Candida albicans adhesion, biofilm formation and gene expression on conventional, milled and 3D-printed denture base materials: an in vitro study

Abstract Background Denture base materials are colonized by Candida albicans , and surface properties influence microbial adhesion. Evidence on subtractively and additively manufactured materials remains limited. This in vitro study examined surface characteristics of conventional, milled and 3D-printed denture base materials and their association with C. albicans adhesion, biofilm formation and gene expression. Methods Specimens of eight conventional, milled and 3D-printed denture base materials were polished to an arithmetic surface roughness (R a ) below 0.2 μm and characterized by surface free energy (SFE), scanning electron microscopy and energy-dispersive X-ray spectroscopy. Initial adhesion of C. albicans DSM 1386 (2 h) was quantified by fluorescence staining. For the materials with the highest and lowest adhesion (Temp Basic, Denture Gingiva Basic Mono), 24-h biofilm formation was quantified by crystal violet staining, and ALS3 and EFG1 expression by RT-qPCR after 2, 4 and 8 h, additionally in two oral clinical isolates. Data were analyzed using (Welch) ANOVA with post hoc tests and one-sample t-tests (α = 0.05). Results Temp Basic showed a significantly lower SFE than all other materials ( p ≤ 0.012) and the highest mean initial adhesion, which differed significantly from PalaXpress, V-Print dentbase and Denture Gingiva Basic Mono ( p ≤ 0.018). Biofilm biomass after 24 h did not differ between Temp Basic and Denture Gingiva Basic Mono ( p = 0.261). In the reference strain, ALS3 and EFG1 expression was significantly higher on Denture Gingiva Basic Mono after 4 h (p ALS3 = 0.009; p EFG1 = 0.038), but not after 28 h. Both clinical isolates likewise showed higher expression after 4 h, without significance in clinical isolate 1; clinical isolate 2 was tested in a single experiment. Conclusions Within the limitations of this in vitro study, SFE alone did not explain material-dependent differences in initial C. albicans adhesion, and higher initial adhesion was not associated with greater biofilm biomass. ALS3 and EFG1 expression after 4 h was higher on Denture Gingiva Basic Mono, significantly in the reference strain and in the same direction in two clinical isolates. Confirmation under clinically relevant conditions, including a salivary pellicle and multispecies biofilms, is required.