A portion of patients undergoing implant restoration require bone augmentation procedures to ensure that there is sufficient bone volume around the implant. For the patients with horizontal bone ridge defects at edentulous sites, with or without mild to moderate vertical bone defects, the shell technique serves as a reliable and minimally invasive bone augmentation method with effective space maintenance. The shell technique involves fixating 1 mm cortical bone blocks to the recipient site, using retention screws and filling the gap between the bone block and recipient bed with particulate bone substitute materials, and covering the barrier membrane to achieve bone augmentation. The overlying tension-free soft tissue closure seals the surgical site while local peripheral blood releases osteoclasts and cytokines that gradually degrade the bone block. The rigid fixation of the bone block ensures a stable internal environment for osteogenesis and a new bone regeneration cycle. Although this technique demonstrates favorable bone augmentation outcomes, it is highly technique-sensitive. There are certain differences in the application scenarios and osteogenic processes for autologous and allogeneic bone shells. The selection of bone blocks and particulate bone substitute materials significantly influences the osteogenic biological process and the predictability of bone augmentation results. Complications associated with the shell technique possess distinct characteristics, such as the immunogenicity of allogeneic bone fragments, soft tissue cracking, and bone fragment loosening. Their prevention and subsequent management substantially impact the success rate of osteogenesis. This article delves into the biological mechanisms of osteogenesis in the bone block technique, summarizing the indications, clinical outcomes, classification of bone blocks, and surgical workflow management, as well as complication prevention and management, aiming to provide a reference for the future application and development of the bone shell technique.

Objective:To prepare nanosilver-hybridized polylactic acid-glycolic acid copolymer (PLGA) microspheres loaded with simvastatin (SIM), and to evaluate its sustained release effect in vitro. Methods:The emulsification-solvent evaporation method was used to prepare SIM-loaded PLGA microspheres. Silk fibroin (SF) was used to modify the surface of SIM-loaded PLGA microspheres by hydrophobic interaction. Then, the microspheres were continually modified by electrostatic adsorption to chitosan (CTS) and nano-silver (AgNPs) to prepare SF-AgNPs-CTS-SF-SIM-PLGA microspheres. Scanning electron microscope, Fourier transform infrared spectrometer, energy spectrometer, Zeta potential meter were used to analyze the SIM-loaded microspheres. The external release properties of the SIM-loaded microspheres were also investigated.Results:The average diameter of the prepared PLGA microspheres was about 9.67 μm. The results of Fourier transform infrared spectroscopy and energy spectroscopy showed that the AgNPs-CTS-SF-SIM-PLGA microspheres have been successfully constructed. The Zeta potential results indicated that the SIM-loaded microspheres were all in a stable state. The in vitro release results showed that the SF-AgNPs-CTS-SF-SIM-PLGA microspheres had a good in vitro release effect, could delay the drug release rate and prolong the drug release time. Conclusions:The SF-AgNPs-CTS-SF-SIM-PLGA microspheres have antibacterial and osteogenic effects, and exhibit a good in vitro release effect. They can be used for local sustained-release administration in the oral cavity, which make makes them potentially useful in the treatment of periodontitis.