Ability of deproteinized cancellous bovine bone to induce new bone formation

Anabolic potential of bone mineral in human periosteal fibroblasts using steroid markers of healing

A deproteinized natural cancellous bone mineral (B) was studied in a cell culture model for its anabolic potential using two radiolabelled steroid substrates, 14C-testosterone (14C-T) and 14C-4-androstenedione (14C-4-A) independently; in the presence or absence of the anti-androgen finasteride (F) and minocycline (M). Culture medium was assayed for the biologically active metabolite 5 alpha-dihydrotestosterone (DHT) a marker of regenerative potential and wound healing. Confluent monolayer cultures of human periosteal fibroblasts were incubated in Eagle's minimum essential medium with each of the substrates 14C-T and 14C-4-A. Incubations were performed with previously established optimal concentrations of B5 (milligrams/ml), M25 (μg/ml) and F5 (μg/ml) alone and in combination (n=6) for 24h. The eluent was solvent extracted with ethyl acetate (2 ml x 2) and subjected to TLC in a benzene/acetone solvent system (4:1 v/v) for separation of metabolites; they were quantified using a radioisotope scanner. The yield of DHT was increased over controls in response to B and M with both substrates 14C-T and 14C-4-A by 1.7, 1.8-fold and 1.7, 1.6-fold respectively (n=6; p<0.001; one way ANOVA). Combined incubations of B and M resulted in similar yields. F inhibited DHT yields with both radiolabelled substrates by 2-3-fold (n=6; p<0.001) which was overcome by a combined incubation of F+B to values similar to those of controls (p<0.01). Documented pro-anabolic effects of minocycline were applicable as a standard for confirmation of responses to B. Significant increases in yields of DHT in response to B and M with both substrates indicate their anabolic potential in periosteal fibroblasts with implications for wound healing.

Clinical, Histological, and Histomorphometrical Analysis of Maxillary Sinus Augmentation Using Inorganic Bovine in Humans: Preliminary Results

The aim of the present study was to evaluate bone formation after maxillary sinus augmentation using bovine bone substitute material Bio-Oss alone by means of clinical, histological, and histomorphometrical examination of human biopsies. Deproteinized bovine bone (DPBB, Bio-Oss) was used to fill cavities after elevation of the sinus mucosa following major sinus pneumatization. Twenty patients with edentulous posterior maxillae were treated with 20 sinus augmentation procedures using a 2-stage technique. Residual lateral maxillary bone height was less than 3 mm. Forty-nine Straumann endosseous implants were used to complete the implant-prosthetic rehabilitation. Forty cylinder-shaped bone biopsies were taken from the augmented maxillary region 8 months after grafting during the second-stage surgery before implant placement. All implants were loaded 3 months after insertion, and no failures were recorded. Histomorphometrical analysis showed an average percentage of newly formed bone of 17.6% (±2.8%) and a proportion of residual bone substitute material of 29.9% (±4.9%) of the total biopsy area. Intimate contact between newly formed bone and Bio-Oss was detected along 28.2% (±6.8%) of the particle surfaces. The results also showed that in all cases, the DPBB granules had been interconnected by bridges of vital newly formed bone. Inorganic bovine bone appears to be biocompatible and osteoconductive, and it can be used with success as a bone substitute in maxillary sinus augmentation procedures.

Morphological evidences of Bio-Oss® colonization by CD44-positive cells

OBJECTIVES

Our objectives were to examine vascular and cellular colonization in anorganic bovine bone (ABB) after 6 months of healing in human maxillary sinus augmentation grafts.

MATERIAL AND METHODS

Fifty unilateral maxillary sinus augmentation procedures were performed on 50 consecutive patients. Bone cores were obtained through the implant receptor sites 6 months later and evaluated with morphological image analysis and immunohistochemical techniques.

RESULTS

Image analysis revealed a mean of 35.44 ± 16% vital bone, 31.66 ± 15% non-mineralized tissue, and 32.72 ± 25% remnant ABB particles. In our patients, neovascularization in 46.3% of cases was demonstrated within ABB particles 6 months after sinus floor augmentation surgery. Neovascularization of ABB particles was inversely related to age, directly to osteoclast number per mm², and not influenced by habits or disease. CD44-positive cells colonization was found in 74% of cases. An important correlation was found regarding CD44 expression and number of vessel in ABB particles (r = 0.624 P < 0.001, Pearson). Osteopontin expression was detected on the interstitial boundary of bone with ABB particles and within the osteocyte lacunae and bone canaliculi and was relationship with presence of CD44-positive cells inside ABB particles (r = 0.388, P = 0.046, Pearson).

CONCLUSION

In conclusion, images compatible with osteone colonized by osteocytes CD44 positive and neovascularization in ABB particles were observed after 6 months of graft maturation. These biologic events have not previously been morphologically and immunohistochemically documented.

Phenotypic characterization of mononuclear inflammatory cells following equine hydroxyapatite/collagen block grafting in rats

To measure the inflammatory changes associated with the implantation of an equine hydroxyapatite and collagen-containing block graft (eHAC block) in a rodent model system, an eHAC block graft was implanted subcutaneously in rats. Control groups included saline, turpentine oil, and human mineralized particulate allograft (hMPA). Animals were sacrificed and tissue samples obtained after three days, as well as after 1, 2, 4 and 8 weeks. A panel of immunologic probes was used to identify circulatory monocytic cells (ED1), resident mononuclear phagocytes (ED2), mononuclear phagocytes of lymphoid origin (ED3), expression of Ia antigen (OX6), T-cells (OX19), and B-cells (OX33). Immunocytochemical localization was performed and mononuclear cells localized with each immunologic probe counted. Rat sera obtained after eight weeks were used for nitrocellulose dot-blotting to assess circulating anti-equine immunoglobulins. Statistical analysis was performed using two-way analysis of variance, in conjunction with the Bonferroni correction to account for multiple comparisons. A transient increase in monocytes at 3 days and 1 week was observed in all groups, but was significantly higher in the turpentine control (P < 0.0001). A significant increase in the numbers of mononuclear cells detected with clones ED2 and ED3 was observed in specimens from the turpentine group, in contrast to the other groups in the 3 day to 4 week interval (P < 0.0001), as well as within all time periods (P < 0.0001). A statistically significant difference in numbers of ED3-positive cells was observed in the hMPA group compared to the saline and the eHAC block groups after one week (P < 0.0001). Significantly more OX6-positive cells were observed in the turpentine group, compared to other groups (3 days to 1 week; P < 0.0001). T-lymphocytes were essentially absent except for rats given turpentine (after 1 week). No B-lymphocyte response was found and none of the rats developed systemic anti-equine antibodies. These data indicate that a cellular immune response is not elicited following implantation with the eHAC block graft, which might serve as an alternative material for regenerative therapy.

Bucco-Lingual Crestal Bone Changes Around Implants Immediately Placed in Fresh Extraction Sockets in Association or not With Porcine Bone: A Non-Blinded Randomized Controlled Trial in Humans

Background: The aim of the present randomized controlled clinical trial was to assess the bucco-lingual bone changes of implants immediately placed in fresh extraction sockets in association or not with porcine bone. Methods: Forty patients were included in the present study, and were randomly assigned to the control (n = 20) and test (n = 20) groups. Each patient received a single implant placed into an immediate extraction site of a molar or a first upper premolar with a flapless approach. In the control sites no grafting material was placed, while in the tests a deantigenated collagenated bone substitute of porcine origin was used to fill the gaps between the implant and the extraction socket. The bucco-lingual bone width was measured at different time points: at the time of surgery (T0), at 90 days (T1), at 110 days (T2) and after 6 months of masticatory function (T3). The values were statistically analyzed between and within the treatment groups (p>0.05). Results: All the implants were osseointegrated. Four control implants were excluded from the analysis due to the exposure of the coronal portion of the fixture. At T1, T2 and T3, statistically significant differences were found by comparing the mean width of the bucco-lingual bone between control and test groups. The mean values decreased during the observation period in both groups; statistically significant differences within controls were detected at T1, T2 and T3, and at T2 and T3 within tests. Conclusions: The outcomes of present study suggested that porcine bone enabled to avoid bucco-lingual crestal bone changes in implants immediately placed in fresh extraction sockets.

Microscopic and radiographic analysis of the effect of particle size of demineralized bovine cancellous bone matrix on the repair of bone defects in femurs of rabbits

The bone tissue has a great regenerative potential, with ability to completely restore its structure and original functions. In some situations, though, bone defects cannot be self-repaired, thus requiring the use of grafts for a correct treatment and good prognosis. This work aimed at microscopically analyzing the effect of the particle size of demineralized bovine cancellous bone matrix in micro and macrogranular forms on the repair of bone defects in femurs of rabbits, with blood clot used as control. At 1, 3 and 6 months after implantation of the materials, the animals were killed and the anatomic specimens were removed. A foreign body-type granulomatous reaction containing macrophages and multinucleated giant cells in contact with the implanted particles was observed. These results suggest a failure in demineralization and/or interruption of the antigenic potential during production of the biomaterial. It is concluded that the size of the particles did not influence the evolution of the repair process of bone defects, acting only as bone-filler substances, and that the material implanted should be improved by quality control during production, since it may represent a good alternative for bone graft.

Comparison of cell viability and morphology of a human osteoblast-like cell line (SaOS-2) seeded on various bone substitute materials: An in vitro study

BACKGROUND

Many studies have shown favorable results following the use of different bone graft materials. The aim of the present study was to evaluate the biocompatibility of four different bone graft materials regarding cell viability and morphology of Human osteoblast-like cells (SaOS-2) in vitro.

MATERIALS AND METHODS

The effects of Bio-Oss(®), Tutodent(®), Osteon(®), and Cerasorb(®) were studied on the human osteoblast-like cell line to evaluate various parameters. Human osteoblast-like cells were seeded onto the mentioned bone substitute materials (BSMs). Cell differentiation; cell viability and alkaline phosphatase (ALP) activity of the seeded cells were evaluated by means of scanning electron microscopy, cell viability test and phase contrast microscopy Analysis of variance (ANOVA). Tamhane's post-hoc, Kruskal-Wallis Test, and Dunn's Test were used. The results were considered to be statistically significant at P<0.05.

RESULTS

The control group (SaOS-2 cells which were incubated in Dulbecco Modified Eagle Medium without any kind of bone graft materials) had the highest level of cell viability (P<0.001), followed by Tutodent(®), Osteon(®), Cerasorb(®), and Bio-Oss(®). There was no significant difference in MTT assay results between Tutodent(®) and the control group (P=0.032). All tested bone graft materials showed significantly higher ALP activity than the control (P<0.001). The Tutodent(®) group showed the best cell growth among all experimental groups, followed by the Osteon(®) group. The former had a higher spindle-like morphology with good attachment to the surface. Cells cultivated on the surfaces of the Cerasorb(®) and Bio-Oss(®) granules had more round morphologies.

CONCLUSION

This in vitro study demonstrated that all tested BSMs can provide good cell differentiation but a lower rate of proliferation.

In vivo and in vitro comparison of three different allografts vitalized with human mesenchymal stromal cells

Bone allografts are commonly used by orthopedists to provide a mechanical support and template for cellular colonization and tissue repair. There is an increasing demand for bone graft substitutes that are safe and easy to store but which are equally effective in supporting new bone growth. In this study, we compared three different human bone allografts: (1) the cryopreserved allograft (frozen), (2) the gamma-irradiated and cryopreserved allograft (γ-irradiated), and (3) the solvent dehydrated and γ-irradiated-processed bone allograft (Tutoplast(®) Process Bone [TPB]). Human mesenchymal stromal cells (hMSCs) have the potential to differentiate into osteogenic, chondrogenic, and adipogenic lineages. Our results showed that hMSC seeding efficiency was equivalent among the three bone allografts. However, differences were observed in terms of cell metabolism (viability), osteoblastic gene expression, and in vivo bone formation. Frozen allografts had the higher frequency of new bone formation in vivo (89%). Compared with frozen allografts, we demonstrated that TPB allografts allowed optimal hMSC viability, osteoblastic differentiation, and bone formation to occur in vivo (72%). Further, the frequency of successful bone formation was higher than that obtained with the γ-irradiated allograft (55%). Moreover, after hMSC osteoinduction, 100% of the TPB and frozen allografts formed bone in vivo whereas only 61% of the γ-irradiated allografts did. As healthcare teams around the world require bone-grafting scaffolds that are safe and easy to store, the TPB allograft appears to be a good compromise between efficient bone formation in vivo and convenient storage at room temperature.

Osteoinductivity of demineralized bone matrix is independent of donor bisphosphonate use

BACKGROUND

Demineralized bone matrix is commonly used as a bone graft substitute, either alone or to supplement an osteoconductive material, because of its osteoinductive properties. The aging of the population has led to an increase in the number of prospective donors of demineralized bone matrix who have taken bisphosphonates to prevent osteoclast-mediated bone resorption. The aim of this study was to determine whether oral bisphosphonate usage affects the osteoinductivity of demineralized bone matrix from donors.

METHODS

Sex-matched and age-matched pairs of samples were provided by four tissue banks (three or four pairs per bank). Demineralized bone matrix donors without bisphosphonate treatment had a mean age (and standard deviation) of 69.1 ± 2.5 years, and donors with bisphosphonate treatment had a mean age of 68.9 ± 2.0 years. Each pair included one donor known to have taken bisphosphonates and one who had not taken bisphosphonates. Demineralized bone matrix previously confirmed as osteoinductive was the positive control, and heat-inactivated demineralized bone matrix was the negative control. Demineralized bone matrix incubated with 1 mL of phosphate-buffered saline solution containing 0, 0.002, 2.0, or 2000 ng/mL of alendronate was also tested. Gelatin capsules containing 15 mg of demineralized bone matrix were implanted bilaterally in the gastrocnemius muscle of male nude mice (eight implants per group). The mice were killed thirty-five days after implantation, and hind limbs were recovered and processed for histological analysis. Osteoinductivity was measured with use of a qualitative score and by histomorphometry.

RESULTS

Nine of fifteen samples from donors who had had bisphosphonate treatment and ten of fifteen samples from patients who had not had bisphosphonate treatment were osteoinductive. Qualitative mean scores were comparable (1.7 ± 0.4 for those without bisphosphonates and 1.9 ± 0.7 for those with bisphosphonates). Osteoinductive demineralized bone matrix samples produced ossicles of comparable size, regardless of bisphosphonate usage. Histomorphometric measurements of the area of new bone formation and residual demineralized bone matrix were also comparable. The addition of alendronate to control demineralized bone matrix did not affect its osteoinductivity.

CONCLUSIONS

Demineralized bone matrix samples from donors treated with bisphosphonates and donors not treated with bisphosphonates have the same ability to induce bone formation. However, it is not known if the quality of the new bone is affected, with subsequent consequences affecting bone remodeling.

Risk of prion disease transmission through bovine-derived bone substitutes: a systematic review

BACKGROUND

Despite the causal association between variant Creutzfeldt - Jakob disease and bovine spongiform encephalopathy (BSE), bovine origin graft materials are widely used during dental surgical procedures. The aim of this study was to assess the risk of BSE transmission through anorganic bovine bone substitutes.

METHODS

Electronic database of MEDLINE was searched to identify relevant studies regarding our focused questions, presence of BSE prion infectivity in raw bovine bone, BSE prion inactivation by bone substitute manufacturing process, protein contents in anorganic bovine bone substitutes, and validity of current BSE diagnostic methods. Search terms yielded 1,704 titles. After title/abstract screening and duplicates removal, 36 full-text articles were screened for inclusion.

RESULTS

A total of 16 studies were included in the final analysis. No eligible studies were identified regarding the efficacy of BSE prion inactivation by the treatments used for anorganic bovine bone manufacturing. BSE infectivity and PrP(Sc) , pathological prion, were detected in bovine bone marrow and serum samples. Proteins were detected in Tutoplast® (bovine), Bio-Oss®, and tibia samples treated at the similar condition for Bio-Oss deproteinization. Inconsistent results of different BSE diagnostic tests were not unusual findings (Iwata et al. 2006; Arnold et al. 2007; Murayama et al. 2010), and a study by Balkema-Buschmann and colleagues showed an apparent discrepancy between BSE infectivity and detection of PrP(27-30), the current surrogate marker for prion disease infectivity.

CONCLUSION

This review indicates that bovine-derived graft biomaterials may carry a risk of prion transmission to patients.

Functionalization of deproteinized bovine bone with a coating-incorporated depot of BMP-2 renders the material efficiently osteoinductive and suppresses foreign-body reactivity

The repair of critical-sized bony defects remains a challenge in the fields of implantology, maxillofacial surgery and orthopaedics. As an alternative bone-defect filler to autologous bone grafts, deproteinized bovine bone (DBB) is highly osteoconductive and clinically now widely used. However, this product suffers from the disadvantage of not being intrinsically osteoinductive. In the present study, this property was conferred by coating DBB with a layer of calcium phosphate into which bone morphogenetic protein 2 (BMP-2) was incorporated. Granules of DBB bearing a coating-incorporated depot of BMP-2--together with the appropriate controls (DBB bearing a coating but no BMP-2; uncoated DBB bearing adsorbed BMP-2; uncoated DBB bearing no BMP-2)--were implanted subcutaneously in rats. Five weeks later, the implants were withdrawn for a histomorphometric analysis of the volume densities of (i) bone, (ii) bone marrow, (iii) foreign-body giant cells and (iv) fibrous capsular tissue. Parameters (i) and (ii) were highest, whilst parameters (iii) and (iv) were lowest in association with DBB bearing a coating-incorporated depot of BMP-2. Hence, this mode of functionalization not only confers DBB with the property of osteoinductivity but also improves its biocompatibility--thus dually enhancing its clinical potential in the repair of bony defects.

Development, characterization and clinical use of a biodegradable composite scaffold for bone engineering in oro-maxillo-facial surgery

We have developed a biodegradable composite scaffold for bone tissue engineering applications with a pore size and interconnecting macroporosity similar to those of human trabecular bone. The scaffold is fabricated by a process of particle leaching and phase inversion from poly(lactideco-glycolide) (PLGA) and two calcium phosphate (CaP) phases both of which are resorbable by osteoclasts; the first a particulate within the polymer structure and the second a thin ubiquitous coating. The 3-5 μm thick osteoconductive surface CaP abrogates the putative foreign body giant cell response to the underlying polymer, while the internal CaP phase provides dimensional stability in an otherwise highly compliant structure. The scaffold may be used as a biomaterial alone, as a carrier for cells or a three-phase drug delivery device. Due to the highly interconnected macroporosity ranging from 81% to 91%, with macropores of 0.8∼1.8 mm, and an ability to wick up blood, the scaffold acts as both a clot-retention device and an osteoconductive support for host bone growth. As a cell delivery vehicle, the scaffold can be first seeded with human mesenchymal cells which can then contribute to bone formation in orthotopic implantation sites, as we show in immune-compromised animal hosts. We have also employed this scaffold in both lithomorph and particulate forms in human patients to maintain alveolar bone height following tooth extraction, and augment alveolar bone height through standard sinus lift approaches. We provide a clinical case report of both of these applications; and we show that the scaffold served to regenerate sufficient bone tissue in the wound site to provide a sound foundation for dental implant placement. At the time of writing, such implants have been in occlusal function for periods of up to 3 years in sites regenerated through the use of the scaffold.

A meta-analysis of histomorphometric results and graft healing time of various biomaterials compared to autologous bone used as sinus floor augmentation material in humans

BACKGROUND

To date, no studies have been published in which histomorphometric data from a large group of patients comparing various biomaterials for sinus floor augmentation procedures were evaluated.

MATERIALS AND METHODS

A meta-analysis of the English literature from January 1993 till April 2009 was carried out. Out of 147 titles, according to our criteria, 64 articles were selected for analysis describing the use of autologous bone and their alternatives, such as allogenic, xenogenic, and alloplastic materials.

RESULTS

On the basis of autologous bone grafting, a reference value for total bone volume (TBV) of 63% was found. Particulation of the bone graft resulted in a general reduction of −18% in TBV. Delayed implant placement reduced the TBV with −7%. Overall TBV was 8% or 6% higher if a biopsy was, respectively, taken before 4.5 months or after 9.0 months after initial sinus augmentation surgery. Allogenic, xenogenic, alloplastic, or combinations of graft materials all resulted in a significant lower amount of TBV compared to autologous bone grafting ranging from −7% to −26%. Inventorying the effect of "biopsy time" for autologous bone, the TBV was significantly higher before 4.5 and after 9.0 months of healing time compared to period in between. Surprisingly, no significant differences in TBV with respect to "biopsy time" for bone substitutes were found.

CONCLUSIONS

On the basis of the aspect of TBV autologous bone still has to be considered to be the gold standard in sinus augmentation surgery. However, the consequence of the TBV for implant survival is still unraveled yet.

Reconstruction of a mandibular defect with autogenous, autoclaved bone grafts and tissue engineering: An in vivo pilot study

Reconstruction of bone defects with autogenous, autoclaved bone grafts has already been described but does have one major insuperable problem-the loss of the ostoinductive potential of the graft. In this study, we investigated if autogenous, autoclaved grafts in combination with tissue engineered bone can overcome this problem. An en-bloc resection was done in the mandible of eight pigs. The grafts were autoclaved and filled with autogenous, osseogen differentiated bone marrow cells and compared with four animals without bone marrow cells. After 120 days, the specimens were qualitatively and quantitatively evaluated by means of microradiography and light microscopy. Within the experimental group, osseous remodeling was detected in all cases and new bone formation was visible. Quantitative assessment of the osseous bridging of the osteotomy sites was significantly higher in the test group in comparison with the control group (p = 0.03). The histological evaluation by means of an osseous integration of the grafts revealed a statistically significant difference between both groups as well (p = 0.01). The results of this study indicate that the method investigated hereby represents a further possibility in the therapy of bony defects, such as those arising as a result of tumor operations.

Effects of fibrin-binding oligopeptide on osteopromotion in rabbit calvarial defects

PURPOSE

Fibronectin (FN) has been shown to stimulate bone regeneration in animal models. The aim of this study was to evaluate the capacity of bovine bone mineral coated with synthetic oligopeptides to enhance bone regeneration in rabbit calvarial defects.

METHODS

Oligopeptides including fibrin-binding sequences of FN repeats were synthesized on the basis of primary and tertiary human plasma FN structures. Peptide coated and uncoated bone minerals were implanted into 10 mm calvarial defects in New Zealand white rabbits, and the animals were sacrificed at 4 or 8 weeks after surgery. After specimens were prepared, histologic examination and histomorphometric analysis were performed.

RESULTS

At 4 weeks after surgery, the uncoated groups showed a limited amount of osteoid formation at the periphery of the defect and the oligopeptide coated groups showed more osteoid formation and new bone formation in the center of the defect as well as at the periphery. At 8 weeks, both sites showed increased new bone formation. However, the difference between the two sites had reduced.

CONCLUSIONS

Fibrin-binding synthetic oligopeptide derived from FN on deproteinized bovine bone enhanced new bone formation in rabbit calvarial defects at the early healing stage. This result suggests that these oligopeptides can be beneficial in reconstructing oral and maxillofacial deformities or in regenerating osseous bone defects.

Implant Installation With Ridge Augmentation Using Autogenous Bone Harvested From an Adjacent Site

In general, autogenous bone is the most predictable material of choice for augmentation procedure. However, the autogenous bone graft procedure requires an additional surgical wound, and the amount of graft is limited because of the donor site. In this case, autogenous corticocancellous bone cores were harvested adjacent to the implant surgical site and the defect, which was distal to the implant surface, was treated with autogenous bone and deproteinized bovine bone. The implant-supported prosthesis was functioning well up to 6 months without any probing depth or gingival inflammation.

Maxillary sinus floor augmentation on humans: Packing simulations and 8 months histomorphometric comparative study of anorganic bone matrix and β-tricalcium phosphate particles as grafting materials

The present study compares the behaviour of an anorganic bone matrix material and a synthetic β-Tricalcium phosphate employed as grafting materials in a sinus floor augmentation two step protocol in humans. In order to estimate the initial occupation level for the two materials, an 'in vitro' simulation has been performed to analyse macroporosity created due to particle packing in terms of porosity and interparticle distances. Grafting in the sinus floor augmentation was performed by filling the defects only with pure grafting materials without autogenous bone addition. The new-bone generated is 100% based on the osteoconductive properties of the grafted materials in contact with physiological fluids. The implants were placed 8 months after the grafting procedure. All the implanted positions were biopsied and embedded in methacrylate resin. Histomorphometric analyses were done over thin film undecalcified sections. Packing simulations allow establishing a comparison of the resorbed volumes related to the initial occupancy of the grafting materials inside the defect. The nature of this interconnected pore network is very alike for either material so new-bone generated was similar (~35 vol.%).

Histological and histomorphometrical analyses of biopsies harvested 11 years after maxillary sinus floor augmentation with deproteinized bovine and autogenous bone

OBJECTIVE

The purpose of the present study was to histologically and histomorphometrically evaluate the long-term tissue response to deproteinized bovine bone (DPBB) particles used in association with autogenous bone and to compare particle size after 6 months and 11 years, in the same patients, in order to determine possible resorption.

MATERIAL AND METHODS

Twenty consecutive patients (14 women and six men) with a mean age of 62 years (range 48-69 years) with severe atrophy of the posterior maxilla were included in this study. Thirty maxillary sinuses with <5 mm subantral alveolar bone were augmented with a mixture of 80% DPBB and 20% autogenous bone. Eleven years (mean 11.5 years) after augmentation, biopsies were taken from the grafted areas of the 11 patients who volunteered to participate in this new surgical intervention. The following histomorphometrical measurements were performed in these specimens: total bone area in percentage, total area of the DPBB, total area of marrow space, the degree of DPBB-bone contact (percentage of the total surface length for each particle), the length of all DPBB particles and the area of all DPBB particles. The length and the area of the particles were compared with samples harvested from the same patients at 6 months (nine samples) and pristine particles from the manufacturer.

RESULTS

The biopsies consisted of 44.7+/-16.9% lamellar bone, 38+/-16.9% marrow space and 17.3+/-13.2% DPBB. The degree of DPBB to bone contact was 61.5+/-34%. There were no statistically significant differences between the length and area of the particles after 11 years compared with those measured after 6 months in the same patients or to pristine particles from the manufacturer.

CONCLUSION

DPBB particles were found to be well integrated in lamellar bone, after sinus floor augmentation in humans, showing no significant changes in particle size after 11 years. To cite this article: Mordenfeld A, Hallman M, Johansson CB, Albrektsson T. Histological and histomorphometrical analyses of biopsies harvested 11 years after maxillary sinus floor augmentation with deproteinized bovine and autogenous bone.

Bone grafts engineered from human adipose-derived stem cells in perfusion bioreactor culture

We report engineering of half-centimeter-sized bone constructs created in vitro using human adipose-derived stem cells (hASCs), decellularized bone scaffolds, and perfusion bioreactors. The hASCs are easily accessible, can be used in an autologous fashion, are rapidly expanded in culture, and are capable of osteogenic differentiation. hASCs from four donors were characterized for their osteogenic capacity, and one representative cell population was used for tissue engineering experiments. Culture-expanded hASCs were seeded on fully decellularized native bone scaffolds (4 mm diameter x 4 mm thick), providing the necessary structural and mechanical environment for osteogenic differentiation, and cultured in bioreactors with medium perfusion. The interstitial flow velocity was set to a level necessary to maintain cell viability and function throughout the construct volume (400 microm/s), via enhanced mass transport. After 5 weeks of cultivation, the addition of osteogenic supplements (dexamethasone, sodium-beta-glycerophosphate, and ascorbic acid-2-phosphate) to culture medium significantly increased the construct cellularity and the amounts of bone matrix components (collagen, bone sialoprotein, and bone osteopontin). Medium perfusion markedly improved the distribution of cells and bone matrix in engineered constructs. In summary, a combination of hASCs, decellularized bone scaffold, perfusion culture, and osteogenic supplements resulted in the formation of compact and viable bone tissue constructs.

Experimental immediate loading of dental implants in conjunction with grafting procedures

The aim of this study was to evaluate immediate loading (IL) of dental implants in conjunction with grafting procedures. A total of 107 IL implants were inserted in six mini pigs. Before implant placement, crestal or apical defects were created, which were treated with bone chips, phycogene hydroxyapatite (HA), bovine HA, or bovine HA enhanced with a synthetic peptide. Crestal grafts were stabilized with titanium membranes. All bridges were in function and showed signs of chewing wear after 4-month loading. Three out of 107 implants showed no osseointegration (2.7%). Most of the crestal defects showed incomplete regeneration, due to an infection of the membranes (74.3%) The difference in height between surgical and remaining defect was calculated as defect development, which was 2.3 +/- 2.08 mm for bone chips with an area of regenerated bone of 22.8 +/- 3.34% and 0.7 +/- 2.22 mm for phycogene HA with 11.3 +/- 4.36% regenerated bone. Bovine HA showed an increase of defects 1.3 +/- 2.47 mm with only 7.9 +/- 1.7% bone regeneration. Bovine HA enhanced with a peptide showed a defect development of 1.1 +/- 1.42 mm with an area of regenerated bone of 18.2 +/- 2.38%. In conclusion, local grafting procedures did not disturb the course of osseointegration for immediate loaded implants if primary stability was reached. The regeneration of apical defects was uneventful even with immediate loading. Crestal defects required membrane fixation with a careful flap elevation to avoid membrane exposure and loss of the graft.

Healing of onlay mandibular bone grafts covered with collagen membrane or bovine bone substitutes: a microscopical and immunohistochemical study in the sheep

The objective of this study was to evaluate the role of collagen membrane and Bio-Oss coverage in healing of an onlay graft to the mandible. Twelve adult sheep each received an onlay bone graft (experiment 1), bone graft+Bio-Gide (experiment 2), and bone graft+Bio-Oss/Bio-Gide (experiment 3) on the lateral surface of the mandible. The animals were euthanized at 4, 8, 12 or 16 weeks after surgery, and findings were analysed by routine microscopy and immunohistochemistry for proliferation (Ki67) and apoptotic (Caspase-3) markers. Grafts were fully incorporated in all specimens. Pronounced resorption was observed in experiment 1. Minimal loss of graft volume was seen in experiment 2 specimens without membrane displacement. A remarkable increase in the augmented region of the mandible was observed in experiment 3. A high number of osteoclasts were expressed within the grafts during the early healing period, and thereafter declined markedly. Osteoblasts within the grafts expressed a moderate level of Ki67 at 8 weeks, which thereafter declined markedly. The strongest expression of Caspase-3 on the bone surface was observed after 16 weeks. In conclusion, the effect of collagen membrane coverage on bone graft volume maintenance was dependent on membrane stability during healing. An autogenous bone graft covered with Bio-Oss particles resulted in a remarkable increase in augmented lateral surface of the mandible. The late stage of bone graft healing was associated with a high apoptotic induction pathway of osteoblasts lining the surfaces of the new bone, demonstrated by strong positive Caspase-3 immunoreactivity.

A mineralization-associated membrane protein plays a role in the biological functions of the peptide-coated bovine hydroxyapatite

BACKGROUND AND OBJECTIVE

Anorganic bovine mineral coated with a cell-binding peptide (P-15) is superior to anorganic bovine mineral alone in the treatment of periodontal osseous defects. However, the molecular interactions between P-15 and periodontal ligament fibroblasts remain unclear.

MATERIAL AND METHODS

We first compared the in vitro osteogenic activities between periodontal ligament fibroblasts cultured with anorganic bovine mineral alone and with the P-15/anorganic bovine mineral combination. We then harvested the periodontal ligament cell lysate, incubated it with various graft materials, and then washed it to remove unbound proteins. The bound proteins were eluted from graft materials and analyzed using electrophoresis, followed by mass spectrometry and then western blotting. Finally, a neutralizing antibody against one bound protein was added to the cell cultures to repeat the osteogenic assays to clarify its role in the in vitro effects of the P-15/anorganic bovine mineral combination.

RESULTS

Cells treated with P-15/anorganic bovine mineral were more viable and showed greater osteogenic activities than cells treated with anorganic bovine mineral alone and the no-graft control. Annexin II, a mineralization-associated protein, bound to P-15/anorganic bovine mineral significantly more than to anorganic bovine mineral alone. The addition of neutralizing antibody for annexin II decreased the osteogenic activities of the P-15/anorganic bovine mineral combination.

CONCLUSION

Annexin II of periodontal ligament fibroblasts interacted with the peptide of P-15, and was partially responsible for better in vitro osteogenesis in the P-15 graft.

Osteoinductivity of demineralized bone matrix in immunocompromised mice and rats is decreased by ovariectomy and restored by estrogen replacement

The osteoinduction potential of human demineralized bone matrix (DBM) in females with low estrogen (E2) is unknown. Moreover, the osteoinductivity of commercial human DBM is tested in male athymic rats and mice, but DBM performance in these animals may not reflect performance in female animals or provide information on E2's role in the process. To gain insight, human DBM was implanted bilaterally in the gastrocnemius of twenty-four athymic female mice (10 mg/implant) and twenty-four athymic female rats (15 mg/implant). Eight animals in each group were sham-operated (SHAM), ovariectomized (OVX), or ovariectomized with E2-replacement (OVX+E2) via subcutaneous slow release capsules of 17beta-estradiol. OVX and OVX+E2 animals were pair-fed to SHAM animals. Four animals from each group were euthanized at 35 days and four at 56 days. Animal weight, uterine weight, and blood estrogen levels confirmed that pair feeding, ovariectomy, and E2 replacement were successful. Histological sections of implanted tissues were evaluated qualitatively for absence or presence of DBM, ossicle formation, and new bone or cartilage using a previously developed qualitative scoring system (QS) and by histomorphometry to obtain a quantitative assessment of osteoinduction. OVX mice had a small but significant QS decrease at 35 days compared to SHAM mice, confirmed by quantitative measurement of ossicle, marrow space, and new bone areas. The QS in rats was not affected by OVX but histomorphometry showed decreased new bone in OVX rats, which was restored by E2. The QS indicated that the number of new bone sites was not reduced by OVX in rats or mice at 56 days, but the relative amount of new bone v. marrow space was affected and differed with animal species. Residual DBM was less in OVX animals, indicating that DBM resorption was affected. Cartilage was present in rats but not in mice, suggesting that endochondral ossification was slower and indicating that bone graft studies in these species are not necessarily comparable. These results show the importance of E2 in human DBM-induced bone formation and suggest that E2 may be needed for clinical effectiveness in post-menopausal women.

Microvessel density and vascular endothelial growth factor expression in sinus augmentation using Bio-Oss

AIM

The aim of this study was to evaluate microvessel density (MVD) and vascular endothelial growth factor (VEGF) expression in sinus augmentation with Bio-Oss.

METHODS

Twenty patients participated in this study. The sinuses were filled with 100% Bio-Oss. Implants were inserted after 3 months in group A, and 6 months in group B. A trephine was used to harvest bone cores. As control, the pre-existing subantral bone was used.

RESULTS

The mean MVD in control bone was 23.6 +/- 1.8. In the sites augmented with Bio-Oss, at 3 months, the MVD was 23.3 +/- 2.1, while in the sites retrieved at 6 months the MVD was 29.5 +/- 2.4. The difference in MVD between the control bone and group A was not statistically significant. The difference between the control bone and group B was statistically significant (P < 0.05). The statistical analysis showed that the difference in MVD between group A and group B was statistically significant (P < 0.05).

CONCLUSIONS

Bio-Oss seemed to induce an increase in MVD that reached a higher value after 6 months. The percentage of vessels positive to VEGF was higher in group A than in group B. Our data also showed a higher percentage of vessel and stromal cells positive to VEGF and higher MVD values in areas where there was newly formed bone compared with areas where maturation processes were occuring, and this fact could point to a close spatial relationship between angiogenesis and osteogenesis.

Maxillary sinus augmentation with different biomaterials: a comparative histologic and histomorphometric study in man

OBJECTIVE

Rehabilitation of the edentulous posterior maxilla with dental implants can be difficult because of insufficient bone volume caused by pneumatization of the maxillary sinus and crestal bone resorption. Different biomaterials have been used for sinus augmentation. The aim of the study was to compare different materials in maxillary sinus augmentation in man.

METHODS

A total of 94 patients participated in this study. Inclusion criteria were maxillary partial (unilateral or bilateral) edentulism involving the premolar/molar areas, and the presence of 3-5-mm crestal bone between the sinus floor and alveolar ridge. A total of 362 implants were inserted. There were 9 biomaterials used in the sinus augmentation procedures. Each patient underwent 1 biopsy after 6 months. A total of 144 specimens were retrieved.

RESULTS

None of the 94 patients had complications. All implants were stable, and x-ray examination showed dense bone around the implants. Mean follow-up was 4 years. There were 7 implants that failed. Histologic resultsshowed that almost all the particles of the different biomaterials (i.e., autologous bone, demineralized freeze-dried bone allograft Biocoral [Inoteb, St. Gonnery, France], Bioglass [US Biomaterials, Alachua, FL], Fisiograft [Ghimas, Bologna, Italy], PepGen P-15 [Dentsply Friadent CeraMed, Lakewood, CO], calcium sulfate, Bio-Oss [Geistlich Pharma AG, Wohlhusen, Switzerland], and hydroxyapatite) were surrounded by bone. Some biomaterials were more resorbable than others. Included are the histomorphometry clarified features of the newly formed bone around the different grafted particles.

CONCLUSION

All biomaterials examined resulted in being biocompatible and seemed to improve new bone formation in maxillary sinus lift. No signs of inflammation were present. The data are very encouraging because of the high number of successfully treated patients and the good quality of bone found in the retrieved specimens.

Orthodontic movement after periodontal regeneration of class II furcation: a pilot study in dogs

PURPOSE

The effect of orthodontic movement on the periodontal tissues of maxillary second pre-molars, after regenerative treatment for class II furcations, was evaluated in four mongrel dogs.

MATERIAL AND METHODS

Class II furcation lesions were created. After 75 days they were treated with bovine bone mineral matrix and guided tissue regeneration with absorbable membrane. After 2 months of daily plaque control, each of the dog's furcation pre-molars was randomly assigned to a test or control group. Orthodontic appliances were placed on both sides of the maxilla using third pre-molars and canines as anchorages. In the test group, bodily orthodontic movement of the second pre-molars was performed in the mesial direction for 3 months while control pre-molars remained unmoved. The dogs were sacrificed for histometric and histologic analyses.

RESULTS

There were no statistically significant differences between the two groups in total bone and biomaterial areas or linear extension of periodontal regeneration on the radicular surfaces. In the test group, however, there was a tendency to a greater quantity of bone and a lesser quantity of biomaterial.

CONCLUSION

The orthodontic movement was not pre-judicial to the results obtained with the regenerative periodontal treatment.

Use of growth factors to modify osteoinductivity of demineralized bone allografts: lessons for tissue engineering of bone

Biologically active bone graft substitute materials are needed for repair and regeneration of skeletal tissues. Current approaches are focused on the use of osteoinductive agents, including bone morphogenetic proteins (BMP) in combination with biodegradable carriers. Demineralized freeze-dried bone allograft (DFDBA) can provide an osteoconductive surface and, at the same time, function as a time-release carrier for BMP. Donor variability, however, limits the predictability of DFDBA as an osteoinductive material. This article examines the use of growth factors, including platelet-rich plasma, platelet-derived growth factor, enamel matrix derivatives, and BMP-2, to enhance the osteoinductive properties of human DFDBA.

Differentiation of osteoblasts in three-dimensional culture in processed cancellous bone matrix: quantitative analysis of gene expression based on real-time reverse transcription-polymerase chain reaction

Processed bovine cancellous bone (PBCB) is an attractive material for tissue engineering of bone. It is biocompatible, osteoconductive, nonimmunogenic, and porous and its biomechanical properties are close to those of native bone. In this study, differentiation of primary rat osteoblasts (rOBs) incubated on PBCB was investigated in vitro. rOBs were isolated and expanded in two-dimensional culture. Expanded rOBs were seeded into PBCB disks and cultured either in basal medium (BM) or differentiation medium (DM) containing ascorbic acid, beta-glycerol phosphate, and dexamethasone. Alkaline phosphatase (ALP) activity and RNA expression of ALP, bone sialoprotein (BSP), collagen type I (COL1), osteocalcin (OC), and osteopontin (OPN) were assessed by chemiluminescence assay and quantitative real-time RT-PCR over 14 days. Histologic analysis was performed on day 14. ALP increased over the observation period independent of stimulation. OPN and BSP expression was significantly higher in the DM group whereas COL1 and OC expression was significantly higher in the BM group. Matrix calcification was detectable only in the DM group by von Kossa stain. The observed expression patterns suggest a physiological response of rOBs to the differentiation stimulus. PBCB is a suitable matrix for in vitro differentiation of osteoblasts. Cell-seeded PBCB is a potential osteogenic construct for in vivo application.

Bone Augmentation with Bioactive Glass in Three Cases of Dental Implant Placement

This study reports the clinical use of a bioactive bone graft material, PerioGlas®, in the treatment of dental extraction sites before dental implant placement, to effect bone regeneration and to give early fixation to the implant.

PerioGlas®, granules, ranging from 90 to 710 mm, are implanted after tooth extraction in three patients; after 6 months bone biopsies were performed in the site of the glass implantation and observed under Electron Scanning Microscopy.

All the granules showed a biodegradation involving precipitation of calcium phosphate that worked as a scaffold for osteoblasts colonization. All cases examined showed the bioactivity of PerioGlas® granules resulting in new bone formation and biodegradation of the glass. After a two-year clinical follow-up all the implants were successfully loaded and appeared stable.

Evaluation of bone healing enhancement by lyophilized bone grafts supplemented with platelet gel: A standardized methodology in patients with tibial osteotomy for genu varus

Orthopedic practice may be adversely affected by an inadequate bone repair that might compromise the success of surgery. In recent years, new approaches have been sought to improve bone healing by accelerating the rate of new bone formation and the maturation of the matrix. There is currently great interest in procedures involving the use of platelet gel (PG) to improve tissue healing, with satisfactory results both in vitro and in maxillofacial surgery. Otherwise, to our knowledge, only a preliminary clinical study was undertaken in the orthopedic field [Kitoh et al., Bone 2004;35:892-898] and the efficacy of PG is still controversial. Our paper focuses on the effect on bone regeneration by adding PG to lyophilized bone chips used for orthopedic applications. The clinical model and the laboratory methodology were standardized. As a clinical model, we employed the first series of patients of a randomized case-control study undergoing high tibial osteotomy (HTO) for genu varus. Ten subjects were enrolled: in 5 patients lyophilized bone chips supplemented with PG were inserted during tibial osteotomy (group A); 5 patients were used as a control (group B) and lyophilized bone chips without gel were applied. Forty-five days after surgery, computed tomography scan guided biopsies of grafted areas were obtained and the bone maturation was evaluated by a standardized methodology: the osteogenic and angiogenic processes were semi-quantitatively characterized by using histomorphometry, and the mineral component of the lyophilized and host bone was analyzed by using X-ray diffraction technique with sample microfocusing and microradiography. Lyophilized bone with PG seems to accelerate the healing process, as shown by new vessel formation and deposition of newly formed bone, with no evidence of inflammatory cell infiltrate, when compared with lyophilized bone without gel. On the contrary, lyophilized bone undergo a resorption process, and a fibrous tissue often fills the spaces between chips. A histiocytic/giant-cell reaction is sometimes present. Otherwise, no differences have been found concerning microstructure. Our findings show the reliability of the methodology used to monitor early bone repair. The completion of the study and the evaluation of the ultimate clinical outcome are necessary in order to verify PG in vivo effects in orthopedic surgery.

Histological study on sinus lift grafting by Fisiograft and Bio-Oss

The work aims to provide a histological investigation of Fisiograft, a PLA/PGA copolymer, used as filler for bone defects in humans. The study was performed on biopsies of sinus lifts where Bio-Oss and Fisiograft gel were applied as graft material. Bone regeneration was satisfactory in all sinus lifts, even when Fisiograft was applied alone. Due to remarkable osteoclast activity, Bio-Oss granules were cleared from the majority of biopsy cores. At histology, Fisiograft gel appeared as globes enveloped by fibroblasts, displaying an epithelial-like cell appearance. Due to its solubility in solvents, undegraded Fisiograft (recorded for 7 months or more) did not stain whereas degraded Fisiograft stained positive. The loose connective tissue, that surrounded Fisiograft and bone contained isolated mastocytes. Bone grew inside the loose connective and often reached the surface of Fisiograft by intervening cells. The results seem to indicate that Fisiograft may be considered both a polymer useful for fastening bone substitutes inside a defect and in addition a material capable of prompting bone regeneration, with or without the use of a bone substitute. In addition to space-former and space-maintainer functions, Fisiograft shows potential bone stimulation function, which may be labelled as osteopromotive capability.

In vitro and in vivo evaluation of differentially demineralized cancellous bone scaffolds combined with human bone marrow stromal cells for tissue engineering

Mineralized and partially or fully demineralized biomaterials derived from bovine bone matrix were evaluated for their ability to support human bone marrow stromal cell (BMSC) osteogenic differentiation in vitro and bone-forming capacity in vivo in order to assess their potential use in clinical tissue-engineering strategies. BMSCs were either seeded on bone-derived scaffolds and cocultured in direct cell-to-scaffold contact, allowing for the exposure of soluble and insoluble matrix-incorporated factors, or cocultured with the scaffold preparations in a transwell system, exposing them to soluble matrix-incorporated factors alone. Osteoblast-related markers, alkaline phosphatase (ALP) activity and bone sialoprotein (BSP) and osteopontin (OP) mRNA expression were evaluated in BMSCs following 14 days of cocultivation in both systems. The data demonstrate that BMSCs from some donors express significantly higher levels of all osteoblast-related markers following cocultivation in direct cell-to-scaffold contact with mineralized scaffolds in comparison to fully demineralized preparations, while BMSCs from other donors display no significant differences in response to various scaffold preparations. In contrast, BMSCs cocultured independently with soluble matrix-incorporated factors derived from each scaffold preparation displayed significantly lower levels of ALP activity and BSP mRNA expression in comparison to untreated controls, while no significant differences were observed in marker levels between cells cocultured similarly with different biomaterial preparations. In addition, BMSCs were seeded directly on mineralized and partially or fully demineralized biomaterials and implanted in subcutaneous sites of athymic mice for 8 weeks to evaluate their in vivo bone-forming capacity. The ex vivo incorporation of BMSCs into all bone-derived scaffold preparations substantially increased the mean extent and frequency of samples containing de novo bone formation over similar nonseeded controls, as determined by histological and histomorphometrical analysis. No statistically significant differences were observed in the extent or frequency of bone formation between various scaffold preparations seeded with BMSCs from different donors. These results demonstrate that the in vivo osteoinductivity of bone-derived scaffolds can be modulated by ex vivo incorporated BMSCs and the extent of scaffold demineralization plays a significant role in influencing in vitro osteogenic differentiation of BMSCs depending on the coculture system and BMSC donor.

Adsorption of recombinant human bone morphogenetic protein rhBMP-2m onto hydroxyapatite

Recombinant human mature bone morphogenetic protein 2 (rhBMP-2m) has been expressed to study its adsorption onto precipitated hydroxyapatite (HA). The influence on the adsorption process of different parameters such as pH and concentrations of calcium, phosphate or NaCl has been investigated. Although the adsorption proceeds rapidly at the initial stages, the maximum adsorbed amount is reached after four hours. The process is notably influenced by adding calcium or phosphate to the system but, while calcium ions increase the adsorption of rhBMP-2m onto HA, phosphate ions inhibit it. The influence of pH and NaCl concentration are notable but less important than those of calcium and phosphate. The adsorption data fit well to a Langmuir adsorption isotherm. The values of the isotherm parameters have been calculated and discussed, and an adsorption mechanism has been proposed.

Treatment of intrabony defects with bovine-derived xenograft alone and in combination with platelet-rich plasma: a randomized clinical trial

BACKGROUND

In the treatment of periodontal intrabony defects, the benefits of adding platelet-rich plasma (PRP) to a bone replacement grafting material have not been tested. The purpose of this study was to compare the clinical outcomes obtained by the combination of PRP and a bovine derived xenograft (BDX) to those obtained from the use of the bone replacement graft alone.

METHODS

Thirteen patients were enrolled in a randomized, split mouth, double-masked clinical trial. Bilateral defects were matched according to their intrasurgical measurements. Qualifying defects had loss of attachment of > or = 6 mm, a radiographically detectable defect of > or = 4 mm, at least two remaining osseous walls, and not primarily related to a furcation involvement. After the hygienic phase, at the baseline examination, probing depth (PD), clinical attachment level (CAL), and recession (REC) were measured. During open flap debridement, the defects were randomly assigned to receive either BDX mixed with PRP or BDX alone. Baseline osseous intrasurgical measurements were obtained. Post-surgical follow-up and maintenance were performed and PD, CAL, and REC were remeasured at 6 months. The mean baseline and 6-month PD, CAL, and REC of the deepest buccal and lingual measurements related to the defect for each group were computed. The change from baseline to 6 months for each parameter measured was calculated. Pre- and postoperative comparisons were made between treatment groups at 6 months.

RESULTS

Randomization of the defects resulted in comparable groups (P > or = 0.05). At 6 months, paired t test comparisons within groups showed statistically significant benefits with both treatment modalities (P < or = 0.05). The mean changes (delta) at 6 months for the test and the control groups at the deepest sites were: PD reduction: 3.54 and 2.53 mm; CAL gain: 3.15 and 2.31 mm; and REC: -0.38 and -0.23 mm, respectively. Paired t test comparisons yielded significant differences between treatments for PD and CAL (P < or = 0.05).

CONCLUSION

In this 6-month clinical trial, the addition of a high concentration of autologous platelets to a bovine derived xenograft to treat intrabony defects significantly improved their clinical periodontal response.

Bucco-Lingual Crestal Bone Changes After Immediate and Delayed Implant Placement

BACKGROUND

Implants placed immediately after tooth extraction offer several advantages, but many authors have reported problems in filling the residual gap between the implant and the socket walls. Barrier and grafting techniques have been tested and yield varying results, so it has been suggested that the timing of implant placement may be important for success. The aim of this study was to analyze bone healing and coronal bone remodeling around 35 implants, 20 placed immediately after tooth removal and 15 placed 6 to 8 weeks after extraction.

METHODS

All the implants were submerged and placed within the alveoli confines, leaving circumferential defects because the implants did not contact the bone at their coronal aspects; stabilization was achieved in the bone apically. After implant placement the mean distance from buccal bone to lingual bone was 10 mm (SD 1.522) for immediate implants and 8.86 mm (SD 2.356) for delayed implants. No membrane or filling materials were used. Primary flap closure was accomplished in all cases.

RESULTS

At second-stage surgery all peri-implant defects were filled, and the mean distance from buccal bone to lingual bone was 8.1 mm (SD 1.334) for immediate implants and 5.8 mm (SD 1.265) for delayed implants. This pattern of coronal bone remodeling, showing a narrowing of the bucco-lingual width, was clinically similar for the two groups, although it should be noted that the delayed implants exhibited smaller bucco-lingual bone width already at the first measurement: it can be speculated that early remodeling may start immediately after tooth extraction and continue, non-uniformly, even after delayed implant placement.

CONCLUSIONS

This study suggests that circumferential defects could heal clinically without any guided bone regeneration (GBR) in both experimental groups, and that the procedure was virtually free from complications in the postoperative period, probably because of the absence of barrier membranes and/or grafting materials. Histologically, peri-implant defects of over 1.5 mm heal by connective tissue apposition, rather than by direct bone-to-implant contact, but clinically this healing may be very successful. No histological analysis was carried out in the present study, but even the largest residual gaps were filled with hard tissue that could not be probed. Thus, such outcomes can be considered clinically successful. The different rate of bone remodeling around immediate or delayed implants could have implications for the preferred timing of implant placement in sites of high esthetic concern.

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.

Bone regeneration in rabbit sinus lifting associated with bovine BMP

Autogenous bone is considered the optimal grafting material for sinus lifting, although its harvesting causes great patient discomfort. Various approaches have been taken in order to obtain sinus lifting with preexisting tissue. However, because of the unsuitability of such tissue, additional materials have been required. Alternatively, biomaterials from humans or other animals are used. In this study, the efficacy of using morphogenetic bovine bone protein (BMPb) to augment the maxillary sinus floor was examined. Four grafting materials were employed: lyophilized bovine bone powder, absorbable collagen flakes, natural hydroxylapatite, and synthetic hydroxylapatite. Two groups of rabbits were studied. In one group, graft material only was used. In the other, graft material was combined with 0.5 mg BMPb. During 8 weeks of observation, polyfluorochrome tracers were injected in subcutaneous tissue to evaluate new bone- deposition periods. Following sacrifice, the samples were examined under fluorescent and light microscopes. Results indicated 33.34% more newly formed bone in BMPb animals than in controls. Graft-material resorption increased, but natural HA showed no significant alterations. The results show that the use of BMPb, although providing osteoinduction, might not promote sufficient bone formation. Nonetheless, this material could provide an alternative to autogenous grafts, thereby avoiding patient discomfort.

Growth and proliferation of human osteoblasts on different bone graft substitutes: an in vitro study

The purpose of this study was to investigate the effect of different bone graft substitutes onto the growth and proliferation pattern of bone cells derived from human iliac cancellous bone. Five different bone graft materials were used to investigate the effect on the proliferation of osteoblasts in vitro: phytogene hydroxyapatite (Algipore), alpha-Tricalcium phosphate (Bio-Base), bovine hydroxyapatite (low temperature) (Bio-Oss), bovine hydroxyapatite (high temperature) (Osteograf), and bovine hydroxyapatite (high temperature) enhanced with p-15, synthetic peptide (PepGen p-15). The osteoblasts were derived from human iliac cancellous bone and seeded with the different bone substitutes. The cell proliferation and viability (WST-1), alkaline phosphatase as an early marker of osteoblast proliferation, was evaluated after 6 and 9 days. The cultures were examined for cell growth pattern and morphology by normal light and scanning electron microscopy. The human osteoblasts showed a different proliferation pattern according to the type of applied bone graft substitute. PepGen P-15 showed the highest proliferation and differentiation rate followed by Osteograf, Algipore, and Bio-base. Bio-Oss showed the lowest. These results were confirmed by electron microscopy and light microscopy evaluation in which similar growth pattern were observed. Distinct bone graft materials have different impact onto the proliferation pattern of human osteoblasts in vitro.

A histological evaluation of the involvement of Bio-OssR in osteoblastic differentiation and matrix synthesis

This study was designed to investigate the responses of bone cells to a deproteinized bovine bone material, Bio-Oss (Geistlich-Pharma, Wolhunsen, Switzerland), which was grafted in artificial bone defects of rat femurs. Standardized bone defects in the cortical bone of the right femurs were grafted with Bio-Oss particles. Narrow penetrations were prepared on the bottom of the cavity, enabling osteogenic cells to migrate from the bone marrow. A defect in the left femur without Bio-Oss was used as a control. The treated femurs were histochemically examined at 1, 3, 5, 7, and 14 days after the operation. At day 1, no osteogenic migration into the cavities occurred in either the control or experimental groups. At day 3, alkaline phosphatase (ALPase) immunohistochemistry showed a migration of the positive cells at the bottom of the cavities of the experimental groups, but not in the control ones. At day 5, new bone formation was recognized at the bottom of the cavity of both groups. In the experimental group, ALPase-positive cells were localized on Bio-Oss and/or on the thin bone matrix that covered this material. The superficial layer of Bio-Oss underlying the newly formed bone exhibited osteocalcin immunoreactivity. Transmission electron microscopy revealed osteoblasts depositing bone matrices--including collagen fibers--on the surface of Bio-Oss. At days 7 and 14, woven bone occupied the previous cavities of both control and experimental groups, accompanied by osteoclasts. Thus, Bio-Oss appears to serve as a scaffold for osteogenic cells as well as to promote osteoblastic differentiation and matrix synthesis.