Bluephase

For this study, the resin composites Venus^® Diamond (Kulzer GmbH, Hanau, Germany), GrandioSO (VOCO GmbH, Cuxhaven, Germany), Estelite Σ Quick (Tokuyama Dental, Altenberge, Germany), and the compomer Dyract^® eXtra (Dentsply Sirona, Bensheim, Germany) were used. All composites are chracterized in Table 6.
The materials were applied to rectangular molds (7 mm × 11 mm × 1.5 mm), covered by a glass plate, and polymerized using a calibrated dental light curing unit (bluephase, 1.200 ± 10% mW/cm², Ivoclar Vivadent GmbH, Ellwangen, Germany) for 20 s.
The light-cured specimens were then cleaned twice by an ultrasonic treatment in distilled water for 10 min each and subsequently disinfected with 70% ethanol for 30 min. The finished specimens were afterwards stored separately in distilled water at 8 °C until testing.
As controls, bovine enamel samples were used. Therefore, rectangular enamel specimens (7 mm × 11 mm × 1.5 mm) were prepared from bovine incisors and subsequently surface polished, cleaned three times in an ultrasonic bath for 10 min each, and disinfected in a 70% ethanolic solution (30 min). The bovine enamel samples were then stored separately in distilled water at 8 °C until use.

For this study, the resin composites Venus^® Diamond (Kulzer GmbH, Hanau, Germany), GrandioSO (VOCO GmbH, Cuxhaven, Germany), Estelite Σ Quick (Tokuyama Dental, Altenberge, Germany), and the compomer Dyract^® eXtra (Dentsply Sirona, Bensheim, Germany) were used. All composites are chracterized in Table 6.
The materials were applied to rectangular molds (7 mm × 11 mm × 1.5 mm), covered by a glass plate, and polymerized using a calibrated dental light curing unit (bluephase, 1.200 ± 10% mW/cm², Ivoclar Vivadent GmbH, Ellwangen, Germany) for 20 s.
The light-cured specimens were then cleaned twice by an ultrasonic treatment in distilled water for 10 min each and subsequently disinfected with 70% ethanol for 30 min. The finished specimens were afterwards stored separately in distilled water at 8 °C until testing.
As controls, bovine enamel samples were used. Therefore, rectangular enamel specimens (7 mm × 11 mm × 1.5 mm) were prepared from bovine incisors and subsequently surface polished, cleaned three times in an ultrasonic bath for 10 min each, and disinfected in a 70% ethanolic solution (30 min). The bovine enamel samples were then stored separately in distilled water at 8 °C until use.

Gelatin from porcine skin (type A, 300 bloom corresponding to a molecular weight range of 50 to 100 kDa), Glycidyl methacrylate (GC, ≥ 97.0%) and triethylamine were provided by Sigma-Aldrich Chemie GmbH (Steinheim, Germany). Riboflavin and glycine were obtained from Sigma-Aldrich (St. Louis, MO, USA). Dimethyl Sulfoxide (DMSO) was purchased from Fluka Chemie, Germany. Dialysis tubing cellulose membrane (Mwt cut-off 14,000, average diameter 16 mm) was acquired from Merck, Germany. Mineral trioxide aggregate (Angelus, Londrina, PR, Brazil). Theracal LC (Bisco, Schaumburg, IL, USA). Glass ionomer (SDI, Bayswater, Victoria, Australia). Single bond universal adhesive and composite restorative filing (3 M-ESPE, St. Paul, MN, USA). At λmax 460 nm and 1100 mW/cm², a blue light-emitting diode lamp (LED-lamp) (Bluephase, Ivoclar Vivadent, Amhest, NY, USA) was utilized for irradiation. The distance between the irradiation light source and the capped material was almost 0 cm. The irradiation time was ca. ≥ 50 s.

The DC was investigated by ATR-FTIR (n = 3). The tests were carried out at a wavelength range between 700 cm⁻¹ and 4000 cm⁻¹ with a resolution of 4 cm⁻¹. One test consisted of 26 measurements with an interval of 30 s. For this purpose, one drop of each adhesive group was applied on the diamond crystal to cover the sampling area and polymerized after four initial measurements (120 s) for 60 s (>1000 mW/cm², Bluephase, Ivoclar Vivadent GmbH, Ellwangen, Germany). A background scan was carried out between each test. The benzyl groups were taken as reference and the DC was estimated from the height of the vinyl group peaks before and after polymerization, as described elsewhere [23 (link)].

Five specimens (diameter 6 mm; thickness 2 mm) from each adhesive were prepared in a teflon form and light cured for 60 s from both sides (>1000 mW/cm², Bluephase, Ivoclar Vivadent GmbH, Ellwangen, Germany). Afterwards, the specimens were dried in a desiccator and weighted each two days until the difference between the two following measurements was below or equal 0.1 mg (m₀).
After drying, the diameter and the thickness of the specimens were estimated to determine the volume (V_m0). Then the specimens were stored in distilled water at 37 °C and weighted every second day. The cycle was repeated until the difference between two measurements was again below or equal 0.1 mg (m₁). Next, the specimens were dried in a desiccator and weighted again every second day until they reached a steady value (m₂). Based on the determined values, WS and SF could be calculated by the following equations: $$WS=\frac{\left(m_1-m_2\right)}{V_{m_0}}$$
$$SF=\frac{\left(m_0-m_2\right)}{V_{m_0}}$$