Toxicity and cytokine release from human dental pulp stem cells after exposure to universal dental adhesives cured by single peak and polywave LEDs.

OBJECTIVES: to assess the impact of universal adhesives, cured with single-peak and polywave LEDs, on the metabolic activity and cytokine release of human dental pulp stem cells (hDPSCs). In addition, analyze the degree of conversion (DC) of the adhesives cured with the different LEDs. METHODS: Discs (5 mm diameter, 1 mm thick) were prepared using three universal adhesives: Single Bond Universal (SBU, 3 M ESPE), Optibond Universal (OBU, Kerr), and Zipbond Universal (ZBU, SDI). These discs were cured for 40 s using a single-peak (DeepCure, 3 M ESPE) or a polywave light-emmiting diode (LED) curing unit (Valo Grand, Ultradent). After 24 h, the specimens were placed in 24-well culture plates, each containing 1 mL of culture medium for 24 h. hDPSCs (1.8 ×104) were seeded in 96-well plates and allowed to grow for 24 h. Subsequently, the cells were exposed to the extracts (culture medium containing eluates from the adhesive discs) for an additional 24 h. Cells not exposed to the extracts were used as a control group. The mitochondrial metabolism was assessed using the MTT assay and the cytokine release evaluated through MAGPIX. The degree of conversion of the adhesives was analyzed using FTIR (n = 5). The results were analyzed by ANOVA two-way and Tukey's test. RESULTS: OBU and ZBU eluates caused a statistically significant reduction in mitochondrial metabolism, regardless of the LED used, indicating their cytotoxicity. In contrast, SBU did not significantly affect the MTT results, resembling the control group. A higher release of cytokines IL-1, IL-6, IL-10, and TNF-α were found in association to ZBU. SBU, on the other hand, increased the release of IL-8. OBU did not influenced the cytokine release. SBU presented the higher DC, while OBU and ZBU had similar DC, lower than SBU. SIGNIFICANCE: In conclusion, universal adhesives exhibit toxicity towards hDPSCs, but the extent of toxicity varies depending on the adhesive material. ZBU was associated with increased cytokine release, particularly pro-inflammatory mediators, from hDPSCs. The different LEDs did not influenced the cytotoxicity of the evaluated adhesives.

Interaction of different concentrations of 10-MDP and GPDM on the zirconia bonding.

OBJECTIVES: To analyze the influence of different concentrations of 10-MDP and GPDM used, combined or not, on the bonding to zirconia. METHODS: Specimens of zirconia and a resin-composite (7 mm length, 1 mm width, and 1 mm thick) were obtained. The experimental groups were obtained according to the functional monomer (10-MDP and GPDM) and the concentrations (3 %, 5 %, and 8 %). For the groups with combined 10-MDP and GPDM, the agents were used with a proportion of 50 %/50 % wt until reaching the 3 %, 5 % and 8 % concentrations. All monomers were diluted in ethanol to obtain the primers. Two control groups were established: ethanol (negative control) and a commercial reference Monobond N (positive control). The zirconia surface treatment was performed with the primer application followed by the bonding to a resin-composite sample with a light-curing resin cement. Twenty-four hours after the adhesive procedure, a microtensile test was performed and the failure pattern of each sample was analysed with a stereoscopic magnifying glass. Data were analysed by a two-way ANOVA and Dunnet test. RESULTS: All experimental primers presented a higher bond strength than the negative control (ethanol). Excepting the 8 % GPDM primer, all groups presented statistically similar bond strength compared to the positive control, with a predominance of adhesive failure. SIGNIFICANCE: 10-MDP, GPDM, and the combination of both for the concentrations tested promote an effective chemical bonding to zirconia. However, using 10-MDP and GPDM in the same primer has no synergistic effect.