Color Stability, Physical Properties and Antifungal Effects of ZrO₂ Additions to Experimental Maxillofacial Silicones: Comparisons with TiO₂

(1) Background: Color changes, physical degradation, and fungal infections are challenges to the longevity of maxillofacial polydimethylsiloxane (PDMS) elastomers. This study aimed to evaluate color changes, physical properties, and antifungal properties of PDMS loaded with ZrO₂ and TiO₂ submicron- and nano-sized particles. (2) Methods: A 1% weight of 40 nm or 200 nm diameter ZrO₂ or TiO₂ nanoparticles was mixed into PDMS with 2% functional intrinsic yellow pigment and polymerized. Control materials contained 13% weight 200 nm silica. Samples were exposed to 3000 h of UVB radiation (200 µW/cm²) or darkness. Color parameters L*a*b* and ∆E_ab*, ultimate tensile strength, strain, elastic modulus, and Shore A hardness were measured. Candida albicans growth was measured using XTT and confocal microscopy, and data were analyzed with the Dunnett test (p < 0.01). (3) Results: TiO₂ 200 nm showed the least color change after 3000 h of UVB radiation, followed by TiO₂ 40 nm (p < 0.05). The silica-containing control group was superior in all physical property measurements due to higher additive content (p < 0.05). TiO₂-containing materials exhibited significantly lower C. albicans growth (p < 0.01) than those loaded with ZrO₂ or SiO₂. (4) Conclusions: TiO₂ nanoparticles of 40 nm and 200 nm, when added to pigmented PDMS at 1% weight, provided the best resistance to color change and significantly lowered C. albicans activity compared to silica- and zirconia-filled elastomers. Particle size differences rendered minor differences for most properties. The incorporation of low-level submicron- and nano-sized TiO₂ particles has the potential to improve color stability and antifungal activity in silicones designated for maxillofacial prostheses and may be extended to denture reline applications.