The pits and fissures on the occlusal surfaces of posterior teeth are the sites most commonly affected by carious demineralisation. Unfortunately, their microscopic anatomy is variable and complex, with no external indicators of depth or sub-surface morphology. Incipient carious demineralisation is often hidden at the base of fissures in areas that are inaccessible to tooth brushing and benefit least from fluoride and from the buffering and clearance actions of saliva for plaque and dietary acids.
Early detection is one of the fundamental principles of minimally invasive dentistry as there is incontrovertible evidence that, up to a certain point, the disease process is reversible by remineralisation and carious lesions may be arrested. Detection is defined as an objective method of determining whether or not disease is present. Diagnosis of a detected lesion is the summation of all available data to inform decisions regarding lesion activity, prognosis, recall frequency and management options tailored to the need of the individual.
Visual examination is considered to be the most important method for monitoring the occlusal surfaces of posterior teeth and detecting and diagnosing carious lesions. Pain or sensitivity to cold, hot, and sweet stimuli are subjective symptoms, only likely to occur late in chronic lesions where tubular infill and tertiary dentine not until lesions become cavitated that sensitivity occurs as insulation is lost.
To help clinicians make predictable diagnostic decisions, a classification system was developed, aiming to correlate the visual appearance of pits and fissures and their histopathology.
This has evolved to include all tooth surfaces (including restored ones) into the International Caries Detection and Assessment System (ICDAS) which uses a standardised protocol to visually assess tooth surfaces and code them using a 0-6 scoring system.
Multiple publications on its use have reported good intra- and interexaminer reproducibility, improved diagnostic accuracy and more predictable evidence based treatment decisions. The ICDAS codes allow diagnostic information to be simply communicated to the patient and may be recorded in their notes to document both lesion-monitoring and minimally invasive management decisions, and to act as a medico-legal record.
ICDAS codes:
ICDAS 0: This correlates to sound tooth surface, with no detectable demineralisation after five seconds of air drying.
ICDAS 1: This describes the first visual change in enamel and is commonly referred to as a white spot lesion. These incipient lesions result from an increase in porosity and correlate histologically to an enamel lesion extending up to half its thickness. The opacity (or white/ brown discolouration) is often matte and is restricted to the pit/fissure.
Code 1 lesions are visible only after prolonged air drying (>5 seconds), which reveals a difference in refractive index between demineralised and adjacent enamel as shown in figure 1.
ICDAS 2: Here, a distinct change in enamel is seen and is visible when the tooth surface is wet or dry (fig 2). The ?lesion is often wider than the pit or fissure and histologically is expected to involve the whole thickness of enamel up to the enamel-dentine junction (EDJ). ICDAS codes 1 and 2 both correlate to early stages of the caries process.
ICDAS 3: This corresponds to a more established lesion where localised enamel breakdown is visible when the tooth surface is wet or dry. A ballended probe may be used to confirm presence of micro-cavitation. Although histological demineralisation may be considered to involve the outer or middle third of dentine, code 3 relates to lesions where there is no clinical visual sign of dentine involvement and forms an important boundary regarding management options.
While great variation exists, pits and fissures coded 1, 2, 3 may be amenable to preventive or minimum intervention management techniques such as sealants or preventive resin restorations (PRR).
ICDAS 4 - These very commonly observed non-cavitated established lesions exhibit no clinically visible dentine, but demonstrate distinct dentine involvement, often via a dark underlying shadow, as the lesion spreads laterally subjacent to the EDJ and towards the pulp (fig 4).
Unfortunately, a poor relationship exists between their visual appearance and the level of bacterial infection, making the choice of minimally invasive management options more contentious.
ICDAS 5 - Here, a distinct cavity with exposed dentine is detected. The dentine may be immediately visible or revealed after very careful cleaning using a suitable technique (fig 5).
Cavitation is considered to be a critical turning point in the disease process as it cannot be reversed. The presence of an active biofilm that is impossible to remove by oral hygiene procedures means that lesion progression is inevitable and may eventually result in gross cavitation if dentine caries undermines the overlying enamel.
Histologically, demineralisation may be expected to involve the inner (pulpal) third of dentine and while minimally invasive techniques (such as PRR) may still be successfully employed, more traditional restorative techniques are often necessary.
ICDAS 6: This describes an extensive cavity with distinct dentine involvement and constituting over 50 per cent of the occlusal surface. This corresponds to a late stage of the caries process where demineralisation is likely to involve the inner third of dentine and the lesion may extend into the pulp chamber.
Addendum
A simplified, modified version of the ICDAS system has also been described (mICDAS) which uses just five codes to link visual appearance to the expected underlying damage. Codes 0, 1 and 2 are identical in both systems but mICDAS 3 incorporates both ICDAS codes 3 and 4 and mICDAS 4 corresponds to ICDAS 5 and 6.
References available on request.