Polymethyl methacrylate (PMMA) is the most widely used material for the fabrication of acrylic bases for removable dentures due to its favorable characteristics, including low density, resistance to biodegradation in the oral cavity due to its low solubility, excellent esthetics, cost-effectiveness, biocompatibility, and ease of handling, processing, and polishing [1,2]. On the other hand, the mechanical properties of PMMA are not ideal for withstanding masticatory forces, as it exhibits low flexural and impact resistance [3], as well as dimensional changes due to polymerization shrinkage, which can result in crack propagation and microporosity formation, potentially leading to denture fracture [4].

The predictable occurrence of micropores, cracks, and fissures in PMMA facilitates the adhesion and colonization of pathogenic microorganisms, contributing to the development of biofilms and, consequently, to local and systemic infections [5]. Denture biofilms are particularly prone to harbor Candida species due to the affinity of these microorganisms for acrylic surfaces, which is mainly attributed to the hydrophobicity and rough surface topography of the acrylic bases [6]. The surface roughness of the internal region of an acrylic denture base may range from 3 to 7.6 µm, which is significantly higher than the 0.2 µm threshold required for microbial adhesion [7].

The surface features of PMMA, especially in the internal region of the denture, facilitate Candida spp. colonization at depths of up to 631 µm [8], thereby favoring the development of denture stomatitis (DS). This condition can affect up to two-thirds of maxillary complete denture wearers and is considered the most frequent form of oral candidiasis and the most common oral lesion among the elderly [9]. DS is primarily associated with Candida colonization, particularly Candida albicans, on both the denture-bearing mucosa and the internal surface of acrylic bases [10]. Its treatment remains challenging due to high recurrence rates within a few weeks after conventional therapies, mainly because of the difficulty in eradicating complex denture biofilms with antifungal agents [11].

Some strategies have been proposed to modify PMMA acrylic resin in order to improve its physical-mechanical properties and reduce Candida adhesion and colonization on denture bases [12,13]. A promising approach involves the modification of PMMA with nanosystems such as nanoparticles and nanofibers [[14], [15], [16]]. Nanofibers are characterized by high surface area, tunable porosity, and good mechanical performance [17], which make them ideal candidates for biomedical applications such as drug delivery systems and structural reinforcement [18]. Previous studies have demonstrated that the incorporation of nanofibers such as carbon, polyvinyl alcohol, and cellulose into PMMA enhances hardness, flexural strength, and impact resistance, without inducing cytotoxic effects [[19], [20], [21]].

Cerium (Ce) has gained attention as a relevant chemical element due to its wide range of scientific and technological applications [22,23]. Its electronic, magnetic, catalytic, and microbiological properties are associated with its unique valence states, as Ce is the only lanthanide stable in both trivalent and tetravalent forms, while others are predominantly trivalent [24]. Due to the pleiotropic antimicrobial activity of its precursor, cerium nitrate, Ce has shown significant efficacy against Gram-positive bacteria [25], Gram-negative bacteria [26], and C. albicans [27]. Cerium nitrate has been found to be effective in disrupting preformed Candida biofilms as well as inhibiting their formation in vitro [22,23]. Furthermore, it exhibits biocompatibility, immunomodulatory effects, and low cost [28].

No studies to date have been identified in the available literature that associate the antifungal activity of Ce with the reinforcing effect of nanofibers for the modification of PMMA acrylic resin. This study is the first to report the spinning of PMMA-Ce nanofibers, their characterization, and subsequent incorporation into PMMA denture base resin in different proportions: 0.5 %, 1 %, 2.5 %, and 5 %. The modified acrylic resin was characterized and then evaluated with respect to its antifungal effect against C. albicans, physical-mechanical properties, and cytotoxicity. The null hypotheses of the study were: 1) PMMA modified by PMMA-Ce nanofibers would not exhibit antifungal, anti-adhesive, or anti-biofilm activity against C. albicans; 2) the addition of nanofibers would not improve flexural strength, Knoop microhardness, surface roughness, contact angle, or color parameters (L*, a*, b*) of the modified resin; and 3) the addition of nanofibers would not influence the cytotoxicity of the modified acrylic resin.