Color evaluation
Color measurements were made using a VITA Easyshade spectrophotometer (Easyshade; Vident, Brea, CA, USA). Color evaluation was performed by one operator using the matrix previously described to standardize the placement of the spectrophotometer device in the same place during consecutive color evaluations [The color was determined using the parameters of the Easyshade device, which indicated the following values: L*, a* and b*, where L* represents the value from 0 (black) to 100 (white); a* and b* represent the shade, where a* is the measurement along the red-green axis and b* is the measurement along the yellow-blue axis. The color comparison before and after each period of treatment (Table 