1 Characteristics of RPMT RPMT is based on the computer description of object geometry, structure and connection status, which can automatically and rapidly materialize design ideas into prototypes with certain structure and function or directly manufacture objects, and can shorten the conversion time from CAD model to physical model by more than 80%. With the development of diagnostic technology characterized by digital imaging technology (CT, MRI, 3D B-ultrasound, etc.), it is easy to reconstruct local cross-sectional images of the human body in 3D by computer, and these data can be transferred to the RPMT system to create the tissue entity of this part of the structure. It is particularly suitable for the direct production of small batches, complex (e.g., fluted, convex shoulders, hollow, nested, etc.) and shaped objects; it is easy to modularize and switch between devices with different process principles; it allows remote manufacturing services with the help of the Internet; it is available in a wide range of materials (e.g., resin, plastic, paper, paraffin, film, metal or ceramic powder, foil, silk, etc.); theoretically, the raw material utilization rate can reach 100 Theoretically, the raw material utilization rate can be up to 100%, and the manufacturing process is vibration and noise free, making it an environmentally friendly and efficient manufacturing technology. At present, the highest precision can be 0.001mm, layer thickness ±0.005mm, and the maximum size of molded parts can be 800mm×1600mm×500mm (such as SSM-1600 of Tsinghua University) with a speed of several hours to tens of hours/piece by using special molding equipment. 2 The significance of RPMT in maxillofacial surgery The purpose of maxillofacial surgery is not only to meet the physiological and functional needs of the patient’s facial organs, but also to restore the patient’s appearance with maximum personalization, which requires: careful and thorough preoperative planning; explaining the postoperative results to the patient; and keeping the surgical operation as simple as possible. The direct or indirect intervention of RPMT undoubtedly simplifies these problems, as it can play an important role in aiding diagnosis (fractures, ankylosis and even obstructed teeth), planning, simulation of surgery (e.g., Gateno et al. used RPMT for predicting distraction osteogenesis), and treatment, making it possible to perform complex orthopedic procedures that were originally done in several operations in a single visit. Statistics have been done: after applying RPMT, the correct diagnosis rate increased by 29.60%, the accuracy of operation increased by 36.23%, and the operation time increased by 17.63%. Not only that, RPMT has also been attracting attention in recent years for its application in basic research fields such as tissue engineering in maxillofacial surgery, and it has become an important method for manufacturing cell carrier scaffolds. Broadly speaking, the application of RPMT can be divided into 3 stages: the primary stage, biological solid models for diagnosis and surgery; the intermediate stage (compatible biological models), implants for therapeutic and rehabilitation engineering; and the advanced stage (advanced biological models), artificial organs (“real” bone that can participate in metabolic processes). 3 Several rapid prototyping techniques applied in the field of maxillofacial surgery RPMT is usually classified according to the principle of the manufacturing process. The following are some of the more mature technologies applied in the field of maxillofacial surgery and their characteristics: (1) Stereo Lithography Apparatus (SLA), also known as photosensitive liquid phase curing, stereolithography, stereoscopic modeling. This technology uses photosensitive resin as raw material, and scans point by point with a computer-controlled ultraviolet laser with the outline of each layered section of the intended prototype as the trajectory, curing the resin in the scanned area, placing a new layer of resin while the table moves, and so on until the manufacturing is completed. Anderl et al. used the SLA model to plan and operate on an 8-month-old child with a severe midface cleft (from the anterior cranial fossa to the hard palate), with the following results Hollister et al. used the SLA model to create a restoration of the lateral mandibular joint defect in a small Yucatan pig with a screwed-in nail. SLA can also be used for microfabrication, and the Kyushu Institute of Technology in Japan has produced a model of approximately 50 μm. The disadvantage of SLA is that it is difficult to generate microstructures with bioactivity; the volume change during molding makes it difficult to control. (2) Laminated Object Manufacturing (LOM). LOM can produce large-size prototypes; the price of equipment and molding materials is low, and the model is free of internal stress and deformation, with high precision. The LOM process is developing towards the diversification of available materials (e.g., sheet metal and ceramic materials). LOM can be used clinically for hard tissue replacement of craniofacial bone defects caused by congenital, traumatic, post-craniectomy decompression, infection, etc. For example, Ono et al. used HA ceramics to repair complex jaw defects (up to 14.7 cm × 12.0 cm) in 9 patients by LOM. The shortcomings of LOM are that the material resistance and bond strength are closely related to the selected substrate and adhesive species, and waste separation is time-consuming. (3) Selected Laser Sintering (SLS). It is precisely guided by the laser beam so that the material powder sintering or melting after solidification to form a three-dimensional prototype or model. Generally no binder is added and there is no subsequent treatment, so a high-strength model can be formed; no support is required; the accuracy of the model is high (up to ±0.01mm when the particle size is less than 0.1mm); if wax powder is used, a precision casting wax model can be manufactured directly. The early SLS method was less competent for the fabrication of tissue engineering cell scaffolds because of the difficulty in removing the powder between the pores. The current development of SLA has been able to adjust the internal microstructure (pores and pore size) of the sintered product by controlling the parameters. For example, Cheah et al. used the principle that the pore size of microtubules increases in the X-Z plane when the laser energy is reduced and the scanning speed is increased to create a drug retardation device by controlling the formation of dense and porous zones, which is significant for the reconstruction of defects in the area of maxillofacial bone tumors; Tan et al. controlled different ratios of two materials on a commercial SLS device, using polyether ether ketone -The shortcomings of SLS are that it is difficult to precisely control the absorbed power per unit area in sintering; sometimes the surface of the model is relatively rough and needs to be cured and polished by proper baking. (4) Fused Deposition Modeling (FDM), also known as melt stacking method, melt extrusion into the mold. Is the use of hot melt nozzle, so that the semi-flowing state of the material according to the CAD layered data control path extrusion and deposition in the developed position of solidification molding, gradually deposited, solidified to form a model. Eppley et al. performed cranial reconstruction in 13 patients by FDM to produce personalized pseudofacial restorations, which greatly saved intraoperative operation time. rohner et al. used FDM to produce a biodegradable polyhexolactone (PCL), a carrier for bone marrow stromal cells Schantz et al. created a 15 mm defect in the skull of a New Zealand white rabbit and used FDM with PCL and fibrin glue as raw materials to “replicate” the defect with some porosity “cranial bone “Cao et al. proposed a symbiotic weight-bearing resorbable scaffold of chondrocytes and osteoblasts through FDM for the difficult repair of articular cartilage defects, and the results demonstrated the great potential for repairing osteochondral defects. The results demonstrate the great potential for repairing osteochondral defects. The disadvantage is that the precision is relatively low; there is also volume variation; the FDM method is only suitable for making scaffolds that do not add active substances such as growth factors during processing because of the need for heating. (5) Normal temperature multi-insufflation forming (TMF). This method is to mix the materials that can be formed and cured separately into different containers and mixed and formed by multi-injections. The outstanding advantage is that it can eliminate the damage to the active material caused by high temperature, and the compounding of human bone growth factor is not by the current popular post-compounding method, but by special treatment, so that it can achieve multi-dimensional compounding in the rapid forming stage; and has a slow-release effect, which is greatly conducive to the healing of bone in the defect area; the manufacturing process can change the material to produce a variety of different materials, colors, mechanical properties It is possible to change the material during the manufacturing process to produce a variety of composite or non-homogeneous materials and porous structures with different combinations of material, color, mechanical properties, thermal properties, and functional gradient material stacking and forming. Therefore, it is promising to be the main process method for the preparation of bioengineered scaffolds (fine structure injection molding). In China, Yanchun Shi et al. of Tsinghua University made a porous cylinder with diameter and height of 5 mm by TMF technique by compounding polylactic acid (PLA) with molecular weight close to 100,000 with HA, collagen and BMP, and found that it significantly facilitated bone tissue healing after it was placed into the radial bone defect in dogs. 4 Prospects In addition to the most established techniques mentioned above, many more techniques have been practical. Such as three-dimensional spray bonding, photomask method, digital accumulation, and the latest direct shell method and other techniques. RPMT is currently being vigorously applied to the medical field abroad. There is still a lot of room for development in terms of standardization of software and hardware, curvilinearization of slicing method, further intelligence of processing, and integration of equipment technology. There is also a great potential for the use of RPMT to produce human tissues and organs to assist in diagnosis and surgical procedures. For maxillofacial surgery, due to its “regional” specificity, there will be more “uses” for RPMT.