Relevant optical properties for gingiva-colored resin-based composites.

Objectives: To evaluate the optical properties of gingiva-colored resin-based composites (GCRBCs).

Methods: Five discs (8 mm diameter x 1mm height) of 17 shades of GCRBCs were prepared. Diffuse reflectance was measured against white and black backgrounds using a calibrated spectroradiometer, CIE D65 illuminant and the CIE 45⁰/0⁰ geometry. Relative translucency parameter was calculated using ΔE (RTP). Translucency differences were evaluated using published data of 50:50% translucency perceptibility (TPT) and acceptability (TAT) thresholds. Scattering (S) and absorption (K) coefficients and transmittance (T%) were calculated using Kubelka-Munk's equations. Data were statistically analyzed using Kruskal-Wallis, Mann-Whitney tests, and VAF coefficient.

Results: The RTP values of the 17 evaluated shades ranged from 8.69 to 21.34. There were perceptible translucency differences (TPT=0.62) between different shades of the same brand and between composites designated with the same shade of different brands. Spectral distributions of S, K and T were wavelength-dependent. Although the spectral behavior of the S and K coefficients and T% were similar for all the gingival composites evaluated, the values of these parameters presented statistically significant differences between shades, which would justify the differences found in the relative translucency parameter.

Conclusions: The optical properties S, K and T% of GCRBCs were significantly different, resulting in perceptible translucency differences between the same shade of different commercial brands and between different shades of the same brand.

Clinical Significance: Translucency differences of gingiva-colored composites may significantly influence their masking ability affecting the clinician's choice of restorative material.