Recent Research by Chinese Scholars: Functional Hydrogel Advances in Treating Dental Hard Tissue and Pulp Diseases

Recently, a review article titled “Recent Advances in Functional Hydrogels for Treating Dental Hard Tissue and Endodontic Diseases” was published in ACS Nano by a collaborative team including authors Pan Keqing and Li Huixu from the School of Stomatology, Qingdao University (corresponding authors), Zhang Ding from the School of Materials Science and Engineering, National Institute for Advanced Materials, Nankai University (corresponding author), and Bao Pingping from the Oral Hospital, Tianjin Medical University (corresponding author), and a researcher from the School of Pharmacy, Xinjiang Medical University (corresponding author). The review discussed the latest developments in the field of functional hydrogels for the treatment of dental hard tissue and pulp diseases.

The study introduced the working principles and treatment effects of functional hydrogels in different diseases, discussed the challenges and opportunities in their clinical application in dentistry, and proposed potential future directions for the development of functional hydrogels in oral health. This was achieved through a systematic analysis and summary of the recent advances in functional hydrogels for treating dental hard tissue and endodontic diseases. The research findings were published in ACS Nano with the title “Recent Advances in Functional Hydrogels for Treating Dental Hard Tissue and Endodontic Diseases” (IF = 15.8).

Hydrogels, as highly hydrated three-dimensional polymer networks, have become one of the most popular soft materials in recent years. Due to their excellent biocompatibility, injectability, similarity to biological soft tissues, and outstanding self-healing properties, hydrogels have been widely used in various biomedical fields, including wound hemostasis, skin healing, drug delivery, and tissue reconstruction. It is well-known that the oral environment is constantly wet and subject to movements during eating and speaking. Therefore, in addition to good biocompatibility and antibacterial properties, functional hydrogels for oral applications also need to possess properties such as mechanical strength, wet adhesion, and fatigue resistance.

Tooth Whitening

Researchers analyzed the application of hydrogels in tooth whitening and their mechanism of action through adsorption and decomposition of pigments. They developed a novel injectable hydrogel film for photodynamic tooth whitening (Figure 3a). The hydrogel film incorporated bismuth chloride (Bi12O17Cl2) and cuprous oxide (Cu2O) nanoparticles into the sodium alginate hydrogel precursor, which rapidly formed through dynamic crosslinking with calcium ions. The Cu2O nanoparticles endowed the hydrogel with broad-spectrum antibacterial properties, while the Bi12O17Cl2 nanoparticles acted as photosensitizers, generating ROS under green light irradiation to effectively degrade tooth pigments, whiten the teeth, remove biofilms, and prevent cavities. Furthermore, this tooth whitening technique showed no significant damage to enamel and biological cells.

Enamel Regeneration

Enamel is a hard mineralized tissue that resists bacterial invasion and is composed of tightly arranged hydroxyapatite crystals. Dental caries, a common enamel pathology, is an acid-induced non-cellular reactive lesion with a complex demineralization and remineralization process. Once enamel is damaged, it can accelerate dentin lesions. Therefore, early prevention and treatment of enamel caries are crucial.

CS-QP5 hydrogel incorporating enamel peptides was found to effectively inhibit cariogenic biofilm, promote initial enamel remineralization, and possess antibacterial properties, demonstrating its caries-preventive potential. To address the problem of bacterial overload in fluoride treatment, a Pluronic F127-alginate hydrogel that releases both nitric oxide and fluoride was developed for dual treatment. In addition, a full-length enamel protein-chitosan hydrogel was developed to repair carious lesions by stabilizing mineral clusters’ growth, resulting in seamless integration with the native enamel and significantly improved hardness. A hydrogel biomimetic mineralization model successfully regenerated mineralized tissue similar to enamel, with mechanical properties close to natural enamel, providing a new approach for enamel regeneration.

Dentin Repair

Dentin, with different composition and structure from enamel, is softer than bone but harder than enamel. Dentin caries develops faster than enamel caries. Researchers designed a composite mineral hydrogel that can load dentin matrix and promote hard tissue regeneration. For severe dentin caries, traditional pulp capping materials have limitations. Therefore, researchers developed an injectable Gel-MA/NGR1 hydrogel to induce reparative dentin formation. In addition, the exposure of dentin tubules accelerates caries progression and leads to dentin hypersensitivity, so a long-term stable desensitizer is needed to occlude dentin tubules. Researchers developed a robust ultra-thin nanofilm using lysozyme and polyethylene glycol (lyso-PEG) as a fast amyloid-like assembly for treating tooth sensitivity. The nanofilm exhibits anti-fouling properties, ease of remineralization, and long-term stability. It can be easily formed as a colorless coating on dentin by simple immersion or spray. Lyso-PEG has a high affinity for dentin tubules, enabling deep penetration and effective antibacterial activity. Moreover, the lyso-PEG nanofilm can induce dentin remineralization, enhance interface bioactivity, and provide an effective solution for dentin tubule treatment.

Pulp Regeneration

In pulp regeneration therapy, collagen hydrogels can regulate stem cell differentiation and promote cell survival and selective differentiation. Injectable thermosensitive hydrogels have been used as promising materials for pulp regeneration. Researchers developed an HPCH/CW/Exo hydrogel by embedding extracellular vesicles, which exhibits excellent mechanical properties and biocompatibility. The hydrogel can be easily injected into the root canal, spontaneously gel in situ, and fill the root canal space after encapsulating stem cells, significantly promoting dentin and vascular formation. Animal experiments have demonstrated its ability to generate new pulp tissue, showing its potential clinical application value.

The application of hydrogels in wound healing and other fields faces multiple challenges, such as balancing biocompatibility and mechanical properties, strong wet adhesion and durability requirements in the dynamic and moist oral environment, the need for more clinical research to validate the effects, and potential influences of immune reactions on hydrogel treatment efficacy. Future research should focus on addressing these challenges to promote the widespread application of hydrogels in the treatment of oral diseases.

This article is sourced from “For Better Science.”