[Features peculiar to bone regeneration of postoperative defects of the mandible in the roentgenographic image].
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Critical-sized defects (CSDs) were prepared in 60 rabbit skulls, divided evenly among five treatments and two time periods. The treatments consisted of rabbit demineralized bone matrix (DBM) and four different doses of transforming growth factor-beta 1 (TGF-beta 1) (0, 0.4, 4, and 40 micrograms) delivered in 3% carboxymethyl cellulose and Gelfilm. Quantitative assessments of bone formation in the CSDs were accomplished with computerized radiomorphometry and histomorphometry. Results indicated that rabbit DBM and 40 micrograms TGF-beta 1 promoted more new bone formation at 4 weeks than the other treatments. By 8 weeks, bone formation in the CSDs was equivalent for all but the 0-microgram dose of TGF-beta 1. The results from the study suggest a single therapeutic dose of TGF-beta 1 delivered in an appropriate carrier to a critical-sized intraosseous wound should promote bone formation.
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The aim of this study was to investigate the long-term effect of the ceramic beta-tricalcium phosphate (beta-TCP) at different sites of alveolar reconstruction and to evaluate its properties. From 1997 to 2002, beta-TCP was implanted as bone substitute in 152 patients using a standardized study protocol. Main indications were the filling of large mandibular cysts (n=52), secondary and tertiary alveolar cleft grafting (n=38), periodontal defects (n=24) and maxillary sinus floor augmentation (n=16). For defects exceeding 2cm in diameter, beta-TCP was combined with autologous bone taken from the retromolar area, the maxillary tuberosity or the chin region. A radiological, clinical and ultrasonographical examination was carried out 4, 12 and 52 weeks postoperative. In 16 cases, biopsies were taken after 12 months indicating complete bony regeneration. While wound-healing disturbances occurred in 9.2% of cases, partial loss of the bone substitute material was found in 5.9%, while total loss occurred in only 2%. Complete radiological replacement of beta-TCP by autologous bone was found after approximately 12 months, indicating its osteoconductive properties. Because of its versatility, low complication rate and good long-term results, synthetic, pure-phase beta-TCP is a suitable material for the filling of bone defects in the alveolar region.
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The aim of this study was to prevent wear debris from reaching the interface of the acetabular cup and femoral component by using a partially occlusive expanded polytetrafluoroethylene membrane. This membrane initially acted as a physical seal, which became incorporated by bone and soft tissue, forming a secondary biologic seal, preventing loosening. An animal model was developed to test the hypothesis. The model replicated the mechanisms of loosening where the effects of wear debris were studied. Using femoral heads with the appropriate roughness, a goat model produced the radiologic and histologic presentation of loosening as observed in total hip replacements in humans. Loosening was assessed by measurement of the radiolucent lines, and was attributed to wear debris by histologic investigation. The expanded polytetrafluoroethylene membrane prevented acetabular implant loosening to a statistical significance of 0.02 in a blinded assessment when compared with the control groups. Loosening of the first 5 mm of the proximomedial aspect of the femur also was prevented. The authors of the current study prevented wear particle-induced osteolysis in the acetabular component by using an expanded polytetrafluoroethylene membrane to seal the bone-cement interface.
The aim of these studies was to see if a combination of osteopromotive membranes of expanded polytetrafluoroethylene (e-PTFE; GORE-TEX) and BMP, known to separately promote bone healing, would be stimulatory if combined. Bilateral transosseous 'critical size' defects at the mandibular angles in adult male rats were treated with either (i) various BMP preparations only; ii) lateral and medial coverage with e-PTFE membranes only; iii) a combination of various BMPs and membranes; or iv) left untreated. Two semi-purified bovine BMPs (bBMP), comprising collagen as carrier material, and recombinant human (rh) BMP-2 (1, 2 or 8 micrograms), delivered in either biodegradable beads of polylactide/polyglycolide acid (PLA/PGA) or purified collagen, were tested. After 12 or 24 days, block biopsies were taken for histological analysis. The different materials were well tolerated by the hosts and elicited large amounts of newly formed bone widely spread in the surrounding soft tissue. The combinations of bBMP and membranes did not improve the rate of bone healing compared to membranes only. In contrast, the combination of rhBMP-2 in PLA/PGA with membranes was more efficacious than membrane placement only and resulted in bone bridging at 24 days, with a bone contour resembling the original anatomy. The combination of membrane placement with rhBMP-2 may be of value in the clinic for bone regenerative purposes. The results are also of general importance for choosing carrier materials for delivery of other growth-stimulatory substances in combination with membranes.
Reparative callus formation upon tubular bone was studied after surgical injuries of different degrees. Thirty-seven young rats were divided into three groups. In the periosteum group the bone was scraped, in the fissure group we made a slit reaching the medulla, and in the defect group a standard defect was sawn. Rats were killed at 6, 12 and 18 days. The formed callus was studied histologically and histomorphometrically. The results suggest than even the primary osteochondrogenic callus formation is dependent on the mode of injury. At six days the three groups differed both qualitatively and quantitatively in regard to callus formation. At 12 and 18 days the total area of woven bone was proportional to the degree of trauma according to the linear regression line Y = 0.883 x X + 0.226 (r = 0.876, P less than 0.001). In the fissure and defect groups reparative bone filled the hole proportionally to the same extent. Periosteal and endosteal woven bone formed round the bone. Medullary bone formation was limited mainly to the area immediately adjacent to the trauma, the result being a cylinder-shaped callus. Cartilage formation was most abundant at six days and was related to the amount of woven bone in the external callus (r = 0.854, P less than 0.001) and to the trauma area (r = 0.707, P less than 0.05).
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In bony defects of the cranium, bone healing may be complicated by prolapse of surrounding tissue into the defect. This tissue acts as an impediment to prevent the migration of osteogenic cells, leading to impaired bone formation. It has been previously shown that a membrane placed over the bony defect inhibits the connective tissue cells from entering the wound and theoretically improves bone formation. The use of a proven resorbable material, Lactosorb, is used in this animal model and has shown a significant increase in autogenous bony formation. The majority of previous work was accomplished with nonresorbable material that resulted in foreign body formation. This paper is unique because resorbable material in the animal model is relatively inexpensive and easy to use and has allowed successful autogenous bony regeneration.
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