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This study synthesized and characterized graphene nanoplatelets silanized with 3-(trimethoxysilyl)propyl methacrylate (MPS-GNP) for morphological and chemical characteristics. In addition, we modified a dentin bonding agent using different concentrations of MPS-GNP to study its interaction within the resin matrix of the adhesive, degree of conversion (DC), biological, and mechanical properties after bonding to tooth. Both 0.25% and 0.5% MPS-GNP-modified bonding agents showed comparable DC values to the unmodified control adhesive (range: 41%-43%). However, a statistically significant reduction in the DC was found when 0.25% and 0.5% non-silanized GNP was doped with the adhesive (<38%) ( p < 0.05). On day 30, the bacterial viability of 0.5% GNP and MPS-GNP groups remained very low under 22% with the highest dead cell count ( p < 0.05). GNP incorporated within the resin matrix of the dentin bonding agent showed clear evidence of several interfacial gap formations and non-union between the GNP surface and resin matrix, while the MPS-GNP modified dentin bonding agent showed MPS-GNP with no gap formation with complete union between the graphene surface and resin matrix. The decrease in the μTBS was least pronounced for 0.25% and 0.5% MPS-GNP groups. After 12 months of ageing, the groups 0.25% and 0.5% MPS-GNP also showed the highest BS as compared to the rest of the groups. Statistically significant reduction was seen in nanohardness at the hybrid layer and adhesive layer for GNP groups after 4 months of storage. The addition of up to 0.5% MPS-GNP showed optimized DC, antibiofilm activity, and micro-tensile bond strength without affecting the standard adhesion characteristics as compared to GNP alone.

The aim of this study was to characterize multiscale interactions between high intensity focused ultrasound (HIFU) and dentin collagen and associated matrix-metalloproteinases, in addition to the analysis of the effect of HIFU on bacterial biofilms and biological properties. Dentin specimens were subjected to 5, 10 or 20 s HIFU. XPS spectra were acquired and TEM was performed on dentin slabs. Collagen orientation was performed using Raman spectroscopy. Calcium measurements in human dental pulpal cells (hDPCs) were carried out after 7 and 14 days. For macrophages, CD36+ and CD163+ were analysed. Biofilms were analyzed using CLSM. Tandem mass spectroscopy was performed for the detection of hydroxyproline sequences along with human MMP-2 quantification. Phosphorus, calcium, and nitrogen were detected in HIFU specimens. TEM images demonstrated the collagen network appearing to be fused together in the HIFU 10 and 20 s specimens. The band associated with 960 cm-1 corresponds to the stretching ν1 PO43-. The control specimens showed intensive calcium staining followed by HIFU 20 s > HIFU 10 s > HIFU 5 s specimens. Macrophages in the HIFU specimens co-expressed CD80+ and CD163+ cells. CLSM images showed the HIFU treatment inhibiting bacterial growth. SiteScore propensity determined the effect of HIFU on the binding site with a higher DScore representing better site exposure on MMPs. Multiscale mapping of dentin collagen after HIFU treatment showed no deleterious alterations on the organic structure of dentin.