Acellular dermal matrix as a membrane for guided tissue regeneration in the treatment of Class II furcation lesions: a histometric and clinical study in dogs

BACKGROUND: The purpose of this study was to evaluate acellular dermal matrix (ADM) as a membrane for guided tissue regeneration (GTR) in the treatment of mandibular Class II furcation lesions and to compare it to a bioabsorbable membrane. METHODS: Class II furcation lesions were created surgically and chronified in six mongrel dogs on the buccal surfaces of mandibular third and fourth premolars, bilaterally. After 1 month, GTR was performed. Each side was assigned randomly to the control group (CGr: bioabsorbable membrane made of polyglycolic acid: trimethylene carbonate) or the test group (TGr: ADM as a membrane). Clinical measurements of the width and thickness of the keratinized tissue (WKT and TKT, respectively) were made before GTR. The dogs were sacrificed 12 weeks following GTR, and histomorphometric analysis was performed. Area measurements were taken of new tissue, epithelium, connective tissue, and new bone; bone height and new cementum were measured. RESULTS: The formation of new bone, cementum, and periodontal ligament were similar in both groups. There were no statistically significant differences between the groups for any histomorphometric measurement. The TGr had a statistically significant increase in WKT and TKT after 3 months. The mean TKT gain was 1.03 mm for the TGr and 0.26 mm for the CGr (P <0.05). CONCLUSION: The ADM demonstrated histomorphometric results similar to the bioabsorbable membrane and resulted in a greater increase in the thickness of the keratinized tissue.     

Acceleration of de novo bone formation with a novel bioabsorbable film: a histomorphometric study in vivo

Objective:  Different types of barrier membranes have been used in periodontal applications for the technology of guided tissue regeneration (GTR). The aim of this study was to characterize the biological effect of novel calcium alginate film (CAF) on bone tissue regeneration by using rabbit mandible defects model.
Methods:  A critical size defect (5 mm in diameter) was created in the bilateral corner of mandible of 45 adult rabbits. The defects were covered with CAF served as the experimental group, or conventional collagen membrane (CCM) or left empty as the controls. Animals were killed after 1, 2, 4, 6 and 8 weeks. Morphological and histomorphometric studies were performed to evaluate their bone regeneration pattern and biological effects.
Results:  Histological sections showed that bone regeneration pattern was centripetal in growth from defect rim. The quantitative histometry analysis revealed a significantly greater percentage of newly generated bone in CAF defects than that in CCM defects and empty defects from 2 to 6 weeks post-operation ( P  < 0.01). After 6 and 8 weeks, significantly more mature lamella bone had formed with CAF than with CCM. Empty control defects showed bone formation starting from the defect margins and incomplete healing even after 8 weeks.
Conclusion:  The CAF guided early bone growth and appeared more effective as a bioabsorbable GTR membrane than CCM. This study with mandible defect model suggests that bone defects augmented with CAF may offer most promising results from a histological and histomorphometric perspective.     

Comparative analysis of collagen membranes for the treatment of implant dehiscence defects

Guided bone regeneration (GBR) evolved from the concept of guided tissue regeneration (GTR) and has been used for reconstructing sites with bone deficiencies associated with dental implants. For GBR, the use of absorbable collagen membranes has been increasing, but, at present, scientific information on the use of collagen membranes for GBR is limited. This study was aimed to clinically and histomorphometrically compare two collagen membranes, Bio-Gide(R) and BioMend ExtendTM, for the treatment of implant dehiscence defects in eight mongrel dogs. Implant dehiscence defects were surgically created in edentulous ridges, followed by the placement of three endosseous implants bilaterally in the mandible. Each implant dehiscence defect was randomly assigned to one of three treatment groups: (1) control (no membrane), (2) porcine dermis collagen barrier (Bio-Gide) or (3) bovine tendon collagen barrier (BioMend Extend). Dogs were sacrificed at 4 and 16 weeks (four dogs each) after treatment. Histomorphometric analysis included percentage linear bone fill (LF), new bone-to-implant contact (BIC) and area of new bone fill (BF). The results of the study revealed no significant differences among groups for any parameter at 4 weeks. However, at 16 weeks, more LF, BIC, and BF were noted in the membrane-treated groups than controls. BioMend Extend-treated defects demonstrated significantly greater BIC than control (P < 0.05) at this time point. BIC at 16 weeks was significantly greater than 4-week BIC (P < 0.05). Membrane exposure occurred in 9 out of 15 sites examined, resulting in significantly less LF and BIC than the sites without membrane exposure (P < 0.05). The results of this study indicate that: (1) GBR treatment with collagen membranes may significantly enhance bone regeneration, manifested at late stage (16 weeks) of healing; and (2) space maintenance and membrane coverage were the two most important factors affecting GBR using bioabsorbable collagen membranes.     

聚四氟乙烯膜及几丁质膜在即刻种植中应用的实验研究

目的通过动物实验，比较研究国产聚四氟乙烯膜、几丁质膜和钛加强的聚四氟乙烯膜在牙即刻种植中引导种植体周围骨缺损区新骨生成的作用。方法12条杂种狗，拔除左侧下颌四个前磨牙，即刻植入4枚长10mm种植体，3枚种植体分别覆盖几丁质膜、聚四氟乙烯膜、钛加强的聚四氟乙烯膜，另一枚种植体不盖膜作为对照。术后于2、4、8、12周取材，通过X线、组织学定性及定量观察骨缺损的修复情况。结果盖膜的三组从第2周开始就有明显的骨再生，到第12周时骨缺损区已完全为新骨充填；对照组在任何时间点，新骨的量明显少于盖膜的三组；盖膜的三组之间新骨量没有明显的差异。结论聚四氟乙烯膜、几丁质膜和钛加强的聚四氟乙烯膜均能引导种植体周围骨缺损区的骨再生。     

脱细胞真皮基质作为GTR屏障膜治疗Ⅱ度根分叉缺损的实验研究

目的:观察脱细胞真皮基质(acellular dermal matrix,ADM)作为引导组织再生(guided tissue regeneration,GTR)屏障膜在治疗Ⅱ度根分叉缺损时的牙周组织再生情况。方法:在犬的两侧下颌第三、四前磨牙制造Ⅱ度根分叉缺损模型,将ADM作为GTR屏障膜覆盖在根分叉缺损区表面,于术后8周观察和测量根分叉处牙周组织的再生情况,并与空白对照组作比较。结果:术后8周,ADM组和空白对照组的临床附着丧失(clinical attachment loss,CAL)平均分别为1.90 mm和2.85 mm,差异有统计学意义(P<0.05);ADM组的新骨面积、新骨高度、新生牙骨质高度分别为8.23 mm2、4.52 mm、4.72 mm,明显大于对照组的1.75 mm2、0.91 mm、0.94 mm,而上皮和结缔组织面积则小于对照组,分别为0.02、0.54 mm2和0.10、5.56 mm2,差异均有统计学意义(P<0.05)。结论:ADM作为GTR屏障膜治疗下颌Ⅱ度根分叉缺损,能比空白对照组获得更多的临床附着和再生牙周组织。     

Ossification of a novel cross-linked porcine collagen barrier in guided bone regeneration in dogs

BACKGROUND: Collagen membranes for guided bone regeneration (GBR) and guided tissue regeneration (GTR) are used extensively as bioabsorbable barriers. Cross-linking of collagen increases its biodurability and enables the control of its degradation kinetics and barrier function. A novel cross-linking technology was used to produce a porcine type I collagen membrane (GLYM). The purpose of this study was to evaluate the safety, efficacy, and degradation kinetics of GLYM compared to a non-cross-linked bilayer type I and III porcine collagen membrane (BCM) in surgically created defects in dogs. METHODS: After tooth extraction, two mandibular bilateral critical size defects were created in 12 beagle dogs that were randomly assigned to one of five groups: GLYM + bovine bone mineral (BBM), BCM + BBM, BBM alone, sham-operated, or GLYM alone. Dogs were euthanized after 8, 16, and 24 weeks, and sites were prepared for qualitative, semiquantitative, and quantitative light microscopy analyses. RESULTS: Membrane-protected sites displayed bone filling between the BBM particles with almost complete restoration of the original ridge morphology that increased with time up to 16 weeks and remained unchanged at 24 weeks. Both membranes showed marked degradation within 16 to 24 weeks, with BCM inconsistency that was undetectable in one of four sites at 8, 16, and 24 weeks. Membrane ossification was observed in all GLYM sites and in only one BCM site, which progressed with time to 24 weeks. Bone increased by approximately 1 mm on the lingual side, where the GLYM membrane was in direct contact with bone. CONCLUSIONS: Both membranes were safe and effective in supporting bone regeneration in critical size alveolar ridge defects in dogs and completely degraded within 24 weeks with marked BCM inconsistency. In areas of direct contact with bone, all GLYM sites were progressively ossified with time and augmented the original alveolar ridge. To the best of our knowledge, this is the first report of complete ossification of a collagen barrier membrane in GBR procedures.     

异种脱细胞真皮基质引导即刻种植种植体周围骨缺损再生能力的实验研究

目的：运用异种脱细胞真皮基质进行引导骨组织再生术（guided bone regeneration,GBR）评价修复种植体周围骨缺损能力,为临床应用提供指导。方法：在4只成年Beagle犬下颌第2、3、4前磨牙新鲜拔牙创即刻植入种植体,并在颊侧形成3mm×3mm×5mm骨缺损区,按自身同期对照研究设计,右侧为实验侧,骨缺损区上覆盖海奥膜;左侧为空白对照侧,骨缺损区不覆盖海奥膜。术后1、4个月分别处死一组动物,摘取下颌骨,采用大体观察、x线摄片、组织学观察测定等方法检测缺损区骨组织再生的情况。结果：实验侧种植体周围骨缺损区较空白对照侧新骨生成量多,加速了骨组织的再生过程。结论：异种脱细胞真皮基质具有良好的生物相容性和可降解性,可用作骨组织引导再生膜,促进骨缺损的再生修复。     

牛心包引导骨组织再生的实验研究

目的评价戊二醛(GA)处理的牛心包作为引导骨组织再生材料的可行性。方法在II只狗的双侧下领骨颊侧骨板各制备一个1.0 cm x1.Ocmx0.5cm大小的骨缺损,随机在一侧骨缺损覆盖GA牛心包,另一侧不覆盖膜作为对照侧。术后2周,4周,8周,16周采用Dental-CT及组织学切片观察骨缺损修复情况。结果①10只狗伤口愈合良好,1只狗(16周组)牛心包处理区伤口愈合欠佳;316周内牛心包未见明显吸收,周围仅少量炎性细胞浸润;③牛心包覆盖侧骨缺损修复速度快于对照侧。结论①GA牛心包有良好的引导骨组织再生作用,牛心包有可能成为一种新的引导骨组织再生材料;②GA处理的牛心包有良好的生物相容性。     

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。     

rhBMP-2/Co/PLGA复合生物膜对腭裂骨缺损修复的实验研究

目的:观察引导性骨再生(guidedboneregeneration,GBR)技术修复腭裂骨缺损的效果。方法:16只成年犬分为2组:实验组8只,对照组8只。实验组将rhBMP-2/Co/PLGA复合生物膜植入骨缺损区,对照组植入Co/PLGA复合生物膜。分别于术后第4、8、12、24周,对其上颌骨进行三维CT扫描观察,同时进行新骨组织学检查。结果:从影像学、组织学检查的结果看,实验组的新骨形成优于对照组。结论:植入rhBMP-2/Co/PLGA复合生物膜可用于修复腭裂骨缺损。     

Changes in alveolar bone height and width following post-extraction ridge augmentation using a fixed bioabsorbable membrane and demineralized freeze-dried bone osteoinductive graft

BACKGROUND: It has been shown that the amount of healed bone following guided bone regeneration (GBR) with demineralized freeze-dried bone allograft (DFDBA) and a bioabsorbable membrane is significantly less than the initial quantity. A study was designed to determine if the amount of GBR would be affected by using an osteoinductive DFDBA and bioabsorbable membrane and membrane stabilization. METHODS: Eleven extraction sites (10 patients) were treated with DFDBA and bioabsorbable membrane before placing endosseous implants. Standardized alveolar height and width measurements were taken after extraction, GBR, and 4 months postoperatively, at predetermined measurement points (sites midpoint and 3 mm mesial and distal from the midpoint) and classified as augmented (<1 mm increase of GBR height or width) or grafted (>1 mm increase). Five membranes were stabilized. RESULTS: Three mm from the crest, augmented points exhibited a complete loss of augmented width. There was also some loss of pre-GBR bone width (ranging from 4.7% to 20%) at augmented and grafted points. Five mm from the crest, augmented points lost 83.3% to 92.3% of augmented width and grafted points lost 12.9% to 18% of pre-GBR width. Loss of augmented height ranged from 93.5% to 100%. Augmented (except distal) and grafted measurement points lost 2.1% to 12% of pre-GBR height. Comparing tacked and non-tacked sites, the former manifested less loss of augmented bone width, the latter augmented bone height. CONCLUSIONS: Results indicate a complete loss of augmented width 3 mm from the crest and almost complete loss in height and width 5 mm from the crest. Membrane stabilization appeared beneficial.     

Formation of bone around titanium implants placed into zero wall defects: pilot project using reinforced e-PTFE membrane and autogenous bone grafts

Background: Guided bone regeneration (GBR) frequently is used to augment implants with various types of bone defects. The defects often are grafted with different materials, yet there is insufficient evidence that these materials enhance bone-to-implant contacts. Purpose: The purpose of this pilot project was to test the principle of GBR to promote bone formation adjacent to commercially pure titanium implants placed within zero-wall defects. Histologic and histomorphometric measurements were used to evaluate new bone formation. Materials and Methods: Under appropriate anesthesia, deep, wide defects were created within the mandibles of two large dogs. Buccolingual bone was removed to the depth of the defects leaving only the mesial and distal walls. Of the eight implants placed, three were augmented with titanium-reinforced expanded polytetrafluoroethylene (e-PTFE) barriers and autogenous bone chips. Three sites were augmented with barrier membranes only, and two sites were not augmented or grafted and served as controls. Seven months after surgery the dogs were sacrificed and block sections were taken for histologic evaluation. Results: Histologic and histomorphometric measurements were used to evaluate new bone formation. Results from this evaluation revealed bone formation at the membrane-only sites and the membrane-plus-bone grafted sites. The bone grafts were completely incorporated by the newly formed marginal compact bone. For all treated sites, there was poor bone-to-implant contact. Histomorphometric measurements showed a trend toward greater bone formation at membrane-treated sites compared with control sites. However, autogenous bone grafting did not seem to affect the amount of newly regenerated bone. Conclusions: Within the limits of this pilot project, findings show trends toward bone healing, indicating constant and enhanced bone regeneration over the exposed implant. Bone contact to the implant surface generally was poor.     

Clinical and histologic assessment of lateral alveolar ridge augmentation using a synthetic long-term bioabsorbable membrane and an allograft

BACKGROUND: Guided bone regeneration (GBR) is a widely used procedure for augmenting alveolar ridge width prior to placement of endosseous implants. Various graft materials and barrier membranes (non-resorbable and bioabsorbable) have been used in GBR. The aim of this study was to assess the performance of a new bioabsorbable, synthetic polyglycolic acid/trimethylene carbonate (PGA/TMC) barrier membrane with an increased absorption time in conjunction with a combination of assayed demineralized bone matrix and cortical cancellous chips uniformly dispersed in a thermoplastic biologic carrier. METHODS: At 72 potential implant sites in 38 subjects, ridge width at the crest and 4 mm apical to the crest was measured before and 6 months after a GBR procedure using the long-term (LT) PGA/TMC membrane and an allograft in a thermoplastic carrier. Before placement of endosseous implants, 48 biopsy specimens were obtained from the augmentation sites and analyzed histomorphometrically. RESULTS: The GBR procedure increased the mean ridge width at the crest from 2.4 to 5.2 mm. This 216% change from baseline was significant (P <0.001). The mean width 4 mm apical to the crest increased from 4.4 to 7.5 mm, a significant (P <0.001) 174% change. The histomorphometric analysis showed that the biopsy specimens consisted, on average, of 57% bone (36% graft material and 21% new bone) and 43% soft tissue and space. CONCLUSION: Our findings suggest that the LT PGA/TMC barrier membrane, used in conjunction with an allograft, provides lateral alveolar ridge augmentation comparable to that achieved with other materials without the necessity for bone-graft harvesting or a second procedure to remove the barrier membrane.     

Bone remodelling after regenerative procedures around implants placed in fresh extraction sockets: an experimental study in Beagle dogs

Introduction: After a tooth extraction, the height of the buccal wall tends to decrease. The literature indicates that regenerative techniques (guided bone regenerative [GBR] techniques) have succeeded in improving the bone levels. Therefore, this experiment set out to compare the physiological bone remodelling in Beagle dog models after implant placement in a fresh extraction socket, with and without the application of regenerative procedure. Materials and methods: Five dogs were used in this study. Test and control sites were randomly selected. The experimental teeth (fourth pre‐molar and first molar) were hemi‐sected removing the distal roots and placing implants. Porcine bone was placed to fill the gap around the implant on the test sites and a reabsorbable membrane was used to cover the area. The dogs were put down at different times (2 weeks, 1 month and 3 months). The measurements were taken immediately and at 2, 4, 12 weeks after implant placement. Student's test for paired data was used to compare the means of the clinical measurements. Results: At 2 weeks: On the control sites, few signs of resorption were detected at the first molar only, while at the test sites bone levels were placed at the implant shoulder or above. At 4 weeks: On the control site, slight bone remodelling was observed, while on the test site minor signs of resorption or an increase of bone levels were detected. At 12 weeks: The alveolar crest on the control sites showed various degrees of remodelling. On the test sites stable bone levels or an increase of bone crest was observed. Conclusion: With the limits of this study, the findings showed that GBR techniques were able to limit resorption of the alveolar crest after tooth extraction. A pattern of bone remodelling after tooth extraction and implant placement was observed in the control sites (no GBR) as well as in test sites (GBR), and although the exact cause of this is unclear, surgical trauma could play a role. Further studies are necessary to confirm these results and to clarify the precise causes of bone remodelling in fresh extraction sockets. To cite this article:
Barone A, Ricci M, Calvo‐Guirado JL, Covani U. Bone remodelling after regenerative procedures around implants placed in fresh extraction sockets: an experimental study in the Beagle dogs.
Clin. Oral Impl. Res. 22 , 2011; 1131–1137
doi: 10.1111/j.1600‐0501.2010.02084.x     

Vertical ridge augmentation with guided bone regeneration in association with dental implants: an experimental study in dogs

AIM: To evaluate the effect of using guided bone regeneration (GBR) with a titanium-reinforced e-PTFE membrane in alveolar bone defects with titanium implants. MATERIAL AND METHODS: Following extraction of three mandibular premolars and a molar on both sides of the jaw in three dogs, alveolar bone defects (depth: 5-7 mm) were produced. After 4 months, three implants were inserted into each defect to a depth of approximately 4 mm, so that their coronal portion was protruding about 5 mm. Four sides in the dogs were assigned to a test group and the remaining two sides to a control group. The 12 implants in the test group were covered with a reinforced e-PTFE membrane. The space under the membrane was filled with peripheral venous blood from the animal, and the flaps were sutured over the membrane. The six control implants received no membrane before the suturing of the flaps to complete wound closure. The animals were sacrificed after 6 months, and non-decalcified histological specimens of the implants and surrounding tissues were prepared. RESULTS: Histologic and histomorphometric analyses revealed a significantly (Mann-Whitney test; P=0.08) larger amount of bone fill in the test group (mean=57.42%) than in the controls (mean=11.65%), and clinical evaluation of one test site showed that the implants were completely covered with tissue resembling bone. In most of the specimens, bone had grown in height close to, or in direct contact with the membrane. However, the new bone generally was not in direct contact with the implants. Regularly, a zone of dense connective tissue was interposed between the implants and the newly formed bone. CONCLUSION: The formation of even considerable amounts of bone following vertical ridge augmentation with GBR and implants was not accompanied by predictable osseointegration of the implants.     

A feasibility study evaluating an in situ formed synthetic biodegradable membrane for guided bone regeneration in dogs

Purpose: The aim was (1) to evaluate the soft‐tissue reaction of a synthetic polyethylene glycol (PEG) hydrogel used as a barrier membrane for guided bone regeneration (GBR) compared with a collagen membrane and (2) to test whether or not the application of this in situ formed membrane will result in a similar amount of bone regeneration as the use of a collagen membrane. Material and methods: Tooth extraction and preparation of osseous defects were performed in the mandibles of 11 beagle dogs. After 3 months, 44 cylindrical implants were placed within healed dehiscence‐type bone defects resulting in approximately 6 mm exposed implant surface. The following four treatment modalities were randomly allocated: PEG+autogenous bone chips, PEG+hydroxyapatite (HA)/tricalcium phosphate (TCP) granules, bioresorbable collagen membrane+autogenous bone chips and autogenous bone chips without a membrane. After 2 and 6 months, six and five dogs were sacrificed, respectively. A semi‐quantitative evaluation of the local tolerance and a histomorphometric analysis were performed. For statistical analysis, repeated measures analysis of variance (ANOVA) and subsequent pairwise Student's t‐test were applied (P<0.05). Results: No local adverse effects in association with the PEG compared with the collagen membrane was observed clinically and histologically at any time‐point. Healing was uneventful and all implants were histologically integrated. Four out of 22 PEG membrane sites revealed a soft‐tissue dehiscence after 1–2 weeks that subsequently healed uneventful. Histomorphometric measurement of the vertical bone gain showed after 2 months values between 31% and 45% and after 6 months between 31% and 38%. Bone‐to‐implant contact (BIC) within the former defect area was similarly high in all groups ranging from 71% to 82% after 2 months and 49% to 91% after 6 months. However, with regard to all evaluated parameters, the PEG and the collagen membranes did not show any statistically significant difference compared with sites treated with autogenous bone without a membrane. Conclusion: The in situ forming synthetic membrane made of PEG was safely used in the present study, revealing no biologically significant abnormal soft‐tissue reaction and demonstrated similar amounts of newly formed bone for defects treated with the PEG membrane compared with defects treated with a standard collagen membrane.     

Study on regeneration of mandibular bone with bioabsorbable organic/inorganic composite membrane

Guided bone regeneration (GBR) has attracted much attention as a means to treat bone defects and congenital malformation. However, presently available materials are not ideal and further improvements are necessary. Hence we have been developing a novel bioabsorbable composite material beta-TCP/CPLA for the GBR technique. The polymeric matrix is a copolymer of poly-L-lactide acid and fatty polyester (CPLA) that is biodegradable by hydrolysis, and the ceramic filler is beta-tricalcium phosphate (beta-TCP) that is bioabsorbable and has good osteoconductivity. The materials were evaluated by in vivo and in vitro experiments. Furthermore, animal experiments with mandibular bones defects in dogs were carried out. Good bone regeneration was observed in the case of the treatment with beta-TCP/CPLA membrane whereas almost no bone regenerated in the cases without the membrane. beta-TCP/CPLA membranes were suggested to have promising properties for bone defect treatment.     

Alveolar bone formation at dental implant dehiscence defects following guided bone regeneration and xenogeneic freeze‐dried demineralized bone matrix

The present study evaluated rate and extent of alveolar bone formation in dental implant dehiscence defects following guided bone regeneration(GBR) and implantation of xenogeneic freeze‐dried demineralized bone matrix (xDBM). A total of 16 titanium plasma‐sprayed (TPS) and 16 hydroxyapatite‐coated (HA) titanium cylinder implants were inserted in 4 mongrel dogs following extraction of the mandibular premolar teeth. Four implant sites per jaw quadrant (2 TPS and 2 HA implant sites) were prepared into extraction sockets in each dog. Buccal alveolar bone was removed to create 3 x 5 mm dehiscence defects. Two jaw quadrants in separate animals received GBR, GBR+xDBM, xDBM (control), or gingival flap surgery alone (GFS; control). Thus, four conditions were available for each implant type (TPS or HA): GBR, GBR+xDBM; xDBM and GFS. The animals received fluorescent bone labels to allow observations of rate and extent of bone formation. Animals were sacrificed at 12 weeks postsurgery and block sections were harvested for histologic analysis. There were no apparent histologic differences between TPS and HA implant defects. GBR and GBR+xDBM resulted in almost complete bone closure of the dental implant dehiscence defect. Rate of bone formation appeared higher following GBR alone. Extent of bone formation appeared somewhat greater following GBR+xDBM; however, delayed. xDBM alone did not adequately resolve the bony defect. In conclusion, GBR results in rapid, clinically relevant bone closure of dental implant dehiscence defects. Adjunctive implantation of xDBM does not appear to significantly improve the healing response in the model used.     

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     

Guided bone regeneration for immediate non‐submerged implant placement using bioabsorbable materials in Beagle dogs

The aim of the present study was to evaluate the combined application of different bioabsorbable materials for healing of residual peri‐implant defects after placement of non‐submerged implants into fresh extraction sockets. Second and third mandibular premolars were extracted from 10 Beagle dogs, the coronal part of the distal sockets were surgically enlarged and this was followed by immediate placement of specially designed hollow‐screw non‐submerged dental implants. For each animal, the coronal peri‐implant defects were further treated with one of the 4 following procedures: 1) no treatment, control site: 2) grafting with porous hydroxyapatite (HA); 3) collagen membrane tightly secured around the implant and over the defect and 4) grafting with HA covered with a collagen membrane. After 16 weeks of healing, specimens were removed from the mandibule and prepared for a histomorphometric evaluation. The bone-to-implant contact length (BIC) was measured and compared amongst the different treatment modalities. In the defect area, the irregular bone regeneration was similar between all the treatment procedures ( P >0.10). In the sites covered with a collagen membrane alone, the total BIC (47%) was greater than in control sites (28.7%. P <0.05) or sites grafted with HA (22.2%, P <0.02). Total BIC in sites treated with the HA‐membrane combination (43%) was only significantly different from sites treated with HA ( P <0.10). It is concluded that the use of bioabsorbable materials results in a limited increase of osseointegration when used in conjunction with immediate placement of non-submerged implants, although the principle of the one stage surgical approach can be maintained.