Exploring the Physicochemical, Mechanical, and Photocatalytic Antibacterial Properties of a Methacrylate-Based Dental Material Loaded with ZnO Nanoparticles

Antibacterial Properties of an Experimental Dental Resin Loaded with Gold Nanoshells for Photothermal Therapy Applications

This study explored the chemical and antibacterial properties of a dental resin loaded with gold nanoshells (AuNPs) in conjunction with photothermal therapy (PTT) as a novel method against Streptococcus mutans (S. mutans) to prevent secondary caries. First, a 20-h minimum inhibitory concentration (MIC) assay was performed on solutions of AuNPs with planktonic S. mutans under an LED device and laser at 660 nm. Next, resin blends containing 0, 1 × 1010, or 2 × 1010 AuNPs/mL were fabricated, and the degree of conversion (DC) was measured using an FTIR spectroscopy. Lastly, a colony forming unit (CFU) count was performed following 24 h growth of S. mutans on 6 mm diameter resin disks with different light treatments of an LED device and a laser at 660 nm. The MIC results only showed a reduction in S. mutans at AuNP concentrations less than 3.12 µg/mL under a laser illumination level of 95.5 J/cm2 compared to the dark treatment (p < 0.010 for each). CFU and DC results showed no significant dependence on any light treatment studied. The AuNPs expressed antibacterial effects following PPT against planktonic S. mutans but not in a polymerized dental adhesive resin. Future studies should focus on different shapes, structure, and concentrations of AuNPs loaded in a resin blend.

Antimicrobial photodynamic therapy against a dual-species cariogenic biofilm using a ruthenium-loaded resin-based dental material

BACKGROUND

Streptococcus mutans and Candida albicans are associated with caries recurrence. Therefore, this study evaluated the combination of a Ru(II)-loaded resin-based dental material (RDM) and antimicrobial photodynamic therapy (aPDT) against a dual-species biofilm of S. mutans and C. albicans.

METHODS

An aPDT protocol was established evaluating Ru(II)'s photocatalytic activity and antimicrobial potential under blue LED irradiation (440-460 nm, 22.55 mW/cm2) at different energy densities (0.00, 6.25, 20.25, 40.50 J/cm2). This evaluation involved singlet oxygen quantification and determination of minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MBC/MFC). The biofilm was grown (72 h) on resin disks prepared with Ru(II)-doped RDM (0.00, 0.56, or 1.12 %) and samples were exposed to aPDT or dark conditions. The biofilm was then harvested to analyze cell viability (CFU counts) and formation of soluble and insoluble exopolysaccharides.

RESULTS

The photocatalytic activity of Ru(II) was concentration and energy density dependent (p < 0.05), and MIC/MBC values were reduced for the microorganisms after LED irradiation (40.5 J/cm2); therefor, this energy density was chosen for aPDT. Although incorporation of Ru(II) into RDM reduced the biofilm growth compared to Ru(II)-free RDM for both species in dark conditions (p < 0.05), aPDT combined with an Ru(II)-loaded RDM (0.56 or 1.12 %) potentialized CFU reductions (p < 0.05). Conversely, only 1.12 % Ru(II) with LED irradiation showed lower levels of both soluble and insoluble exopolysaccharides compared to Ru(II)-free samples in dark conditions (p < 0.05).

CONCLUSIONS

When the Ru(II)-loaded RDM was associated with blue LED, aPDT reduced cell viability and lower soluble and insoluble exopolysaccharides were found in the cariogenic dual-species biofilm.

The antimicrobial, physical, and chemical properties of a riboflavin-loaded dental resin intended for antimicrobial photodynamic therapy

BACKGROUND

Dental caries remain a significant global health challenge. Unfortunately, current dental materials lack sufficient antimicrobial power to address the pathogenic species involved in this disease. In this study the potential to load a dental resin blend (RB) with riboflavin (B2) for use in an antimicrobial photodynamic therapy (aPDT) approach was investigated.

METHODS

B2 was added to our experimental RB (0.1 - 10 wt%). Upon investigating the degree of conversion and specimen integrity of the RB as a function of B2 concentration, it was determined that loading should be restricted to 0.1, 1.0, and 1.5 wt%. Subsequent investigation included water sorption (WS) and solubility (SL), as well as shear bond strength (SBS) and flexural strength (FS) of the specimens after 24 h and 28-day water storage. Lastly, the antimicrobial response of Streptococcus mutans (S. mutans) biofilm following 6 h growth and 60 s of blue LED light (1.3 J/cm²) in an aPDT-based approach was measured.

RESULTS AND CONCLUSIONS

Adding up to 1.5 wt% B2 had minimal impact on the FS or SBS of the RB. However, aging for 28-days notably increased the FS by as much as 50% for the 1.5 wt% B2-loaded RB. In addition, adding 1.5 wt% B2 resulted in a significant reduction in WS/SL of the RB. Lastly, while adding B2 did not change the antimicrobial response, this was an initial study under these conditions and future investigation will seek to optimize light parameters to produce a more agonistic response. Overall, a riboflavin-loaded dental resin shows significant promise for utilization in restorative dentistry with aPDT.