The measurement of tooth whiteness by image analysis and spectrophotometry: a comparison

Abstract

Digital image capturing and analysis techniques have been used to measure the colour of teeth and to compare with spectrophotometric results and visual observations. A non-linear image analysis approach was developed and, for the colour range of human teeth, allows device-dependant digital camera colour data to be quantitatively transformed to Commission Internationale de l'Eclairage (CIE) colorimetric values. With reference to a CIE standard illuminant, two different lighting arrays have been used. For flat and non-translucent white and yellow surfaces, spectrophotometric results showed that this transformation achieves required accuracy. It was found, in all of the present studies, which included measurements on the VITA Lumin Vacuum shade guide and extracted teeth, that spectrophotometry invariably underestimated values of the CIE whiteness index. However, the results from these two types of measurement correlated well. There was also a reasonably good correlation between earlier data obtained by visual assessment and the present data by the two instrumental methods. For extracted teeth, both instrumental methods used in this work did not confirm a whitening effect for 2-min brushing with toothpaste, but did show significant whitening results for bleaching with 15% hydrogen peroxide.

Relative Translucency of a Multilayered Ultratranslucent Zirconia Material

“…This method has been used to assess ΔE with established accuracy. 20,21,24,33,37 While ΔE which corresponds to differences in color perception with specimens positioned on the same background is computed according to the formula:…”

“…22,23 Moreover, image analysis is applied in shade matching, [24][25][26] communication between dentists and laboratory technicians, 27,28 diagnosis of gingival inflammation, [29][30][31] oral lesions detection, 32 and evaluation of bleaching results. [33][34][35][36][37] A very high and statistically significant correlation was found between the spectrophotometer and digital imaging analysis for all CIE L*a*b* color values. 27,38 Translucency is material-and thickness-dependent 9,39,40 and vary according to the measuring techniques.…”

Could digital imaging be an alternative for digital colorimeters?

“…The incandescent dental unit lamp has an average colour temperature of 3,800 K. For this reason, dental unit lights should not be used during colour selection as they are too bright and cause glare yielding to eye fatigue. Standard illuminant D65 represents a phase of daylight with a correlated colour temperature of approximately 6,500 K [3,9,10]. Illuminant A, on the other hand, represents light from the full radiator at absolute temperature of 2,856 K, and illuminant F2 represents light from fluorescent lamp with medium colour temperature of 4,230 K. Among these, illuminant A and D65 are commonly recommended.…”

“…In fact, spectrophotometric/colorimetric approach is attractive so it is more commonly used in dentistry, eliminating possible environmental viewing conditions and examiner's experience [11,[14][15][16][17]. On the other hand, computer analysis of digital images produced through a digital camera also enables collection of colour values from the images [9,18,19]. Systematic error due to translucency and surface curvature could be minimised when chargecoupled device (CCD)-based imaging systems (i.e.…”

“…Systematic error due to translucency and surface curvature could be minimised when chargecoupled device (CCD)-based imaging systems (i.e. digital cameras or spectroradiometers) are used [9]. However, their reliability for different shade guides under different colour temperatures are not known, to date.…”