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.     

Alveolar ridge repair in a canine model using rhTGF-beta 1 with barrier membranes

In both normal and membrane-assisted situations, healing events are modulated by the activity of endogenous protein molecules known as cytokines. Due to its mitogenic and chemotactic characteristics, the addition of rhTGF-beta 1 should increase the rate of osteogenesis or increase the potential for bone regeneration in oral osseous defects. This study evaluates the effects of an osteoconductive biodegradable matrix incorporating human recombinant transforming growth factor beta 1 (rhTGF-beta 1) in conjunction with barrier membranes on bone regeneration in canine alveolar ridge defects. A matrix of calcium carbonate and hydroxyethyl starch served as the carrier for test concentrations of 2.0 micrograms/0.8 ml and 20.0 micrograms/0.8 ml of rhTGF-beta 1. One surgically prepared site in each of 13 adult male fox-hounds received 1 of 4 experimental treatment regimens, with 6 sites utilizing barrier membranes. Four sites in each of 2 additional animals, two containing carrier matrix only and 2 with the additional barrier membrane, served as controls. Specimens were retrieved after 2 months of healing and processed for routine light microscopy. The quantity and composition of regenerated bone was examined. Analysis of variance revealed a statistically significant increase (P < 0.05) in the development of bone with the use of rhTGF-beta 1. Likewise, a statistically significant increase in regeneration was found in membrane-protected sites over nonmembrane-protected sites. No statistically significant difference was noted between the low and high dose treatments. The authors conclude that the use of rhTGF-beta 1 in conjunction with a barrier membrane greatly enhances bone regeneration in osseous oral defects.     

Healing of dehiscence-type defects in implants placed together with different barrier membranes: a comparative clinical study

OBJECTIVE: Premature exposure of membranes used in guided bone regeneration (GBR) results in decreased bone formation. The effect of an expanded polytetrafluoroethylene (e-PTFE) and two collagen membrane on bone healing of buccal dehiscence defects around implants in cases with and without premature membrane exposure was clinically evaluated. METHODS: Three groups were established: Group OS (Ossix, n=73 implants, 41 patients), Group BG (Bio-Gide, n=53 implants, 28 patients) and Group GT (e-PTFE, Gore-Tex, n=34 implants, 17 patients). Defect height and width were measured at the time of implant placement and at second stage surgery. Surface area was calculated as half ellipses. When several implants were placed simultaneously, a mean of their defect width and height was calculated. RESULTS: Mean percentage reduction of defect area (92.2+/-13.78% Group OS, 94.6+/-6.69% Group BG, and 97.3+/-4.91% Group GT) and height (81.6+/-23.19%, 85.4+/-12.26%, and 93.4+/-9.39% respectively) did not show statistically significant differences between groups. Differences between groups were not statistically significant for all parameters when cases without spontaneous membrane exposure were compared. However, differences were significant when spontaneous membrane exposure occurred. Mean percentage reduction of defect area among cases where membrane exposure occurred was 91.5+/-10.86% Group OS, 71.5+/-8.61% Group BG, and 73.7+/-13.97% Group GT. Mean percentage reduction of defect height among cases with membrane exposure was 76.4+/-18.28%, 53.4+/-9.86%, and 49.4+/-11.05%, respectively. CONCLUSIONS: Premature exposure of membranes and subsequent and consequent exposure of implants results in impaired bone healing. Certain barrier membranes, as used in group OS, are apparently capable of supporting gingival healing even when prematurely exposed that could be advantageous in GBR procedures.     

Comparison of bioabsorbable and bioinert membranes for guided bone regeneration around non‐submerged implants. An experimental study in the mongrel dog.

The aim of this clinical investigation was to evaluate the effect of guided bone regeneration around non-submerged implants using different barrier membranes. Five adult mongrel dogs were used in this investigation. After having all premolars extracted and implant osteotomies performed in the regions of the former premolars, buccal bone defects were created. Subsequently, 3 implants were placed and the defects treated with 1 of the following 3 modalities: a) guided bone regeneration using an expanded polytetrafluoroethylene membrane, b) guided bone regeneration using a bioabsorbable membrane made from a synthetic copolymer of glycolide and lactide and c) no membrane application. Following implant and membrane placement, the mucoperiosteal flaps were repositioned and tightly sutured around the neck of the implants allowing for a non-submerged healing. After a healing period of 6 months, the animals were sacrificed and the specimens processed for histologic evaluation. The clinical pre-treatment defects between the different treatment groups were not statistically different (bioinert membrane group: 4.9 mm; control group: 4.8 mm; bioabsorbable membrane group: 4.5 mm). The remaining histological defects after 6 months of healing amounted to approximately 2.5 mm in the bioinert membrane group, 5.7 mm in the control group and 6.0 mm in the bioabsorbable membrane group. A significant difference was observed between the bioinert membrane group and the other 2 groups. The mineralized bone-to-implant contact in the bioinert membrane group was 51.5%, in the control group 46.3% and in the bioabsorbable membrane group 37.5%. The values between the bioinert membrane group and the bioabsorbable membrane group were statistically different. The results of this study indicate that bone regeneration with bioinert e-PTFE membranes around non-submerged implants is possible. The utilized absorbable polyglycolic/polylactid membrane did not show any bone regenerative effect and the results did not differ from the control group without membrane application.     

Membrane permeability is unnecessary for guided generation of new bone. An experimental study in the rabbit.

The aim of this investigation was to test the hypothesis that membrane permeability is necessary in bone formation using the principle of guided tissue regeneration. On the forehead of 8 rabbits. titanium test cylinders were anchored in the calvaria. These cylinders were either covered by an expanded polytetrafluoroethylene (e‐PTFE) membrane generating a chamber for bone formation or they were sealed off by cast titanium. The implanted cylinders were covered by resuturing the periosteum and the cutaneous flap. After 8 months of healing. new bone had formed in all cylinders in all animals irrespective of whether the chamber for bone formation was sealed off by cast titanium or the e‐PTFE membrane. Based on these results, we conclude that permeability of the membrane is not necessary in the guided generation of new bone.     

Evaluation of a biodegradable synthetic hydrogel used as a guided bone regeneration membrane: an experimental study in dogs

Objectives: To test whether or not an experimental polyethylene glycol (PEG) membrane maintains the bone graft volume and contributes to the preservation of the ridge contour in comparison with a commercially available synthetic membrane. Materials and methods: In 18 dogs, all mandibular premolars and the first molars were extracted. Ten weeks later, acute standardized defects were prepared. The defects of four dogs were randomly assigned to three modalities: (1) PEG plus deproteinized bovine bone mineral (DBBM) (PEG), (2) a resorbable glycolide trimethylene carbonate membrane plus DBBM (PGA‐TMC), and (3) DBBM alone (DBBM). These dogs were then sacrificed for the baseline measurements. The remaining defects of 14 dogs were randomly assigned to (1) PEG plus DBBM, (2) PGA‐TMC plus DBBM, (3) DBBM, and (4) empty defect. The dogs were sacrificed at baseline (n=4), 4 weeks (n=7), or at 16 weeks (n=7). Mixed model regressions and the non‐parametric Brunner–Langer method were applied for statistical analysis. Results: At baseline, equal tissue augmentation was observed in all groups. At 4 and 16 weeks, the greatest augmented area fractions were calculated for PEG (103%; 107%, respectively), followed by PGA‐TMC (98%; 91%), DBBM (85%; 78%), and empty (46%; 54%), being statistically significant different (P<0.001) between PEG and empty at 4 and 16 weeks, and PEG and DBBM at 16 weeks. The overall decrease (P≤0.01) in the amount of bone graft between baseline and 16 weeks was ?14% (PEG), ?22% (PGA‐TMC), and ?23% (DBBM). Conclusions: The study demonstrates that the combination of the PEG membrane with DBBM maintains the bone graft volume over time better than controls. The PEG membrane with DBBM was also the most effective method to preserve the ridge contour. To cite this article :
Thoma DS, Dard MM, Hälg G‐A, Ramel CF, Hämmerle CHF, Jung RE. Evaluation of a biodegradable synthetic hydrogel used as a guided bone regeneration membrane: an experimental study in dogs.
Clin. Oral Impl. Res. 23 , 2012; 160–168.
doi: 10.1111/j.1600‐0501.2011.02217.x     

两种胶原膜暴露于口腔环境中降解作用的对照研究

目的：本研究通过将两种胶原膜实验性的暴露于动物口腔环境中,探讨其生物降解作用的差别,为两种材料的临床应用提供相关实验依据。方法：健康成年日本大耳白兔8只,体重3.5～4.0kg,雌雄不拘。通过2种外科手术方法制备动物模型。方法1：使用3mm牙龈环切刀,沿上颚中线两侧对称制备圆形粘膜穿孔,潜行分离圆孔周围2mm粘膜组织,将直径5mm的圆形Bio-Gide和海奥胶原膜置入缺损区。方法2：制备边长5mm角形粘膜瓣,潜行分离粘膜瓣周围2mm粘膜组织,将直径5mm的两种胶原膜置入粘膜瓣下,重新复位粘膜瓣并使用可吸收缝线严密缝合。按上述方法在每只动物上颚制备6个缺损,共计48个缺损区,按照随机分组原则,将两种胶原膜按暴露与非暴露分为4组,每组为12个实验样本。术后7天和28天各处死4只动物行大体、组织学观察及图形分析检测膜材料降解吸收替代百分比。结果：1）大体观察：术后7天,两种胶原膜的非暴露组创口已基本愈合,可见炎症反应;两种胶原膜的暴露组呈凹陷状愈合;术后28天,各组的缺损区已愈合,表面无炎症性反应。2）组织学观察：术后7天,两种胶原膜的不同组别均可见大量炎性细胞,但非暴露组相对于暴露组炎症反应较轻,不同处理条件下均可见成纤维细胞浸润;术后28天,两种胶原膜的暴露组炎性细胞减少,成纤维细胞数量增多,两种胶原膜的非暴露组可见炎性细胞浸润、毛细血管增生,成纤维细胞数量增多。3）Bio-Gide胶原膜和海奥口腔修复膜在暴露和非暴露两种处理方式下两者的降解吸收效果无显著性差异（P〉0.05）,但两种胶原膜在暴露条件下降解吸收的程度均高于于非暴露条件（P〈0.05）。结论：1）Bio-Gide胶原膜和海奥口腔修复膜在引导骨再生（GBR）技术中均能起到良好的屏障作用。2）生物胶原膜暴露于口腔环境中将会导致膜的降解吸收加速,增加膜下新生组织感染的风险。     

Guided tissue regeneration in intrabony periodontal defects following treatment with two bioabsorbable membranes in combination with bovine bone mineral graft. A clinical and radiographic study

AIM: Comparison of two bioabsorbable barriers (collagen and polylactic acid (PLA) membranes) combined with a bovine bone mineral (BBM) graft, with an access flap procedure (AFP) alone for treating intrabony defects. MATERIAL AND METHODS: Thirty-four subjects participated in this prospective, controlled clinical trial. Baseline clinical examination (probing depth (PD), clinical attachment level (CAL)) of selected sites was performed 2 months after completion of conservative treatment in conjunction with hard-tissue measurements to ascertain the depth of the defect (cementoenamel junction to the bottom of the defects). After randomly dividing patients into three groups (two membrane groups, one control group), full thickness flaps were elevated and exposed root surfaces planed before filling defects with bone graft and positioning a barrier membrane covering the defect. The control group was treated identically except for the barrier and bone graft placement. Clinical treatment outcomes were finally evaluated 12 months after surgery for changes of PD and CAL. Radiographs at baseline and 12 months were compared using non-standardized digital radiography. RESULTS: A mean reduction in PD value of 5.08 mm and mean CAL gain of 4.39 mm occurred in the collagen-BBM group. Corresponding values for the PLA-BBM group were 4.72 and 3.71 mm, while access flap procedure (AFP) sites produced values of 2.50 and 2.43 mm. All improvements in clinical parameters were statistically significant (p<0.001) within groups for all variables. Both membranes produced statistically greater PD reduction and CAL gain compared with AFP treatment (p<0.05). Comparison between barrier groups failed to reveal any statistically significant difference in probing pocket depth reduction (p=0.56) or in CAL gain (p=0.34). CONCLUSION: Placement of the two barrier membranes used in the present study in combination with BBM graft significantly improved clinical and radiographic parameters of deep intrabony pockets and proved superior to access flap alone.     

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.     

The combined use of bioresorbable membranes and xenografts or autografts in the treatment of bone defects around implants. A study in beagle dogs

The aim of the present investigation was to test the effect of a bioresorbable membrane supported by xenografts or autografts in regenerating bone into peri-implant defects. In 3 dogs, the mandibular premolars P2, P3, P4 and M1 were extracted bilaterally. After 4 months of healing, 3 standardized bone defects were prepared on each side of the mandible and 1 implant per defect was placed. The 6 sites in each dog were distributed into 4 different treatment groups: 2 sites received a Bio-Gide membrane alone (BG); 2 sites received a Bio-Gide membrane supported by Bio-Oss (BG + BO); 1 site received the Bio-Gide membrane supported by autogenic bone harvested from the prepared defects (BG + Aut); 1 site received neither membrane nor bone graft and served as control (C). The soft tissue flaps were adapted and sutured for primary healing. No adverse events occurred during the experimental period. After 16 weeks, the dogs were sacrificed and histomorphometric examinations on non-decalcified ground sections were carried out. The vertical bone growth amounted to 45% (SD +/- 13%) of the defect height in the BG group, to 78% (SD +/- 29%) in the BG + BO group, to 69% (SD +/- 9%) in the BG + Aut group, and to 22% (SD +/- 10%) in C group. The horizontal bone growth measured 78% (SD +/- 16%) in the BG group, 81% (SD +/- 21%) in the BG + BO group, 82% (SD +/- 12%) in the BG + Aut group, and 46% (SD +/- 21%) in the C group. The vertical height of bone growth in contact with the implant measured 17% (SD +/- 12%) in the BG group, 20% (SD +/- 12%) in the BG + BO group, 17% (SD +/- 7%) in the BG + Aut group, and 12% (SD +/- 8%) in the C group. The surface fraction of the graft in direct bone contact measured 89% (SD +/- 9%) in the BG + BO group and 93% (SD +/- 3%) in the BG + Aut group. It is concluded that the bioresorbable membrane tested enhances bone regeneration, in particular in conjunction with the use of a supporting graft material. In addition, deproteinized bovine bone mineral and autogenic bone grafts appeared to be equally well integrated into regenerating bone. Finally, no additional effects in the bone growth was observed with the autogenous bone in comparison with the hydroxyapatite.     

Influence of two barrier membranes on staged guided bone regeneration and osseointegration of titanium implants in dogs. Part 2: augmentation using bone graft substitutes

Objectives: To assess the influence of two barrier membranes and two bone graft substitutes on staged guided bone regeneration and osseointegration of titanium implants in dogs. Materials and methods: Saddle‐type defects were prepared in the lower jaws of 6 fox hounds and randomly filled with a natural bone mineral (NBM) and a biphasic calcium phosphate (SBC) and allocated to either an in situ gelling polyethylene glycol (PEG) or a collagen membrane (CM). At 8 weeks, modSLA titanium implants were inserted and left to heal in a submerged position. At 8+2 weeks, respectively, dissected blocks were processed for histomorphometrical analysis (e.g., mineralized tissue [MT], bone‐to‐implant contact [BIC]). Results: The mean MT values (mm²) and BIC values (%) tended to be higher in the PEG groups (MT: NBM [3.4±1.7]; SBC [4.2±2]/BIC: NBM [67.7±16.9]; SBC [66.9±17.8]) when compared with the corresponding CM groups (MT: NBM [2.5±0.8]; SBC [2.3±1.6]/BIC: NBM [54.1±22.6]; SBC [61±8.7]). These differences, however, did not reach statistical significance. Conclusion: It was concluded that all augmentation procedures investigated supported bone regeneration and staged osseointegration of modSLA titanium implants. To cite this article :
Mihatovic I, Becker J, Golubovic V, Hegewald A, Schwarz F. Influence of two barrier membranes on staged guided bone regeneration and osseointegration of titanium implants in dogs. Part 2: augmentation using bone graft substitutes.
Clin Oral Impl Res. 23 , 2012; 308–315.
doi: 10.1111/j.1600‐0501.2011.02238.x     

Influence of two barrier membranes on staged guided bone regeneration and osseointegration of titanium implants in dogs: part 1. Augmentation using bone graft substitutes and autogenous bone

Objectives: To assess the influence of two barrier membranes and two bone graft substitutes mixed with autogenous bone (AB) on staged guided bone regeneration and osseointegration of titanium implants in dogs. Materials and methods: Four saddle‐type defects each were prepared in the upper jaw of six fox hounds and randomly filled with a natural bone mineral (NBM)+AB and a biphasic calcium phosphate (SBC)+AB and allocated to either an in situ gelling polyethylene glycol (PEG) or a collagen membrane (CM). At 8 weeks, modSLA titanium implants were inserted and left to heal in a submerged position. At 8+2 weeks, dissected blocks were processed for histomorphometrical analysis (e.g., treated area [TA], bone‐to‐implant contact [BIC]). Results: The mean TA values (mm²) and BIC values (%) tended to be higher in the PEG groups(TA: NBM+AB [10.4 ± 2.5]; SBC+AB [10.4 ± 5.8]/BIC: NBM+AB [86.4 ± 20.1]; SBC+AB [80.1 ± 21.5]) when compared with the corresponding CM groups (TA: NBM+AB [9.7 ± 4.8]; SBC+AB [7.8 ± 4.3]/BIC: NBM+AB [71.3 ± 20.8]; SBC+AB [72.4 ± 20.3]). A significant difference was observed for the mean TA values in the SBC+AB groups. Conclusion: It was concluded that all augmentation procedures investigated supported bone regeneration and staged osseointegration of modSLA titanium implants. However, the application of PEG may be associated with increased TA values. To cite this article:
Schwarz F, Mihatovic I, Golubovic V, Hegewald A, Becker J. Influence of two barrier membranes on staged guided bone regeneration and osseointegration of titanium implants in dogs: part 1. Augmentation using bone graft substitutes and autogenous bone.
Clin. Oral Impl. Res. 23 , 2012; 83–89.
doi: 10.1111/j.1600‐0501.2011.02187.x     

聚四氟乙烯膜和几丁质膜引导骨再生的基础实验研究

目的：探讨国产聚四氟乙烯膜和自制几丁质膜引导骨再生的效果以及骨缺损大小与修复程度的关系，为临床应用提供依据。方法：在犬胫骨上段内侧制作直径5mm和7mm的洞穿形骨缺损，分别覆盖几丁质膜、聚四氟乙烯膜、及钛网加强的聚四氟乙烯膜，不覆盖膜做空白对照。术后2、4、8、12周取材，通过组织学及新骨形成量观察骨再生情况，比较不同的膜材料引导骨再生效果。结果：术后第2周开始，直径5mm和7mm骨缺损区覆盖膜的三组均有骨再生，至12周时骨缺损区已完全为新骨充填，对照组骨缺损区均为纤维结缔组织充填，相差显著。直径5mm和7mm的骨缺损区在膜覆盖后骨再生量无显著差别。结论：几丁质膜、聚四氟乙烯膜及钛网加强的聚四氟乙烯膜均能引导骨再生。     

Blood‐filled spaces with and without filler materials in guided bone regeneration. A comparative experimental study in the rabbit using bioresorbable membranes.

The aim of the present study was to evaluate the effect of natural deproteinized bone mineral on the temporal and spatial pattern of bone formation in a guided bone regeneration model system while using a bioresorbable membrane device. A periosteal skin flap was raised uncovering the calvaria of 20 rabbits. A stiff hemispherical dome made of polylactic acid was placed onto the roughened calvaria and anchored by screws. Prior to placement, the dome was either filled with peripheral blood (control group, 8 rabbits) or with blood and OsteoGraf/N‐300 (test group, 12 rabbits). At 1 month, histologic sections revealed bone regeneration in both test and control domes to various degrees. In the test domes, bone height reached 78%(67–83) and bone volume was 11%(&17), while in the control domes, bone height was 45%(1467) and bone volume 6%(1‐I 1). At 2 months, bone height was unchanged in the test group at 70%(67–83) and bone volume had only slightly increased to 16%(1 l‐2 1). In the controls, height increased to 86%(60–100) and volume to 20%(9–27). Thus, in this model system, natural bone mineral fill contributed to accelerate initial bone neogenesis, while it did not contribute to increasing bone volume or bone height at later observation stages.     

Lateral ridge augmentation using different bone fillers and barrier membrane application. A histologic and histomorphometric pilot study in the canine mandible

Lateral ridge augmentation has become a standard treatment option to enhance the bone volume of deficient recipient sites prior to implant placement. In order to avoid harvesting an autograft and thereby eliminating additional surgical procedures and risks, bone grafting materials and substitutes are alternative filler materials to be used for ridge augmentation. Before clinical recommendations can be made, such materials must be extensively studied in experimental models simulating relevant clinical situations. The present pilot study was conducted in three dogs. Different grafting procedures were evaluated for augmentation of lateral, extended (8 x 10 x 14 mm) and chronic bone defects in the mandibular alveolar ridge. Experimental sites received tricalcium phosphate (TCP) granules or demineralized freeze-dried bone allograft (DFDBA) particles. Barrier membranes (ePTFE) were placed for graft protection. These approaches were compared to ridge augmentation using autogenous cortico-cancellous block grafts, either with or without ePTFE-membrane application. After a healing period of six months, the sites were analyzed histologically and histomorphometrically. Autografted sites with membrane protection showed excellent healing results with a well-preserved ridge profile, whereas non-protected block grafts underwent bucco-crestal resorption, clearly limiting the treatment outcome. The tested alloplastic (TCP) and allogenic (DFDBA) filler materials presented inconsistent findings with sometimes encapsulation of particles in connective tissue, thereby reducing the crestal bone width. The present pilot study supports the use of autografts with barrier membranes for lateral ridge augmentation of extended alveolar bone defects.     

Guided bone regeneration (GBR) using membranes and calcium sulphate after apicectomy: a comparative histomorphometrical study

AIM: The purpose of the present study was to evaluate the effects of resorbable and non-resorbable membranes, and calcium sulphate on bone regeneration in osseous defects in conjunction with apicectomy. METHODOLOGY: The mandibular third and fourth premolars of 12 beagle dogs were root treated, and apicectomies were performed. The osseous defects were divided randomly into five groups. In groups A, B and C the osseous defects were covered with e-PTFE membranes, PLGA membranes, and collagen membranes, respectively. In group D, defects were filled with calcium sulphate. Nothing was used in group E, which served as controls. The dogs were sacrificed 4, 8, and 16 weeks after the surgery. Undemineralized sections were obtained and evaluated histomorphometrically. RESULTS: Newly formed cortical bone had closed the defect in the cortical plate in all groups at 16 weeks. The degree of concavity of the new cortical bone at 16 weeks in groups A and D was significantly less than in group B (P < 0.01). The percentage of regenerated bone in group A was significantly greater than in groups B (P < 0.01), C (P < 0.05) and E (P < 0.05). In group D, it was significantly greater than in groups B (P < 0.01) and E (P < 0.05). CONCLUSIONS: The data suggests that e-PTFE membrane is more effective compared to resorbable membranes and controls for bone regeneration after apicectomy, and that calcium sulphate could be substituted for e-PTFE membrane.     

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.     

Immunohistochemical characterization of guided bone regeneration at a dehiscence-type defect using different barrier membranes: an experimental study in dogs

Objectives: The aim of the present study was to evaluate immunohistochemically the pattern of guided bone regeneration (GBR) using different types of barrier membranes. Material and methods: Standardized buccal dehiscence defects were surgically created following implant bed preparation in 12 beagle dogs. Defects were randomly assigned to six different GBR procedures: a collagen‐coated bone grafting material (BOC) in combination with either a native, three cross‐linked, a titanium‐reinforced collagen membrane, or expanded polytetrafluorethylene (ePTFE), or BOC alone. After 1, 2, 4, 6, 9, and 12 weeks of submerged healing, dissected blocks were processed for immunohistochemical (osteocalcin – OC, transglutaminase II – angiogenesis) and histomorphometrical analysis [e.g., bone‐to‐implant contact (BIC), area of new bone fill (BF)]. Results: In general, angiogenesis, OC antigen reactivity, and new bone formation mainly arose from open bone marrow spaces at the bottom of the defect and invaded the dehiscence areas along the implant surface and BOC. At 4 weeks, membranes supporting an early transmembraneous angiogenesis also exhibited some localized peripheral areas of new bone formation. However, significantly increasing BIC and BF values over time were observed in all groups. Membrane exposure after 10–12 weeks was associated with a loss of the supporting alveolar bone in the ePTFE group. Conclusion: Within the limits of the present study, it was concluded that (i) angiogenesis plays a crucial role in GBR and (ii) all membranes investigated supported bone regeneration on an equivalent level.