Reproducibility and reliability of intraoral spectrophotometers

Introduction: In the 1990s computerized tooth colour measuring instruments were introduced on to the dental market that facilitated the practical recording of tooth shades in everyday practice. This experimental study evaluated two such devices; comparing the reproducibility, reliability and interreliability of the dental spectrophotometer QuattroShade (QS, Goldquadrat GmbH, Hannover, Germany) and the VITA Easyshade Advance 4.0 (VES, Vita Zahnfabrik, Bad Säckingen, Germany). Material and Method: Under simulated clinical conditions the tooth colours and L*a*b* data were measured for 2 extracted human teeth (tooth 12 and tooth 21) in three experimental phases. (I) 3 series of measurements were taken using both devices on both teeth. Initially, calibration took place after every measurement, then in the two following series at intervals after every five and ten measurements respectively (n = 250). (II) 51 recruits each made three measurements (n = 153) for tooth 21 using both devices. Equipment was calibrated before each new user. (III) tooth 21 was measured 153 times (n = 153) with calibration after every third reading. The statistical program SPSS (Inc., U.S.A for windows version 24.0) was used to analyse the data. Results: Significant differences (Wilcoxon-test, Friedman-test, p ≤ 0.05) were found between the reproducibility measurements of each device. A comparison of measurements between the devices also showed differences. A correlation between frequent and longer calibration intervals was evident. Less deviation occurred with fewer calibrations (after every ten measurements) than with more frequent calibrations (after each measurement). The reproducibility of the L*a*b* values was higher using the VES when compared to the QS. Concerning reliability, slight differences in delta (Δ) E values were noted for both devices. The QS showed better values between multiple users than the VES. All deviations are not relevant for clinical purposes (ΔE = 0.8–2.2). Conclusion: This study has shown that both devices for tooth colour determination are suitable for daily practice. However, a visual check should still be made with a conventional colour scale. Keywords: digital tooth colour determination, reliability, reproducibility, spectrophotometer