OBJECTIVEWe explored the expressions of the Notch and Wnt signaling pathways and their significance in the repair process of alveolar bone defects by establishing animal models with a composite of autologous bone marrow mesenchymal stem cells (BMSCs) and platelet-rich fibrin (PRF) to repair bone defects in the extraction sockets of rabbits.

METHODSA total of 36 two-month-old male New Zealand white rabbits were randomly divided into four groups, and the left mandibular incisors of all the rabbits were subjected to minimally invasive removalunder general anesthesia. BMSC-PRF compounds, single PRF, and single BMSC were implanted in Groups A, B, and C. No material was implanted in Group D (blank control). The animals were sacrificed at 4, 8 and 12 weeks after surgery, the bone defect was immediately drawn, and the bone specimens underwent surgery after four, eight, and twelve weeks, with three rabbits per time point. The expressions of Notch1 and Wnt3a in the repair process of the bone defect were measured via immunohistochemical and immunofluorescence detection.

RESULTSImmunohistochemistry showed that the expressions of Notch1 and Wnt3a in Groups A, B, and C were higher than that in Group D at the fourth and eighth week after operation (P<0.05). By contrast, the expressions of Notch1 and Wnt3a in Group D were higher than those in Groups A, B, and C at the twelfth week (P<0.05). Immunofluorescence showed that the expressions of both Notch1 and Wnt3a reached their peaks in the new bone cells of the bone defect after four weeks following surgery and gradually disappeared when the bone was repaired completely.

CONCLUSIONNotch1 and Wnt3a signaling molecules are expressed in the process of repairing bone defects using BMSC-PRF composites and can accelerate the healing by regulating the proliferation and differentiation of BMSCs. Moreover, the expressions of Notch and Wnt are similar, and a crosstalk between them may exist it.

Alveolar Bone Grafting ; methods ; Animals ; Blood Platelets ; Bone Marrow Cells ; cytology ; Bone Transplantation ; methods ; Bone and Bones ; abnormalities ; Cell Differentiation ; Fibrin ; administration & dosage ; Male ; Mesenchymal Stem Cell Transplantation ; methods ; Mesenchymal Stromal Cells ; Platelet-Rich Plasma ; Rabbits ; Random Allocation ; Receptor, Notch1 ; metabolism ; Tissue Engineering ; Wnt Signaling Pathway ; Wnt3A Protein ; metabolism ; Wound Healing

BACKGROUND:Less is reported on the influence of cortical bone thickness on displacement and equivalent stress. OBJECTIVE:To analyze the influence of cortical bone thickness on the maximum displacement and equivalent stress at the implant-bone interface through a three-dimensional finite element method,thereby providing some suggestions for oral implantation. METHODS:In this experiment,we selected the cone-shaped CT image data of a patient who was scheduled for mandibular first molar implant restoration.First,we established a mandibular model in Mimics13 software,and then imported it into Solid works 2022 software.According to the related product information,we drew the cone-shaped implant(4.1 mm×10 mm)and the upper prosthesis model.Cortical bone models were obtained according to different cortical bone thicknesses(2.5,2.0,1.5,1.0 mm)and named D1,D2,D3,and D4,respectively.All the models were imported into ANSYS Workbench 2021 software and cross-combined.Finally,we applied vertical and oblique loads to the four groups of models,and analyzed the stress of the models in each group. RESULTS AND CONCLUSION:The peak equivalent stress is lowest in the cancellous bone and highest in the upper prosthesis,that is,at the abutment-implant junction.The peak stress increases with the decrease of cortical bone thickness.The peak stress of the abutment increases with the decrease of cortical bone thickness,and a similar explanation can also be applied to the other implant restoration components.The peak stress in bone tissue and implants increases with the increase of cortical bone thickness.In models D1,D2,D3,the peak stress in implants is higher than that in bone tissue,but the results are reversed in D4.

BACKGROUND:In implant restoration in the aesthetic area,zirconium dioxide is gradually becoming the most commonly used upper restorative material and has achieved better clinical results.Resin-ceramic composite,a new type of dental restorative material,begins to try to be used as an upper restorative material in implant restoration,but there is less research on the application of this material in implant restoration. OBJECTIVE:To compare the biomechanical differences between resin ceramic crowns and zirconia all-ceramic crown implant restorations in three occlusal relationships for restoring maxillary central incisors. METHODS:The cone-beam CT image data of a patient with single-crown implant restoration of maxillary central incisor were selected,and the maxillary bone model was extracted by using Mimics 21.0 software,and the model was imported into Solidworks 2020 software.The crown,adhesive,abutment,central screw,and implant were modeled,and the model of single-crown implant restoration of maxillary central incisor was assembled.After giving the model material property parameters(resin-ceramic composite and zirconia for the upper restoration materials)in ANSYS Workbench 2021 R1 software,three occlusal relationships(edge-to-edge occlusion,normal overjet and deep overbite)were simulated and loaded to analyze the stress distribution of the resin-ceramic crown and zirconia all-ceramic crown implant restoration models. RESULTS AND CONCLUSION:(1)The stress concentration areas in the implant restoration models of the resin-ceramic crown group and the zirconia all-ceramic crown group in different occlusal relationships were distributed in the upper restoration loading point,the abutment-implant connection,the implant neck and the surrounding bone tissue.As the occlusal relationship changed from the edge-to-edge to normal and deep overbite,the peak equivalent forces of the restorative abutment,central screw,implant,and bone tissue in both the resin-ceramic and zirconia all-ceramic crown groups gradually decreased.The highest peak equivalent forces were observed for the upper restorations in deep overbite.The zirconia all-ceramic crown group had the highest peak equivalent force in the adhesive layer in the edge-to-edge relationship,and the resin-ceramic crown group had the highest peak equivalent force in the adhesive layer in the deep overbite.(2)In the edge-to-edge occlusion,the peak equivalent force of the adhesive layer and central screw in the resin-ceramic crown group was slightly smaller than that in the zirconia all-ceramic crown group,and there was no significant difference between the two groups in the peak equivalent force at the upper restoration,restoration abutment,implant,and bone tissue.The peak stresses in the upper restoration,adhesive layer,and central screw of the resin-ceramic crown group were slightly less than those of the zirconia all-ceramic crown group at normal fit,and there were no significant differences between the two groups in the peak equivalent forces at the restoration abutment,implant,and bone tissue.In deep overbite,the peak adhesive,abutment,and central screw stresses were greater in the resin-ceramic crown group than in the zirconia all-ceramic crown group,with no significant differences in the upper restorations,implants,or bone tissue.(3)The results showed that the upper restorative material had no significant effect on the stress distribution of the implant and bone tissue,and had some effects on the stress distribution of the upper restoration,adhesive,restoration abutment,and central screw,but the difference was not significant.The occlusal relationship has a significant influence on the stress distribution in all structures and bone tissue of the implant restoration.The resin-ceramic crowns have a buffering effect on the stresses in the case of edge-to-edge and normal occlusion.