INTRODUCTION:

Dental caries lesions form a significant portion of any dental professional’s daily practice. Oral health care and healthy teeth are important for people from any part of society. The effects of dental caries on growth and physical, emotional, and cognitive development have implications on success and productivity throughout the life span.^1,2Through various epidemiological studies across different parts of the Indian population, it was observed that the prevalence of dental caries was high irrespective of the age groups.³This disease can fall anywhere between non-cavitated surfaces to pulpal lesions or root defects. It is imperative that all such classification systems must be simple, reliable, comprehensive, and reproducible as well as validated by the observers. The need to classify caries with a focus on communication, outcome, prognosis, and treatment planning forms the baseline of the discussion. Classifications of caries are necessary to develop a common language for treatment indication and outcomes.

These systems are used as a prognostic tool to determine the natural history and outcomes, guide treatment decision-making, and predict the possibility of complications. This article reviews the historical evolution, the respective strengths, and shortcomings of each classification system.

HISTORY:

The first attempt in classifying dental caries into various types was by G.V Black in 1908. The classification by G.V Black was based on the concept of “extension for prevention “of caries. However, with a better understanding and improved knowledge of the function of fluoride, various classifications have been put forward with the possibility to limit the size of a cavity by retaining as much natural tooth structure during the treatment of any carious lesion because no restorative material can be regarded as a perfect replacement.

1. Classification by G.V Black [1908]⁴ – The pioneer

Black’s original classification consists of five categories classified based on the tooth type and tooth surfaces involved, with each lesion having a cavity design. Black emphasized that all the affected dentine should be removed and cavities must be extended onto self-cleansing areas to prevent recurrent caries.

Class I: Caries affecting pits and fissures on the occlusal third of molars and premolars, occlusal two-thirds of molars and premolars, and lingual part of anterior teeth.

Class II: Caries involving proximal surfaces of molars and premolars.

Class III: Caries affecting proximal surfaces of anterior teeth without involving the incisal angles.

Class IV: Caries affecting proximal including incisal angles of anterior teeth.

Class V: Caries affecting gingival one-third of facial or lingual surfaces of anterior or posterior teeth.

To Black’s cavity classifications, a sixth category is added by Simon’s (1956)⁵known as the Class VI cavities in the incisal edge or occlusal cusps due to either abrasion, erosion, or attrition.

2. WHO Classification: [1979]⁵

World Health Organisation proposed DMF index to evaluate the caries experience in different populations. This index measures the severity of the lesions as long as the distributions of the lesions in the population are the same. The D/d component of DMFT/deft index is subdivided based on the depth of caries.

D1 - Clinically detectable enamel carious lesions, with intact surfaces (non-cavitated)

D2 - Clinically detectable cavities involving enamel.

D3 - Clinically detectable cavities into dentin

D4 - Lesions extending to pulp

This classification/ index doesn’t record the progression rate of caries and root caries.

3. Root surface caries severity index by Billings: [1985]⁶

With the observations in extracted teeth, Billing developed a caries index for segregating the root lesions by type with treatment categories. This helps to assist in monitoring the progression of lesions following treatment.

The grade I incipient lesions are treated by topical fluoride therapy alone, Grade II (shallow) lesions could be treated successfully by smoothing using abrasive points and fine diamonds in combination with topical fluoride therapy. Grade 3 cavitated lesions involve minimal cavity preparation with restoration using GIC.

Grade I (Incipient): soft surface texture with no surface defect. Variable pigmentation from light tan to brown color

Grade II (Shallow): Soft, irregular, rough surface texture, surface defect (less than 0.50 mm in depth).Variable pigmentation from tan to dark brown.

Grade III (Cavitation): Soft surface texture, cavitation present (greater than 0.50 mm in depth) with no pulpal involvement. Variable pigmentation from light brown to dark brown.

Grade IV (Pulpal): Deeply penetrating lesion with pulpal or root canal involvement. Variable pigmentation from brown to dark brown color.

4. Classification by G.J.Mount [1998]⁷

The concept of the reversible nature of caries in its earliest stage, the increase in restorative materials than in Black’s time, and adhesive materials with minimal microleakage led G.J Mount to reconsider Black’s classification. This classification records the site and the extent of lesions without specifying the cavity designs. The size of the lesion influences the material choice. Dental caries is said to be a slow process and during the early stages, non-invasive intervention can convert the lesion to an inactive state from an active state

SIZE
SITE	Minimal 1	Moderate 2	Enlarge 3	Extensive 4
Pit and fissure 1	1.1	1.2	1.3	1.4
Contact area 2	2.1	2.2	2.3	2.4
Cervical 3	3.1	3.2	3.3	3.4

Size 1. Minimal involvement of dentine, beyond the possibility of treatment by remineralization alone.

Size 2. Moderate dentine involvement - The remaining tooth structure supports the restoration and is less likely to fail under normal occlusal load.

Size 3. Enlarged with weakened cusps and incisal edges (requires protection from occlusal load).

Size 4. Extensive tooth structure loss.

5. Classification by Nyvad [1999]:

WHO index was not reliable in certain populations because of the slow progression of caries. It was necessary to record caries at the non-cavitated level, to prevent its further progression. Hence Nyvad added a new update with lesion activity assessment and provided the best management options for such non-cavitated lesions. Active and inactive caries are differentiated from the visible changes. This is used in both primary and permanent dentitions. All the lesions including fillings are assigned a score.⁸

Score	Category	Criteria
0	Sound	Normal enamel translucency and texture.
1	Active caries (intact surface)	The surface of enamel is whitish/yellowish opaque with loss of luster, rough surface on probing; covered with plaque. No clinically detectable loss of tooth structure.
2	Active caries (surface discontinuity)	Same criteria as score 1. Localized enamel surface defect (microcavity). No undermined enamel or softened floor detectable with the explorer.
3	Active caries (cavity)	Enamel/dentin cavity easily visible with the naked eye; soft/leathery surface on probing. With/without pulp involvement.
4	Inactive caries (intact surface)	Surface of the enamel is whitish, brownish or black. Enamel may be shiny and feels hard and smooth on probing. No clinically detectable loss of substance.
5	Inactive caries (surface discontinuity)	Same criteria as score 4 Localized enamel surface defect (microcavity). No undermined enamel or softened floor detectable with the explorer.
6	Inactive caries (cavity)	Enamel/dentin cavity easily visible with naked eye; surface of cavity may be shiny and feels hard on probing. No pulpal involvement.
7	Filling (sound surface)	Enamel/dentin.
8	Filling + active caries	cavitated/ noncavitated.
9	Filling + inactive caries	cavitated/noncavitated.

Active non-cavitated lesions can be managed by non-operative measures (oral hygiene instructions/ fluorides), whereas inactive non-cavitated can be cleaned by brushing with fluoridated toothpaste. Consumption of fluoride within the optimal levels can result in the emergence of fluoride-resistant oral Streptococcus sp.^9,10

6. International Caries Assessment and Detection System (ICDAS I and II):

In 2002, an International team of caries researchers developed the ICDAS system for caries detection and assessment, which was later modified in 2005 as ICDAS II. The main aim of the committee is to integrate other criteria and provide a standard classification system that can be used for both research and clinical purposes. The ICDAS II included coronal caries, caries associated with restorations and sealants (CARS), and root caries. The bacteria most responsible for causing caries are Streptococcus mutans, lactobacilli, and actinomyces. Understanding oral bacteria assists in not only understanding the pathogenesis of dental caries but also in preventing and treating them.^11,12

The “D”in ICDAS stands for dental caries detection and “A” for evaluation of stages (non-cavitated or cavitated) and activity (active or arrested). Each tooth surface is designated by two digits. The first digit describes the tooth and the second describes the caries lesion.¹³

1. Code for restoration status:

0 = unrestored/unsealed

1 = Sealant, partial

2 = Sealant, full

3 = Tooth colored restoration

4 = Amalgam restoration

5 = Stainless steel crown

6 = Porcelain or gold or PFM crown or veneer

7 = Lost or broken restoration

8 = Temporary restoration

9 = Used for the following conditions

96 = Tooth surface cannot be examined; Surface excluded

97 = Tooth missing because of caries (tooth surfaces will be coded 97)

98 = Tooth missing for reasons other than caries (all tooth surfaces will be coded 98)

99 = Unerupted (tooth surfaces coded 99)

2. Coronal caries (pit and fissure caries/smooth surface caries) codes vary from 0-6 depending on the degree of the lesion

0- Sound tooth surface: No evidence of caries after 5-sec air drying

1- First visual change in enamel: Opacity or discoloration (white or brown) is visible at the entrance to the pit or fissure seen after prolonged air drying

2- Distinct visual change in enamel visible when wet, the lesion must be visible when dry

3- Localized enamel breakdown (without clinical visual signs of dentinal involvement) seen when wet and after prolonged drying

4- Underlying dark shadow from dentine

5- Distinct cavity with visible dentine

6- Extensive distinct cavity with visible dentine.

Code for Root Caries:¹⁴

This criteria is not been tested in any of the clinical studies.

CODE E: If the root surface cannot be visualized directly, then it is excluded.

CODE 0: The root surface with normal anatomical color and no unusual discoloration/surface defect that distinguish it from the surrounding root areas.

CODE 1: Demarcated area on the root surface or at the cementoenamel junction that is discolored with no cavitation (loss of anatomical contour<0.5mm)

CODE 2: Demarcated area on the root surface or at the cement-enamel junction discolored with cavitation (loss of anatomical contour ≥0.5mm)

7. American Dental Association Caries Classification System ( ADA-CCS) [ 2008]¹⁵

In 2008, American Dental Association compiled the information from the discussion of experts in a council meeting and developed easy to use the system in clinical practice.

The extent and the activity of caries are scored for each of its tooth surfaces. The characteristics of active and arrested caries are differentiated by visual changes. Active caries appears white to yellow in color with rough enamel and soft dentine on probing. Whereas, inactive caries appear brownish-black in color with smooth enamel and hard dentine on tactile sensation.

Sound surface - No clinically detectable lesion, normal color, translucency, and gloss of hard tissues.

Initial caries lesion - Clinically detectable lesion with mild demineralization involving enamel/dentin

/cementum. Milder forms are detectable after drying.

Moderate lesion - Vital signs of enamel breakdown or signs of dentin moderately demineralized.

Advanced lesion - Enamel is fully cavitated and dentin is exposed. Dentin lesion is deeply/severely demineralized.

8. PUFA INDEX [2010]:

In all the previous systems, the consequences of untreated dental caries such as pulpal involvement and an abscess is not been recorded. Caries of dentine are assigned for those teeth with pulpal involvement. To overcome the limitations of the above classifications, the PUFA index was developed by Monse et al. Uppercase letters for permanent dentition and lowercase letters for primary dentition.¹⁶

P/p - Pulpal involvement with the opening of the pulp chamber is visible or only roots or root fragments left as a result of the carious process.

U/u - Ulceration due to trauma from sharp edges of a dislocated tooth with pulpal involvement or root.

F/f - Fistula: when pus releasing sinus tract is in relation to a tooth with pulpal involvement is present.

A/a - Abscess: when pus containing swelling is in relation to a tooth with pulpal involvement is present.

When dental caries reaches the pulp following reactions occur- decrease in dentin permeability, tertiary dentin formations, inflammatory and immune responses.¹⁷Recent studies show that there is a possibility of increased systemic responses of inflammatory mediators in the peripheral may also lead to an increase in leucocyte count.¹⁸

9. Caries Assessment Spectrum and Treatment CAST [2011]¹⁹

Frencken and associates, combine ICDAS, PUFA index and M-F of DMF index. CAST spectrum describes the wide range of carious lesions from no caries disease through the sealant, restoration to lesions in enamel, dentine, pulp, and surrounding tissues. This system also allows to calculate the DMF scores, hence used as a tool in epidemiological surveys.

Characteristic	Code	Description
Sound	0	No visible evidence of a distinct carious lesion.
Sealed	1	Pits and fissures are at least partially sealed with a sealant material
Restored	2	Cavity restored with an (in)direct restorative material 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 discoloration in dentine. Shadows of discolored dentine lesion visible through enamel with or without visible localized breakdown.
	5	Distinct cavitation into dentine with no pulpal involvement.
Pulp	6	Involvement of pulp chamber. Distinct cavitation reaching the pulp chamber or only root fragments are present
Abscess / fistula	7	Pus containing swelling/sinus tract related to a tooth with pulpal involvement due to dental caries is present
Lost	8	The tooth has been removed because of caries.
Other	9	Does not match with any of the other categories

FDI Caries Matrix System [2008]²⁰

Federation Dentaire Internationale constructed a framework, integrating the previous classification systems. The objective of this framework is to provide a chart that would act as a base for risk assessment and surveillance, disease prevention, and health promotion.

The matrix consists of three tiers, placed one above the other. The pathology and extent of the lesions are represented along the horizontal axis. + and – indicates lesion activity. Level 1 in the matrix outlines WHO methods of assessment ( D₃MFT); level 2 tier includes D₁MFT, ADA, collapsed ICDAS, and other systems which help in differentiating cavitated and non-cavitated enamel lesions. Level 3 tier represents the full ICDAS system.M, F and PUFA is also been added in this matrix.

Classifications and its Features:

Classification and Year	Basis	Salient features	Demerits
G.V Black ⁴, 1908	Location	First attempt at classification	Degree of lesion is not recorded i.e, even white spot lesions are surgically treated.
WHO⁵ ,1979	Depth of lesion	Used as epidemiological tool. Allows recording of non-cavitated lesions.	Root caries not recorded.
Billing’s root caries Index⁶,1985	Degree and progress of lesions	Provides a treatment plan.
G.J Mount⁷, 1998	Site and extent	Guides in choice of restorative material. Non cavitated lesions are not treated surgically, rather eliminated by remineralisation.	Lesion activity is not assessed
Nyvad⁸,1999	Lesion activity	Provides treatment options for active and inactive lesions.	Difficulty in assessing precavitated. Lesion activity in occlusal surface due to physiological wear.
ICDAS¹³, 2005	Extent of lesion	Records coronal and root caries. Tooth with restoration also recorded. Used in both the dentitions.	Complicated system. Root caries assessment is not validated.
ADA-CCS¹⁵,2008	Extent of lesions	Easy to use	Lesions activity is not yet implemented
PUFA¹⁶,2010	Consequence of untreated lesions	Untreated dental caries conditions recorded. Applicable in both the dentitions.	Unnecessary extension of index. Different score, assigned for fistula and abscess, though it’s the presentation of same condition.
CAST¹⁹,2011	ICDAS + PUFA+ M,F	Wide range of conditions associated with caries recorded.	Suitable only in epidemiological studies

Early Childhood Caries Classification Systems:

The children of today are the adult of tomorrow. Oral health and overall health and well-being are inseparably related. The eating habits of children in various age groups greatly influence their overall health.²¹

Caries' involvement of maxillary incisors within one month of eruption is known as early childhood caries. ECC includes two variants, nursing bottle caries, and rampant caries. The primary difference is that involvement of mandibular incisors is rampant which is usually spared in nursing bottle caries by tongue and salivary action. Age specificity of nursing bottle disease is among infants and toddlers, whereas rampant caries affect all age groups. Obesity and dental caries have become two of the most common health issues in children with dental caries affecting 41% of children of the age group 2-11 years and 10.3% of the children of the same age group are found to be obese.²²

Wyne’s classification: [1999]²³

With various definitions proposed by different authors for ECC. Wyne proposed a diagnostic classification of types of ECC with probable cause and age affected.

Type I: Mild to moderate (2-5 yrs)

· Caries in molars and incisors

· Number of carious teeth increases as cariogenic challenge persists

· Cause: cariogenic semi-solid food and lack of oral hygiene.

Type 2: Moderate to severe

· Labiolingual caries lesion affecting maxillary incisors

· Unaffected mandibular molars.

· Cause: bottle feeding/at will breastfeeding/poor oral hygiene

· Seen after the eruption of teeth

Type 3: Severe/Rampant (3-5 years)

· Caries of all teeth including mandibular incisors.

· Cause: cariogenic food and poor oral hygiene

Drury classification[1999]²⁴

Drury and his associates published an age-wise case definition of ECC, based on total dmfs scores. This classification was proposed in the discussion at the workshop conducted in Bethesda.

<12 months - 1 or more smooth dmf surface

12-23 months - 1 or more smooth dmf surface

24-35 months - 1 or more smooth dmf surface

36-47 months - dmfs score ≥4

48-59 months - dmfs score ≥5

60-71 months - dmfs score ≥6

CONCLUSION:

Although various classification systems are in use, each system has its advantages. The ideal caries classification system remains elusive. With time and use, disadvantages can be recognized, and still there may be many gray areas to require further classifications. An attempt has been made to review almost all classification systems, so that accurate and detailed pictures can be depicted in clinical cases.

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Received on 08.03.2021 Modified on 25.11.2021

Research J. Pharm. and Tech 2022; 15(10):4819-4824.

DOI: 10.52711/0974-360X.2022.00809