Additively Manufactured Zn-2Mg Alloy Porous Scaffolds with Customizable Biodegradable Performance and Enhanced Osteogenic Ability.

The combination of bioactive Zn-2Mg alloy and additively manufactured porous scaffold is expected to achieve customizable biodegradable performance and enhanced bone regeneration. Herein, Zn-2Mg alloy scaffolds with different porosities, including 40% (G-40-2), 60% (G-60-2), and 80% (G-80-2), and different unit sizes, including 1.5 mm (G-60-1.5), 2 mm (G-60-2), and 2.5 mm (G-60-2.5), are manufactured by a triply periodic minimal surface design and a reliable laser powder bed fusion process. With the same unit size, compressive strength (CS) and elastic modulus (EM) of scaffolds substantially decrease with increasing porosities. With the same porosity, CS and EM just slightly decrease with increasing unit sizes. The weight loss after degradation increases with increasing porosities and decreasing unit sizes. In vivo tests indicate that Zn-2Mg alloy scaffolds exhibit satisfactory biocompatibility and osteogenic ability. The osteogenic ability of scaffolds is mainly determined by their physical and chemical characteristics. Scaffolds with lower porosities and smaller unit sizes show better osteogenesis due to their suitable pore size and larger surface area. The results indicate that the biodegradable performance of scaffolds can be accurately regulated on a large scale by structure design and the additively manufactured Zn-2Mg alloy scaffolds have improved osteogenic ability for treating bone defects.

Semi-autonomous two-stage dental robotic technique for zygomatic implants: An in vitro study.

OBJECTIVE: To assess the feasibility and accuracy of a semi-autonomous two-stage dental robotic technique for zygomatic implants. METHODS: Twenty-six zygomatic implants were designed and randomly divided into two groups using 10 three-dimensionally printed resin models with severe maxillary atrophy. In one group, the conventional drilling technique was used, in the other group, the drilling process for the alveolar ridge section (first stage) was completed, after which drilling for the zygoma section (second stage) was done. Based on preoperative planning combined with postoperative cone-beam computed tomography (CBCT), coronal, apical, depth, and angle deviations were measured. Zygomatic implant placement technique-related deviations (sinus slot, intrasinus, and extrasinus) were also recorded and analyzed. RESULTS: The two-stage technical group's coronal, apical, depth, and angle deviations were 0.57 ± 0.19 mm, 1.07 ± 0.48 mm, 0.30 ± 0.38 mm, and 0.91 ± 0.51°, respectively. The accuracy of the two-stage technique was significantly higher than that of the conventional one-stage technique (p < 0.05). The apical deviation in the intrasinus group was 1.12 ± 0.56 mm, which was significantly better than that in the other two groups (p < 0.05). The angle deviation in the sinus slot group was 1.96 ± 0.83°, which was significantly worse than that in the other two groups (p < 0.05). CONCLUSION: Using the semi-autonomous two-stage dental robotic technique for zygomatic implants is feasible and is more accurate than using the conventional one-stage technique. CLINICAL SIGNIFICANCE: The two-stage technique enabled the semi-autonomous robot to overcome the mouth-opening restriction for zygomatic implants and improved accuracy.

Autonomous robotic surgery for zygomatic implant placement and immediately loaded implant-supported full-arch prosthesis: a preliminary research.

OBJECTIVES: A patient with extensive atrophy of the alveolar ridge in the posterior portion of the maxilla was selected to complete an experimental and clinical case of the robotic zygomatic implant to investigate the viability of an implant robotic system in clinical use. METHODS: The preoperative digital information was collected, and the implantation position and personalized optimization marks needed for robot surgery were designed in advance in a repair-oriented way. The resin models and marks of the patient's maxilla and mandible are all printed in 3D. Custom-made special precision drills and handpiece holders for robotic zygomatic implants were used to perform model experiments and compare the accuracy of the robotic zygomatic implant group (implant length = 52.5 mm, n = 10) with the alveolar implant group (implant length = 18 mm, n = 20). Based on the results of extraoral experiments, a clinical case of robotic surgery for zygomatic implant placement and immediate loading of implant-supported full arch prosthesis was carried out. RESULTS: In the model experiment, the zygomatic implant group reported an entry point error of 0.78 ± 0.34 mm, an exit point error of 0.80 ± 0.25 mm, and an angle error of 1.33 ± 0.41degrees. In comparison, the alveolar implant group (control group) reported an entry point error of 0.81 ± 0.24 mm, an exit point error of 0.86 ± 0.32 mm, and an angle error of 1.71 ± 0.71 degrees. There was no significant difference between the two groups (p > 0.05). In clinical cases, the average entry point error of two zygomatic implants is 0.83 mm, the average exit point error is 1.10 mm and the angle error is 1.46 degrees. CONCLUSIONS: The preoperative planning and surgical procedures developed in this study provide enough accuracy for robotic zygomatic implant surgery, and the overall deviation is small, which is not affected by the lateral wall deviation of maxillary sinus.