Alveolar ridge augmentation with a prototype trilayer membrane and various bone grafts: a histomorphometric study in baboons

The Impact of Double Layer Membrane Technique on Bone Regeneration in Postextraction Alveoli – A Pathohistological Experimental Study in Dogs

Post extraction alveolar ridge preservation is a preventive oral surgical procedure aimed to preserve the dimensions of the alveolar ridge after removal of the teeth. According to literature data, the utilization of guided bone regeneration for this purpose is absolutely justified. The aim of this study was to examine the effect of resorbable collagen membranes placed in two layers in respect to the application of membranes placed in one layer to the degree of bone regeneration after a tooth extraction. This experimental study was conducted on six adult dogs. In the first phase all four premolars were extracted on both sides in the lower jaw. After the volume-standardisation with bone drill, three post extraction alveoli were filled with bone substitute of equine origin and then covered with: collagen bioresor bable membrane of porcine origin; collagen bioresorbable membrane of equine origin; pericardial bioresorbable membrane of equine origin. The membranes on the left side were placed in single-layer and on the right side in double-layer manner. After different monitoring periods, histopathological analysis of the samples taken from the experimental regions was performed. A different degree of bone regeneration was achieved between experimental regions in which membranes were placed in one layer and those where membranes were placed in two layers. There was no difference between regions where membranes of different origin were placed in the same manner. The procedure of covering the post extraction alveoli, filled with bone substitute and with resorbable membranes placed in two layers resulted in a higher degree of bone regeneration compared to those where resorbable membranes were placed in one layer.

Barrier membranes: More than the barrier effect?

AIM

To review the knowledge on the mechanisms controlling membrane-host interactions in guided bone regeneration (GBR) and investigate the possible role of GBR membranes as bioactive compartments in addition to their established role as barriers.

MATERIALS AND METHODS

A narrative review was utilized based on in vitro, in vivo and available clinical studies on the cellular and molecular mechanisms underlying GBR and the possible bioactive role of membranes.

RESULTS

Emerging data demonstrate that the membrane contributes bioactively to the regeneration of underlying defects. The cellular and molecular activities in the membrane are intimately linked to the promoted bone regeneration in the underlying defect. Along with the native bioactivity of GBR membranes, incorporating growth factors and cells in membranes or with graft materials may augment the regenerative processes in underlying defects.

CONCLUSION

In parallel with its barrier function, the membrane plays an active role in hosting and modulating the molecular activities of the membrane-associated cells during GBR. The biological events in the membrane are linked to the bone regenerative and remodelling processes in the underlying defect. Furthermore, the bone-promoting environments in the two compartments can likely be boosted by strategies targeting both material aspects of the membrane and host tissue responses.

Guided bone regeneration: materials and biological mechanisms revisited

Guided bone regeneration (GBR) is commonly used in combination with the installment of titanium implants. The application of a membrane to exclude non‐osteogenic tissues from interfering with bone regeneration is a key principle of GBR. Membrane materials possess a number of properties which are amenable to modification. A large number of membranes have been introduced for experimental and clinical verification. This prompts the need for an update on membrane properties and the biological outcomes, as well as a critical assessment of the biological mechanisms governing bone regeneration in defects covered by membranes. The relevant literature for this narrative review was assessed after a MEDLINE/PubMed database search. Experimental data suggest that different modifications of the physicochemical and mechanical properties of membranes may promote bone regeneration. Nevertheless, the precise role of membrane porosities for the barrier function of GBR membranes still awaits elucidation. Novel experimental findings also suggest an active role of the membrane compartment per se in promoting the regenerative processes in the underlying defect during GBR, instead of being purely a passive barrier. The optimization of membrane materials by systematically addressing both the barrier and the bioactive properties is an important strategy in this field of research.

Repair of critical-size bone defects using bone marrow stromal cells: a histomorphometric study in rabbit calvaria. Part I: use of fresh bone marrow or bone marrow mononuclear fraction

OBJECTIVES

The aim of this study was to compare the bone healing observed after the use of (1) a scaffold enriched with fresh bone marrow, (2) a scaffold enriched with bone marrow mononuclear fraction, and (3) a scaffold alone.

MATERIAL AND METHODS

Twenty one rabbits were randomly divided into three groups of six animals and 1 group of 3 animals. Bilateral 12-mm diameter defects were created in the animals' parietal bones. In Control Group, the defects were filled with a xenograft alone (n = 6); in Group 1, with a xenograft enriched with fresh bone marrow (n = 6); in Group 2, with a xenograft enriched with bone marrow mononuclear fraction (n = 6) and in Unfilled Group, nothing was grafted (n = 3). In Groups 1, 2, and Control, one of the calvarial defects was randomly covered with a barrier membrane. The rabbits were sacrificed 8 weeks after surgery, and their parietal bones were harvested and analyzed histomorphometrically.

RESULTS

The histomorphometric analysis showed no difference between Group 1 and the Control Group regarding non-vital mineralized tissue area, but Group 2 showed a statistically significant higher percentage than the Control Group (P < 0.05) for both situations, with membrane (21.24 ± 3.78% and 13.52 ± 3.00%, respectively) and without membrane (20.91 ± 2.01% and 13.08 ± 1.72%, respectively). Group 2 showed the highest percentage of vital mineralized tissue area, followed by Group 1 and the Control Group (P < 0.05) for both situations, with membrane (28.17 ± 3.19%; 21.14 ± 7.38% and 13.06 ± 5.24%, respectively) and without membrane (21.13 ± 0.55%; 12.45 ± 6.34% and 6.56 ± 1.20%, respectively). Group 2 showed the lowest percentage of non-mineralized tissue area, followed by Group 1 and Control Group (P < 0.05) for both situations, with membrane (50.59 ± 6.64%; 58.75 ± 7.14% and 73.41 ± 6.87%, respectively) and without membrane (57.97 ± 1.91%; 71.74 ± 6.63% and 80.37 ± 2.67%, respectively). The sides in which the defects were covered with the barrier membrane showed better bone healing compared with the uncovered sides, in all groups (intragroup comparison, P < 0.05). The Unfilled Group specimens showed no bone formation.

CONCLUSIONS

Both methods using bone marrow stromal cells contributed to enhancing bone healing, especially that using the bone marrow mononuclear fraction. The use of a barrier membrane seemed to have a synergistic effect.

Xenograft enriched with autologous bone marrow in inlay reconstructions: a tomographic and histomorphometric study in rabbit calvaria

Objective. The aim of this study was to evaluate the bone healing after the usage of a scaffold enriched with bone marrow. Study Design. Ten rabbits were divided into 2 groups of 5 animals. Bilateral 12 mm diameter defects were created in the parietal bones. In control group Bio-Oss were inserted in both defects and, in experimental group, Bio-Oss enriched with autologous bone marrow were inserted in both defects. In these two groups, one of the calvarial defects was covered with Bio-Gide. The rabbits were sacrified 8 weeks after surgery and both CT and histomorphometric analysis were done. Results. The CT showed a lower remaining defect area in the experimental group covered with Bio-Gide when compared with control group, with and without Bio-Gide. The histomorphometrics showed no difference between groups regarding the non-vital mineralized tissue area. For vital mineralized tissue area, the experimental group covered with Bio-Gide obtained a higher percentage area when compared with control group, with and without Bio-Gide. For non-mineralized tissue area, the experimental group covered with Bio-Gide obtained a lower percentage area when compared with control group, with and without Bio-Gide. Conclusion. Both autologous bone marrow and membrane can contribute to the enhancement of bone healing.

The comparative analysis of homologous fresh frozen bone and autogenous bone graft, associated or not with autogenous bone marrow, in rabbit calvaria: a clinical and histomorphometric study

The aim of this study was to evaluate the potential of fresh frozen homologous and autogenous grafts, associated or not with autogenous bone marrow, to form bone. Sixty titanium cylinders were used, and were fixed to the skulls of 30 rabbits. These cylinders were filled with (A) autogenous bone (AM) autogenous bone associated with the bone marrow (H) fresh frozen homologous bone (HM) fresh frozen homologous bone associated with the bone marrow (M) pure autogenous bone marrow and (C) blood clot. The animals were sacrificed after 02 and 03 months. After clinical evaluation, the samples were stained with hematoxylin, eosin and Mallory Trichrome dyes for optical microscopy analysis and histomorphometric analysis. Experimental groups that received mineralized materials (A, AM, H, HM) showed the best bone formation results, presenting no statistical difference between them (P > 0.05). Groups that did not receive mineralized materials (M and C) showed the worst results (P < 0.05), but the M group showed better results than the C group. Most of the autogenous and homologous bone particles were resorbed and there was a larger amount of residual particles in the homologous graft (H, HM) when compared with the autogenous graft (A, AM; P < 0.05). These findings suggest that fresh frozen homologous grafts produced similar amounts of new bone when compared with the autogenous grafts. However, the amount of residual bone particles was larger in the homogenous groups, which may indicate a slower remodeling process. The homologous fresh frozen bone seems to be a good osteoconductive material. The use of only autogenous bone marrow showed better results when compared to the bood clot. However, this research indicates that association with mineralized materials is required.

Ridge augmentation and maxillary sinus grafting with a biphasic calcium phosphate: histologic and histomorphometric observations

OBJECTIVES

This retrospective study reports on histologic and histomorphometric observations performed on human biopsies harvested from sites augmented exclusively by biphasic calcium phosphate [BCP: hydroxyapatite (HA)/ tricalcium phosphate (TCP) 60/40] and healed for a minimum of 6 months.

MATERIALS AND METHODS

Five patients benefited from three augmentation regimens (i.e.: one-stage lateral augmentation; two-stage lateral augmentation; and two-stage sinus grafting). In all patients, a degradable collagen membrane served as a cell-occlusive barrier. Core biopsies were obtained from lateral as from crestal aspects 6-10 months after augmentation surgeries. For histologic and histomorphometric evaluations, the non-decalcified tissue processing was performed.

RESULTS

The histological examination of 11 biopsies showed graft particles frequently being bridged by the new bone, and a close contact between the graft particles and newly formed bone was seen in all samples. The mean percentages of newly formed bone, soft tissue compartment, and graft material were 38.8% (+/-5.89%), 41.75% (+/-6.08%), and 19.63% (+/-4.85%), respectively. Regarding bone-to-graft contact values, the percentage of bone coverage of graft particles for all biopsies ranged from 27.83% to 80.17%. The mean percentage of bone coverage was 55.39% (+/-13.03%).

CONCLUSIONS

Data from the present study demonstrated osteoconductivity scores for the BCP material (HA/TCP 60/40) in patients resembling those previously shown for grafting materials of xenogenic and alloplastic origin.

Reconstruction of mandibular segmental defects using the guided-bone regeneration technique with polylactide membranes and/or autogenous bone graft: a preliminary study on the influence of membrane permeability

PURPOSE

Bone maintenance after mandibular reconstruction with autogenous iliac crest may be disappointing due to extensive resorption in the long term. The potential of the guided-bone regeneration (GBR) technique to enhance the healing process in segmental defects lacks comprehensive scientific documentation. This study aimed to investigate the influence of polylactide membrane permeability on the fate of iliac bone graft (BG) used to treat mandibular segmental defects.

MATERIALS AND METHODS

Unilateral 10-mm-wide segmental defects were created through the mandibles of 34 mongrel dogs. All defects were mechanically stabilized, and the animals were divided into 6 treatment groups: control, BG alone, microporous membrane (poly L/DL-lactide 80/20%) (Mi); Mi plus BG; microporous laser-perforated (15 cm(2) ratio) membrane (Mip), and Mip plus BG. Calcein fluorochrome was injected intravenously at 3 months, and animal euthanasia was carried out at 6 months postoperatively.

RESULTS

Histomorphometry showed that BG protected by Mip was consistently related to larger amounts of bone compared with other groups (P <or= .0001). No difference was found between defects treated with Mip alone and BG alone. Mi alone rendered the least bone area and reduced the amount of grafted bone to control levels. Data from bone labeling indicated that the bone formation process was incipient in the BG group at 3 months postoperatively regardless of whether or not it was covered by membrane. In contrast, GBR with Mip tended to enhance bone formation activity at 3 months.

CONCLUSIONS

The use of Mip alone could be a useful alternative to BG. The combination of Mip membrane and BG efficiently delivered increased bone amounts in segmental defects compared with other treatment modalities.

Lateral alveolar ridge augmentation using a synthetic nano-crystalline hydroxyapatite bone substitution material (Ostim®). Preliminary clinical and histological results

OBJECTIVES

The purpose of this preliminary two-center clinical prospective study was to evaluate the tissue composition of augmented sites after the use of a nano-crystalline hydroxyapatite (ncHA) bone substitution material by clinical and histological examinations.

MATERIAL AND METHODS

A synthetic ncHA augmentation material was used without any additives in 14 patients requiring lateral ridge augmentation 6-7 months before (10 patients) or at implant placement (four patients). The ncHA material was covered by a titanium mesh for space maintenance. Clinical and radiographic parameters were evaluated and bone biopsy cores, obtained 6-7 months following augmentation, were assessed histologically and histomorphometrically.

RESULTS

One patient showed gingival swelling, redness and pain at the augmentation site requiring removal of the titanium mesh 6 weeks postoperatively. In seven patients, a premature exposure of the titanium mesh without any inflammatory symptoms was noted. The width of the fixed gingival and the alveolar ridge height did not change significantly at least 6 months following augmentation (P>0.5), whereas a significant gain in alveolar ridge width (P=0.01) was noted. After a median period of prosthetic loading of 24 months, no implant was considered to be a failure. Histology revealed ncHA remnants in peripheral and central parts of biopsy cores obtained from seven patients after at least 6 months without histological symptoms of inflammation, whereas histomorphometry of bone cores revealed no significant differences of the mean percentage area of ncHA in peripheral (23.4%) and central (15.1%) parts of biopsy cores (P=0.262). The mean percentage area of bone colonizing the defect was 52.3%.

CONCLUSIONS

Small amounts of ncHA were found after at least 6 months in bone biopsies. The former defect space was filled with bone. The alveolar ridge width gain was found to be significant after lateral augmentation utilizing ncHA, providing a quantitatively and qualitatively sufficient site for primary stable implant placement.

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.