Use of Antivirals in Denture: A Potential Approach in Dental Practice

The novel coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), which utilizes the angiotensin-converting enzyme 2 (ACE2) receptors expressed in the oral mucosa, ¹ and may lead to several oral lesions associated with COVID-19.

Since the oral cavity is among the major routes for coronavirus transmission, ² it is a top priority to maintain good oral hygiene that may limit viral replication and subsequent transmission. Dentures are the integral parts of dentistry, mostly worn by older adults, and these groups of people are walloped by COVID-19, ³ with significant death. Therefore, the incorporation of antimicrobial components, especially, antivirals in denture preparation might be an effective strategy to enhance the quality of denture and combat against the accumulation and spread of virulent microorganisms.

Poly (methyl methacrylate) (PMMA) has been regarded as an ideal denture base material due to its typical properties. ⁴ Over the past decade researchers have proven that the dentures act as a reservoir for the microorganisms in the oral cavity, ⁵ which contributes in the development of oral diseases, such as denture stomatitis, dental decay, and periodontal diseases locally, and systemic infections, such as aspiration pneumonia and infectious endocarditis. Therefore, to limit the levels of biofilm formation and the growth of potentially harmful microorganisms on dentures, integration of antimicrobial substances to the PMMA resin has been widely considered.

Several antimicrobial agents are being commonly used in denture preparation, such as methacrylic acid monomers, 12-methacryloyloxy dodecylpyridinium bromide (MDPB), silica, and titanium dioxide.^6,7 Typically, these agents incorporate into PMMA via copolymerization and surface modification. However, an earlier study suggested that polyurethane iodine complexes exhibited potent “contact-killing” antimicrobial activity against bacteria, fungi, as well as viruses, thereby inhibited microbial colonization and biofilm-formation. ⁸ Moreover, PMMA films doped with either silver ion nanoparticles (AgNPs) or silver-imidazole polymeric complexes, displayed varying degrees of antiviral activity. ⁹

Most of the commercially available antiviral drugs are designed to deal with the HIV, two hepatitis (B and C), and two influenza (A and B) viruses.^10,11 However, several potential drugs are currently on clinical trials to discover effective treatments for COVID-19. Among these, Kaletra (combination of Lopinavir and Ritonavir) and interferon-β (interferon-beta), having antiviral activity, have shown to reduce viral load and the severity of respiratory illness in COVID-19 patients, and potentially improved health status. ¹² Therefore, systemic antiviral therapy coupled with local use of antiviral components containing dentures could be an effective strategy to limit the virulence of viruses in denture wearer patients affected by COVID-19.

One of the essential parts of the human immune system is the CD4 cells, a type of lymphocyte that prevent infections by stimulating other immune cells, such as macrophages, B lymphocytes (B cells), and CD8 T lymphocytes (CD8 cells). As the coronavirus is an RNA virus, therefore, during infection, RNA virus attaches to these helper cells and by altering the genetic code, it will produce other virions resulting in the host CD4 cell being killed. ¹³ In the case of COVID-19 patients, to minimize the spread of the virus, the incorporation of antiviral agents to PMMA might act by synthesizing polymers with biocidal functional groups at their surface (phosphate-containing monomers), which exhibit an enhanced hydrophilic antimicrobial characteristic, therefore less microbial adherence will occur. However, the biocide-releasing polymers (silver zeolites, silver nanoparticles) act as a carrier for biocide rather than functioning through the actual polymeric part. The releasing of the biocides close to the cell will be in high concentrations, which will therefore inhibit replication (of cells) by binding to and denaturing microbial DNA as well as RNA. ¹⁴

Recently developed graphene oxide (GO) material can be coated with AgNPs and PMMA, which could be used as a potential antimicrobial agent. Kumar and colleagues recently reported that GO combined with AgNPs induced antimicrobial properties of the alloy by increasing photocatalytic properties with marked production of reactive oxygen species (ROS). ¹⁵ Blended GO and PMMA showed more electroconductivity, which suggested an improved mechanical barrier against microbiota. ¹⁶ On the other hand, GO coatings represented improved surface adhesion, mechanical properties, and cell viability to oral tissues. ¹⁷ Further studies have stated that GO coated nickel–titanium (NiTi) alloy are more biocompatible to the oral environment, corrosion-resistant, and stimulate the generation of interleukins (IL), 6 and 8, which might prevent microbiota induced inflammation.^18,19

However, it is more important now than ever to consider the incorporation of antiviral agents, such as polyurethane iodine and silver ion nanoparticles, in denture base PMMA resins, which may impart antiviral activity, thus help denture wearers to improve their oral health. Clinically, this would be very much acceptable to aid edentulous patients under the current pandemic situation.