Depth-Dependent Cellular Response from Dental Bulk-Fill Resins in Human Dental Pulp Stem Cells

Abstract

The proper choice of dental composite resins is necessary based on the minimal cytotoxicity and antiodontogenesis on human dental pulp stem cells for dental pulp-dentin tissue repair and regeneration. The aim of this study was to evaluate the cytotoxicity and antidifferentiation effects of dental bulk-fill resins, able to be polymerized as a bulk status for filling deep cavity of a tooth by single light curing, against human dental pulp stem cells (hDPSCs) from three compartments corresponding to depth (0-2, 2-4, and 4-6 mm) from the light-curing site. Three bulk-fill composite resins (SDR, Venus bulk-fill (VBF), and Beautifil Bulk Flowable (BBF)) and a conventional flowable composite resin (Filtek Z350 XT flowable restorative (ZFF)) were individually filled into a cylindrical hole (h = 2 mm, Ф = 10 mm), and three compartments (total ~6 mm of height) were combined as a single assembly for light curing. The resin samples from the three layers were separated and eluted in the culture medium. The extracts were exposed to hDPSCs, and cytotoxicity and differentiation capability were evaluated. Depth of cure and surface hardness according to depth were determined. All bulk-fill resins except BBF revealed cytotoxicity from 4 to 6 or 2 to 4 mm, while ZFF was cytotoxic at over 2 mm. Depth of cure was detected from 3.55 to 4.02 mm in the bulk-fill resins (vs. ~2.25 mm in conventional resin), and 80% hardness compared with that of a fully polymerized top surface was determined from 4.2 to 6 mm in the bulk-fill resin (vs. 2.4 mm in conventional resin). Antidifferentiation was revealed at a depth of 4-6 mm in the bulk-fill resin. There was a difference in depth of cytotoxicity and antidifferentiation between the bulk-fill composite resins, which was mainly due to different cure depths and ingredients. Therefore, careful consideration of choice of bulk-fill resins is necessary especially for restoration of deep cavities for maintaining the viability and differentiation ability of dental pulp stem cells.

Cytotoxic Effects of Bulk-Fill Composites on L929 Fibroblast Cells

“…In a similar study on the toxicity of fluid and paste bulkfill composite resins conducted on L929 mouse fibroblasts by Demirel et al [29] it was reported that at the end of 72 h composite extracts caused a statistically significant decrease in cell viability level, which is in line with the former. In a study on human pulp cells, by examining the toxic effect of bulkfill composite samples in terms of whether it change at the layers of different polymerization depths [0-2, 2-4 and 4-6 mm] Lee et al [30] stated that as the irradiation depth increased the more toxicity occurred, and the highest cytotoxicity was observed in the layer of 4-6 mm depth. However, Nascimento et al [31] reported that bulk-fill resins exhibited low level and/or no cytotoxicity on L929 cells, except for Opus, which showed more moderate cytotoxicity, as pointed out in the MTT assay index.…”

Effect of Rapid High-Intensity Light-Curing on Increasing Transdentinal Temperature and Cell Viability: An In Vitro Study

“…Additionally, the thickness of dentin is closely related to the diffusion of substances to the pulp through the dentinal tubules [ 49 ]. It is important to note that in bulk-fill composite resins, greater irradiation depth results in greater cytotoxicity, particularly in increments greater than 4 mm [ 50 ]. This may be associated with our results, as we applied a 4 mm thickness in all experimental tests.…”

An overview to biocompatibility of resin based restorative materials

“…Asdada et al 50 evaluated the cytotoxicity and antidifferentiation effects of bulk fill composites against human dental pulp stem cells (hDPSCs) in three compartments corresponding to the depth (0-2, 2-4 and 4-6 mm) from the light source region and found that the cytotoxic effect increased with increasing depth. In order to protect the ability of dental pulp stem cells to survive and differentiate, they said that care should be taken when choosing bulk-fill resins, especially when fixing deep cavities.…”