Investigation of Intra- and Inter-individual Variations of Mineralisation in Healthy Permanent Human Enamel by Raman Spectroscopy

Purpose: To systematically examine mineralisation of healthy human enamel using Raman spectroscopy and provide an understanding of baseline variations that may be inherent in the healthy enamel from individual to individual as well as variations within a tooth. Materials and Methods: Human teeth were obtained in compliance with the NIH guidelines. The teeth were collected fresh within the date of the extraction and kept moist at all times with wet tissue paper without any additional disinfecting treatment. The samples were individually wrapped in wet tissue paper and stored in a -20°C freezer. Prior to Raman analysis, the specimens were thawed at room temperature for 30 min. A Raman microscope was employed with a 10X objective used to focus the laser light (785 nm). Raman spectroscopy scores were validated by microcomputed tomography (μCT) on the two teeth which had the highest and lowest mineralisation found in the Raman scans. Results: Mineralisation levels varied substantially between individuals. The highest Raman-based mineralisation intensity was about 5-fold greater than the lowest mineralisation score. Incisor mineralisation also varied dramatically depending on different sites on the tooth. Conclusions: Clinically applicable non-invasive techniques such as Raman spectroscopy that can quantify mineral content, such as Raman spectroscopy, may help answer whether or not mineralisation is associated with caries risk. Keywords: dental caries, enamel, enamel mineralisation, Raman spectroscopy