Chemical profile of the dentin substrate in non-carious cervical lesions

The molecular structural nature of the dentin substrate in non-carious cervical lesions (NCCLs) is poorly understood. This investigation characterized the chemical structure including inhomogeneities, composition, mineral crystallinity, collagen organization of normal dentin and affected dentin substrates within NCCLs using Raman microspectroscopic mapping/imaging.

Three extracted human pre-molars affected with NCCLs were selected and cavities matching the natural lesion with respect to size and location were prepared on the lingual/palatal surface of each tooth to serve as controls. The specimens were sectioned to expose the gingival and occlusal margins of the NCCLs and the control cavities. Micro-Raman spectra and imaging were acquired at 1.5 microm spatial resolution at positions perpendicular to the lesion surfaces.

The Raman spectra and imaging comparisons showed the distinct compositional and structural alterations in mineral and matrix components of NCCL affected dentin. A heterogeneous hyper-mineralized layer, with characteristic features such as high phosphate/low carbonate content, high degree of crystallinity and partially denatured collagen were revealed in affected dentin substrate of NCCLs.

Generating Raman images based on different strategies from the same data set provides a powerful means to study the structural alterations within heterogeneous dental tissues. Direct overlay of the images indicated that the changes in chemical structure and composition are synchronized. Further studies are required to understand the role that these alterations play in response to acid etching and bonding to these clinically relevant substrates.