Augmentation of skull bone using a bioresorbable barrier supported by autologous bone grafts. An intra‐individual study in the rabbit.

The aim of this experimental investigation was to compare the effect of using autologous particulate bone grafts with and without a bioresorbable barrier covering for augmentation of the rabbit skull bone. For this purpose, bilateral, circular, 8 mm wide and 1 mm deep skull bone defects were prepared and overfilled with particulate bone grafts. The grafts placed in the test sites were covered with a bioresorbable barrier (Guidor® Matrix Barrier). The grafts placed in the control sites were covered only by the repositioned, cutaneous flap. 12 weeks later, the animals were sacrificed, the experimental sites were defleshed and the height and volume of the augmented bone in the test and control sites were measured clinically. Histologically, morphometrical measurements of the bone tissue were performed in decalcified vertical cross‐sections of the experimental sites. Statistically significant differences were found in favour of the coverage of the bone graft particles with the barrier, both with respect to the height and the volume of the augmented bone.     

Measurements of stability changes of titanium implants with exposed threads subjected to barrier membrane induced bone augmentation. An experimental study in the rabbit tibia.

The purpose of the present study was to evaluate in a rabbit model the changes in stability of implants that had been subjected to barrier membrane induced bone augmentation, as compared to untreated controls. One titanium implant was inserted in each proximal tibial metaphysis of 10 rabbits. The implants were placed in such a way that 4–5 threads on one side of the implant were left uncovered by bone. On the test side, the exposed implant surface was treated by means of a barrier membrane technique to provide for bone augmentation, while the contralateral side was untreated. The stability evaluations were made by means of resonance frequency measurements (RIM) at Day 0 and after 8, 16 and 24 weeks of healing. In addition, changes in the area of exposed implant threads were documented and measured on photographs. Removal torque measurements were performed at the day of sacrifice. In this study it was not possible to demonstrate a statistically significant better stability of implants subjected to barrier induced bone augmentation as compared to control implants still having exposed threads as evaluated by RIM and removal torque measurements.     

Guided bone regeneration around dental implants in the atrophic alveolar ridge using a bioresorbable barrier. An experimental study in the monkey.

The aim of this study was to evaluate guided bone regeneration (GBR) around dental implants placed in atrophic alveolar ridges using an experimental, nonporous bioresorbable barrier. In 8 Rhesus monkeys, the maxillary canines and lateral incisors were extracted bilaterally and the remaining alveoli were reduced to create atrophic ridges. After a healing period of 3 months, soft tissue expansion was performed using a subperiosteal tissue expander. After 1 month of tissue expansion, an IMZ implant was placed in the atrophic ridge on each side in such a way that its coronal 4 mm to 5 mm remained circumferentially exposed above the bone level. The test implants were covered with a bioresorbable barrier made of poly (D,L‐lactid‐co‐tri‐methylencarbonate) in a 70/30 ratio, whereas the control implants were covered with a nonresorbable expanded polytetrafluoroethylene (e‐PTFE) barrier. The e‐FTFE barriers were stabilized with titanium minipins while the bioresorbable barriers were analogously fixed using bioresorbable minipins made of poly (L‐lactid‐co‐D,L‐lactid) 70/30. Clinical healing progressed uneventfully in both groups and no soft tissue dehiscences occurred. Histometric and histomorphometric analyses were performed 5 months post surgery. Both test and control implants exhibited direct bone‐to‐implant contact to variable extents. The mean direct mineralized bone‐to‐implant contact length fraction was 32% of the total implant length in the test sites and 58% in the control sites. Control sites exhibited significantly greater bone fill compared to the experimental sites ( P <0.00l). Histologic observations of test specimens demonstrated a moderate inflammatory reaction related to the degradation and resorption products of the barrier. In conclusion, the nonresorbable e FTFE GBR barrier was found to be superior to the bioresorbable barriers tested in the present investigation.     

Bone augmentation by means of a stiff occlusive titanium barrier

It has already been shown that occlusive titanium barriers have osteoconductive properties. These barriers, however, cover only a limited surface area and have only been used in animal experiments. The aim of this study was to evaluate bone neogenesis under a pre-shaped titanium barrier placed over the top of the rabbit skull and the top of highly resorbed edentulous upper-jaw bone in patients. Computed tomography (CT) scans made it possible to pre-shape the titanium barrier according to individual bone shape in human experiments. On the rabbit skull, tissue augmentation of up to 6 mm 1 year after barrier placement was observed, while the original thickness of skull bone was on average between 1.5 and 2.5 mm. The bone, which remained histologically immature for 1 year, grew systematically along the titanium surface, illustrating its osteoconductivity. Even after removal of the barrier, on average, 75.3 and 59.4% of the newly created tissue volume was maintained after 3 and 9 months, respectively. Clinical observations on 10 consecutive patients showed that, in those (5/10) in which the barrier remained unexposed for several months, an increase of the jawbone height and width of up to 16 mm could be observed when the barrier was removed after 12-18 months. As in the rabbits at barrier removal, the bone demonstrated a limited degree of mineralization as ascertained from biopsies. This newly formed osteoid tissue allowed the insertion of 33 screw-shaped titanium implants which in most cases (30/33) successfully osseointegrated to support a fixed prosthesis. The surrounding marginal bone level remained stable even up to 5 years after implant placement. Both animal and clinical data demonstrate that guided bone neogenesis under a subperiosteally placed titanium barrier can reach large volumes.     

Alveolar ridge augmentation using a resorbable copolymer membrane and autogenous bone grafts. An experimental study in the rat

The aim of the present study was to compare the result of maxillary alveolar ridge augmentation by the combined use of mandibular bone grafts and resorbable membranes (Resolut), with that achieved by the use of the same type of bone graft combined with the placement of e-PTFE membranes (Gore-Tex). The experiment was carried out in 30 rats. In one side of the maxillary jaw, the edentulous alveolar ridge between the incisor and the first molar was augmented by means of an autogenous mandibular bone graft that was fixed with a titanium microimplant and covered with a resorbable membrane. The contralateral side, serving as control, was treated in the same way, with the difference that an e-PTFE membrane was placed over the bone graft. Histological analysis at 15, 30, 60, 120 and 180 days after surgery demonstrated that, in both test and control sites where the membrane was properly adapted and not exposed, the bone grafts presented no resorption and were integrated into the maxillary bone at the recipient site. In cases where the membrane was exposed, however, the bone grafts presented extensive resorption and lack of continuity between the graft and the recipient bed. At 60-180 days after surgery, the exposure of both types of membrane had frequently led to complete resorption of the grafts, encapsulation of the titanium microimplant by fibrous connective tissue, or exfoliation of the microimplant. It is concluded that alveolar ridge augmentation can be predictably accomplished by combining mandibular bone grafting with the placement of resorbable or non-resorbable membranes according to the GTR principle, provided that the membrane is properly adapted over the graft and complete closure of the treated area is maintained during healing.     

Influence of barrier occlusiveness on guided bone augmentation. An experimental study in the rat.

The present study was designed to test perforated and non‐perforated barriers for their ability to promote augmentation of bone tissue. More specifically, 1 totally occlusive barrier and 6 barriers with perforation sizes of about 10, 25, 50, 75, 100, and 300 μm and 1 group with no barriers placed (open test chambers) were used to test the effect of a barrier's occlusiveness on the amount and composition of augmented tissue over time. The skull of the rat was used as the experimental area. Prefabricated, flexible silicone frames with an inferior flange for peripheral sealing to the bone surface and a central vertical through hole with a diameter of 3.6 mm and a height of 2 mm were used as test chambers. The barriers were inserted to cover the superior opening of the through hole. The healing periods were 4, 8, and 12 weeks. All test chambers exhibited newly formed skull bone which was augmented over time. The placement of totally occlusive barriers resulted in the slowest rate of bone tissue augmentation but in a highly predictable manner, i.e., there were only small individual variations. Placement of barriers with perforations exceeding 10 pm, on the other hand, resulted in a faster rate of bone augmentation with larger individual variations and a totally different augmentation pattern. A pronounced augmentation of calvarial soft tissue from the sagittal suture of the skull as well as ingrowth of supra‐bony connective tissue through the barriers were also observed. After 12 weeks of healing, no differences in the amount of augmented mineralized bone related to perforation sizes >lO μm were found. The open test chambers also showed bone augmentation, although most of their volume was occupied by suprabony connective tissue.     

Augmentation of intramembraneous bone beyond the skeletal envelope using an occlusive titanium barrier. An experimental study in the rabbit.

The aim of this investigation was to evaluate whether augmentation of intramembraneous bone beyond the skeletal envelope can be predictably achieved by placing a completely occlusive barrier on the skull bone of rabbits, hereby creating a secluded space with bone tissue being the only adjoining tissue. The experiment was carried out in 3 New Zealand white rabbits. In each animal, a midline incision was made down to the bone surface of the skull and a skin‐periosteal flap was raised to expose the skull bone on both sides of the midline. Two prefabricated titanium domes with an inner diameter of 4.5 mm and an inner height of 3.0 mm were installed on each side. The domes were supplied with a horizontal, peripheral flange and a vertical edge, fitting tightly into a circular slit, prepared by a trephine into the skull bone. This arrangement ensured a stable anchorage of the dome and a reliable peripheral sealing of the space. The skin‐periosteal flaps were relocated to cover the domes and sutured. After a healing period of 3 months, the animals were killed and the experimental areas excised and prepared for histological transversal ground sections with each dome in situ. The results demonstrated complete bone fill of all domes, with no signs of ingrowth of other types of tissues, indicating that the use of a barrier with total occlusiveness, sufficient stiffness and stability and reliable peripheral sealing will result in predictable bone augmentation of spaces also beyond the skeletal envelope.     

Morphological and dimensional changes after barrier removal in bone formed beyond the skeletal borders at titanium implants. A kinetic study in the rabbit tibia.

The aim of the present experimental investigation was to study the morphological and dimensional changes of bone, augmented at titanium implants by a membrane technique, taking place after membrane removal. In 12 rabbits, screw-shaped titanium implants were inserted in the tibia metaphyses in such a way that 5 threads became uncovered with bone. Surgery was performed on 2 occasions in order to retrieve specimens with different follow-up times. An e-FTFE barrier and a titanium device were used to provide space for bone formation. In 1 tibia of each rabbit, the membranes and spacers were removed after 8 weeks of healing, and the implants followed for 16 more weeks. Impressions were taken at day 0 and after 8 and 24 weeks of healing and plaster models were produced. In the contralateral tibiae, implants were inserted either 16 or 8 weeks prior to sacrifice. Measurements were made on the plaster models in 3 dimensions at 3.5 points around each implant in a coordinate measuring machine. Specimens taken 8, 16 and 24 weeks after insertion were analysed by means of light microscopical morphometry. The coordinate measurements showed that, in mean, 1.92 mm of bone had been formed during the first 8 weeks. A statistically significant loss of the height of the newly formed bone (0.70 mm) and thereby reduction of bone volume was found 24 weeks postoperatively. The volume decrease of the newly formed bone was more pronounced beside the implants than over the implant body. The histology showed that woven bone had been formed at the implants after 8 weeks. Further bone formation and remodelling and a net increase of mineralized bone were seen. The degree of bone-implant contact and bone area in the threads increased with time. The present study showed that coordinate measurements on plaster models, obtained from the experimental areas, in combination with histology, form a useful technique to study long-term changes of augmented bone. It was found that bone formed by a barrier membrane technique, decreased in volume during a 16-week follow-up period after barrier removal. Less dimensional changes were observed for the bone formed over the implant body. indicating that a solid surface may have a stabilizing effect on the augmented bone.     

Implant placement and simultaneous ridge augmentation using autogenous bone and a micro titanium mesh: a prospective clinical study with 20 implants

This prospective clinical study evaluated bone regeneration around 20 dental implants placed in 15 patients (mean age 39.7 years). Peri-implant bone defects were augmented with autogenous bone grafts harvested intraorally from the mandible (chin or retromolar area). Augmented sites were covered with an individually trimmed micro titanium mesh which was rigidly affixed with microscrews to the residual jaw bone. Height of implant exposure (mean 6.5 mm), i.e. dehiscencies (80%) or fenestrations (20%), and graft height (mean 6.2 mm) were measured in an apico-coronal direction using a periodontal probe. At re-entry (mean interval 6.6 months) the titanium mesh and microscrews were removed and bone regeneration assessed. The mean height of the integrated bone graft was 5.8 mm corresponding to a mean bone fill of 93.5%. The overall postop healing course was excellent with only one site developing a soft tissue dehiscence with subsequent mesh exposure (complication rate 5%). This study demonstrated that a micro titanium mesh in combination with autogenous bone grafts is effective for treatment of peri-implant bone defects.     

Influence of decortication of the donor bone on guided bone augmentation. An experimental study in the rabbit skull bone

The aim of the present study was to evaluate if early access to the endosteal bone compartment by removal of the outer cortical bone plate will enhance bone augmentation in a secluded space. Two titanium cylinders were placed on the skull of each of 8 rabbits. Each cylinder was placed into a circular slit, secured to the skull bone via two mini-screws and supplied with a titanium lid. On the test side, the outer plate of the cortical bone, demarcated by the slit, was removed. The subsequent bleeding resulted in blood fill of the cylinders to various degrees. On the control side, the corfical bone plate was left intact and no bleeding was observed at the time of the placement of the titanium lids. After 3 months, the animals were sacrificed to obtain histology and histomorphometry. No differences in the total amount of augmented bone tissue, in relation to the total experimental area (75.5% +/- 10.9% at the test sites and 71.2% +/- 13.5% at the control sites) or of the augmented mineralized bone tissue in relation to the total amount of augmented bone tissue, was revealed (17.8% +/- 3.0% and 16.0% +/- 4.9% respectively). There was no difference in the morphological appearance of the augmented bone between test and control sites and there were no obvious similarities in the appearance between the newly formed bone tissue and the donor bone. The augmented bone consisted of slender bone trabeculae, distributed in abundant marrow spaces. A conspicuous finding was that the bone trabeculae tended to climb along the inner walls of the titanium cylinder. It is concluded that decortication of the calvarial bone in the rabbit does not result in more bone formation beyond the skeletal envelope after a healing period of 3 months compared to no removal of the cortical bone plate inside a secluded experimental area.     

Vertical alveolar ridge augmentation by means of a titanium mesh and autogenous bone grafts

The aim of this study is to evaluate a surgical protocol for vertical ridge augmentation in the maxilla and mandible using autogenous onlay bone graft associated with a titanium mesh. A group of 18 partially edentulous patients, presenting the need for vertical bone augmentation of at least 4 mm, were treated before implant placement. During the first surgery, an autogenous bone graft was harvested from either the mandibular ramus or the mental symphysis and secured by means of titanium screws. Particulate bone was added and a titanium micro-mesh was used to stabilize and protect the graft. After a mean interval of 4.6 months, meshes and screws were removed and 37 endosseous implants were successfully placed. The desired bone gain was reached in all patients. Mean vertical bone augmentation obtained was 4.8 mm (range 4-7 mm). No major complications were recorded at recipient or donor sites. Abutment connection was carried out 2-3 months after implant placement. No implant was lost. Clinical parameters and probing depth, after prosthetic reconstruction, demonstrated the presence of a healthy peri-implant mucosa. The preliminary results suggest that, by using the presented technique, patients can be successfully rehabilitated by means of implant-supported prosthesis 6-7 months after the first surgery, even in case of severely atrophied maxilla.     

非血管化髂骨和下颌骨与钛种植体结合的比较研究

目的 :研究非血管化髂骨和下颌骨与钛种植体结合的组织学特点。方法 :12只杂种犬随机分为 6组。切取 15mm× 5mm的下颌骨骨质 ,将骨块移植于对侧下颌骨人工骨缺损区 ,然后切取同样大小的髂骨骨块 ,移植于下颌骨骨缺损区 ,同时植入 2枚钛种植体 ,用种植体固定骨块。术后不同时间点取材 ,组织学观察。结果 :髂骨移植后早期以溶解坏死为主 ,6周时开始重建 ,种植体为混合界面 ;12周时改建基本完成 ,种植体形成骨结合。而下颌骨移植后早期移植骨吸收不明显 ,只是哈佛氏管扩大 ,与种植体界面间未见新骨形成 ;12周时移植骨内出现新生骨 ,骨吸收停止 ,种植体为混合界面 ,界面有不成熟的新生骨沉积 ,新骨与原骨结合不紧。 18周 ,种植体形成骨结合。 2 4周 ,移植的髂骨和下颌骨与骨床均融为一体 ,下颌骨与髂骨相比整体致密。结论 :髂骨与下颌骨移植后的修复过程及它们与钛种植体的骨结合过程不同 ,但均能形成骨性结合。下颌骨与种植体形成骨结合的时间比髂骨长     

Influence of surface roughness of barrier walls on guided bone augmentation: experimental study in rabbits

Background: By using the guided tissue regeneration concept it is possible to augment bone, beyond the skeletal envelope, provided certain biologic, surgical, and barrier-related demands are met. Among barrier-related factors of importance are the surface properties. Purpose: The aim of this study was to evaluate whether different surface roughness of the barrier wall influences the amount and morphology of augmented bone in a secluded space, using a titanium cylinder as barrier device placed on the rabbit skull. Materials and Methods: Cylinders of commercially pure titanium were fabricated by machining, using a turning tool. The inner cylinder wall was either left untreated or grit-blasted with titanium dioxide to increase surface roughness. The topographic profile of the inner surface of two cylinders (1 turned and 1 grit-blasted) was measured in vitro to achieve a numeric characterization of each type of surface topography. Two cylinders, one with grit-blasted and one with turned inner walls, were surgically placed and secured to the skull bone of each of eight rabbits. The plate of the cortical bone, facing the experimental area framed by the cylinder wall was removed, and care was taken to ensure total blood fill of the cylinders. After 3 months, the animals were sacrificed to obtain histology for histomorphometry. Results: The relative volume of augmented tissue in the grit-blasted cylinders (77.9 ± 10.5%) did not differ significantly from that in the turned cylinders (73.4 ± 5.5%, p =.118), neither did the volume of mineralized bone (20.1 ± 8.2% vs. 22.1 ± 7.2%, p =.064). The trabecular density of the augmented bone was higher close to the walls of both the turned and the grit-blasted cylinders compared to the overall trabecular density within the cylinders, but with no significant difference between the two groups. However, the area of mineralized bone in direct contact with the inner surface of the titanium cylinder was significantly larger in the grit-blasted (33.9 ± 13.3%) compared to the turned cylinders (12.0 ± 8.5%, p =.01). Conclusions: The use of titanium barriers with a grit-blasted inner surface compared to barriers with a turned surface resulted in the formation of similar amounts of bone beyond the skeletal envelope of the rabbit skull. However, a larger area of augmented mineralized bone was found in direct contact with the inner surface of the grit-blasted cylinders.     

The effect of hyperbaric oxygen treatment on bone tissue reactions to c.p. titanium implants placed in free autogenous bone grafts. A histomorphometric study in the rabbit mandible.

This study aimed to investigate the effect of hyperbaric oxygen (HBO) therapy on the tissue reactions to commercially pure (c.p.) titanium implants placed in free autogenous bone graft by a 1-stage procedure. Eighty c.p. titanium implants were placed in the bone grafted from iliac crest to bilateral mandible of 40 Japanese white rabbits without tapping. Twenty rabbits underwent daily a HBO treatment for 60 min under 2.4 ATA during 20 consecutive days and the other untreated 20 rabbits served as controls. The implants with surrounding bone tissue were retrieved 20, 30, 60, 90 and 120 days after surgery, fixated, dehydrated and embedded in resin. About 20 microns thick ground sections were prepared prior to microscopical observations. The bone area and the bone-to-implant contact inside the threads were calculated separately in the grafted bone and in the host bone for each implant. After 30 and up to 120 days, the HBO treated group showed more bone-to-implant contacts in the grafted bone as compared to the non-HBO treated group. In the host bone there were no differences observed between HBO and non-HBO treated groups. This study indicated that HBO treatment was beneficial for the tissue incorporation of c.p. titanium implants when placed immediately in free autogenous bone grafts.     

A prospective clinical study of bone augmentation techniques at immediate implants

The efficacy of combinations of membranes and autogenous bone grafts at immediate implants were compared in a prospective study. Sixty-two consecutively treated patients each received an immediate implant for a single tooth replacement at a maxillary anterior or premolar site. Dimensions of the peri-implant defect at the implant collar were measured as follows: vertical defect height (VDH), horizontal defect depth (HDD) and horizontal defect width (HDW). Each implant randomly received one of five augmentation treatments and were submerged with connective tissue grafts: Group 1 (n=12)--expanded polytetrafluoroethylene membrane only, Group 2 (n=11)--resorbable polylactide/polyglycolide copolymer membrane only, Group 3 (n=13)--resorbable membrane and autogenous bone graft; Group 4 (n=14)--autogenous bone graft only, and Group 5 (n=12)--no membrane and no bone graft control. At re-entry, all groups showed significant reduction in VDH, HDD and HDW. Comparisons between groups showed no significant differences for VDH (mean 75.4%) and HDD (mean 77%) reduction. Significant differences were observed between groups for HDW reduction (range, 34.1-67.3%), with membrane-treated Groups 1, 2 and 3 showing the greatest reduction. In the presence of dehiscence defects of the labial plate, HDW reduction of 66.6% was achieved with membrane use compared with 37.7% without membranes. Over 50% more labial plate resorption occurred in the presence of a dehiscence defect irrespective of the augmentation treatment used. The results indicate that VDH and HDD reduction at defects adjacent to immediate implants may be achieved without the use of membranes and/or bone grafts.     

The effect of hyperbaric oxygen treatment on bone tissue reactions to c.p. titanium implants placed in free autogenous bone grafts. A histomorphometric study in the rabbit mandible.

This study aimed to investigate the effect of hyperbaric oxygen (HBO) therapy on the tissue reactions to commercially pure (c.p.) titanium implants placed in free autogenous bone graft by a 1‐stage procedure. Eighty c.p. titanium implants were placed in the bone grafted from iliac crest to bilateral mandible of 40 Japanese white rabbits without tapping. Twenty rabbits underwent daily a HBO treatment for 60 min under 2.4 ATA during 20 consecutive days and the other untreated 20 rabbits served as controls. The implants with surrounding bone tissue were retrieved 20, 30, 60, 90 and 120 days after surgery, fixated, dehydrated and embedded in resin. About 20 μm thick ground sections were prepared prior to microscopical observations. The bone area and the bone‐to‐implant contact inside the threads were calculated separately in the grafted bone and in the host bone for each implant. After 30 and up to 120 days, the HBO treated group showed more bone‐to‐implant contacts in the grafted bone as compared to the non‐HBO treated group. In the host bone there were no differences observed between HBO and non‐HBO treated groups. This study indicated that HBO treatment was beneficial for the tissue incorporation of c.p. titanium implants when placed immediately in free autogenous bone grafts.     

Lateral ridge augmentation by the use of grafts comprised of autologous bone or a biomaterial. An experiment in the dog

OBJECTIVE: The present investigation was performed to determine if a block of Bio-Oss used as an onlay graft can be used as a scaffold for new bone formation. MATERIAL AND METHODS: Five mongrel dogs were used. The mandibular premolars were extracted. On both sides of the mandible, the buccal bone plate was resected and defects, about 25 mm long, 8 mm high and 5 mm wide, were produced After 3 months of healing, a second surgical procedure was performed. In the left side, a block of Bio-Oss was adjusted to the buccal bone wall. The graft had the shape of a cylinder and was retained with a miniscrew and covered with a collagen membrane. In the contra-lateral side of the mandible, a block biopsy was first obtained from the ascending ramus. This bone graft had the shape of a cylinder that was 8 mm in diameter and 3 mm thick. The graft was transferred to the experimental site, adjusted to the buccal wall, retained with a miniscrew, and covered with a membrane. The flaps were repositioned and closed with sutures to ensure a complete coverage of the experimental sites. After 6 months of healing, the dogs were sacrificed and the experimental sites dissected. The biopsies were processed for ground sectioning. The sections were stained in toluidine blue, examined in the microscope, and a number of histo- and morphometric assessments made. RESULTS: The study demonstrated that cortical bone used as an onlay graft in the lateral aspect of the alveolar ridge, during a 6-month period of healing integrated with the host bone but underwent marked peripheral resorption. Thus, close to 30% of the height and 50% of the length of the graft was replaced with connective tissue. It was further observed that while the dimensions of a graft which contained a scaffold of cancellous bovine bone mineral remained unchanged, only moderate amounts of new bone formed at the base of this graft. CONCLUSION: Grafts of autologous cortical bone, placed on the surface of a one-wall defect, may undergo marked resorption during healing. A similar graft of Bio-Oss may retain its dimension, and limited amounts of new bone will form within the biomaterial.     

A volumetric study of guided bone regeneration around titanium implants in the New Zealand white rabbit

Previous studies have shown the ability for bone to grow under occlusive membranes. This study was undertaken to determine the time required for bone to form in the space created under the membrane and to determine the amount of bone that may be grown under the membrane. Thirty-two New Zealand white rabbits were divided into three groups. A Brånemark implant, having a diameter of 3.75 mm with a length of 7 mm, was placed in each tibia and Gore-Tex membrane was draped over the implant on the experimental side and tethered to the wound margin. Sixteen rabbits were sacrificed at six weeks, eight at twelve weeks, and eight at eighteen weeks. At six weeks the available space under the membrane was filled to 68 per cent, at twelve weeks it was 45 per cent, and at eighteen weeks 54 per cent. A comparison of bone height measurements on test and control sides showed a significant difference (p=0.0001) at the three time intervals. A comparison of grown bone volumes (test vs control) was also statistically significant (p=0.0001). The ability to grow bone under an occlusive membrane was confirmed but the long-term survival rate and ability to support load needs to be investigated.     

Effect of barrier membranes and autologous bone grafts on ridge width preservation around implants

Background: The purpose of this study was to explore the effect of barrier membranes and autologous bone grafts on the preservation of ridge width around implants. Materials and Methods: Sixty‐one patients were chosen from a database of case series; treatment assignment was based on clinical judgment. The patients received a total of 76 implants:34 implants with guided tissue regeneration procedures, 27 with autologous bone grafts, and 15 without ridge preservation procedures (control group). Results: The ridge width around the 76 implants decreased an average of 1.4 mm (95% CI, ‐1.9 to‐1.1 mm). Implants placed with autologous bone grafts or membranes tended to have worse outcomes. When compared to the no augmentation group, implants placed with guided tissue regeneration and autologous bone grafts resulted in 0.1 mm of additional bone loss (95% CI, ‐1.7 to ‐1.5 mm; p <.93) and 0.8 mm of additional bone loss (95% CI, ‐2.3 to 0.7 mm; p <.28), respectively. Conclusions: Autologous graft procedures or barrier membranes do not appear to improve crestal ridge preservation around implants.