Oral health is crucial to daily life, yet many people worldwide suffer from oral diseases. With the development of oral tissue engineering, there is a growing demand for dental biomaterials. Addressing oral diseases often requires a two-fold approach: fighting bacterial infections and promoting tissue growth. Hydrogels are promising tissue engineering biomaterials that show great potential for oral tissue regeneration and drug delivery. In this review, we present a classification of hydrogels commonly used in dental research, including natural and synthetic hydrogels. Furthermore, recent applications of these hydrogels in endodontic restorations, periodontal tissues, mandibular and oral soft tissue restorations, and related clinical studies are also discussed, including various antimicrobial and tissue growth promotion strategies used in the dental applications of hydrogels. While hydrogels have been increasingly studied in oral tissue engineering, there are still some challenges that need to be addressed for satisfactory clinical outcomes. This paper summarizes the current issues in the abovementioned application areas and discusses possible future developments.

Herein, polylactic acid cast films were prepared with different melt-draw ratios via an extrusion casting process. The structure and properties of the prepared films were characterized. The results showed that with the increasing melt-draw ratios (MDRs), an oriented structure appeared at first, and then, a chi structure crystal was formed at higher MDRs. The vertical shish crystals showed a higher melting point than the oriented structure. The PLA molecules were extended by melt-stretching, and weak hydrogen bonds appeared between the carbonyl and methyl bond in the neighbourhood extended PLA molecular chain segments. The hydrogen bond limited the molecular mobility in the amorphous region, which increased the weight fraction of the rigid amorphous region. The stretching-induced crystallization occurred during the melt-stretching process, but the formed crystals were not strictly α form or α′ form. At lower MDRs, mainly an oriented structure was formed, and with the increase in MDR, meridional streaks in SAXS patterns appeared, accompanying the shish formation. The kebab and oriented structure signals superimposed together; this led to irregular equatorial scattering patterns. In this study, we provide a new insight into PLA crystallization via melt-extrusion cast flow.