Fig. 1
From: Tooth whitening with an experimental toothpaste containing hydroxyapatite nanoparticles
The 3D-printed repositioning system for the color measurement. A bovine tooth was embedded in the sample holder (a and b). The size of the measuring window of the sample holder is identical to that of the spectrophotometer (c). The embedded tooth was placed on the lower-left corner of the position locator (d), which was fixed on the spectrophotometer. The sample was held firmly by the movable arm during the color measurement (e)