Determining when to stop caries excavation can be a challenge because the visual and tactile evaluation of a carious lesion is subjective.

To standardize the caries excavation process, there are various products on the market to help dentists determine when to stop their tooth preparations. One of the more commonly used products is caries detection dye.

Caries detection dyes were first introduced to dentistry in the 1970s. These early solutions were composed of red fuchsin in a propylene glycol solution. The theory behind the use of these early solutions was that they would stain degraded, carious dentin while leaving the sound dentin unstained.

Concerns about the carcinogenic properties of red fuchsin led to its replacement with other dyes. Most modern caries detection dyes utilize different colored dyes based on a propylene glycol solution. The science behind recent caries management developments, namely the emerging science related to oral biofilms and the use of silver diamine fluoride, can be explored by watching Spear’s new course, “Medical Management of Dental Caries: The Science Behind It and the Methods To Do It.”

Mechanism of action and accuracy

Although caries detection dyes are used to identify dentin infected with cariogenic bacteria, these dyes don't stain the bacteria in the lesion. Rather, the propylene glycol penetrates areas of dentin with loose collagen fibers. This causes the caries detection solution to stain degraded collagen rather than bacteria.

Since the caries detection dye stains only degraded collagen, and not the bacteria that caused the carious lesion, these dyes are used under the assumption that removing the degraded collagen will remove the bacteria causing the carious lesion.

Various studies investigated the accuracy of caries detection dyes and both laboratory and clinical studies found caries detection dyes have a high rate of false positives. This is attributed to solutions non-selectively stain demineralized collagen.

Multiple studies showed high rates of false positives are commonly observed at the DEJ and in the circumpulpal dentin, which can lead to the excessive removal of healthy, non-carious tooth structure and unnecessary pulp exposure.

Other studies also highlighted concerns with esthetics and decreased bond strengths in areas stained by caries detection dyes.

Evidence of stain from caries detection dye on sound dentin.

Although caries indicating dyes are not highly specific, the intensity of the stain can be utilized to selectively remove stained areas. In general, areas with a darker, more intense stain tend to have a greater degree of demineralization and carious bacteria. Areas with a lighter stain may not be affected and can be left in place.

As a result, some protocols for the conservative treatment of deep carious lesions advise removing the darkly stained dentin while leaving the lightly stained dentin in place and ensuring a peripheral seal of healthy tooth structure when using a caries detection dye during caries excavation.

Can these be effectively used?

Although there are drawbacks to using caries detection dyes, they can be useful when used judiciously. Dark, intensely stained areas can be removed with confidence; however, lightly stained areas of dentin do not need to be aggressively excavated.

Indiscriminately removing dentin stained by caries detection dyes will lead to over preparation and can increase the risk of an inadvertent pulpal exposure.

Andy Janiga, D.M.D., practices at the Center for Dental Excellence in Nashua, NH and is a contributor to Spear Digest.


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