Three-dimensional (3D) printing has become an important component of digital orthodontics and has expanded its role from model fabrication to the production of a wide range of customized appliances. This review summarizes the current clinical applications of 3D printing in orthodontics, including diagnostic models, indirect bonding trays, customized brackets, clear aligners and retainers, as well as other adjunctive devices such as miniscrew guides, space maintainers, and expanders. In addition, emerging applications such as smart materials and 4D printing are briefly discussed. Current evidence indicates that 3D printing has improved workflow efficiency, appliance customization, and manufacturing flexibility in orthodontic practice. However, the level of clinical evidence remains uneven across different applications. While some uses, such as model fabrication and indirect bonding trays, have become relatively well established, others, particularly direct-printed aligners and advanced functional appliances, are still in the early stages of clinical translation. Important challenges remain in terms of printing accuracy, material durability, esthetic stability, biocompatibility, post-processing protocols, and long-term clinical validation. Overall, 3D printing is reshaping orthodontic workflows and offers significant potential for personalized treatment, but broader clinical adoption will depend on stronger evidence, improved material performance, and more standardized manufacturing protocols.

Bone formation is an essential process in maintaining bone homeostasis during bone remodeling induced by mechanical force. As the product of bone formation, mineralized collagen is critical for bone strength and quality. However, the effects of mechanical forces on the formation of mineralized collagen remain obscure. Therefore, we applied mechanical force, either tensile force or compressive force, to the in vitro biomimetic mineralization system for 24, 48, and 72 hours. According to the morphological observation under scanning electron microscopy and high-resolution transmission electron microscopy, there was elevated production of minerals depositing along the collagen fibrils in the force-loading groups. We were able to detect the early transformation of crystals and the main components contained amorphous precursor and hydroxyapatite identified by X-ray diffraction. Besides, the changes in the binding energy of elements indicated that the mechanical force accelerated the surface chemical reaction. Furthermore, the comparison and semiquantitative analysis among the spectrum of corresponding groups showed that mechanical forces could affect the bond vibration as well as mechanical properties. Taken together, we confirmed the promoting effects of mechanical force on the formation of mineralized collagen, and this study has made a tentative exploration of the effects of orthodontic force on the formation of mineralized collagen, complementing the biological phenomena occurring in the process of bone remodeling. These findings are expected to provide a theoretical basis for further research into the underlying mechanisms.