Influence of Various Plasma-Activated Liquids on Dentin’s Intrinsic Enzymatic Activity

Endogenous matrix metalloproteinases (MMPs) are activated in dentin during carious lesion progression and restorative procedures, degrading the tooth-restoration interface and contributing to restoration failure. This study investigated by means of in situ zymography whether cold atmospheric plasma activation (PA) of distilled water (DW) and phosphate-buffered saline (PBS) modulates endogenous dentinal MMP activity. A Dielectric Barrier Discharge-rod source generated PA liquids, treating DW and PBS for 22 min. Chemical characterization demonstrated that PADW yielded 9.61 mg/L H2O2, 18.3 mg/L NO2−, 375.70 mg/L NO3−, and a pH of 3.2. PAPBS yielded 9.79 mg/L H2O2, 36.01 mg/L NO2−, 505.74 mg/L NO3−, and a pH of 7.13. Both liquids served as 1 min dentin pretreatments in a simulated restorative procedure using a universal adhesive and resin composite, tested after 24 h. MMP activity was assessed via in situ zymography with fluorescein-conjugated gelatin and confocal microscopy. Data were statistically analyzed (p < 0.05). PADW increased dentinal enzymatic activity, while PAPBS reduced it (p < 0.05). Non-activated PBS elicited higher baseline MMP activity than non-activated DW. The divergent responses likely reflect differences in RONS composition, pH, and initial ionic content between the two liquids. The precise mechanism underlying PA liquid interactions with dentinal MMPs warrants further investigation.