Implant Placement Using the Bone Ring Technique With and Without Membrane Placement: A Preclinical 12-Month Study in Dogs
The bone ring technique is applied for vertical augmentation, in which the dental implant and autogenous block bone graft are simultaneously inserted. We investigated the healing of bone around implants placed simultaneously using the bone ring technique with and without membrane placement after a 12-month healing period. Vertical bone defects were created on both sides of the mandible of Beagle dogs. Implants were inserted into the defects through bone rings and fixed with membrane screws as healing caps. The augmented sites on one side of the mandible were covered with a collagen membrane. Samples were harvested 12 months after implantation and assessed histologically and by microcomputed tomography analysis. All implants remained throughout the healing period; however, except for 1 implant, they showed lost caps and/or exposure to the oral cavity. The implants had contact with newly formed bone despite frequent bone resorption. The surrounding bone appeared mature. The medians of bone volume and percentages of total bone area and bone-to-implant contact within the bone ring were slightly higher in the group with membrane placement than in that without membrane placement. Nevertheless, none of the evaluated parameters were significantly affected by the membrane placement. In the present model, soft tissue complication was frequent, and the membrane application did not reveal the effect at 12 months after implant placement using the bone ring technique. Sustained osseointegration and maturation of surrounding bone were observed in both groups after a 12-month healing period.
Intraoperative view. In 2 vertical ridge defects on each side of the mandible, created using a trephine drill, a bone ring with a dental implant is secured using a membrane screw (a). On one side of the mandible, the augmented area is covered with a collagen membrane (b). The treated areas are covered with soft tissue and sutured (c).
Histomorphometric parameters. Morphometric analysis is performed using 2 regions of interest (R1 and R2) (a). R1 (red boxed area) is set from 1 mm above the implant shoulder (IS) to 5 mm down and 4 mm wide from the center of the implant, with consideration for grafted area. R2 (blue boxed area) is positioned inferiorly to R1, down to the tip of the implant. Relative values of tissues in the green clear area in R1 and in the orange clear area in R2 are calculated (as percentages). The percentages of bone-to-implant contact (BIC) are measured on the implant surface from the first (fBIC) to last contact point (last BIC) as shown by the light blue line in R1 and the green line in R2. Linear distances are measured as the vertical distance from the IS to the first point of bone-to-implant contact (IS-fBIC) and from the IS to the top of the surrounding bone (IS-TSB) (b). Staining with toluidine blue combined with basic fuchsin.
Histological observation of the peri-implant bone level and the bone surrounding the implant. Histological observations with (M Group) and without membrane (NM Group) are shown in M-a,b,c and NM-a,b,c, respectively. The boxed areas in M-a and NM-a are shown in M-b,c and in NM-b,c, respectively. Uniform tissue spreads in the resorbed peri-implant bone in the M Group (M-a). The surrounding bone is mature (M-b), with the presence of the residual bone graft (GB) and the remnants of the membrane (M) above the bone (M-c). Despite bone resorption around the implant in the NM Group, the bone tissue is predominantly mature (NM-a). Within the mature peri-implant bone are the blood vessels (NM-b) and the remains of the grafted bone (NM-c). Staining with toluidine blue combined with basic fuchsin. Scale bars in a = 1 mm; scale bars in b and c = 200 μm.
Histological observation in the membrane group. The boxed areas in the image of the bone tissue surrounding the implant (a) are shown in b, c, and d. Panel e shows the image of fluorescent labeling of bone in the area corresponding to c. The cortical bone is in contact with the implant surface (b). New bone is also located near the bone surface (b) and around the canals with blood vessels (c). The trabecular bone has contact with the implant surface apical to the area where the cortical bone spreads (d). The labeled bone appears to be around the vascular canals, corresponding to the new bone in the stained section (e). Staining with toluidine blue combined with basic fuchsin. Scale bar in a = 1 mm; scale bars in b–e = 200 μm.
Histological observation in the nonmembrane group. The boxed areas in the image of the bone tissue surrounding the implant (a) are shown in b, c, and d. The boxed areas in a are shown in b, c, and d. Figure e shows the image of fluorescent labeling of bone in the area corresponding to c. The superficial bone around the implant (b) and the bone around canals with the blood vessels (c) show the appearance of new bone, making contact with the implant. The bone deposited onto the implant surface is also observed in the cancellous bone area (d). The labeled lines are located around the blood vessels sprinkled over the compact bone near the implant, which appears to run toward the implant (e). Staining with toluidine blue combined with basic fuchsin. Scale bar in a = 1 mm; scale bars in b–e = 200 μm.
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