The use of digital imaging for colour matching and communication in restorative dentistry

Key Points Demonstrates the difficulties of matching teeth and the need for an objective and reliable means of shade matching. Digital images acquired under standard lighting conditions can provide reliable colour measurements. The use of digital images in shade matching will allow technicians to view variations in tooth colour and improve communication between technicians and clinicians. Objective To develop a shade matching method based on digital imaging and to compare observers' ability using this method with the conventional one set against a spectrophotometric 'gold standard'. Methods Two Vita Lumin shade guides were used in this study, nine shades being selected from the first Vita Lumin shade guide, A2, A3, A3.5, B2, B3, B4, C1, C2 and C3. A second shade guide was used to match the selected shades. A Nikon Coolpix 990 digital camera with Nikon SB21B ring flash was used to record the digital images of the shade tabs of the two shade guides and the images were processed using Adobe Photoshop software. A total of 27 samples (three replicates of each shade of the nine tabs selected) were matched with a digital shade guide prepared from the digital images of the second shade guide by 10 observers on a computer screen (computerised matching method). The 10 observers also matched the same shade tabs using the conventional matching method simulated in a phantom head. In addition, colour values were obtained from the digital images using Adobe Photoshop and quantified according to an internationally recognised scale as CIELAB colour values, L * ,a * ,b * . The relationship of the digitally derived CIELAB values to the CIELAB values obtained using a reflectance spectrophotometer was investigated. Results The cross tabulation statistical analysis showed a statistically significant difference (p