Mussel-inspired compound enhances adhesion of dental filling

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Mussel-inspired compound enhances adhesion of dental filling material

A mussel-inspired compound has been found to improve the durability of the resin–dentine bond and the longevity of dental fillings. (Image: C E Newman/Shutterstock)

HONG KONG, China: Moisture is one of the greatest challenges for dental fillings, as it reduces adhesive performance. To overcome this obstacle, researchers from the Faculty of Dentistry of the University of Hong Kong (HKU), Wuhan University and Peking University Shenzhen Hospital turned to nature and found an answer in a mussel-derived compound. After studying its performance in various tests, they found that the compound can improve the durability of the resin–dentine bond and thus the longevity of dental fillings.

Dental fillings are clinically challenging, since the restoration’s success is affected by factors such as the moist environment of the oral cavity and mechanical stress caused by chewing. Failure of the resin–dentine bond results in increased visits and costs for the patient.

Lead researcher Dr Cynthia Kar Yung Yiu, clinical professor of paediatric dentistry at HKU, explained in a press release that mussels need to maintain their adhesive properties under harsh conditions, such as humidity, extreme temperature changes and pH values, and mechanical shocks—circumstances similar to the conditions in the oral cavity.

The wet adhesion property of mussels has long been of interest to scientists, and several studies have focused on how this quality could be used in clinical practice. Such applications have included surgical protein glues for wound closure, microneedle bandages for cardiac tissue regeneration and materials for drug delivery.

The properties of mussels have also been widely used in dental applications. As reported by Dental Tribune International, mussel-derived solutions have enhanced dental implant coatings, helped create more biocompatible implants, advanced the treatment of dentine hypersensitivity and inspired the development of tougher products for restorative dentistry.

Evaluation of clinical performance

The wet adhesion property of mussels is attributed to a derivative of the amino acid tyrosine, called dopa, in the mussel adhesive protein which the marine organisms secrete to stick to surfaces in moist environments. The research team evaluated the performance of a mussel-derived compound based on this (DMA) as a functional monomer in dental adhesives regarding the durability of the resin–dentine bond.

The team compared the durability of the control group with three solutions containing different concentrations of DMA in various tests. The results showed that DMA successfully linked with dentine collagen, polymerised with the adhesive without affecting the degree of conversion or elastic modulus, strengthened the integrity of the resin–dentine interface, prolonged the durability of the bond and inhibited the activity of endogenous metalloproteinases, which are involved in the degradation of collagen and of the resin–dentine interface. The findings indicate that DMA can polymerise with resin monomers without hampering the adhesive’s mechanical strength and may prevent bond failure caused by a sudden change in stress.

Co-author Dr James Kit Hon Tsoi, associate professor of dental material science at HKU, summarised the research findings and gave an outlook for the future: “This research discovered that DMA is effective in strengthening the resin–dentine bond and improves its durability. The cytotoxicity is also similar to the resin monomers in traditional dental adhesives. It is believed that this compound may be commercialised in the future.”

Remaining challenges

Despite the performance of DMA, the researchers raised concerns about its limited shelf life. During testing, the DMA solution turned a faintly yellow colour after two months, a characteristic that would prove unpractical for clinical usage. Thus, future studies may consider adding antioxidants to the DMA solution in order to avoid this effect.

The study, titled “Enhancing resin-dentin bond durability using a novel mussel-inspired monomer”, was published in the September 2021 issue of Materials Today Bio.

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