COMPARISON OF THE ACCURACY OF DIGITAL AND INSTRUMENTAL METHODS FOR TOOTH SHADE DETERMINATION

Abstract

The aim of this study was to compare the accuracy of digital and instrumental methods for tooth color determination under clinical conditions, considering the influence of different lighting environments and digital image processing parameters, and to evaluate the feasibility of their combined use to improve reproducibility. Materials and Methods. Sixty patients aged 17–55 years were enrolled and divided into three groups according to the primary shade selection method. In the first group, measurements were performed using a CM-200S colorimeter; in the second group, an intraoral 3D scanner (Shining 3D) was applied; in the third group, parallel measurements with both devices were conducted. A total of 120 photo sessions were performed under various lighting conditions, including natural daylight, warm and cool artificial lighting, dental chair light, and special photolight. Color parameters were analyzed in the CIELAB color space (L*, a*, b*) with ΔE values calculated using both CIE76 and CIEDE2000 formulas. Digital images were processed using darktable and CloudCompare software. A proprietary Lab GUI application was developed to standardize region-of-interest selection and automate color parameter computation. Statistical analysis  included calculation of mean ΔE values and evaluation of variability under different lighting scenarios. Scientific novelty. This study provides a comprehensive comparison of instrumental (colorimetry and 3D scanning) and digital photographic methods with simultaneous assessment of spectral composition and illuminance intensity effects on tooth color determination. A combined shade-matching algorithm is proposed, integrating instrumental reference data with digital analysis through the Lab GUI software to minimize operator-related bias. Instrumental methods demonstrated practical equivalence (ΔE = 0.25), while digital measurements revealed lighting-dependent variability thresholds relevant for clinical interpretation. Conclusions. Both the colorimeter and the intraoral 3D scanner showed high agreement and can be considered reliable reference tools for tooth color assessment. Digital photographic analysis is significantly influenced by lighting conditions: the most stable results were achieved under neutral daylight, whereas warm, cool, and mixed lighting produced systematic shifts in a* and b* parameters and increased ΔE values. A combined approach, using instrumental methods as reference and digital techniques as flexible clinical tools under strict standardization, appears to be the most rational strategy for accurate shade matching in restorative dentistry.