Revealing acid-induced enamel damage: Deep UV Raman and multivariate analysis of hydroxyapatite loss

Area of Science:

• Biophotonics
• Dental Materials Science
• Biochemistry

Background:

• Orthophosphoric acid etching is an in vitro model for hydroxyapatite loss and surface conditioning in dental enamel.
• Understanding molecular alterations is crucial for diagnostic and restorative dentistry.

Purpose of the Study:

• To investigate molecular alterations in human enamel following orthophosphoric acid etching using deep ultraviolet (DUV) Raman spectroscopy.
• To assess the potential of DUV Raman spectroscopy for non-destructive, label-free analysis of early dental enamel changes.

Main Methods:

• DUV Raman spectroscopy was applied to intact human tooth surfaces after acid etching.
• Resonance enhancement and fluorescence suppression techniques were utilized for high-quality spectral acquisition.
• Partial Least Squares Discriminant Analysis (PLS-DA) was employed for chemometric analysis.

Main Results:

• A reduction in the phosphate band (∼950 cm⁻¹) and a relative increase in the protein-associated amide band (∼1620 cm⁻¹) were observed.
• The mineral-to-organic ratio (I₉₅₀/I₁₆₂₀) decreased, indicating hydroxyapatite demineralization and organic matrix exposure.
• Intra-tooth comparisons were emphasized to minimize variability and accurately characterize localized chemical changes.

Conclusions:

• DUV Raman spectroscopy is a sensitive, non-destructive, and label-free technique for assessing early structural changes in dental enamel.
• The observed spectral changes correlate with hydroxyapatite demineralization and organic matrix exposure.
• Findings support the application of DUV Raman spectroscopy in diagnostic and restorative dentistry.