Compositional Changes of Teeth With Wedge-Shaped Noncarious Cervical Lesions

Objectives: To address the knowledge gap regarding dental tissue integrity in teeth with wedge-shaped noncarious cervical lesions (NCCLs), this study evaluated differences in organic composition and mineralization level between sound and NCCL-affected teeth.
Methods: Extracted teeth obtained from the biorepository at the University of Iowa College of Dentistry were examined to verify the presence or not of an NCCL. Selected teeth, consisting of five sound and five moderate NCCL (> 1mm deep lesion), were cut into halves (mesial and distal), embedded in epoxy, and analyzed for surface chemical characterization under RAMAN spectroscopy. Fifteen spectra were analyzed for each condition (sound and NCCL) and location (crown and root, dentin and enamel). Spectral analyses generated compositional ratios: mineral-to-matrix ratio (MMR), A vs. B type hydroxyapatite, proteoglycans, collagen cross-linking, and glycation. Compositional ratio averages were compared between sound and NCCL-affected samples and evaluated using Two-way Anova and Tukey’s post-hoc (a = 0.05).
Results: NCCL-affected coronal and root dentin had a lower carbonate-to-hydroxyapatite ratio than sound (p=0.01). Coronal dentin had a higher MMR (p=0.019) compared to root dentin for both sound and NCCL-affected specimens. Regarding organic compositional differences, sound root dentin had a lower Amide1-to-CH₂ ratio (collagen structure) compared to NCCL-affected root dentin (p=0.008). NCCL-affected coronal and root dentin had lower proteoglycans-to-collagen ratios compared to sound specimens (p<0.001). There were no significant differences between the sound and NCCL-affected samples for glycation or the mineralization ratios used for enamel (p>0.05).
Conclusions: Multiple differences in the mineralization and organic composition between sound and NCCL-affected teeth were highlighted. NCCL-affected teeth have lower hydroxyapatite carbonation and lower levels of proteoglycans within the dentin extracellular matrix compared to sound teeth. Increased collagen structure ratio was observed in root dentin of NCCL specimens. Coronal dentin had higher MMR when compared to root dentin.