# Level of Agreement in Subjective Selection of Gingival Colour
## 4 Discussion
### Electronic Device  
Spectrophotometers have been said to have a precision of over 96% [45] and an accuracy of 66.8% to 92.6% [46] in the dental colour space, since they were initially designed and used to quantify dental colour. These electronic devices may also have the potential to evaluate gingival colour in a reliable manner [47]. [PERSON] et al. [48] found that the repeatability and reproducibility of colour readings with spectrophotometers on gingival tissue were almost perfect (ICC \(>\) 0.9), whereas the results of [PERSON] and colleagues displayed a limited degree of reproducibility [47]. There are issues--such as gingival curvature, certain characteristics of the gingival surface, the degree of translucency, contact with the gingival tissue, the phenomenon of edge loss, and the failure to adequately maintain electronic devices for colour recording--which can alter the chromatic results obtained [45]. To minimise the impact of these phenomena, a spectrophotometer with a \"wide window\" was used. Using instrumental methods results in a greater level of agreement in the dental shade match than when colour is recorded using visual methods [49], in addition to a higher level of precision and reproducibility [16]. In quantitative terms, published figures range from 30% to 67% alignment between subjective visual comparisons and spectrophotometric results in the dental context [24, 50, 51], while other authors have not identified any relationship between the two methods [52, 53]. The lack of standardised gingival shade tabs means that the spectrophotometer can only provide colour coordinates: this is why it has not been possible to provide results in the form of percentages of agreement with gingival shade guide terms and why the differences have been shown in terms of the CIEDE2000 and traditional Euclidean formulae. In this study, all the colour differences identified between the results of visual selection and spectrophotometry fall significantly above the published clinical acceptability threshold for the gingival colour space (4.1 units for CIELAB* and 2.9 units for the CIEDE2000 formula) [54], as was the case in [PERSON] and colleagues' research [51]. Another study, focused on the dental colour space, identified a difference of 7.35 units for \(\Delta\)Eab* between the visual comparison and the spectrophotometric readings [50]. It is important to note that the two formulae (CIELAB* and CIEDE2000) show a higher level of agreement in the gingival colour space [55].  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**CIELAB (\(\Delta\)Eab*)**} & \multicolumn{3}{c}{**CIEDE2000 (\(\Delta\)E00)**} \\  & **Male** & **Female** & **\(p\)** & **Male** & **Female** & **\(p\)** \\ \hline Mesial papilla & 12.08 (5.30) & 12.63 (5.16) & 0.386 & 9.48 (4.99) & 9.98 (4.84) & 0.400 \\ Distal papilla & 10.29 (4.92) & 11.56 (4.80) & 0.076 & 8.96 (4.95) & 8.74 (4.64) & 0.776 \\ Free gingival margin & 13.12 (5.53) & 11.92 (5.03) & 0.146 & 10.30 (5.09) & 9.27 (4.62) & 0.183 \\ Middle zone & 11.96 (4.10) & 11.01 (4.97) & 0.234 & 9.05 (3.69) & 8.46 (4.44) & 0.410 \\ Mucogingival line & 11.87 (4.80) & 13.02 (5.34) & 0.154 & 8.64 (5.05) & 10.38 (5.71) & **0.042** \\ \hline \hline \end{tabular}
\end{table}
Table 7: Means (standard deviations) of the colour differences between the gingiva and the shade tab selected by the male observer and the female observer, by gingival zone.