Emerging trends of injectable hydrogels for vital pulp therapy: A comprehensive review

BACKGROUND: Injectable hydrogels are widely used in biomedicine and tissue engineering. Recently, they have been introduced as promising capping materials for vital pulp therapy (VPT) owing to their biocompatibility, in situ adaptability, minimal immunogenicity, and ability to modify the cellular activities of dental pulp exposed to caries or accidental injuries. Although injectable hydrogel-based biomaterials facilitate pulp healing and reparative dentine formation, their clinical utility has not been fully explored. OBJECTIVES: This review highlights the gaps in current research, including the lack of studies on the long-term in vivo effects of injectable hydrogels and comprehensive interactions between injectable hydrogel and the dentine-pulp complex, which impede clinical translation, especially for VPT. METHODS: A comprehensive literature search was conducted in PubMed and Scopus in April 2024 using relevant keywords related to injectable hydrogels and VPT. Eligible articles published between 2014 and 2024 included laboratory, animal and clinical studies, addressing the biological function, design, or clinical applicability of injectable hydrogels for VPT. RESULTS: This review covers various biomaterial-based injectable hydrogels developed using hyaluronic acid, gelatine methacryloyl, chitosan, collagen, decellularized extracellular matrix, self-assembling peptides, and nanoparticles for VPT, highlighting possibilities for future clinical translation and innovation. Laboratory studies on injectable hydrogels provide promising results, including enhanced pulp healing, reduced inflammation, homogeneous reparative dentine formation, and also key innovations to enhance the functionality, adaptability, and characteristics of novel injectable hydrogels developed for VPT. CONCLUSION: Hydrogels functionalized with advanced biomaterials and bioengineering approaches can overcome the existing shortcomings, enabling their smooth transition into clinical practice. Nevertheless, further research is required to elucidate their long-term effects and optimal application methods.