Dental caries is a highly preventable and costly disease. Unfortunately, the current management strategies are inadequate at reducing the incidence and new minimally invasive strategies are needed. In this study, a systematic evaluation of specific light parameters and aqueous curcumin concentrations for antimicrobial photodynamic therapy (aPDT) was conducted. Aqueous solutions of curcumin were first prepared and evaluated for their light absorbance after applying different ~56 mW/cm² blue light treatments in a continuous application mode. Next, these same light treatments as well as different application modes were applied to the curcumin solutions and the molar absorptivity coefficient, reactive oxygen species (ROS) release, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) for Streptococcus mutans and the MIC and minimum fungicidal concentration (MFC) for Candida albicans were measured. After up to 1 min of light treatment, the molar absorptivity of curcumin when added to culture media was lower than that for water only; however, at higher energy levels, this difference was not apparent. There was a noted dependence on both ROS type and cariogenic microorganism species on the sensitivity to both blue light treatment and application mode. In conclusion, this study provides new information towards improving the agonistic potential of aPDT associated with curcumin against cariogenic microorganisms.

While resin-based materials meet the many requirements of a restorative material, they lack adequate, long-lasting antimicrobial power. This study investigated a zinc oxide nanoparticle (ZnO NP)-loaded resin-blend (RB) toward a new antimicrobial photodynamic therapy (aPDT)-based approach for managing dental caries. The results confirmed that up to 20 wt% ZnO NPs could be added without compromising the degree of conversion (DC) of the original blend. The DC achieved for the 20 wt% ZnO NP blend has been the highest reported. The effects on flexural strength (FS), shear bond strength to dentin (SBS), water sorption (WS), solubility (SL), and viability of Streptococcus mutans under 1.35 J/cm² blue light or dark conditions were limited to ≤20 wt% ZnO NP loading. The addition of up to 20 wt% ZnO NPs had a minimal impact on FS or SBS, while a reduction in the bacteria count was observed. The maximum loading resulted in an increase in SL. Furthermore, 28-day aging in 37 °C water increased the FS for all groups, while it sustained the reduction in bacteria count for the 20 wt% resin blends. Overall, the ZnO NP-loaded resin-based restorative material presents significant potential for use in aPDT.

This study aimed to assess the potential of experimental dental resins containing ZnO nanoparticles (ZnO-NPs) for antimicrobial photodynamic therapy (aPDT) as a functional tool for the modulation of cariogenic biofilm in long-term. Minimum inhibitory and bactericidal concentrations (MIC/MBC) of ZnO-NPs against Streptococcus mutans were initially determined under different energy densities of blue LED irradiation (0.00, 1.35, 6.75, or 20.25 J/cm²) to optimize aPDT parameters. Experimental dental resins were then formulated with 0 % (control), 5 %, 10 %, and 20 % ZnO-NPs. Resin disks (1 mm x 6 mm) were prepared to evaluate the antimicrobial and photocatalytic potential of the experimental groups associated with 0 (dark), 1, 2, or 4 light cycles of blue-light irradiation (20.25 J/cm², each cycle). The CFU count and Live/Dead assays were performed on a cariogenic biofilm model (S. mutans) on fresh and 6-month aged resin disks. Blue light at 20.25 J/cm² decreased MIC (from 250 µg/mL to 125 µg/mL) and MBC (from 1000 µg/mL to 500 µg/mL), establishing the optimal aPDT protocol. Experimental resins with 5 %, 10 %, or 20 % ZnO-NPs, when exposed to 4 cycles of blue light, significantly reduced biofilm viability compared to controls, both initially and after aging. The 20 % ZnO-NP resin sustained > 3.log10 CFU reduction after 6 months, even with 2 cycles of light. Live/Dead assays showed > 50 % dead cells with the 20 % ZnO-NP resin after 2 light cycles. ZnO-NP-loaded dental resins associated with blue light aPDT offer promise as a long-lasting antimicrobial alternative, potentially enhancing the control of pathogenic biofilms.

Objectives: To evaluate the effects of a blue light photosensitizer (PS), Ruthenium II complex (Ru), on the chemical, physical, mechanical, and antimicrobial properties of experimental dental resin blends. Methods: The experimental resin (BisEMA, TEEGDMA, HPMA, ethanol, and photoinitiator) was loaded with Ru at 0.00%, 0.07%, 0.14%, 0.28%, 0.56%, 1.12%, 1.2%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% w/w. Samples were evaluated for the degree of conversion (DC) after 30 and 60 s curing-time ( n = 6). Selected formulations (0.00%, 0.28%, 0.56%, 1.12%) were further tested for shear bond strength (SBS) ( n = 15); flexural strength (FS) ( n = 12); and antimicrobial properties (CFUs), in dark and light conditions. These latter tests were performed on specimens stored for 24-h or 2-month in 37°C water. Water sorption (WS) and solubility (SL) tests were also performed ( n = 12). Data were analyzed either by a one- or two-factor general linear model (α = 0.05). Results: Overall, Ru concentration above 1.2% resulted in reduced DC. In SBS results, only the 1.12%Ru resin blend samples had statistically lower values compared to the 0.00%Ru resin blend at 24-h storage ( p = 0.004). In addition, no differences in SBS were detected among the experimental groups after 2-month storage in water. Meanwhile, FS increased for all experimental groups under similar aging conditions ( p < 0.001). Antimicrobial properties were improved upon inclusion of Ru and application of light ( p < 0.001 for both) at 24-h and 2-month storage. Lastly, no detectable changes in WS or SL were observed for the Ru-added resins compared to the 0.00%Ru resin blend. However, the 0.28% Ru blend presented significantly higher WS compared to the 0.56% Ru blend ( p = 0.007). Conclusions: Stable SBS, improved FS, and sustained antimicrobial properties after aging gives significant credence to our approach of adding the Ruthenium II complex into dental adhesive resin blends intended for an aPDT approach.

This study evaluated the effects of delayed post-polymerization on color, degree of conversion (DC), flexural strength (FS), and cellular response of a 3D-printed dental interim resin. Specimens were divided into six groups based on delays of 0 h, 2 h, 4 h, 6 h, 8 h, and 10 h before post-polymerization. Color was characterized using a spectrophotometer (n = 10), DC (n = 10) with FTIR-ATR, and FS (n = 10) with a universal testing machine. Cellular response (n = 30) was assessed through cell viability and pro-inflammatory gene expression of the gingival fibroblast cell line (L929) and human monocytic cell line (THP-1). Delayed post-polymerization significantly affected color (L* and b*; both P < 0.001,) and color difference (P = 0.016). L* values at 6 h, 8 h, and 10 h significantly decreased compared to 0 h (P < 0.001), while b* values showed a significant decrease in all groups. (P < 0.001). No significant difference was found in a* (P = 0.417) or translucency (P = 0.394). DC significantly decreased at 8 h and 10 h (P < 0.05). There was no significant difference in FS. Cytotoxicity and pro-inflammatory gene expression (IL-6 and TNF-α) were not significantly affected by time delays. Within the limitations of this study, a delay of up to 6 h before post-polymerization did not compromise FS, FM, cell viability, or pro-inflammatory gene expression. However, notable changes in DC and color suggest that the appearance and polymerization characteristics may be adversely affected, while mechanical and biological properties remained stable.