Medicated denture base resins

Poly (methyl methacrylate) (PMMA) acrylic resin is the most widely used denture base material for the fabrication of removable dentures, implant-supported prostheses, and intraoral maxillofacial prostheses¹ . Because of its advantageous qualities, ease to process, accurate stability and adaptation, superior aesthetics, and being economical PMMA has satisfied all of the ideal qualities of denture base material.

The poly methyl meth acrylate denture base, on the other hand, is prone to bacterial growth in the intra oral cavity. PMMA denture base is devoid of ionic charge which favors biofilm formation by restricting the adsorption of defensins and histatins on thedenture surface ². Hydrophobic interaction, electrostatic interaction, and mechanical attachment also account for bacterial adhesion³. Porosity, surface roughness, baddenture hygiene, and repeated and night time wearing of dentures are the local factors that result in formation of biofilm⁴. Dietary insufficiency, systemic diseases, immune compromised states, and xerostomia are contributing factors form microbialcolonization⁵.

A huge variety of microorganisms is detected on dentures and different detachable dental appliances, in addition to in the oral cavity of denture wearers.Candida albicans and Candida glabrata are generally discovered on surfaces of the denture.

MEDICATED DENTURE BASE RESINS

ANTIMICROBIAL AGENTS

POLYMERIC BIOCIDES

1. Methallyl phosphate monomers

•  PMMA with phosphate groups enables adsorption of salivary microbials and inhibits microbial adherence on the polymer denture base.
•  The presence of 15% phosphate content in poly methyl metacyrlate denture base dramatically lowered C. albicans⁷
•  In vitro investigations on the physical properties of the experimental 10% phosphate-containing PMMA denture base mentioned comparable impact strength, flexuralstrength and modulus, fracture toughness, and watersorption to unmodified PMMA⁸

2. Methacrylic acid monomers

• Methacrylic acid monomer with methyl methacrylate (MMA) monomer when copolymerises, it results in a denture base with anegative charge.
• Using a modified PMMA denture base containing 10% methacrylic acid resulted in significant reduction in Candidia albicans adherence.⁸
• There was a significant drop in transverse and flexural strength.,When the ratio of methacrylic acid concentration was increased from 5% to 10%, the physical properties of the resin changed.

3.12-methacryloyloxy dodecylpyridinium bromide (MDPB)

• Combining a quaternary ammonium dodecylpyridinium with a methacryloyl group leads to synthesis of a polymerizable bactericide known as MDPB⁹.
• A copolymerizable chemical called methacryloyloxyundecylpyridinium bromide (MUPB) in denture base resins against Candida albicans, Candida dubliniensis, Candida glabrata, Lactobacillus casei, Staphylococcus aureus, and Staphylococcus mutans was investigated bt Regis et al for antibacterialefficacy.
• The difference is both is that there is one fewer carbon atom in the intermediate aliphatic chain in MUPB when compared to MDPB and a more cost-effective monomer¹⁰ .

4.2-tert-butylaminoethyl methacrylate (TBAEMA)

• TBAEMA (tert-butylaminoethyl methacrylate) is a monofunctional acrylate monomer with amino groups which works well as a contact biocide.When TBAEMA is added to the MMA monomer, it copolymerizes, allowing the pendant amino groups to appear on the acrylic resin surface.¹¹ .
•  Although Modified PMMA denture bases have shown significantantimicrobial activity against S. Aureus and S. mutans, but they have no significant effect on C. Albicans¹² .

BIOCIDE-RELEASING POLYMERS

1.Silver zeolites

• The use of silver as an antibacterial agent has a protracted history. It has been said to intervene with sulfhydryl groups on metabolic enzymes and proteins in the tissue structure of microorganisms¹³ . Silver additionally prevents mobileular replication via adhering to and denaturing bacterial DNA and RNA..
• Because the ion exchange mechanism is charge-neutral, the rate of release is regulated; silver cannot be released unless another ion takes its place on the zeolite¹⁴.

2. Silver nanoparticles (AgNPs)

• Because the dimensions of materials are reduced to the atomic level, nanoparticles have properties that are distinct from their bulk analogues
• AgNPsare reported to be particularly efficient against bacteria, viruses, and other eukaryotic microorganisms at very low concentrations.
• PMMA–AgNPs formulation successfully reduced C. albicansadhesionwithout impairing normal cell proliferation and metabolism has been proven inresearch ¹⁵.
• Decreasedmitochondrial function after exposure to AgNPs in various cells (murine neuroblastoma cells, hepatic cells, germline stem cells, human skin carcinoma, human epidermal keratinocytes and fibroblasts) has been shown through in vitro cell line studies¹⁶

3.Titanium Dioxide Nanoparticles

• Photocatalysisproduces high antibacterial activity in titanium dioxide nanoparticles (TiO2NPs) and has the ability to degrade organic compounds and germs on its surface. S. mutans, E. coli, and other bacteria have been found to be killed by powdered TiO2.
• Sufficient bonding between nanoparticles and PMMA denture base have beennoted and tio2np has been experimentally formulated
• Acrylicresin containing 5 wt percent apatite-coated TiO2 photocatalyst was found to have antifungal properties by Shibata et al¹⁷

POLYMERIC SURFACE COATINGS

• Surface coating materials can change the hydrophobic characteristic of PMMA denture bases to a hydrophilic surface.
• Silica being inherently hydrophilic can be used to coat and modify PMMA denture bases to create a hydrophilic surface

• Arai et al revealed that a TiO2 coating on the PMMA denture foundation gave the denture surface hydrophilic characteristics and prevented Streptococcus sanguinis and Candida albicans adherence¹⁸.

•  When applied as a thin layer, poly(dimethyl siloxane) is a self-bonding polymer, By forming an inert mono-molecular layer on the resin’s surface and changes the surface chemistry. This type of layer is chemically stable and lasts for the same amount of time as the substrate to which it is adhered.

PHYTOCHEMICAL OR PHYTOMEDICAL COMPONENTS

• Plant extracts and Essential oils have been related to therapeutic properties,and the incorporation of herbal and organic additives into dental materials has been proposed¹⁹ .
• The cinnamon tree (Cinnamomumzeylanicum) possesses favorable analgesic, antiseptic, antispasmodic, astringent, insecticide, and antimicrobial properties.
• Eugenol, cinnamaldehyde, citral, and geraniol, amongst different phytochemicals found in C. Zeylanicum leaves, can also additionally play a function in inhibiting C.albicans biofilm formation on DBR surfaces and oral epithelial cells. Furthermore, monoterpene compounds found in essential oils have hydrophobic characteristics, permitting lipophilic systems to be deleted and inhibits microbial membrane synthesis spore germination, and cellular respiration.
• Hinoki cypress (Chamaecyparisobtusa) extract has been utilised in various household health products, such as detergent, toothpaste, and cosmetics as Chamaecyparisobtusa essential oil prevents the formation of pathogen germs. At pH 5.5, DBR containing microencapsulated C. obtusa essential oil discharged the antimicrobial agent and prevented C. albicans development
• Neem trees (Azadirachtaindica) are native to India’s subcontinent, and itsproperties are much like those of henna powder, therefore they have been utilized in conventional medicines. Over a 21-day period, autopolymerizing and heatpolymerizing DBR materials containing neem extract confirmed antibacterial efficacy against C. Albicans.
• Another study using neem powder at various concentrations, including 0, 0.5, 1, 1.5, 2, and 2.5 wt%, incorporated into heat-polymerizing DBR showed a substantial reduction of C. albicans colony-fomring units at higher concentrations.
• Tea tree oil (TTO) is derived from a well-known Australian native plant (Melaleucaalternifolia) and has long been used as an antibacterial. It includes about 48 volatile compounds, the most important of which is terpinen-4-ol, which is responsible for the antibacterial effects²⁰
• According to a study of the literature²¹, Tulsi antibacterial properties have been evaluated against Candida albicans, Staphylococcus aureus, gastrointestinal pathogens, Klebsiella, Escherichia coli, and Proteus

• The pomegranate, Punicagranatum Linn., is a fruit-bearing deciduous shrub or small Asian tree²¹ with the botanical name Punicagranatum Linn. According to a review of the literature, certain researchers, such as Vasconcelos et al, observed that extracts of Punicagranatum peel were effective against S. epidermidis, S. aureus,S.mutans, S.sanguinis, and S. salivarius at various concentrations²² .

ANTI FUNGAL AGENTS

Antifungal drugs included into denture base materials have the potential to be a reasonable way to prevent denture stomatitis. Five commonly used antifungal agents are listed in fig. 3

• Nystatin, a polyene fungicidal drug with water-insoluble components, offers The broadest spectrum of activity of all antifungals. The nystatinpolyenes bind To ergosterol, which is a key component of fungal cell membranes. When present in sufficient concentrations, it forms pores in the membrane that lead to potassiumleakage, acidification, and fungus death.
• In comparison to other antifungals, this drug has some advantages, such as high effectiveness in inhibiting Candida spp. rare detection of resistant fungal strains, and accessible cost.
• Azole antifungals, such as miconazole, ketoconazole, and itraconazole, work by interfering with ergosterol synthesis and specific enzymes in fungi. They primarily function by blocking the enzyme cytochrome P450 14-alpha- demethylase, which is involved in the sterol biosynthesis pathway that converts lanosterol to ergosterol, causing oxidative damage.
• Azoles are relatively water insoluble and are fungistatic in nature, yet they may have fungicidal properties in some in vivo circumstances. Azole agents, such as miconazole, also have antiparasitic and antibacterial effects²³