Vita classical shade guide

Participants were recruited from patients consulting the aforementioned Department of Dental Medicine from February to March 2017. Data collection was carried out during the period extending from April 2017 to February 2018. Patients were included in the study based on history-taking and clinical examination, taking into account the following inclusion criteria: age from 18 to 35 years and the presence of the 12 anterior teeth (VITA Classical shade guide, VITA-Zahnfabrik, Bad Säckingen, Germany). The exclusion criteria were as follows: patients with nonvital anterior teeth, tooth decay, periodontal disease, prosthetic restoration and/or resin composite restoration in the 12 anterior teeth, enamel hypoplasia, racks or fractures, dentin hypersensitivity, fluorosis, and tetracycline discoloration. In addition, patients should not have received previous teeth bleaching with dentifrice during the last six months or during the last two years in case of in-office/at-home bleaching. The two groups were pair-matched by sex, age, and socioeconomic level.

The examiner (DJ) responsible for recording the color of each tooth was trained to use a Vita Classical shade guide ordered by value (VITA Zahnfabrik, Bad Säckingen, BW, Germany).^19,20 The shades of 20 non-stained bovine incisors were recorded at two distinct times with a 7-day gap between evaluations. This data was scored and the level of intra-examiner reproducibility was determined by the Kappa coefficient. The examiner was considered calibrated after a Kappa coefficient = 0.647, which is considered a substantial agreement.²¹

Patients for this clinical trial were recruited through social media. Volunteers that met the eligibility criteria read and signed an informed consent form before being enrolled in the study. To facilitate communication between the research staff and the volunteers, we set up a social network group via WhatsApp ^® .
Volunteers were required to be between 18 to 40 years old and in good general health (self-reported by the patient as not being under medical treatment) and good oral health (not in need of surgical, endodontic, periodontal and restorative treatment). The participants were required to have maxillary anterior teeth without caries, restorations and/or endodontic treatment. Canines needed to be shade A2 or darker (Vita Classical shade guide, Vita-Zahnfabrik, Bad Säckingen, Germany).
Patients who had already undergone tooth bleaching, using orthodontic apparatus, prosthesis, with severe internal tooth discoloration (tetracycline stain, fluorosis or endodontic treatment) were excluded from the study. Additionally, pregnant and lactating women, patients with bruxism or pathologies that could cause some type of sensitivity (gingival recession, dentin exposure, visible cracks) and patients taking anti-inflammatory or analgesic drugs were not included in the study.

A Chroma Meter (TS7X, 3nh, Shenzhen, China) with the CIELAB color system was used to evaluate the color of the 3D-printed PEEK. The CIELAB system is three-dimensional, where a* axis is relative to the green (-) to red (+) opponent colors, b* axis represents the blue (-) to yellow (+) opponents, and L* axis measures relative white (100) to black (0) color. The disc-shaped specimens (5 per group) were printed using the prepared filaments separately with a diameter of 15 mm and a thickness of 3 mm. Pure PEEK specimens were printed using Jugao-MT45 PEEK filaments from the same company.
All specimens were polished by hand with 1500, 2400, and 3000 grit sandpapers to smoothen the surface (STARCKE, Melle, Germany). The color measurements were performed with a white as well as a black background and repeated for each sample to measure the L, a*, and b* values (Table 1, Table 2). The white PEEK specimens (D1, D2, D3) were compared to the VITA Classical shade guide (Vita Zahnfabrik, Bad Säckingen, Germany) and pink specimens (G1, G2, G3) were compared to the Shofu gingiva shade guides (Shofu Dental Corp., Fukuoka, Japan) and IPS ceramic gingiva shade guide (Ivoclar Vivadent, Schaan, Liechtenstein) (Figure 1). The color difference (ΔE*) was observed and calculated according to the classical CIE76 formula [22 (link)]: