Back To Search Results

Dental Caries Classification Systems

Editor: Melina Brizuela Updated: 11/12/2023 7:33:54 PM


Dental caries is a prevalent chronic disease. If left untreated, caries may progress to tooth destruction and exodontia. Dental caries is a complex multifactorial disease of individual, biological, behavioral, and environmental factors.[1] The clinical sign of dental carious is a lesion of varying severity, ranging from opacity in the enamel to frank cavitation exposing dentin. Accurately diagnosing dental caries promotes effective treatment planning, prevents disease progression, and supports optimal patient outcomes.

Various classification methods for dental carious lesions have been developed, each with advantages and limitations. Newer classification systems, like the International Caries Detection and Assessment System (ICDAS) and the American Dental Association Caries Classification System (ADA CCS), have evolved from the traditional Black classification to include the current understanding of the carious process, maximize healthy tooth surfaces, and prevent extension of the carious lesion.

Issues of Concern

Register For Free And Read The Full Article
Get the answers you need instantly with the StatPearls Clinical Decision Support tool. StatPearls spent the last decade developing the largest and most updated Point-of Care resource ever developed. Earn CME/CE by searching and reading articles.
  • Dropdown arrow Search engine and full access to all medical articles
  • Dropdown arrow 10 free questions in your specialty
  • Dropdown arrow Free CME/CE Activities
  • Dropdown arrow Free daily question in your email
  • Dropdown arrow Save favorite articles to your dashboard
  • Dropdown arrow Emails offering discounts

Learn more about a Subscription to StatPearls Point-of-Care

Issues of Concern

G.V. Black Classification of Dental Caries 

The G.V. Black classification of dental caries lesions first introduced in 1896 and now outdated, is the most influential dental caries classification system.[2] This system is based on the anatomical site of the lesion and initially divided carious lesions into 5 classes; a sixth class was later added. (See Table 1. G.V. Black Classification of Dental Caries.) This classification system also suggested a cavity design for each class utilizing materials available at the time of publication, such as silicate cement, amalgam, and gold. These recommendations resulted in cavities that would be unnecessarily large by modern standards.[2]

Table 1. G.V. Black Classification of Dental Caries.

 Class  Anatomical description
 Class I  Pits and fissures
 Class II  Contact area; posterior teeth
 Class III  Contact area; anterior teeth
 Class IV  Incisal edge
 Class V  Cervical third

The G.V. Black classification system was not designed to identify the initial lesion before cavitation or the increasing complexity of the restoration.[2] At the time of publication of this system, the clinical standard was to surgically remove all lesions, including white spots, and create space and retention for nonadhesive restorations that weakened the tooth structure. These outdated concepts have been abandoned as the understanding of the carious process and technology have improved, and more accurately refined classification systems for dental caries lesions have subsequently been created.[2][3]

Mount-Hume Classification System

More than 100 years later, Mount and Hume published a caries classification system following the current and more conservative approach to caries.[3] The Mount-Hume classification system incorporated the advent of fluoride and adhesive restorative materials, the use of which modified the old principles of cavity design.[3] Mount and Hume classified caries based on their site and size.[2] (see Table 2. Mount-Hume Site Classification of Caries. and Table 3. Mount-Hume Size Classification of Caries.) The size classification was updated in 2006 to include Size 0, referring to non-cavitated lesions, and modify the definition of Size 1.[2]

Table 2. Mount-Hume Site Classification of Caries.

 Site  Description
 Site 1  Pits, fissures, and minor defects on exposed enamel surfaces of all teeth.
 Site 2

 Approximal enamel surfaces immediately cervical to the contact area between any pair of adjacent teeth.

 Site 3

 The cervical one-third of the crown around the full circumference of any tooth or, following gingival recession,

 the exposed root surface.

Table 3. Mount-Hume Size Classification of Caries

 Size  Description
 Size 0

 The earliest identifiable lesion that represents the initial stage of demineralization.

 Includes 'white spot' or an 'early erosion' lesions.

 Surgical treatment will probably not be required.

 Size 1

 Minimal surface cavitation with the involvement of dentin.

 Just beyond the possibility of treatment by remineralization alone.

 Size 2

 Moderate loss of tooth structure. Cavitation has progressed beyond minimal.

 The remaining tooth structure is sound, well supported by dentin, and not likely to fail under normal occlusal load.

 Size 3

 Cavitation has progressed beyond moderate.

 A cusp or incisal corner is sufficiently weakened that some level of protection for the remaining tooth structure is required.

 Size 4

 Extensive caries, erosion, or trauma has led to bulk loss of tooth structure.

 A cusp or an incisal edge has already been lost, or the root structure is involved on two or more adjacent surfaces.

International Caries Detection and Assessment System

In 2002, an international team of caries researchers, epidemiologists, and restorative dentists proposed a new system to diagnose and classify dental caries, the International Caries Detection and Assessment System (ICDAS I). The ICDAS was modified in 2005 to the  ICDAS II.[4]

The ICDAS was developed to include the current knowledge about the pathogenesis of caries development, detecting carious lesions at an early stage, and quantifying the degree of demineralization. The ICDAS features an individualized scoring system to detect and assess primary coronal and root caries and caries associated with restorations and sealants (CARS). Using the ICDAS for root caries is yet to be implemented in epidemiological studies.[4]

The detection arm of the ICDAS determines the features of the caries lesion. These features include the location of the lesion, whether it is coronal or radicular, and its restorative status.[4] The assessment arm stages the lesion as cavitated or noncavitated, and active or inactive.[4] 

Employing the ICDAS requires 2 steps. Step 1 is classifying each tooth surface (buccal, lingual/palatal, mesial, distal, and occlusal) into sound, sealed, restored, crowned, or missing, and assigning a code from 0 to 9 to each tooth surface, as described in Table 4. The ACDAS Classification of Restoration, Sealant, or Missing Teeth Status.[4] A noteworthy feature of the ICDAS is its differentiation of completely sealed from partially sealed surfaces; partially sealed surfaces are at increased risk of caries compared to sound dental surfaces.[5]

Table 4. ICDAS Classification of Restoration, Sealant, or Missing Teeth Status.

 Code  Description
 0  Unrestored or unsealed

 Sealant, partial

 *Sealant that does not cover all pits and fissures on a tooth surface


 Sealant, full

 *Sealant that covers all pits and fissures on a tooth surface


 Tooth-colored restoration

 4  Amalgam restoration
 5  Stainless steel crown
 6  Porcelain, gold, porcelain-fused-to-metal crown or veneer
 7  Lost or broken restoration
 8  Temporary restoration

 Tooth is missing; other special cases

 9-6: Tooth surface cannot be examined because of access limitations

 9-7: Tooth missing due to caries

 9-8: Tooth missing for reasons other than caries

 9-9: Unerupted

Step 2 of the ICDAS system assigns a code from 0 to 6 to each tooth surface according to the caries status.[4] (See Table 5. ICDAS Classification of Caries Status) Code 0 is a sound tooth surface. Developmental defects such as hypoplasia and dental fluorosis are also classified as code 0. Code 1 is "the first visual sign of caries" in the enamel. An opacity or change in color can be appreciated when the tooth surface is dried, but the same surface looks sound when wet. Code 1 also differentiates between occlusal and smooth surface lesions.

ICDAS code 2, described as "distinct visual change," characterizes a lesion that is noncavitated but can be seen when the tooth is wet with saliva. Code 2 lesions in pits and fissures are not just confined to this area, but most of them extend to the dentinal half of the enamel or even to the outer third of the dentin.[6] When the carious lesion has progressed to localized enamel loss without exposing dentin or producing an underlying shadow in dentin, it is an ICDAS code 3.

ICDAS code 4 describes a lesion evolved to affect dentin, clinically seen as an underlying shadow. ICDAS code 5 refers to cavitation that exposes the dentin and is known as "distinct cavitation." If a caries affects half or more of the tooth structure, it is an "extensive" cavitation and classified as ICDAS code 6.

 Table 5. ICDAS Classification of Caries Status.

 Code  Caries Status  Description
 Code 0 Sound tooth surface

There should be no evidence of caries defined as either no or questionable change in enamel translucency after the suggested air drying time of 5 seconds. Surfaces with fluorosis, tooth wear, extrinsic or intrinsic stains, or developmental defects, such as enamel hypoplasia, will be recorded as sound. Surface with multiple stained fissures should be scored as sound if staining is seen in other pits and fissures, and is due to a condition that is consistent with noncarious habits, such as frequent tea drinking.

 Code 1: Pits and fissures Initial visual change in enamel

There is no evidence of any change in color attributable to carious activity when seen wet, but after prolonged air drying, a carious opacity or discoloration, such as a white or brown lesion, is visible that is not consistent with the clinical appearance of sound enamel 


when there is a change of color due to caries seen wet or dry which is not consistent with the clinical appearance of sound enamel and is limited to the confines of the pit and fissure area. The appearance of these carious areas is inconsistent with that of stained pits and fissures, as defined in code 0.

 Code 1: Smooth tooth surfaces Initial visual change in enamel There is no evidence of any change in color attributable to carious activity on the buccal or lingual surface when seen wet, but after prolonged air drying, a carious opacity or discoloration is visible that is not consistent with the clinical appearance of sound enamel. 
 Code 2 Distinct visual change in enamel

The tooth must be viewed wet. When wet, there is a carious opacity or brown carious discoloration wider than the natural fissure or fossa that is inconsistent with the clinical appearance of sound enamel. The lesion must still be visible when dry.

 Code 3 Localized enamel breakdown because of caries with no visible dentin or underlying shadow

The tooth viewed wet may have a clear carious opacity or white spot lesion or brown carious discoloration wider than the natural fissure or fossa that is inconsistent with the clinical appearance of sound enamel. Once dried, there is carious loss of tooth structure at the entrance to, or within, the pit, fissure, or fossa. There is visual evidence of demineralization characterized by opaque, white, brown, or dark brown walls at the entrance to or within the fissure or pit. Although the pit or fissure may appear substantially and unnaturally wider than normal, the dentin is not visible in the walls or at the base of the cavity or discontinuity.

If in doubt or to confirm the visual assessment, the WHO/CPI/PSR* probe can be used gently across a tooth surface to confirm the presence of a cavity apparently confined to the enamel. This is achieved by sliding the ball end along the suspect pit or fissure. A limited discontinuity is detected if the ball drops into the surface of the enamel cavity or discontinuity.

 Code 4 Underlying dark shadow from dentin with or without localized enamel breakdown A shadow of discolored dentin is visible through an apparently intact enamel surface, which may or may not show signs of localized breakdown characterized by a loss of surface continuity that does not show the dentin. The shadow appearance is often seen more easily when the tooth is wet. The darkened area is an intrinsic shadow that may appear grey, blue, or brown in color. The shadow must clearly represent caries that started on the tooth surface being evaluated. If, in the opinion of the examiner, the carious lesion started on an adjacent surface and there is no evidence of any caries on the surface being scored, then the surface should be coded “0.”
 Code 5 Distinct cavity with visible dentin

Cavitation in opaque or discolored enamel exposes the dentin beneath. The tooth viewed wet may have darkening of the dentin visible through the enamel. Once dried, there is visual evidence of loss of tooth structure at the entrance to or within the pit or fissure-frank cavitation. There is visual evidence of demineralization at the entrance to or within the pit or fissure, and in the examiner's judgment, dentin is exposed.

The WHO/CPI/PSR* probe can be used to confirm the presence of a cavity apparently in dentin. This is achieved by sliding the ball end along the suspect pit or fissure, and a dentin cavity is detected if the ball enters the opening of the cavity and, in the opinion of the examiner, the base is in dentin. In pits or fissures, the thickness of the enamel is between 0.5 and 1.0 mm. The deep pulpal dentin should not be probed.

 Code 6 Extensive distinct cavity with visible dentin Obvious loss of tooth structure, the cavity is both deep and wide, and dentin is clearly visible on the walls and at the base. An extensive cavity involves at least half of a tooth surface or possibly reaching the pulp.
    *WHO/CPI/PSR: World Health Organization/Community Periodontal Index/Periodontal Screening and Recording

The benefit of the ICDAS is the accurate detection of dental caries, particularly noncavitated lesions. However, it requires twice as much time to record the ICDAS as the Decayed-Missing-Filled (DMF) Index or other classification systems.[7][8][9] The ICDAS relies heavily on clinician training, leading to interobserver variability and affecting the consistency of the diagnosis.[7] Therefore, mainly due to time constraints, the use of the ICDAS in the clinical setting should be reserved for detecting early lesions, particularly in children.[8][9]

Decayed-Missing-Filled Index

The Decayed-Missing-Filled (DMF) index has been the primary indicator of caries experience in the population for more than half a century.[10] It is the sum of the number of teeth (DMFT) or surfaces (DMFS) decayed, missing, or filled in an individual. The 28 permanent teeth are quantified; third molars are typically excluded.

The DMFT score for an individual will range from 0 to 28. A score of 0 means no teeth are decayed, missing, or filled. A score of 28 means that all teeth are affected. If a tooth or surface is both restored and decayed, it is quantified as decayed. The DMFS score for an individual will range from 0 to 128, as anterior teeth have 4 surfaces and molars and premolars have 5 surfaces. Missing or crowned teeth pose a problem to the DMFS; controversy exists regarding how many surfaces should be counted as missing or restored in such teeth.[10] Assigning the maximum value of surfaces may overestimate the caries experience of the individual; similarly, giving a lower value may underestimate the scope of the problem.[10] The 1939 revision of the DMF recommends assigning 3 surfaces to missing and crowned teeth, as three is the most common number of dental surfaces affected by caries in extracted teeth.[10]

One of the main disadvantages of the DMF index is that decayed and restored teeth, even when well-restored, carry equal importance.[10] Consequently, the DMF score assigned can never improve. If an individual has 3 decayed, 2 restored, and 2 missing teeth, the resulting DMF score is 7. However, when the 3 decayed teeth are restored, the DMF score will remain 7: 0 decayed, 5 restored, and 2 missing teeth.[10]

Other disadvantages of the DMF index are its inability to differentiate between active and inactive lesions or detect incipient lesions. In a study comparing the DMF index and ICDAS, operators using the DMF index recorded two-thirds of the samples as sound and caries-free compared to operators recording one-fifth of the samples as such.[9] This illustrates how the DMF index does not account for initial lesions, can underestimate the disease burden, and contribute to the progression of carious lesions.[8][9][11] Combining ICDAS with the Caries Assessment Spectrum and Treatment Index (CAST) is a more practical approach for caries detection, especially for detecting early-stage lesions and facilitating treatment decisions.[8]

American Dental Association Caries Classification System

In 2008, recognizing the difficulties presented by the plethora of available caries classification systems, the American Dental Association (ADA) commissioned a team of experts to develop a reliable, valid, and easily applicable system now known as the American Dental Association Caries Classification System (ADA CCS).[1] The ADA CCS aims to build on existing classification systems and create a practical, evidence-based approach for use in various clinical settings while serving as a valuable resource for researchers and promoting consistency and comparability across studies.[1]

The ADA CCS scores each tooth surface based on the presence or absence of caries, anatomy, severity, and activity status of the lesion. Furthermore, it categorizes caries lesions into four groups: sound, initial, moderate, and advanced.[1] (See Table 6. American Dental Association Caries Classification System.)

Table 6. American Dental Association Caries Classification System.

  Sound Initial Moderate Advanced
Clinical presentation

No clinically detectable lesion. Dental hard tissue appears normal in color, translucency, and gloss.

Earliest clinically detectable lesion compatible with mild demineralization. Lesion limited to enamel or to shallow demineralization of cementum or dentin. Mildest forms are detectable only after drying. When established and active, lesions may be white or brown with a loss of normal gloss. Visible signs of enamel breakdown or signs the dentin is moderately demineralized. Enamel is fully cavitated, and dentin is exposed. Dentin lesion is deeply or severely demineralized.
Other labels No surface change or adequately restored Visually noncavitated  Established, early-cavitated, shallow cavitation, microcavitation Spread, disseminated, late-cavitated, deep cavitation. 
Infected dentin None Unlikely Possible Present
Appearance of occlusal surfaces ICDAS 0 ICDAS 1 & ICDAS 2 ICDAS 3 & ICDAS 4 ICDAS 5 & ICDAS 6
Radiographic presentation of the approximal surface

E0* or RO+

No radiolucency. 

E1 or RA1

E2 or RA2

D1 or RA3

Radiolucency may extend to the dentinoenamel junction or outer one-third of the dentin.

Note: radiographs are not reliable for mild occlusal lesions.

D2 or RB4 

Radiolucency extends into themiddle one-third of the dentin.

 D3 or RC5

Radiolucency extends into the innerone-third or the dentin.

* E0-E2 DI-D3 notation svstem.[12] 

+RO, RA1-RA3, RB4, and RC5-RC6 ICCMS radiographic scoring system (RC6 = into pulp). (Pitts NB, Ismail Al, Martignon S, Ekstrand K, Douglas GAV, Longbottom C. ICCMS Guide for Practitioners and Educators. Accessed April 13, 2015.)

Nursing, Allied Health, and Interprofessional Team Interventions

The management of dental caries is complex and challenging. Classification systems unify concepts and provide clarity on diagnosis and treatment planning. Much has changed since Black developed his pioneering classification system in 1896, which has influenced the development of more complex classification systems that consider not only the location of the lesion but also its depth, radiographic appearance, and activity status. Classification systems promote the detection of caries at earlier stages, facilitate prompt intervention, and prevent the progression of disease. All members of the dental team, including dentists, dental nurses, dental hygienists, and dental therapists, must be familiar with the most common caries classification systems to foster interprofessional communication, promote understanding of disease processes, and improve patient outcomes.



Young DA, Nový BB, Zeller GG, Hale R, Hart TC, Truelove EL, American Dental Association Council on Scientific Affairs, American Dental Association Council on Scientific Affairs. The American Dental Association Caries Classification System for clinical practice: a report of the American Dental Association Council on Scientific Affairs. Journal of the American Dental Association (1939). 2015 Feb:146(2):79-86. doi: 10.1016/j.adaj.2014.11.018. Epub     [PubMed PMID: 25637205]


Mount GJ, Tyas JM, Duke ES, Hume WR, Lasfargues JJ, Kaleka R. A proposal for a new classification of lesions of exposed tooth surfaces. International dental journal. 2006 Apr:56(2):82-91     [PubMed PMID: 16620036]


Mount GJ, Hume WR. A new cavity classification. Australian dental journal. 1998 Jun:43(3):153-9     [PubMed PMID: 9707777]


Ismail AI, Sohn W, Tellez M, Amaya A, Sen A, Hasson H, Pitts NB. The International Caries Detection and Assessment System (ICDAS): an integrated system for measuring dental caries. Community dentistry and oral epidemiology. 2007 Jun:35(3):170-8     [PubMed PMID: 17518963]

Level 2 (mid-level) evidence


Ismail AI, Gagnon P. A longitudinal evaluation of fissure sealants applied in dental practices. Journal of dental research. 1995 Sep:74(9):1583-90     [PubMed PMID: 7560420]


Ekstrand KR, Ricketts DN, Kidd EA. Reproducibility and accuracy of three methods for assessment of demineralization depth of the occlusal surface: an in vitro examination. Caries research. 1997:31(3):224-31     [PubMed PMID: 9165195]


Dikmen B. Icdas II criteria (international caries detection and assessment system). Journal of Istanbul University Faculty of Dentistry. 2015:49(3):63-72. doi: 10.17096/jiufd.38691. Epub 2015 Oct 21     [PubMed PMID: 28955548]


Campus G, Cocco F, Ottolenghi L, Cagetti MG. Comparison of ICDAS, CAST, Nyvad's Criteria, and WHO-DMFT for Caries Detection in a Sample of Italian Schoolchildren. International journal of environmental research and public health. 2019 Oct 25:16(21):. doi: 10.3390/ijerph16214120. Epub 2019 Oct 25     [PubMed PMID: 31731559]


Melgar RA, Pereira JT, Luz PB, Hugo FN, Araujo FB. Differential Impacts of Caries Classification in Children and Adults: A Comparison of ICDAS and DMF-T. Brazilian dental journal. 2016 Oct-Dec:27(6):761-766. doi: 10.1590/0103-6440201600990. Epub     [PubMed PMID: 27982192]


Broadbent JM, Thomson WM. For debate: problems with the DMF index pertinent to dental caries data analysis. Community dentistry and oral epidemiology. 2005 Dec:33(6):400-9     [PubMed PMID: 16262607]


Gugnani N, Pandit IK, Srivastava N, Gupta M, Sharma M. International Caries Detection and Assessment System (ICDAS): A New Concept. International journal of clinical pediatric dentistry. 2011 May-Aug:4(2):93-100. doi: 10.5005/jp-journals-10005-1089. Epub 2010 Apr 15     [PubMed PMID: 27672245]


Anusavice KJ. Present and future approaches for the control of caries. Journal of dental education. 2005 May:69(5):538-54     [PubMed PMID: 15897335]