The aim of this in vivo study was to investigate the influence of age on optical properties of pure enamel and enamel-dentine complex.

A spectrophotometric study was performed on two different age groups: young (10-35 years old) and adult (36-60 years old). In both groups, the tooth's total area of the upper right central incisor was recorded. Areas of 2mm thick pure enamel and 3mm enamel-dentine complex were detected and their L a b and CR evaluated.

For 2mm pure enamel medians in the young group were L 74.8, a 3.1, b 15.1, against white background; and L 65.5, a 0.9, b 10.3 against black background. The correspondent opacity was 75%. In the adult group medians were L 70.0, a 4.1, b 15.4 against white background; and L 61.2, a 1.6, b 9.6, against black background. The correspondent opacity was 75%. For 3mm enamel-dentine complex medians in the young group were L 77.8, a 3.0, b 19.8 against white background; and L 74.2, a 1.1, b 15.9, against black background. The correspondent opacity was 89%. In the adult group medians were L 73.4, a 4.0, b 18.5 against white background; and L 71.0, a 2.0, and b 15.3 against black background. The correspondent opacity was 90%.

The application of this method on a larger group of subjects of different ages may serve as a database for a more exact characterization of optical properties of natural enamel and dentine.

L values in enamel, as well as a* value of 3mm thick enamel-dentine complex and 2mm pure enamel were significantly higher in the young age group.

L and a values of enamel over white and black backgrounds were statistically different within the 2 age groups considered. L values over white background and a values over black background of the enamel dentine complex seem to change with age. The opacity (CR) for enamel nor for enamel dentine complex does not change within the two age groups considered in this study.