Vita classical guide

The color was assessed visually under standardized light conditions (same place, time, natural light source, all assessments were performed between 10:00 AM and 3:00 PM) by two previously calibrated operators, who showed a previous agreement (Visual Scales) of at least 85% as determined using weighted k-statistics. The viewing geometry, object-observer distance, visual angle, and background color were held constant. Each operator evaluated three times each tooth. If both operators coincided in their selection, the determined value remained as definitive, if there was a discrepancy, a calibrated third operator (professor of restorative dentistry) defined between both colors.
The Vita classical Guide (Vita Classic, Vita Zahnfabrik) and Bleached guide (Vita Bleached Guide, Vita Zahnfabrik) were used for subjective evaluation using the tab arrangement proposed by Ontiveros and Paravina [22 (link)]. The observers assessed the color of both central incisors at the start of the study, at each session of whitening, and 1 week, 1 month, 6 months and one-year post-treatment. The color was recorded on the middle third of the labial surface as established by the guidelines of the American Dental Association [23 ]. The difference in tooth color was calculated as the number of units that the tooth changed according to the shade guide arrangement (ΔSGU).

Participants were recruited on social media. This approach was carried out by sharing posts on both the Instagram feed and stories of the @bleachingbond research group user account. Additionally, the authors and other members of the research team reposted this content to further amplify its reach. Participants who met the eligibility criteria, before being included in the study, agreed to participate and their guardians read and signed informed consent forms.
Inclusion criteria were adolescents aged from 12 to 16 years with vital teeth free from caries lesions, periodontal disease, and endodontic treatment, with both mandibular canines presenting A2 or darker color according to the VITA Classical guide (VITA Zahnfabrik, Bad Säckingen, Germany), and in good general and oral health. Participants who were on chronic medication, who had undergone previous tooth bleaching, had previous tooth sensitivity, used fixed orthodontic appliances or prostheses, had parafunction, gingival recession, discoloration due to fluorosis or tetracycline, were pregnant or breastfeeding, had visible cracks in the teeth, or were smokers were excluded.^{2 (link),12 (link)}

The color of each upper central incisor was assessed by comparison with shade tabs of two commercially available dental shade guides (Vita classical Guide and Vita Bleached guide, Vita Zahnfabrik) and objectively with spectrophotometer (Vita Easy Shade® Compact, Vita Zahnfabrik) that was previously calibrated according to the manufacturer instructions. To standardize this evaluation, a silicone matrix was made (Zetaplus, Zhermack, Rovigo, Italy) with a 6 mm-diameter window on the buccal surface that allowed the positioning of the tip of the spectrophotometer on the middle third of the labial surface of the teeth.