Engineered Bi₂O₃ and BaSO4-PMMA composites for intraoral applications: Achieving radiation shielding and structural durability through microparticle synergy

Intraoral shielding materials for radiotherapy must combine mechanical durability with photon attenuation. PMMA is clinically used but provides limited shielding PURPOSE: To develop PMMA microcomposites containing bismuth oxide (Bi₂O₃) or barium sulfate (BaSO₄) microparticles and evaluate mechanical properties, surface roughness, and transmitted-dose reduction under a nominal 6 MV photon beam. METHODS: PMMA composites with Bi₂O₃ or BaSO₄ (40 or 70 wt%) were fabricated, irradiated to 54 Gy, and tested for Knoop microhardness (KNH), flexural strength (FS), surface roughness (Ra), and transmitted dose using thermoluminescent dosimeters (TLD); morphology was assessed by SEM. RESULTS: 70%Bi added to the AR, significantly increased the KHN, compared to AR neat, 12.6 and 9.21, respectively. However, after radiation, there was no significant difference between groups. In addition, the 54 Gy radiation dose results in a significant increase in KHN only in the AR group. Adding Bi₂O₃ and BaSO₄ to the AR altered the surface topography; Ra differed among groups at 0 Gy, with significant contrasts between AR and the other groups. The surface topography was altered, and the average roughness (Ra) varied across groups at 0 Gy, with significant differences between AR and the other groups. 40%Bi and 40%Ba. SEM showed clusters and porosities, with larger but fewer agglomerates in Bi₂O₃ composites and more numerous, smaller agglomerates in BaSO₄ composites. After irradiation, 70%Bi showed the highest mean mechanical values (12.6 KHN; 85.8 MPa) The greatest reduction in transmitted dose occurred in 40%Bi (26.29%), corresponding to ∼14 Gy lower cumulative transmitted dose under the present setup. At 54 Gy, Ra differences persisted: AR differed from 40%Ba and 70%Ba but not from Bi₂O₃ groups; Ra decreased for 40%Bi and 40%Ba. SEM indicated increased surface porosity in BaSO₄ groups and localized surface damage in 70%Ba. CONCLUSIONS: Within the limitations of this in vitro study, Bi₂O₃-filled PMMA microcomposites provided the most favorable balance between transmitted-dose reduction and mechanical performance under 6 MV photon irradiation.