Flexural Properties of Experimental Composites With Zinc-Doped Mesoporous Bioactive Glass

Objectives: Experimental composites based on zinc-doped mesoporous bioactive glass nanospheres (Zn-MBGN) were developed as functional restorative materials, serving as a source of antimicrobial and remineralising ions. This study evaluated the flexural strength (FS) and flexural modulus (FM) of experimental composites after 24 hours and after stimulated ageing.
Methods: Twelve groups of experimental composites were prepared with increasing amounts (1,3,5 or 7%) of non-silanised MBGN, 1ZnMBGN or 5ZnMBGN, using an identical combination of 35wt% Bis-GMA/TEGDMA base (60/40) and 55wt% silanised barium-glass fillers with 3-9wt% inert silica nanofillers up to total filler content of 65wt%. The inert control group contained 10wt% inert silica nanofillers instead of MBGN particles. A total of 260 specimens (n=10) were prepared and tested after 24 hours of dark storage in distilled water at 37°C or after stimulated ageing (3 months of dark storage in distilled water at 37 °C and 10,000 cycles of thermocycling). FS and FM were assessed using a three-point bending test (ISO/DIN 4049:1998).
Results: 7%-1ZnMBGN had highest FS after 24-hours (168.99 ± 15.41 MPa) and after stimulated ageing (158.19 ± 11.77 MPa). Inert control had lowest FS after 24-hours (126.74 ± 13.09 MPa) and 7%-5ZnMBGN after stimulated ageing (84.01 ± 15.80 MPa). FS values increase with increasing 1ZnMBGN, but decrease with increasing 5ZnMBGN content in both the 24-hour and stimulated ageing groups. In the 24-hour group, FM was statistically similar for most of the materials. After stimulated ageing, FM increased by 52-72% for all materials.
Conclusions: All materials, before and after stimulated ageing, had FS over 80 MPa, and thus satisfied the ISO requirements for polymer-based restorative materials. The mechanical properties analysed in the present study show that materials with 1ZnMBGN have the greatest potential for clinical application.
This work was supported by the Croatian Science Foundation under the project number HRZZ-IP-2024-05-2884.