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[Morphologic analysis of guinea pig bone regeneration following curettage].

Interrelation of stromal and hemopoietic elements in the regenerative process of the guinea-pig bone marrow at different time after curettage has been morphologically studied. The bone marrow regenerative process in the depleted medullary cavity of the guinea-pig tibial bone passes through several phases following each other: blood clot formation, rough-fibrillary osseous tissue formation, its resorption, development of sinusoids and formation of reticular stroma with subsequent repopulation of hemopoietic elements in it. The leading role in the process of the bone marrow restoration belongs to the reticular stroma creating specific microconditions for hemopoiesis.

Animals↗

Association of porous hydroxyapatite and bone marrow cells for bone regeneration.

The preparation of hybrid material with osteoinductive capacity may be achieved by association of cultured autologous bone cells with a porous ceramic vehicle. We optimized culture conditions for rabbit marrow stromal stem cells (MSCs), notably by selection from batches of fetal calf serum. Rabbit MSCs formed colony-forming unit-ribroblastic (CFU-Fs) in vitro. Their alkaline phosphatase (ALP) activity was doubled in the presence of dexamethasone. Autologous rabbit serum allowed the formation of ALP-positive CFU-Fs, but results were highly variable depending on the rabbit. We tested the osteogenic potential of autologous cultured (with or without dexamethasone addition in the culture medium) and noncultured rabbit MSCs associated with a porous hydroxyapatite ceramic after a dorsal intramuscular implantation. Nucleated cells (10(7) or 10(8)/mL) were used for the preparation of autologous hybrid material. A significantly higher number of implants containing bone was obtained with a suspension of 10(7) cells/mL cultured in the presence of 10(-8) M dexamethasone. Some positive implants were also obtained with a suspension of 10(8) noncultured cells/mL. We demonstrated the feasibility of preparing rabbit autologous hybrid materials following a process for controlling culture conditions, cell characterization and cell/material association.

Alkaline Phosphatase↗

Immunological phenotype of lymphoid cells in regenerating bone marrow of children after treatment for acute lymphoblastic leukemia.

Bone marrow samples from 8 children treated for acute lymphoblastic leukemia (ALL) were investigated at cessation of cytostatic treatment and during 18 months thereafter. The course of the percentage of lymphoid cells and characterization of these cells by means of monoclonal antibodies, peanut agglutinin (PNA) binding and S-phase determination are shown. The percentage of lymphocytes rises in the first 1.5 months, followed by a non-significant decline. The percentage of cells in S-phase is higher at 0 months than at 6, 15 and 18 months. The percentage of T-cells does not change significantly. In the first 1.5 months a sudden rise in the percentage of common-ALL-antigen (cALLA)-positive lymphocytes occurs. The number of B-cells rises to a peak at 6 months. PNA positively increases to a maximum at 3 months and is correlated with positivity for markers of the B-cell lineage. The percentages of B-cells, cALLA-positive, and PNA-positive lymphocytes do not change significantly after they reach their maximum values and are still high at 18 months. Our results show that after cessation of chemotherapy for ALL a lymphoid cell regeneration occurs in the bone marrow consisting of cells of the B-cell lineage; many of these are cALLA-positive, but are discernible from their malignant counterparts by PNA-positivity.

Antibodies, Monoclonal↗

Regeneration of bone graft donor sites.

When crestal volume is greatly insufficient for the placement of dental implants, bone grafting is usually the most reliable ridge augmentation procedure. The grafts are most often taken in parietal or mandibular symphysis regions. Though not too noticeable, it seems contra-indicated and even potentially dangerous to leave zones like the cranium to repair spontaneously. Guided bone regeneration techniques have shown their ability to regenerate new bone under difficult conditions in jaws. Their use in bone graft donor sites is simple and the results are consistent. This report shows that 2 types of resorbable membranes are equally as efficacious in terms of new-bone formation.

Adult↗

Histologic and ultrastructural analysis of regenerated bone in maxillary sinus augmentation using a porcine bone-derived biomaterial.

BACKGROUND: The purpose of the present study was the histologic and ultrastructural evaluation of a biomaterial composed of cortical pig bone in the form of granules. METHODS: After maxillary sinus augmentation using this biomaterial, 10 specimens were retrieved after 5 months in 10 patients using this biomaterial. The specimens were processed to be observed under light microscopy (LM) and transmission electron microscopy (TEM). Histomorphometric measurements were presented by means +/- standard deviations. RESULTS: LM showed that most of the particles were surrounded by newly formed bone. In some areas, the osteoid matrix was present; however, mainly compact bone was present at the interface. There was no evidence of an acute inflammatory infiltrate. The newly formed bone was 36% +/- 2.8% and marrow spaces were 38% +/- 1.6%, whereas residual grafted material was 31% +/- 1.6%. Under TEM, all phases of bone formation (osteoid matrix, woven, and lamellar bone) were observed in proximity with the biomaterial particles. The bone-biomaterial interface showed a close contact between the porcine bone particles and the surrounding bone that had mainly features of mature bone with numerous osteocytes. A lamina limitans was sometimes present at this interface. CONCLUSIONS: According to our knowledge, this is the first study presenting data on TEM of a porcine bone-derived biomaterial used in sinus augmentation procedures in humans. Our findings show that this is a biocompatible biomaterial that can be used for maxillary sinus augmentation procedures without interfering with the normal reparative bone processes.

Absorbable Implants↗

Encapsulation of apatite particles for improvement in bone regeneration.

The layering of fluorapatite on hydroxyapatite bodies provides a means of decreasing the solubility of hydroxyapatite, providing fluoride for possible stimulation of bone formation and delaying the release of calcium and phosphate from the more soluble hydroxyapatite. The purpose of this work was to encapsulate hydroxyapatite particles with fluorapatite spanning a thickness more than several crystallites deep. A three-step procedure was employed. Hydroxyapatite powder was immersed in an electrolyte solution until an equilibrium was established between the solid and the dissolved calcium at pH 4.67 and 37 degrees C. Equilibrium was determined by measurement of dissolved calcium with a calcium-specific ion-specific electrode. A 5x10(-2) M ammonium fluoride added to the suspension resulted in a rapid decrease of both calcium and fluoride in the solution. Analysis with X-ray diffraction indicated that a fluoride rich layer containing calcium fluoride deposited onto the particle surface. Scanning electron microscopy revealed submicron spherical precipitate clusters on the hydroxyapatite particles. These clusters transformed to fluorapatite by soaking in a 0.1 M K(2)HPO(4) solution at pH 8 and 70 degrees C. A total time of 10 h was necessary for complete transformation of CaF(2) into fluorapatite.

Journal Article↗

Horizontal ridge augmentation using autogenous block grafts and the guided bone regeneration technique with collagen membranes: a clinical study with 42 patients.

OBJECTIVE: To analyze the clinical outcome of horizontal ridge augmentation using autogenous block grafts covered with an organic bovine bone mineral (ABBM) and a bioabsorbable collagen membrane. MATERIAL AND METHODS: In 42 patients with severe horizontal bone atrophy, a staged approach was chosen for implant placement following horizontal ridge augmentation. A block graft was harvested from the symphysis or retromolar area, and secured to the recipient site with fixation screws. The width of the ridge was measured before and after horizontal ridge augmentation. The block graft was subsequently covered with ABBM and a collagen membrane. Following a tension-free primary wound closure and a mean healing period of 5.8 months, the sites were re-entered, and the crest width was re-assessed prior to implant placement. RESULTS: Fifty-eight sites were augmented, including 41 sites located in the anterior maxilla. The mean initial crest width measured 3.06 mm. At re-entry, the mean width of the ridge was 7.66 mm, with a calculated mean gain of horizontal bone thickness of 4.6 mm (range 2-7 mm). Only minor surface resorption of 0.36 mm was observed from augmentation to re-entry. CONCLUSIONS: The presented technique of ridge augmentation using autogenous block grafts with ABBM filler and collagen membrane coverage demonstrated successful horizontal ridge augmentation with high predictability. The surgical method has been further simplified by using a resorbable membrane. The hydrophilic membrane was easy to apply, and did not cause wound infection in the rare instance of membrane exposure.

Adolescent↗

Regenerate bone formation and remodeling during mandibular osteodistraction.

The purpose of this study was to evaluate the newly formed bone during the consolidation period of mandibular osteodistraction using quantitative histology. Seventeen skeletally mature conditioned male beagle dogs underwent 10 mm of bilateral mandibular lengthening. After distraction, the regenerates were allowed to consolidate for 0, 2, 4, 6, or 8 weeks, at which time the animals were sacrificed and tissues harvested for standard histologic and histomorphometric analyses. Mineralization began at the host bone margins by the end of the distraction period, followed by a progressive increase in trabecular bone, with a concomitant decrease in the amount of fibrous tissue. Between 4 to 6 weeks of consolidation, 3 types of relatively mature distraction regenerates were evident. The mineral apposition rate gradually increased from the end of distraction to the fourth week of consolidation, at which time it remained constant until sometime before the eighth week, when it tapered off slightly as remodeling increased.

Animals↗