Repeatability of Colour Reading with a Clinical and a Laboratory Spectrophotometer

Corresponding Author: Dr. Gabriele Corciolani, Via Derna 4, 58100 Grosseto (Italy) E-mail: [email protected]; Tel/Fax: +39056425384 Abstract Objectives: The aim of this study was to evaluate the repeatability of readings with a clinical spectrophotometer in comparison with a laboratory one. Materials and Methods: A stand alone clinical spectrophotometer (Easyshade, Vita) and a laboratory one (PSD1000, Ocean Optics) were evaluated. Five ceramic disks were produced in different layering, with a fixed total thickness of the samples being maintained. Metal disks of 15mm in diameter and 0.7mm thickness were cast. The ceramic system used for layering was Omega 900 (Vita), and the colour selected for the trial was A3. The colour evaluation of each sample was repeated 5 times with each spectrophotometer to verify the scanning repeatability. The spectrophotometer repeatability was statistically evaluated analyzing the coefficient of variation (CV), which represents the ratio of the standard deviation to the mean of the CIELab* colour values. Results: An excellent scanning repeatability for both the spectrophotometers tested was demonstrated. Very low values of the coefficient of variation (0,002<CV<0,111) were obtained for Ocean Optics PSD1000 as well as for Easyshade, by both fixing the handpiece of the device to a graded stand (0<CV<0,022) and holding it by hand (0,008<CV<0,913). Discussion: Although manufacturing differences do not allow a direct comparison to be made between the two instruments tested, the reading values obtained from the tests showed an excellent scanning repeatability, both for the clinical spectrophotometer (Easyshade) and for the laboratory one (PSD1000). Conclusions: The repeatability of the readings with the clinical device were acceptable and comparable to the laboratory one and it can therefore be considered reliable. However, further studies are necessary to verify the exact connection between the colour values obtained from the clinical spectrophotometer and the absolute CIELab* values specific for each shade.