Relyx veneer

Within the assessment pairs, the substrate of the test and the reference samples differed in one value of lightness (Figure 2). Glass-ceramic platelets, mimicking minimal-invasive restorations, with the same shade as used for the substrate of the reference sample were cemented on top of the test and the reference sample in different thicknesses (0.1, 0.2, 0.3, 0.4, 0.5 mm). The bonding surfaces of the substrate and the ceramic restoration were etched according to the manufacturer's instructions using a hydrofluoric acid (Vita Adiva Cera-Etch; Vita Zahnfabrik).
Thereafter, a bonding agent (Vita Adiva C-Prime, Vita Zahnfabrik) and a transparent light-curing composite cement (RelyX Veneer; 3M ESPE, Seefeld, Germany) were used for the adhesive cementation (40 s, 1'200 mW/cm 2 with Bluephase PowerCure; Ivoclar Vivadent).

The experimental RBLAs were formulated by combining 50% of mass fraction of urethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate (TEGDMA) (Esstech Inc.; Essington, PA, USA). For the luting agents, 0.4% mass fraction of camphorquinone (Sigma-Aldrich; St. Louis, MO, USA) was used as photosensitizer, and 0.8% mass fraction of ethyl 4-dimethylaminobenzoate (Sigma-Aldrich) was used as coinitiator (Table 1). The monomers and mass fractions of the luting agents were defined in pilot studies. Therefore, three different RBLAs were prepared using different inorganic filler contents: 55 wt% (low), 65 wt% (intermediate), and 75 wt% (high). Barium borosilicate glass particles (2 μm average size) coated with 1% mass fraction of silane coupling agent (V-119-4120; Essington, PA, USA) were used as inorganic filler content. The materials were mechanically mixed using a centrifugal mixer (SpeedMixer DAC150; FlackTek, Landrum, SC, USA) at 1500 rpm during 20 s to produce homogeneous materials. 19 (link) A light-cured RBLA (RelyX Veneer; 3M ESPE), widely employed for the adhesive cementation of CLV, was used as commercial reference. This luting agent presents 66 wt% fraction of inorganic filler content according to the manufacturer, 31 which is similar to the intermediate experimental luting agent tested.

This in vitro study evaluated the influence of inorganic filler content of experimental RBLAs on the color of CLVs. RBLAs with low (55 wt%), intermediate (65 wt%), or high (75 wt%) filler loading were evaluated. The commercial resin luting agent RelyX Veneer (3M ESPE; St Paul, MN, USA) was tested as a reference, with 66 wt% fraction of inorganic filler content. All luting agents were translucent in shade. The response variables tested were ΔE 00 and TP (n=10) based on CIEL*a*b* color coordinates measured with a spectrophotometer (Easyshade Advanced 4.0; Vita Zahnfabrik, Bad Säckingen, Germany).
The feldspar ceramic CAD/CAM blocks (I14 A1 Vitablocs Mark II for Cerec; Vita Zahnfabrik, Bad Säckingen, Germany) were evaluated over a simulated dental substrate (A2D shade) and the ΔE 00 was calculated by CIEDE2000 color difference metric 21 (link) under three conditions: (i) (B × IL), before (without luting agent) versus immediately after luting; (ii) (B × IW) before versus 24 h after luting and water immersion; and (iii) (IL × WI) immediately after luting versus 24 h in water immersion. The TP was calculated using CIEL*a*b* color coordinates measured over black and white backgrounds.