Raman spectroscopy may help discriminate various zones of carious dentine lesion: Study

Carious tissue discrimination in clinical operative caries management relies traditionally on the subjective hardness of carious dentine. Biochemical alterations within the lesion have the potential to discriminate the lesion zones objectively.

Therefore, M.Alturki and colleagues aimed to determine the correlation between the biochemical proportions of amide I and phosphate moieties as these are the most prominent peaks found in dentine with the Knoop microhardness of carious dentine zones, using non-contact Raman spectroscopy.

423 scan points from 20 carious dentine lesion samples examined using high-resolution Raman spectroscopy was used for analysis. The peak ratio of the characteristic vibration mode of amide I (1650 cm⁻¹) and phosphate (960 cm⁻¹) bands were calculated, following a straight- line path through the lesion to the pulp and correlated to corresponding Knoop microhardness measurements.

The authors noted that when using logistic regression analysis, clear correlations were found between the Knoop microhardness and Raman peak ratio cut-off values between caries-infected and caries-affected dentine (81.5 % sensitivity / 92.7 % specificity), with a lower specificity (2.7 %) found between caries-affected and sound dentine.

Hence, they concluded that "non-contact Raman spectroscopy can be used in vitro to discriminate objectively between the different zones of a carious dentine lesion at high resolution, using the Raman peak ratios, amide I : phosphate ν₁."

However, the clinical significance of the study was that specific biochemical alterations have the potential to be used in-vitro and in-vivo to identify the end-point of selective carious lesion excavation.