Calvarial bone regeneration by a combination of natural anorganic bovine-derived hydroxyapatite matrix coupled with a synthetic cell-binding peptide (PepGen): an experimental study in rats

Objectives: The aim of this study was to evaluate histologically the effect of natural anorganic bovine‐derived hydroxyapatite matrix (ABM) coupled with a synthetic cell‐binding peptide on the healing of critical size calvarial defects in rats. Material and methods: Sixteen 4‐month‐old rats were used in the study. A 5 mm trephine defect was created in each parietal bone of every animal. One defect was left untreated (control) while the contralateral defect was treated with a natural ABM coupled with a synthetic cell‐binding peptide (test). At 60 and 120 days post‐operatively, groups of eight animals were sacrificed and 7–10‐μm‐thick decalcified sections were produced from both test and control sides. Three sections, 100 μm apart, representing the central area of each defect were selected for the histometric analysis. Results: Histological analysis showed limited bone formation in both control and test defects at both observation periods. The control defects healed with fibrous connective tissue occupying the midportion of the defect and minimal new bone formation at the periphery. In the test defects, the major part of the defect was occupied by graft particles embedded in connective tissue. After 60 days of healing the residual defects accounted up to 94.6% of the original defect dimensions in the control specimens and 90.6% in the test specimens. The differences between test and control defects were not statistically significant (P=0.06). After 120 days of healing, the residual defects accounted up 89.9% of the original defect dimensions in the control specimens and 85% in the test specimens. The difference was not statistically significant (P=0.33). Conclusion: The ABM coupled with a synthetic cell‐binding peptide failed to substantially promote new bone formation in rat calvarial defects.     

Bone repair and augmentation using block of sintered bovine-derived anorganic bone graft in cranial bone defect model

Objective: To histomorphometrically investigate the repair of critical size defects (CSDs) and bone augmentation in cranial walls using block of sintered bovine-derived anorganic bone (sBDAB) graft.
Material and methods: Forty guinea-pigs were divided into test ( n =20) and CSD control ( n =20) groups. In each animal, a full-thickness bone defect with 9.5 mm diameter was made in the frontal bone. The defects were filled with an sBDAB block soaked in blood in the test group and with blood clot in the CSD control group. The skulls were collected at 0 h ( n =2) and 30, 90 and 180 days ( n =6/group and period) postoperatively. The volume density and total volume of newly formed bone, sBDAB, blood vessels and connective tissue, vertical thickness of removed bone plug, sBDAB block and graft area were evaluated.
Results: The vertical thickness of the adapted sBDAB block was 3.8 times higher than that of the removed bone plug and did not show significant difference between periods, filling in average 29.8% of the total graft region. The sBDAB block exhibited complete osseointegration with the borders of the defect at 90 days. At 90 and 180 days, the vertical thickness of the graft was 279% in the average, and the total volume of bone augmentation was, respectively, 78.8% and 148.5% higher compared with the removed bone plug. The defects of the CDS control group showed limited osteogenesis and filling by connective tissue plus tegument.
Conclusion: The sBDAB block can be used to promote repair of CSDs and bone augmentation in the craniomaxillofacial region, due to its good osteoconductive and slow resorptive properties.     

Guided bone generation in a rabbit mandible model after periosteal expansion with an osmotic tissue expander

Objectives: To evaluate the space‐maintaining capacity of titanium mesh covered by a collagen membrane after soft tissue expansion on the lateral border of the mandible in rabbits, and to assess bone quantity and quality using autogenous particulate bone or bone‐substitute (Bio‐Oss^®), and if soft tissue ingrowth can be avoided by covering the mesh with a collagen membrane. Material and methods: In 11 rabbits, a self‐inflatable soft tissue expander was placed under the lateral mandibular periosteum via an extra‐oral approach. After 2 weeks, the expanders were removed and a particulated onlay bone graft and deproteinized bovine bone mineral (DBBM) (Bio‐Oss^®) were placed in the expanded area and covered by a titanium mesh. The bone and DBBM were separated in two compartments under the mesh with a collagen membrane in between. The mesh was then covered with a collagen membrane. After 3 months, the animals were sacrificed and specimens were collected for histology. Results: The osmotic soft tissue expander created a subperiosteal pocket and a ridge of new bone formed at the edges of the expanded periosteum in all sites. After the healing period of 3 months, no soft tissue dehiscence was recorded. The mean bone fill was 58.1±18% in the bone grafted area and 56.9±13.7% in the DBBM area. There was no significant difference between the autologous bone graft and the DDBM under the titanium mesh with regard to the total bone area or the mineralized bone area. Scanning electron microscopy showed that new bone was growing in direct contact with the DBBM particles and the titanium mesh. There is a soft tissue ingrowth even after soft tissue expansion and protection of the titanium mesh with a collagen membrane. Conclusion: This study confirms that an osmotic soft tissue expander creates a surplus of periosteum and soft tissue, and that new bone can subsequently be generated under a titanium mesh with the use of an autologous bone graft or DBBM. To cite this article:
Abrahamsson P, Isaksson S, Andersson G. Guided bone generation in a rabbit mandible model after periosteal expansion with an osmotic tissue expander.
Clin. Oral Impl. Res. 22 , 2011; 1282–1288.
doi: 10.1111/j.1600‐0501.2010.02108.x     

Resorption of deproteinized bovine bone mineral in a porcine calvaria augmentation model

Objectives: The original aim of the study was to determine the osteoconductive capacity of deproteinized bovine bone mineral (DBBM) of different particle sizes underneath acrylic hemispheres in vivo. However, the model failed and allowed us to report on the resorption of DBBM. Material and methods: Acrylic hemispheres were filled with and without a DBBM at a small particle size of 125–250 μm and at the regular particle size of 250–1000 μm. The hemispheres were positioned on the calvaria of eight minipigs. Histological and histomorphometric analysis was performed after 12 weeks. Results: We found that the acrylic hemispheres were displaced and a dense fibrous capsule sequestered the augmented area. Histology showed severe resorption activity and the presence of multinucleated cells on the surface of DBBM particles in areas adjacent to the fibrous capsule. Histomorphometric analysis revealed that only less than half of the originally augmented area, which was approximately 30 mm², remained after 12 weeks. The amount of residual DBBM (median 0.9 and 3.49 mm²) and bone (median 7.22 and 7.51 mm²) in the augmented area was similar in the small and the regular particle size group. Conclusion: The model represents a pathologic situation of excess resorption of DBBM and bone in an augmented area. The underlying cellular mechanisms remain to be uncovered. To cite this article:
Busenlechner D, Tangl S, Arnhart C, Redl H, Schuh C, Watzek G, Gruber R. Resorption of deproteinized bovine bone mineral in a porcine calvaria augmentation model.
Clin. Oral Impl. Res. 23 , 2012; 95–99.
doi: 10.1111/j.1600‐0501.2011.02198.x     

Evaluation of bone response to various anorganic bovine bone xenografts: an experimental calvaria defect study

This in vivo study investigated the in vivo performance of two newly developed synthetic bone substitutes and compared them to commercially available xenografts (Bio-Oss, Geistlich Pharma AG, Switzerland; OsteoGraf, Dentsply, USA). The materials were tested in a rabbit calvaria model, and the bone forming properties were observed at 4 and 8 weeks after implantation by means of histomorphometry and micro computed tomography (micro-CT). Defects without any graft material were used as negative controls. Micro-CT showed that all materials tested presented new bone formation that filled the defects at both time points, whereas the negative control presented less bone formation, with soft tissue infiltration into the defects. Comparable bone fill percentages were observed for histomorphometric and micro-CT results. Even though no statistically significant difference was found quantitatively between all of the bone graft substitute groups, a higher mean decrease in graft material filling the defects, along with higher remodelling activity, was evident for the experimental materials compared to the commercially available xenografts at 8 weeks. The results indicate that the experimental materials possess high degradability, along with osteoconduction comparable to commercially available xenografts.     

Evaluation of implant osseointegration with different regeneration techniques in the treatment of bone defects around implants: an experimental study in a rabbit model

Aim: The aim of this study was to evaluate the osseointegration of implants placed in areas with artificially created bone defects, using three bone regeneration techniques. Material and methods: The experimental model was the rabbit femur (16), where bone defects were created and implants were placed. The peri‐implant bone defects were filled with a deproteinized bovine bone mineral, NuOss^? (N), NuOss^? combined with plasma rich in growth factors (PRGF) (N+PRGF), NuOss^? covered by an RCM⁶ membrane (N+M), or remained unfilled (control group [C]). After 4 and 8 weeks, the animals were euthanized and bone tissue blocks with the implants and the surrounding bone tissue were removed and processed according to a histological protocol for hard tissues on non‐decalcified ground sections. The samples were studied by light and electron scanning microscopy, histometric analysis was performed to assess the percentage of bone in direct contact with the implant surface and a statistical analysis of the results was performed. Results: In the samples analyzed 4 weeks after implantation, the percentage of bone tissue in direct contact with the implant surface for the four groups were 57.66±24.39% (N), 58.62±20.37% (N+PRGF), 70.82±20.34 % (N+M) and 33.07±5.49% (C). In the samples with 8 weeks of implantation time, the percentage of bone in direct contact was 63.35±27.69% (N), 58.42±24.77% (N+PRGF), 78.02±15.13% (N+M) and 40.28±27.32% (C). In terms of the percentage of bone contact, groups N and N+M presented statistically significant differences from group C in the 4‐week trial test (P<0.05; ANOVA). For the 8‐week results, only group N+M showed statistically significant differences when compared with group C (P<0.05; ANOVA). Conclusion: In conclusion, the NuOss^? granules/RCM⁶ membrane combination presented a percentage of bone contact with the implant surface statistically greater than in the other groups. To cite this article:
Guerra I, Branco FM, Vasconcelos M, Afonso A, Figueiral H, Zita R. Evaluation of implant osseointegration with different regeneration techniques in the treatment of bone defects around implants: an experimental study in a rabbit model.
Clin. Oral Impl. Res. 22 , 2011; 314–322.
doi: 10.1111/j.1600‐0501.2010.02002.x     

Clinical evaluation of anorganic bovine-derived hydroxyapatite matrix/cell-binding peptide (P-15) in the treatment of human infrabony defects

The purpose of the present study was to compare the clinical outcomes of infrabony periodontal defects following treatment with an anorganic bovine-derived hydroxyapatite matrix/cell-binding peptide (ABM/P-15) flow to open flap debridement. Twenty-six patients, each displaying one infrabony defect with probing depth >/=6 mm and vertical radiographic bone loss >/=3 mm participated in the present study. Patients were allocated randomly to be treated with ABM/P-15 flow (test group) or open flap debridement (control group). At baseline and at 12 months after surgery, the following clinical parameters were recorded by a blinded examiner: plaque index, gingival index, probing depth (PD), clinical attachment level (CAL), and gingival recession. Both treatments resulted in significant improvements between baseline and 12 months, in terms of PD reduction and CAL gain (p < 0.001). At 12 months following therapy, the test group showed a reduction in mean PD from 7.8 +/- 1.6 mm to 3.5 +/- 1.0 mm and a change in mean CAL from 8.5 +/- 2.1 mm to 4.6 +/- 1.2 mm, whereas in the control group the mean PD decreased from 7.5 +/- 0.8 mm to 4.9 +/- 0.7 mm and mean CAL from 8.2 +/- 1.2 mm to 6.4 +/- 1.4 mm. The test group demonstrated significantly greater PD reductions (p = 0.002) and CAL gains (p = 0.001) compared to the control group. In conclusion, treatment of infrabony periodontal defects with ABM/P-15 flow significantly improved clinical outcomes compared to open flap debridement.     

Osteoconduction of different sizes of anorganic bone particles in a model of guided bone regeneration

The aim of this study was to evaluate the effect of two different sizes of anorganic bone particles (300-500 and 850-1000 μm) on the formation of new bone in a model of guided bone regeneration. In both groups, newly formed bone was seen histologically adjacent to the original surface of the skull, and there were outgrowths to the centre of the secluded graft 4 weeks after implantation. Some particles near the surface were in contact with the newly formed bone, and osteoconductive bone growth was present along their surface. Ten weeks after implantation the area created by grafting with small particles seemed to have a denser structure than that created with large particles. Histomorphometric analysis showed a higher density of newly formed bone in the small-particle group than in the large-particle group both 4 and 10 weeks after implantation. The total contact length between newly formed bone and particles and the ratio of bone:space between the particles were also significantly higher in the small-particle group at both time points. We conclude that the size of grafted particles of bone and the spaces between particles are important determinants of osteogenesis during guided bone regeneration.     

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     

Optimal microvessel density from composite graft of autogenous maxillary cortical bone and anorganic bovine bone in sinus augmentation: influence of clinical variables

Objectives: The objectives of this study were to assess the microvessel density (MVD) of intra‐sinus grafts after 6 months of wound healing and to study the relationship between revascularization processes and patient clinical variables and habits. Material and methods: We performed 45 maxillary sinus augmentations with different implant placements in 25 consecutive patients, obtaining bone cores of the grafted area for histological, histomorphometric and immunohistochemical study. Biopsies were also taken from pristine bone in the posterior maxilla (control). Results: All implants survived at 24 months. Biopsies of sinus augmentation areas showed significantly greater remodeling activity vs. pristine bone, with significantly more osteoid lines. The morphometry study revealed 34.88±15.2% vital bone, 32.02±15.1% non‐mineralized tissue and 33.08±25.4% remnant anorganic bovine bone particles. The number of CD34‐positive vessels was 86.28±55.52/mm² in graft tissue vs. 31.52±13.69/mm² in native tissue (P=0.002, Mann–Whitney U=46). The larger amount of non‐mineralized tissue in grafts was directly correlated with a higher MVD (r=0.482, P=0.0001, Pearson's test). MVD was affected by the presence of periodontitis or tobacco and alcohol consumption. Conclusion: The angiogenesis and revascularization obtained by this type of graft achieve adequate tissue remodeling for osseointegration and are influenced by periodontal disease and tobacco or alcohol consumption. To cite this article:
Galindo‐Moreno P, Padial‐Molina M, Fernández‐Barbero JE, Mesa F, Rodríguez‐Martínez D, O'Valle F. Optimal microvessel density from composite graft of autogenous maxillary cortical bone and anorganic bovine bone in sinus augmentation: influence of clinical variables.
Clin. Oral Impl. Res. 21 , 2010; 221–227
doi: 10.1111/j.1600‐0501.2009.01827.x     

A comparative study of barrier membranes as graft protectors in the treatment of localized bone defects. An experimental study in a canine model

Guided bone regeneration is a predictable and well-documented surgical approach for the treatment of deficient alveolar ridges prior to endosseous implant placement. The purpose of this study was to compare a new resorbable membrane (GORE RESOLUT ADAPT Regenerative Membrane, i.e. 67% glycolide (PGA) : 33% trimethyline carbonate (TMC)) with Bio-Gide, a resorbable collagen membrane. Five canines were used in the study. Three saddle-type osseous defects were created bilaterally in edentulous areas of the mandible. The defects were filled with assayed, canine demineralized freeze-dried bone (DFDB) in a thermoplastic gelatin matrix. Using a randomized block design, four sites were covered with PGA : TMC membranes of four different porosities, one site was covered with a collagen membrane and one site consisted of DFDB alone (control). At 3 months, the animals were euthanized and the mandibles were removed en bloc for laboratory processing. A total of 30 sites were reviewed microradiographically and underwent histomorphometric analysis for bone regeneration, soft tissue presence and remaining graft material. All sites exhibited uneventful healing. A significantly higher percentage of bone regeneration was seen in the sites protected by the PGA : TMC membrane. A higher component of soft tissue was visible beneath the collagen membrane as compared with the PGA : TMC membrane. The control sites exhibited noticeable deformation of the regenerated bone secondary to collapse of the overlying periosteum. The authors conclude that the PGA : TMC membrane protected the DFDB-filled defect and allowed a greater amount of bone regeneration than the defect protected by the collagen membrane or the control.     

Evaluation of an in situ formed synthetic hydrogel as a biodegradable membrane for guided bone regeneration

The aim of the present study was to test whether or not the application of an in situ formed synthetic hydrogel made of polyethylene glycol (PEG) used as a biodegradable membrane for guided bone regeneration will result in the same amount of bone regeneration as with the use of an expanded polytetrafluoro-ethylene (ePTFE) membrane. In eight New Zealand White rabbits, four evenly distributed 6 mm diameter defects were drilled into the calvarial bone. Three treatment modalities were evenly distributed among the 32 defects: hydroxyapatite (HA)/tricalciumphosphate (TCP) granules covered at the outer and inner surface with a PEG membrane (test), HA/TCP granules covered at the outer and inner surface with an ePTFE membrane (positive control) and HA/TCP granules alone without membranes (negative control). After 4 weeks, the animals were sacrificed and the calvarial bones were removed. The area fraction of newly formed bone was determined by histomorphometrical analysis of the vertical sections from the middle of the defect and by micro-computed tomography of the entire defect. Multiple regression analysis (SAS GLM) was used to model the amount of new bone formation. The quantitative histomorphometric analysis clearly revealed higher values of newly formed bone for the two membrane groups compared with the negative control group. The average area fractions of newly formed bone measured within the former defect amounted to 20.3+/-9.5% for the PEG membrane, 18.9+/-9.9% for the ePTFE membrane, and 7.3+/-5.3% for the sites with no membrane. The micro-computed tomography also showed higher values of new bone formation for the PEG and for the ePTFE groups compared with the negative control group. The GLM revealed a highly significant effect of the treatment on the amount of bone formation (P=0.0048). The values for the negative control group were significantly lower than the ones found in the PEG membrane group (P=0.0017), whereas the ePTFE membrane group showed no significant difference from the PEG membrane group. It is concluded that the PEG membrane can be used successfully as a biodegradable barrier membrane in the treatment of non-critical-size defects in the rabbit skull, and leads to similar amounts of bone regeneration as an ePTFE membrane.