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Increased esthetic demands, good mechanical properties, and ease of application have increased the use of composite resins in preventive and restorative dentistry. The incorporation of natural products in composite resins, thereby making them eco-friendly, has recently gained popularity. Some of the benefits include lower cost, lower toxicity, higher sustainability, lightweight, etc.
Rice husk, a natural sheath that forms around rice grains during their growth, can be obtained as a natural fiber from agroindustrial waste and can be used as filler in composites materials in various polymer matrices.
Dental composite made of rice husk
Rice husk is a biomass waste from rice having high silica content. It also has high strength, resistance to bacterial decomposition, hard surface, low density, and is inexpensive. Some researchers have recently explored its use as a filler in dental composite resin to minimize environmental pollution and reduce composite material costs. Packable and flowable composite resins were manufactured using rice husk silica as a filler. This process involved the extraction of silica from rice husk and precipitation of silica.
A systematic review and meta-analysis found that the rice-husk composites had inferior physical and mechanical strengths and lower surface roughness than commercially available composite resins. This meta-analysis, conducted on eleven articles and one book section, suggested that the reason for inferior mechanical properties could be the low filler loading. However, it did demonstrate comparable color stability with other commercially available composite resins. Flowable rice husk composites showed lower compressive strength than hybrid flowable composites, although their hardness values were superior to commercially available flowable composites.
This study recommends using rice husk dental composite with increased filler loading for future approaches. Some studies have also suggested the incorporation of zirconia nano-powder to improve the compressive strength, fracture strength, and hardness values and reduce polymerization shrinkage of the rice husk composite. Methods such as reinforcing rice husk dental composites with solid elements like alumina and zirconia, incorporating resin monomers like ormocers, using coupling agents like zirconate, and adding antibacterial agents have also been used been suggested to improve the properties of rice husk dental composites and prevent secondary caries.
Rice husk is an inexpensive source of silica for use as filler particles in dental composites. These composites have been found to have acceptable clinical performance in terms of physical, mechanical, and optical properties. Hence, rice husk dental composites are considered a potential emerging biomaterial in dentistry, and more strategies must be explored to improve its properties.
Lin, GSS, Cher, CY, Cheah, KK, Noorani, TY, Ismail, NH, Ghani, NRNA. Novel dental composite resin derived from rice husk natural biowaste: A systematic review and recommendation for future advancement. J Esthet Restor Dent. 2021; 1- 9. doi:10.1111/jerd.12831