Determine the degree of conversion (DC) and in vitro pulpal temperature (PT) rise of low-viscosity (LV) and high-viscosity (HV) conventional resin-based composites (RBC), bulk-fill and short-fibre reinforced composites (SFRC). The occlusal surface of a mandibular molar was removed to obtain dentine thickness of 2 mm above the roof of the pulp chamber. LV and HV conventional (2 mm), bulk-fill RBCs (2-4 mm) and SFRCs (2-4 mm) were applied in a mold (6 mm inner diameter) placed on the occlusal surface. PT changes during the photo-polymerization were recorded with a thermocouple positioned in the pulp chamber. The DC at the top and bottom of the samples was measured with micro-Raman spectroscopy. ANOVA and Tukey's post-hoc test, multivariate analysis and partial eta-squared statistics were used to analyze the data (p < 0.05). The PT changes ranged between 5.5-11.2 °C. All LV and 4 mm RBCs exhibited higher temperature changes. Higher DC were measured at the top (63-76%) of the samples as compared to the bottom (52-72.6%) in the 2 mm HV conventional and bulk-fill RBCs and in each 4 mm LV and HV materials. The SFRCs showed higher temperature changes and DC% as compared to the other investigated RBCs. The temperature and DC were influenced by the composition of the material followed by the thickness. Exothermic temperature rise and DC are mainly material dependent. Higher DC values are associated with a significant increase in PT. LV RBCs, 4 mm bulk-fills and SFRCs exhibited higher PTs. Bulk-fills and SFRCs applied in 4 mm showed lower DCs at the bottom.

Detection of unreacted monomers from pre-heated resin-based dental composites (RBC) is not a well-investigated topic so far. The objectives were to determine the temperature changes during the application and polymerization, the degree of conversion (DC) and unreacted monomer elution of room temperature (RT), and pre-heated thermoviscous [VisCalor Bulk(VCB)] and high-viscosity full-body contemporary [Filtek One Bulk(FOB)] bulk-fill RBCs. The RBCs’ temperatures during the sample preparation were recorded with a K-type thermocouple. The DC at the top and bottom was measured with micro-Raman spectroscopy and the amounts of eluted BisGMA, UDMA, DDMA, and TEGDMA were assessed with High-Performance Liquid Chromatography. The temperatures of the pre-heated RBCs decreased rapidly during the manipulation phase. The temperature rise during photopolymerization reflects the bottom DCs. The differences in DC% between the top and the bottom were significant. RT VCB had a lower DC% compared to FOB. Pre-heating did not influence the DC, except on the bottom surface of FOB where a significant decrease was measured. Pre-heating significantly decreased the elution of BisGMA, UDMA, DDMA in the case of FOB, meanwhile, it had no effect on monomer release from VCB, except TEGDMA, which elution was decreased. In comparison, RBC composition had a stronger influence on DC and monomer elution, than pre-cure temperature.

Monomers leached from resin-based composites (RBCs) may reach intrapulpal concentrations of the millimolar (mM) range, which could contribute to inflammation. The aim of this investigation was to assess the cytotoxicity of triethylene glycol dimethacrylate (TEGDMA) monomers on pulp cells as well as to identify molecular mechanisms leading to apoptosis. Pulp cells were harvested from molars extracted for orthodontic reasons and cultured through an explant method. To assess cytotoxicity, cells underwent a 5-day exposure to 0.75, 1.5, and 3 mM TEGDMA and were subject to cell counting and WST-1 staining. Based on the findings, cells were subsequently exposed to 0.1, 0.2, 0.75, 1.5, and 3 mM TEGDMA for 24 h to uncover the details of apoptosis. Changes in the production or cleavage of the apoptosis-specific proteins caspase-8, caspase-9, caspase-3, caspase-12, and Apoptosis-Inducing Factor (AIF) were measured by Western blot. The 5-day study showed concentration- and time-dependent cytotoxicity. Significant cell death was detected after 24 h with TEGDMA concentrations of 1.5 and 3 mM. One-day exposure to TEGDMA led to the activation of caspase-8, -9, -3, and -12 and an increased AIF production. Results suggest that relevant concentrations of TEGDMA monomers, leached from RBCs, induce apoptosis in pulp cells through both caspase-dependent as well as caspase-independent mechanisms. Endoplasmic reticulum stress and the activation of caspase-independent apoptotic pathways may be further mechanisms by which monomers induce apoptosis in pulp cells.

Air-abrasion is a popular prophylactic procedure to maintain oral hygiene. However, depending on the applied air-abrasive powder, it can damage the surface of the tooth and restorations, making it susceptible to plaque accumulation. The purpose of this study was to investigate the effect of 5 s and 10 s air-abrasion of calcium carbonate on surface roughness (Ra) of enamel, nanofill, and microhybrid resin-composites and the effect of post-polishing with two-step rubber- (RP) or one-step brush polisher (BP) to re-establish the surface smoothness. Surface topography was visualized by scanning-electron-microscopy. The quantitative measurement of the Ra was carried out with atomic-force-microscopy. Air-abrasion for 10 s decreased the Ra of enamel as a result of abrasion of the natural surface texture. Post-polishing with RP after 10 s air-abrasion did not change the Ra or BP; however, Ra was increased significantly by scratching the surface. Air-abrasion increased the Ra of resin composites significantly, irrespective of the application time. While RP provided a similarly smooth surface to the control in the case of microhybrid resin composite, BP increased the Ra significantly. The Ra for the control group of the nanofill-resin composite was initially high, which was further increased by air-abrasion. RP and BP re-established the initial Ra with deeper and shallower scratches after BP. Both the material and treatment type showed a large effect on Ra.

Objectives: Resin-based composites may leach monomers such as triethylene-glycol dimethacrylate (TEGDMA), which could contribute to intrapulpal inflammation. The aim of this investigation was to examine whether various concentrations of TEGDMA are able to influence dentally relevant Matrix metalloproteinase (MMP)-2, MMP-8, and MMP-9 production, total collagenase/gelatinase activity in pulp cells, and suggest possible signaling mechanisms. Materials and methods: Pulp cells were cultured, followed by a 1-day exposure to sublethal TEGDMA concentrations (0.1, 0.2, and 0.75 mM). Total MMP activity was measured by an EnzCheck total collagenase/gelatinase assay, while the production of specific MMPs and the relative changes of phosphorylated, i.e., activated signaling protein levels of extracellular signal-regulated kinase (ERK)1/2, p38, c-Jun N-terminal kinase (JNK) were identified by western blot. Immunocytochemistry image data was also plotted and analyzed to see whether TEGDMA could possibly alter MMP production. Results: An increase in activated MMP-2, MMP-8, and MMP-9 production as well as total collagenase activity was seen after a 24-h exposure to the abovementioned TEGDMA concentrations. Increase was most substantial at 0.1 (P = 0.002) and 0.2 mM (P = 0.0381). Concurrent p-ERK, p-p38, and p-JNK elevations were also detected. Conclusions: Results suggest that monomers such as TEGDMA, leached from resin-based restorative materials, activate and induce the production of dentally relevant MMPs in pulp cells. Activation of ERK1/2, p38, or JNK and MMP increase may play a role in and/or can be part of a broader stress response. Clinical relevance Induction of MMP production and activity may further be components in the mechanisms of intrapulpal monomer toxicity.