether an enamel carious lesion was inactive or active at the start had no effect on the study outcome three years later. Why should the CAST index be made more complicated by including the detection of inactive and active enamel carious lesions as the preventive measure (fluoride rinsing and fluoride tooth brushing) had the same effect for both stages of enamel carious lesions at baseline?

Validity and reliability of the CAST index

An index, assessing a disease or condition should be valid, reliable, pragmatic in its use and results should be easily reported. The CAST index has not been validated, nor has reliability testing been done, nor have data been presented using this index. However, validating and testing the index’s reliability have started. Results will be presented in future. A manual that will assist examiners in understanding and in using CAST as well as for training purposes is under construction.

CONCLUSIONS

Use of the CAST index enables the total spectrum of carious lesion progression, and rendered care in a population to be covered. This is considered an advantage over the individual use of the ICDAS II, PUFA and DMF indices. The CAST index is particularly useful for assessing stages of carious lesion progression and rendered care in an epidemiological setting. However, using the CAST index for assessing carious lesion progression as part of a clinical trial is not considered appropriate. The use of the CAST index should be field-tested in different age groups in different countries and cultures. There is a need to validate the index and to determine its reliability in different countries and population groups.

Acknowledgement

We are very grateful to Dr. P. Cooley, Prof. A. Plasschaert, Dr. W. van der Sanden, Prof. Dr. A. Sheiham and Dr. A. van Strijp for critically reading the manuscript. We are grateful to FAP-DF (Fundação de Apoio à Pesquisa do Distrito Federal), Brasilia, and to the Radboud University Nijmegen Medical Centre, the Netherlands, for financially supporting the study. We thank the Education Department of the local government, directors, teachers and students of the participating schools in Paranoá for hosting us during the treatment days and for permission to carry out the study in Brasilia.