Dental Caries Diagnostic Testing

Procedures

Dental explorers have traditionally diagnosed carious lesions; however, studies have shown that this method causes irreversible harm to the tooth surface and favors the lesion's progression.[3] Dental explorers can disrupt remineralization and transfer cariogenic bacteria to adjacent teeth. Furthermore, using dental explorers to assess occlusal surfaces can result in misdiagnosis - a deep fissure that seems to be a "sticky occlusal surface" could be misdiagnosed for dental caries. Dental explorers should only be used to remove stains and soft plaque from tooth surfaces.[4] Visual examination always comes first when assessing for caries. It requires a dry surface and can be enhanced by magnifying loupes.

The International Caries Detection and Assessment System (ICDAS) serves as a valuable tool in detecting and recording caries. The ICDAS classifies carious lesions into six categories, ranging from 0 to 6, where a higher score correlates with a more extensive lesion. The ICDAS can track the changes and progression of carious lesions. It is a specific, accurate, and reproducible classification system.[5] See Table. International Caries Detection and Assessment System Caries Score Table.

Radiographic Diagnosis

Visual-tactile examination of carious lesions is not sufficient for assessing interproximal or occlusal surfaces. Therefore, radiography is commonly used to assess and detect caries, as it gives the practitioner additional information about the clinical progression.

When x-rays go through tooth structures, the beam becomes attenuated according to the different structures within its path. Dental hard tissues and bone appear radiopaque because of their calcified structure, which stops or absorbs the x-rays. Soft tissues are not as calcified as bone or teeth and will allow the x-rays to penetrate through them, making the structure appear radiolucent.[6]

On radiographs, carious lesions appear as low-density areas under the tooth structure. This area represents demineralization and dissolving of hard tissue. When viewed radiographically, interproximal caries begin apical to the contact point and are cone-shaped. The base points toward the periphery and caries spread along the dentin-enamel junction. Occlusal caries affect the base of pits and fissures of tooth structure and first appear as a radiolucent dot at a depth of the fissure. Occlusal caries can be identified as thin radiolucent lines at the dentin-enamel junction.[7] Root and cement caries can be identified as interproximal notched radiolucencies, coronal to the bone height, and apical to the cement-enamel junction.

Recurrent or secondary caries occur in teeth that have already been restored. These caries are identified by low densities areas of demineralization seen adjacent to or under the restoration site. Lining materials are frequently misidentified as recurrent caries, so it is important to distinguish between them.

Various radiographic techniques can be used for caries detection, but posterior bitewing, periapical, and panoramic views are the most popular.

Posterior bitewings capture the occlusion of upper and lower premolars and molars. They are the most common view to detect dental caries and the radiograph of choice to diagnose interproximal caries - traditionally the first radiographs used if a patient has a low-caries risk.[8] Periapical views show the whole tooth, from crown to root, and can help detect anterior proximal caries, periodontal disease, and periapical lesions. Lastly, panoramic views give an overview of the whole maxilla and mandible. This method can serve as a quick way to visualize caries; however, it does not provide sufficient information to detect incipient caries. It is important to note that radiography alone is not an adequate method for caries detection because it cannot distinguish between cavitated and non-cavitated or active and arrested lesions.[9]

Caries Detector Dyes

Although still controversial, caries detector dyes are used by many dentists to aid caries removal and diagnose occlusal caries. They work by staining the collagen associated with less mineralized dentin– they do not stain bacteria nor demarcate the infection front.[10] In a study on the caries detector dyes efficacy, Yip found that areas of tissue with greater concentrations of organic material were stained, regardless of being caries-free.[11] Using caries detector dyes routinely, without a proper understanding of its limitations, may lead to excessive removal of sound dentin and mechanical pulp exposure.[10]

Many caries detector dyes provide irreversible staining. Their use for diagnosing occlusal caries is not recommended as it would be aesthetically unwelcome. The extent of demineralization can be relatively noticed by the intensity of the fluorescent dye, where a higher intensity correlates to more demineralization.[12]

Fibre Optic Transilumination (FOTI)

In dentistry, transillumination refers to the transmission of light through dental tissues to aid in caries diagnosis. However, its uses are much broader, including evaluating developmental defects, like dental fluorosis, root canal orifices, and tooth fractures and cracks.[13]

Fiber-optic transillumination supplements clinical examination, with specificity and sensitivity as high or even higher than radiographs, while avoiding exposing patients to radiation.[14]

FOTI devices must be small, with apertures of 3 mm or less to give a point source and be compact. Although used by some providers, dental curing lights are not recommended for transilluminating teeth since they are associated with a risk of macular degeneration and retinal injury.[13]

Sound dental tissues have a different light transmission index than caries, calculus, external tooth discolorations, and restorative materials, making it possible to distinguish such changes with FOTI. A carious lesion looks like a shadow within the dental structure because it has a lower light transmission index than normal tissue. Calculus appears as a darker area on the tooth surface.[15]

How must the FOTI device be placed on the tooth? 

To assess proximal caries of anterior teeth, the provider should set the probe on the vestibulo-cervical aspect of the tooth and examine the tooth from the lingual face with a mouth mirror. To assess proximal caries of posterior teeth, the provider must set the probe on the cervical region of the tooth, either buccally or lingually. 

A flexible and thin fiber-optic tip has been recently developed to evaluate interproximal caries in posterior teeth, which must be glided below the proximal contact.[13]

Latest Technologies to Evaluate Dental Caries

Newer technologies in the dental field, including fluorescence, electrical conductance, and lasers, allow professionals to detect caries at an earlier stage. These technologies inform the dentist of the extent of demineralization on a specific tooth and allow for early intervention.

Photothermal Radiometry and Modulated Luminescence (PTR-LUM)

PTR-LUM monitors caries-related changes in the tooth's microstructure and can be used adjunctively with radiographs. The measured changes correspond with optical and thermal properties measured by photodetectors and infrared detectors. The resulting PTR-LUM response is viewed on the Canary scale as a number between 1 and 100. A reading between 1 and 20 indicates that the mineralization corresponds with a healthy tooth. A number between 20 and 70 is indicative of demineralization. Lastly, a reading of 70 or greater is a strong indicator of advanced demineralization and decay and requires invasive treatment.[16] Depending on how high the number is, the dental practitioner can decide if invasive or noninvasive treatment is needed.

Laser Fluorescence Caries Detection Devices

A laser fluorescence caries detection device is a non-invasive laser method that allows the early detection of dental caries. It is accurate and sensitive in diagnosing dentinal caries and is widely used in dental practices. The device's diode laser is first irradiated on the surface of a cleaned tooth surface to calibrate the device. After completing calibration, the device scans each tooth, comparing the amount of fluorescence reflected by the grooves or tooth surface and the amount of light absorbed by various dentinal metabolites, including intraoral bacteria and bacterial byproducts. A higher amount of bacteria correlates with a carious cavity. The greater the light absorbed, the higher the chances of a cavity.

In addition to informing the dentist of the presence of a cavity, laser fluorescence caries detection devices can give specific information, including the cavity's location and extension. This advanced laser technology can detect caries in grooves, whereas traditional radiographs cannot.[17] Laser fluorescent readings are interpreted using the Canary Scale, where a value of 0-10 indicates a healthy tooth structure, 21-70 indicates decay, and 71-100 indicates advanced decay. Overall, laser fluorescent detection device is a simple yet effective technology that accurately detects early caries.[2]

Light-Induced Fluorescence 

Light-induced fluorescence can identify incipient caries' demineralization and remineralization progress when treated with a therapeutic agent, like fluoridated mouthwash. It is an excellent way to assess if therapeutic agents allow proper remineralization, as it gives a quantitative measurement.

Light-induced fluorescence utilizes the natural fluorescence of teeth to differentiate caries from healthy enamel. This is because lesions have a lower fluorescent radiance than sound enamel.[1] This tool provides information about the lesion size, percentile fluorescence loss (Delta F), lesion volume (Delta Q), bacterial activity and presence of red fluorescence (Delta R), and staining intensity (Delta E). Demineralization increases fluorescence loss, and remineralization decreases it.

Unfortunately, there are some drawbacks to light-induced fluorescence: the detection of carious lesions can be limited by the presence of saliva or plaque. Staining intensity can enhance the detection of lesions by light-induced fluorescence. However, it can also be decreased artificially by bleached teeth.[18]

Clinical Significance

The dentistry field is progressing towards a more conservative approach when treating dental caries. Newer diagnostic technology can detect initial stages of demineralization, allowing non-invasive intervention as early as possible to prevent further damage; this has invaluable repercussions on the oral health of the individual and broader community. However, more traditional methods, such as fiber optic transillumination, should not be disregarded since sufficient evidence supports its high specificity and sensitivity in caries diagnosis.