Aerosol-generating dental procedures: a reappraisal of analysis methods and infection control measures

BACKGROUND

Dental aerosol-generating procedures (AGPs) have been associated with risk for transmitting infectious agents. However, existing infection control monitoring studies potentially underestimate the extent of contamination, due to methodological inadequacies. These studies employed settle plate methodology which only captures droplets that land on agar plates, but not those suspended in air. Furthermore, bacterial culture was used to determine the extent of contamination, without accounting for non-bacterial sources of contamination.

AIMS

This study sought to bridge these gaps by establishing a monitoring protocol involving active aerosol sampling and analysis of two dental AGPs, root canal treatment (RCT) and scaling.

METHODS

RCT and scaling were performed with standard aerosol mitigation precautions. Aerosols generated throughout each procedure were sampled using the air sampler device, while contamination of operatory fomites and personal protective equipment was sampled using surface swabs, before and post-treatment. The amount of contamination was quantified using bacterial culture and adenosine triphosphate (ATP) assay.

FINDINGS

RCT generated insignificant aerosol and splatter, supporting the infection control procedures' effectiveness. Conversely, scaling significantly increased the amount of aerosol and splatter. When comparing bacterial culture and ATP assay, the magnitude of contamination obtained with ATP assay was greater, suggesting that ATP assay may have detected additional contamination of human origin and bacteria that was not recovered by the culture conditions employed.

CONCLUSIONS

This monitoring protocol is feasible in the dental setting and determines the extent of contamination generated during AGPs. This could be adopted in future studies to overcome the limitations of the existing literature.

Graphene Nanocoating: High Quality and Stability upon Several Stressors

Titanium implants present 2 major drawbacks-namely, the long time needed for osseointegration and the lack of inherent antimicrobial properties. Surface modifications and coatings to improve biomaterials can lose their integrity and biological potential when exposed to stressful microenvironments. Graphene nanocoating (GN) can be deposited onto actual-size dental and orthopedic implants. It has antiadhesive properties and can enhance bone formation in vivo. However, its ability to maintain structural integrity and quality when challenged by biologically relevant stresses remains largely unknown. GN was produced by chemical vapor deposition and transferred to titanium via a polymer-assisted transfer technique. GN has high inertness and did not increase expression of inflammatory markers by macrophages, even in the presence of lipopolysaccharides. It kept high coverage at the top tercile of tapered dental implant collars after installation and removal from bone substitute and pig maxilla. It also resisted microbiologically influenced corrosion, and it maintained very high coverage area and quality after prolonged exposure to biofilms and their removal by different techniques. Our findings show that GN is unresponsive to harsh and inflammatory environments and that it maintains a promising level of structural integrity on the top tercile of dental implant collars, which is the area highly affected by biofilms during the onset of implant diseases. Our findings open the avenues for the clinical studies required for the use of GN in the development of implants that have higher osteogenic potential and are less prone to implant diseases.

Inhibiting Corrosion of Biomedical-Grade Ti-6Al-4V Alloys with Graphene Nanocoating

The identification of metal ions and particles in the vicinity of failed implants has raised the concern that biomedical titanium alloys undergo corrosion in healthy and infected tissues. Various surface modifications and coatings have been investigated to prevent the deterioration and biocorrosion of titanium alloys but so far with limited success. Graphene is a cytocompatible atom-thick film made of carbon atoms. It has a very high surface area and can be deposited onto metal objects with complex shapes. As the carbon lattice has a very small pore size, graphene has promising impermeability capacity. Here, we show that graphene coating can effectively protect Ti-6Al-4V from corrosion. Graphene nanocoatings were produced on Ti-6Al-4V grade 5 and 23 discs and subjected to corrosive challenge (0.5M NaCl supplemented with 2-ppm fluoride, pH of 2.0) up to 30 d. The linear polarization resistance curves and electrochemical impedance spectroscopy analysis showed that the graphene-coated samples presented higher corrosion resistance and electrochemical stability at all time points. Moreover, the corrosion rate of the graphene-coated samples was very low and stable (~0.001 mm/y), whereas that of the uncoated controls increased up to 16 and 5 times for grade 5 and 23 (~0.091 mm/y) at the end point, respectively. The surface oxidation, degradation (e.g., crevice defects), and leaching of Ti, Al, and V ions observed in the uncoated controls were prevented by the graphene nanocoating. The Raman mappings confirmed that the graphene nanocoating presented high structural stability and resistance to mechanical stresses and chemical degradation, keeping >99% of coverage after corrosion challenge. Our findings open the avenues for the use of graphene as anticorrosion coatings for metal biomedical alloys and implantable devices.