BACKGROUND:Hydrogels have become a research hotspot due to their unique advantages in the biomedical field due to their superior mechanical and biological properties.At present,related research involves tissue engineering,wound dressing and so on. OBJECTIVE:To review the advantages and properties of hydrogels and the research progress of their application in the repair of oral and maxillofacial defects,discuss the current limitations and challenges of hydrogels in application and promotion,and provide new ideas for future research directions. METHODS:Relevant literature was searched in PubMed,CNKI,and WanFang database by computer.The search terms were"hydrogel,oral and maxillofacial defects,mechanical properties,tissue engineering,wound dressing"in Chinese and"hydrogel,oral and maxillofacial defects,mechanical properties,guided tissue regeneration,wound dressing"in English.Preliminary screening was carried out by reading titles and abstracts,and articles not related to the topic of the article were excluded.According to the inclusion and exclusion criteria,108 articles were finally included for the result analysis. RESULTS AND CONCLUSION:(1)The hydrogel has good biological activity,mechanical controllability,and stimulation response.(2)Polymer,metal,and ceramic hydrogel composites have appropriate mechanical properties,biodegradability,and controlled release rate,which are suitable for maxillofacial bone tissue engineering.(3)Fibrin-based hydrogel could fill the hollow nerve conduit through the nerve defect area and promote the regeneration and growth of axons to restore the function of maxillofacial nerve.(4)Controlling the interaction between nanomaterials and hydrogels can improve the formation of muscle fiber oriented structure to promote maxillofacial muscle tissue regeneration.(5)Polysaccharide hydrogel has gradually become the first choice for repairing irregular periodontal defects due to its ability to control drug delivery,carry bioactive molecules,and combine with other materials to produce the best scaffold matching the extracellular matrix.(6)Calcium phosphate or calcium carbonate-based hydrogels can be used to fill irregular or fine tissue defects and remineralize hard tissues.The self-assembled hydrogels are simple to prepare and have good biological activity.(7)Salivary gland-derived extracellular matrix-like gel is expected to participate in the treatment of many salivary gland diseases.(8)Hydrogels can be used as wound dressings in combination with biological adhesives,acellular biomaterials,antimicrobials,antioxidants,or stem cells to treat various wounds.(9)Fibrin-based hydrogel has the most potential in the repair of oral and maxillofacial defects.It has excellent biocompatibility,flexibility,and plasticity.It can combine with cells,extracellular matrix proteins,and various growth factors,and promote the osteogenic differentiation of mesenchymal stem cells,axon regeneration and growth,angiogenesis,myotube differentiation,salivary gland tissue regeneration,and periodontal tissue regeneration.It has a broad prospect in the repair of oral and maxillofacial defects.However,its therapeutic effect depends on the function of the substance carried.The complex preparation process,its safety and long-term efficacy,and the special anatomical oral and maxillofacial structure is the problem that hinders its promotion,which also provides directions for future research.