Comparison of color measurements using three different spot measurement colorimetric devices applied to natural teeth

Abstract

Statement of problem

The variability in color measurements between different dental devices complicates the accurate selection of tooth shades, which is crucial for esthetic dental restorations. Understanding the correlations between different devices can provide equations for inter-conversion, facilitating more consistent shade selection.

Purpose

The purpose of this clinical study was to evaluate and compare the colorimetric values measured from human teeth using colorimetric devices of the spot measurement type, including a conventional spectrophotometer, an intraoral spectrophotometer, and an intraoral colorimeter, and to develop inter-conversion equations based on device correlations.

Material and methods

Forty healthy, non-smoking ethnic Korean volunteers aged 25 to 36 years with no anterior restorations or abnormal dental conditions were enrolled. Color measurement was made using a CM-700d spectrophotometer (Konica Minolta) (CM), Vita Easyshade intraoral spectrophotometer (Vita Zahnfabrik) (ES), and ShadeEye NCC colorimeter (Shofu) (SE) under controlled lighting conditions on maxillary central incisors using a transparent ethylene-vinyl acetate tooth guide with holes to ensure precise probe placement. ΔE_ab and ΔE₀₀ values indicated color differences between devices. Statistical analyses included Pearson correlation and regression to assess inter-device variations, with intraclass correlation coefficients calculated for intra-examiner reliability (α=.05).

Results

Mean L* values for CM, ES, and SE in the maxillary central incisors were 66.1, 81.4, and 72.8, respectively. The mean a* values were 0.7, −0.9, and −0.4, while the mean b* values were 10.1, 16.3, and 12.3, respectively. The largest color discrepancies were observed between CM and ES. The r² values between each pair of devices for colorimetric values ranged from 0.111 to 0.488 (P<.01). Intra-examiner reliability was CM: L*=0.916, a*=0.826, and b*=0.797; ES: L*=0.984, a*=0.991, and b*=0.988; and SE: L*=0.940, a*=0.636, and b*=0.996.

Conclusions

The findings suggest that values can be converted between different devices and compared against standard references measured by each device. This will help in understanding changes in tooth color measured on one device in terms of another.