2.3.2. Preliminary phase We first verbally explained the procedures to perform and asked each volunteer to read and sign an informed consent form (appendix 1). A clinic card (appendix 2) was completed for each patient. In each case, a heavy silicone matrix (Speedex® Putty) was prepared for both maxillary lateral incisors. These matrices were drilled at the height of the union of the cervical third with the middle third of the vestibular tooth face to standardize the color measurements with the spectrophotometer (Vita Zahnfabrik, Bad Säckingen, Germany). Another reason was to create a perfect fit with the nozzle of the spectrophotometer to help control the passage of light to the measurement site. The color of each upper lateral incisor was measured using the spectrophotometer, which was previously calibrated according to the manufacturer's instructions using arrays of heavy silicone.