Publication: Development and characterization of flowable composite derived from rice husk using urethane dimethacrylate
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Date
2025-09
Authors
Azlisham, Nor Ain Fatihah
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Abstract
The study aimed to develop and characterize flowable composites (FCs) using silica derived from rice husk as the primary filler, urethane dimethacrylate (UDMA) as the base monomer, and zirconia as the radiopacifying agent. The resin matrix combined UDMA with triethylene glycol dimethacrylate (UDMA:TEGDMA) at ratios of 20:80, 30:70, 50:50, 60:40, 80:20, and 90:10. Commercial FCs, including Revolution Formula 2, G-aenial Universal Flo, and Filtek Supreme Flowable Composite, were used for comparison. The newly developed FCs were categorized into high (20:80, 30:70), medium (50:50, 60:40), and low-flow (80:20, 90:10), based on the flowability evaluation. These newly developed FCs were subsequently characterized for their chemical, physical, and mechanical properties, as well as polymerization shrinkage. Data were statistically analyzed using one-way ANOVA, followed by posthoc Tukey or Games-Howell tests for comparison, except for the depth of cure, which was analyzed using the Kruskal-Wallis. The chemical properties, assessed through Fourier transform infrared (FTIR) and degree of conversion analyses, confirmed the presence of silica and zirconia in the newly developed FCs and showed an increase in the degree of conversion with higher UDMA ratios (55.38 – 68.58%). The physical properties evaluated included radiopacity, viscosity, depth of cure, surface roughness, water sorption and solubility, and wettability. The newly developed FCs at all ratios were radiopaque (2.87 – 3.06 mmAl) and passed the International Organization for Standardization 4049 (ISO 4049) requirement. As the UDMA ratio in the newly developed FCs increased, both viscosity and depth of cure increased Improved surface roughness and reduced water sorption were also observed with higher UDMA ratios. For solubility, the values were independent of the UDMA ratios. Wettability, assessed through contact angle measurements, revealed a significant increase in contact angle after polymerization, indicating a shift from hydrophilic (24.218 – 50.617º) to more hydrophobic behaviour (85.901 – 88.669º). The mechanical properties evaluated included Vickers hardness, flexural strength and modulus, and compressive strength and modulus. Most properties improved with increasing UDMA ratios, with some flexural strength values (79.61 – 102.1 MPa) meeting the requirement of ISO 4049. Polymerization shrinkage was also reduced as the UDMA ratio increased. Overall, higher UDMA ratios (80:20, 90:10) exhibited superior chemical, physical, and mechanical properties, along with reduced polymerization shrinkage. Moderate (50:50, 60:40) and lower UDMA ratios (20:80, 30:70) demonstrated intermediate and inferior performance, respectively. These findings suggest that the newly developed FCs, particularly at higher UDMA ratios, could serve as viable alternatives to commercially available FCs, supporting a green-based industry that reduces waste and promotes sustainability
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