Researchers have recently found out that short-term dental dehydration produces clinically unacceptable changes in tooth color, hence clinical shade matching must be done within the first two minutes of any clinical procedure, as published in the Journal of Dentistry.
Dental restorations should mimic sound tooth structures in terms of color and optical properties especially in the anterior region. However, closely matching natural teeth with a restoration can be one of the most challenging procedure in restorative dentistry. Shade matching includes color determination, color communication with dental lab and color reproduction with dental restoration for indirect techniques or color determination and selection of the appropriate material and application method when using direct techniques. Therefore, color selection is the first critical step in the restoration procedures and should be carried out properly.
Hence, Javier Ruiz-López and colleagues from the Department of Optics, Faculty of Science, University of Granada, Granada, Spain conducted the study to determine in-vivo chromatic and whiteness changes produced by short-term dental dehydration.
The authors measured the spectral reflectance of 452 upper incisors (226 centrals and 226 laterals) of 113 participants using a spectroradiometer at baseline and after short-term dehydration (minutes 2, 4, 6, 8 and 10). CIE L*a*b* color coordinates (L*, a*, b*, C*ab and hab) and whiteness index for dentistry (WID) were calculated.
Color differences were computed and interpreted based on their respective 50:50% perceptibility (PT) and acceptability thresholds (AT). Statistical analysis was performed using the related samples Wilcoxon signed-rank test.
The following results were observed-
a. L* showed an increasing trend with dehydration, while a*, b*, C*ab and hab have a decreasing tendency.
b. All chromatic coordinates showed statistically significant differences (p < 0.003) at each interval of dehydration compared with baseline, except a* for all teeth.
c. For and values were higher than PT after 2 min of teeth dehydration and higher than AT after 6 and 8 min, respectively.
d. The percentage of teeth exceeding corresponding PT was higher than 50% after 2 min.
e. WID index increased with dehydration time, while whiteness differences were clinically perceptible after 4 min.
f. Statistically significant differences were found for WID between all dehydration intervals (except 8−10 min).
g. The percentage of teeth exceeding whiteness PT was higher than 50% after 6 min of teeth dehydration.
Hence, it was concluded that "Short-term dental dehydration produces clinically unacceptable changes in tooth color and clinically perceptible increase in tooth whiteness level and clinical shade matching must be done within the first two minutes of any clinical procedure that requires precise chromatic determination but implies a risk of tooth dehydration."