A Dusty Affair: SIRT1-S682 Modulation Orchestrates ERK–FN1–p38–NF-κB Signaling and Composite-Dependent IL-8 Responses in Gingival Keratinocytes Exposed to Dental Dust and Eluates

Dental composite dust generated during finishing procedures or mastication may adversely affect gingival epithelia. However, the mechanistic distinction between particulate and chemical (eluate) exposures and their respective signaling consequences remains insufficiently defined. Dust particles and corresponding eluates from three restorative composites, Admira Fusion, Ceram.x Spectra ST, and Filtek Supreme XTE, were evaluated under standardized high-dose in vitro exposure conditions. Human gingival keratinocytes were assessed for proliferation, adhesion, differentiation, fibronectin (FN1) remodeling, and IL-8 secretion, alongside analysis of ERK, p38, and NF-κB signaling and phosphorylation of the stress-responsive regulator SIRT1 at Ser682 (SIRT1-S682). Particulate exposure elicited more pronounced impairment of cellular adhesion, proliferation, and differentiation than eluates. Dusts derived from Ceram.x Spectra ST and Filtek Supreme XTE suppressed ERK activity, reduced FN1 abundance, and decreased nuclear SIRT1-S682, consistent with a generalized stress response. In contrast, Admira Fusion dust preserved FN1, activated ERK signaling, reduced SIRT1-S682, and induced robust IL-8 secretion. Across all materials, particulate exposure reduced nuclear SIRT1-S682 without affecting total SIRT1 levels, indicating a shared permissive stress modification. Notably, only Admira Fusion coupled this permissive state with p38 activation and sustained NF-κB p65 Ser536 phosphorylation, resulting in transcriptionally active NF-κB and elevated IL-8 production, whereas Ceram.x Spectra ST and Filtek Supreme XTE failed to activate this ERK–FN1–p38–NF-κB axis, yielding either transcriptionally inactive NF-κB or no detectable enrichment. These findings support a material-associated in vitro response pattern in which a shared SIRT1-S682 reduction is accompanied by distinct ERK/FN1, p38, NF-κB, and IL-8 readouts. SIRT1-S682 reduction alone did not define the inflammatory phenotype, because it occurred across particulate exposures, whereas IL-8 secretion was observed only under conditions that also showed p38 activation and comparatively maintained NF-κB p65 Ser536 phosphorylation. This signature arises from the convergence of a permissive SIRT1-S682 background with ERK- and p38-dependent MAPK signaling to enable NF-κB-mediated IL-8 expression, highlighting that both composite composition and particulate properties critically determine inflammatory potential and underscoring the importance of incorporating particulate fractions into cytocompatibility testing strategies.