Influences of TiO2 and SiO2 nanofillers on the mechanical performance of a maxillofacial silicone elastomer after two years of outdoor tropical weathering: An in vitro study.

Abstract

The present study evaluated the influence of 3% and 10% (by weight) silicon dioxide (SiO2) and titanium dioxide (TiO2) nanoparticles (NPs) on the tear strength, tensile strength, and elongation at break of a room-temperature vulcanizing (RTV) maxillofacial silicone elastomer (MFSE; A-2000) after two years of natural tropical weathering. A total of 160 specimens (80 dumbbell-shaped and 80 trouser-shaped) were allocated to non-weathered and weathered groups, each divided into five subgroups (n = 8): unfilled control, 3% SiO2, 10% SiO2, 3% TiO2, and 10% TiO2. Weathered specimens were exposed outdoors in a hot, humid tropical climate for two years. Mechanical properties were measured using a universal testing machine. Data were analyzed using two-way ANOVA followed by Tukey HSD post-hoc tests (α = 0.05). In non-weathered specimens, 3% SiO2 increased tear strength by 34% (17.89 ± 0.31 vs. 13.38 ± 1.07 N/mm; P < 0.001) and tensile strength by 35% (4.28 ± 0.27 vs. 3.16 ± 0.13 MPa; P < 0.001) compared with the unfilled control. After natural tropical weathering, only the 3% SiO2 group maintained a significantly higher tear strength (14.03 ± 2.10 N/mm) than the unfilled group (11.09 ± 1.53 N/mm; P = 0.007). Weathering significantly reduced tear strength in all NP-filled groups (P < 0.001) but increased tensile strength across all groups (P < 0.01), with the smallest increase observed in the 10% TiO2 group (+10.1%; P = 0.004). Elongation at break decreased significantly in all groups following weathering (P < 0.001); however, NP-filled groups retained substantially higher elongation values (losses of 13.1-17.6%) than the unfilled control (loss of 51.1%). In conclusion, the incorporation of 3% SiO2 NPs significantly enhanced the mechanical properties of A-2000 MFSE both before and after two years of natural tropical weathering, whereas higher loading (10%) offered no additional benefit. These findings support the use of low-content SiO2 NPs to improve the long-term durability of maxillofacial prostheses.