Freeze-dried demineralized bone in dental implant reconstruction

Rebuilding deficient alveolar bone to assist in reconstruction for dental implants is a frequent task for the oral and maxillofacial surgeon. Freeze-dried demineralized bone is being used with increasing frequency. It is a reliable, safe and inexpensive bone source and has very few limitations. Freeze-dried demineralized bone processing is reviewed and its safety is emphasized to aid the general practitioner in discussing the concepts with prospective patients. Cases are presented showing the most frequent uses of the material.     

Effect of allogeneic, freeze-dried, demineralized bone matrix on guided bone regeneration in supra-alveolar peri-implant defects in dogs

This randomized, split-mouth design study evaluated the adjunctive effect of allogeneic, freeze-dried, demineralized bone matrix on guided bone regeneration in a critical-size, supra-alveolar, peri-implant defect model. Contralateral supra-alveolar peri-implant defects, 5 mm in height, each including two titanium implants, were surgically created in five beagle dogs. Demineralized bone matrix in autologous blood was placed over the implants in one randomly selected mandibular jaw quadrant. A space-making expanded-polytetrafluoroethylene membrane was used to provide guided bone regeneration bilaterally. Following a 16-week healing interval, tissue blocks were harvested and prepared for histometric analysis. Differences between experimental conditions (guided bone regeneration sites with and without demineralized bone) were evaluated using paired t tests (n = 4). Demineralized bone particles were discernible, with limited signs of resorption. The bone matrix particles appeared to be solidified within a dense connective tissue matrix and in close contact with the implants. Limited matrix remineralization was apparent adjacent to the alveolar crest. No statistically significant differences were found between experimental conditions for any parameter examined. Peri-implant defect height averaged 5.0 +/- 0.2 mm and 4.9 +/- 0.4 mm, vertical bone regeneration 1.5 +/- 0.9 mm and 1.1 +/- 0.4 mm, osseointegration within the extent of the defect 10.0 +/- 3.9% and 15.3 +/- 5.3%, osseointegration within the extent of regenerated bone 30.4 +/- 13.7% and 52.1 +/- 17.9%, and osseointegration within the alveolar base 68.8 +/- 13.1% and 74.4 +/- 7.1% for guided bone sites with and without demineralized bone, respectively (P > .05). The results suggest that freeze-dried demineralized bone has no adjunctive effect on guided bone regeneration in supra-alveolar peri-implant defects, that guided bone regeneration has a limited potential to enhance alveolar regeneration in this defect model, and that a 16-week healing interval appears insufficient for turnover and maturation of demineralized bone under provisions for guided bone regeneration.     

Mandibular reconstruction using a microvascular method in the transplantation of a fibular flap

The best results in mandibular reconstruction are achieved by transplantation of vascularised bone. This transplant has an own blood supply therefore its surviving is not influenced by the non-sterile environment of the oral cavity and the insufficient blood supply of the operated area (caused by scar or radiation). A new promising method for reconstruction of a wide segmented defect of the mandible is vascularised fibular flap transplantation. Eight consecutive patients treated with fibular flap transplantation in 1993 and 1994 were reviewed. Osteo- and osteo-cutan flaps were used for reconstruction of the composite tissue defects. The authors report on the surgical technique and their first experiences. The authors consider the application of the fibular flap the most successful procedure of all types of reconstruction of segmented mandibular defect.     

Comparison of demineralized allogeneic bone matrix grafting (the Urist procedure) and the Ilizarov procedure in large diaphyseal defects in sheep

The bone inductive capability of the Urist and Ilizarov procedures was compared in the repair of large diaphyseal defects in sheep. In 30 animals, a 4 cm segmental defect was created in the middle portion of the right femur and was stabilized with an external fixator. The sheep were divided into four groups according to the type of reconstruction of the defect. In group 1, a demineralized allogeneic bone matrix (DABM) cylinder was used; in group 2, DABM chips; and in group 3, gradual transport of a piece of bone detached from the proximal femoral fragment was used to fill the defect. Group 4 served as a control (the defect was left empty). New bone formation was assessed by serial radiographs until the time of death at 2 or 4 months. Postmortem specimens were analyzed with respect to bone mineral content, uptake of isotopes (45Ca and 3H-proline), and histology. The first signs of new bone formation were radiographically evident at 4 weeks. In the two groups in which reconstruction involved DABM (Urist procedures), new bone failed to form in eight of the 13 animals. Full bridging of the defect was observed at 8 weeks in one animal with a DABM cylinder and two with DABM chips. No decisive difference in bone yield could be demonstrated between the two Urist procedures. In the group treated with the Ilizarov procedure, new bone formation consistently occurred at a high rate; full bridging of the defect was observed in seven of the eight animals. Bone mineral scanning and histologic analysis essentially confirmed the radiographic results. Uptake of isotopes was selectively analyzed in two sheep from each experimental group in which new bone formation was exhibited in the defect; new bone formation was increased compared with that in the contralateral femur but was equal among the three experimental groups. Our study shows that gradual transport of a detached piece of autogeneic bone (Ilizarov procedure) is more effective than implantation of DABM (Urist procedure) in eliciting new bone formation in large diaphyseal defects in sheep. The variable bone induction by DABM may be explained by differences in host immune responses to the implants.     

Regeneration of diaphyseal bone defects using resorbable poly(L/DL-lactide) and poly(D-lactide) membranes in the Yucatan pig model

OBJECTIVES: To determine the effects of tubular resorbable polymer membranes on the healing of a segmental diaphyseal bone defect. DESIGN: A randomized prospective study using the minipig model. Animals were evaluated with in vivo roentgenograms on a biweekly basis until explanted at twelve weeks. SETTING: After surgery, animals were allowed unrestricted activity and weight bearing between twenty-four and forty-eight hours. ANIMALS: Fifteen yearling Yucatan minipigs. INTERVENTION: A 2.5- to 3.0-centimeter mid-diaphyseal defect was created in the middle third of the radius. Animals were assigned in groups of three to receive the following implants: (a) poly(L/DL-lactide), (b) poly(L/DL-lactide)-CaCO3, (c) poly(D-lactide), (d) poly(D-lactide)-CaCO3, and (e) an untreated defect. No adjunctive internal or external fixation was used as the ulna was left intact. MAIN OUTCOME MEASURES: The limbs were studied with in vivo anterior-posterior and lateral radiographs at biweekly intervals for the presence and pattern of bone formation. All limbs were explanted at twelve weeks postimplantation for methyl-methacrylate embedding and histologic and microradiographic study. RESULTS: The bone defects covered with membranes were completely reconstituted by six to eight weeks. Untreated defects healed with less bone formation and in a more disorganized pattern. Histologic evaluation of the implants demonstrated that the entire lumen of the implant was filled with bone, with some periosteal bone formation occurring on the outer surface of the membrane. There was direct apposition of bone onto the membrane surface or minimal fibrous tissue interposition between membrane and new bone. There was no foreign body or adverse reaction to the membrane. Untreated defects showed woven bone formation with clefts and irregularly shaped margins occupied by fibrous tissues or surrounding muscle tissues. CONCLUSIONS: This study supports the concept that a membrane enhances bone defect healing by excluding nonosseous tissues from a defect and providing structural scaffolding for periosteal and endosteal bone regeneration.     

Repair of bone defect of distal end of radius and its functional restoration

The treatment of the bone defect of the distal part of the radius included repair of the bone defect and restoration of the function of the wrist joint. Since 1979, three operative methods were used to treat 13 cases, and they were grafting of the vascularized fibula by anastomrsis fibular vessels, grafting of upper part of fibular with lateral inferior genicular artery and grafting vascularized scapula flap. Follow-up had been carried out from 1 to 10 years. The result was satisfactory. The discussion included the repair of the defect of the middle or distal part of the radius, the operative methods, main attentions and indications. It was considered that it should be based on the length of bone defect while the operative method was considered.     

Evaluation of bovine-derived bone protein with a natural coral carrier as a bone-graft substitute in a canine segmental defect model

The efficacy of a bone-graft substitute (bovine-derived bone protein in a carrier of natural coral) in the healing of a segmental defect of a weight-bearing long bone was evaluated. Twenty dogs, divided into two groups, underwent bilateral radial osteotomies with creation of a 2.5 cm defect. On one side of each dog, the defect was filled with autogenous cancellous bone graft. Contralateral defects received, in a blinded randomized fashion, cylindrical implants consisting of natural coral (calcium carbonate) or calcium carbonate enhanced with a standard dose of bovine-derived bone protein (3.0 mg/implant; 0.68 mg bone protein/cm3). The limbs were stabilized with external fixators, and all animals underwent monthly radiographs. They were killed at 12 (group 1) or 24 (group 2) weeks, and regenerated bone was studied by biomechanical testing and histology. Radiographic union developed in all 20 radii with autogenous cancellous bone grafts and in all 10 of the radii with the composite implants. None of the radii with implants of calcium carbonate alone showed radiographic evidence of union. This represented a statistically significant difference between implant types. In addition, calcium carbonate implants both with and without bone protein demonstrated radiographic evidence of near total resorption of the radiodense carrier by 12 weeks. This resorption facilitated radiographic evaluation of healing. Mean values for biomechanical parameters of radii with the composite implants exceeded those for the contralateral controls at 12 and 24 weeks; the difference was statistically significant at 12 weeks. Histology revealed scant residual calcium carbonate carrier at either time in the defects with calcium carbonate implants; however, a moderate amount was present in defects with the composite implants. In these specimens, the residual carrier was completely surrounded by newly formed bone that may have insulated the calcium carbonate from further degradation. The present study used a carrier of granular calcium carbonate reconstituted with bovine type-I collagen to deliver an osteoinductive protein to the defect site. This carrier is of nonhuman origin (eliminating the risk of disease transmission or antigenicity) and resorbs rapidly. In this model, bovine-derived bone protein in a natural coral carrier performed consistently better than the gold standard autogenous cancellous bone graft in terms of the amount of bone formation and strength of the healed defect. This may have implications for removal of hardware or resumption of weight-bearing in certain clinical situations. These data also indicate that coralline calcium carbonate alone represents a poor option as a bone-graft substitute in this critical-sized segmental defect model.     

Temperature-responsive size-exclusion chromatography using poly(N-isopropylacrylamide) grafted silica

This article reviews studies presented during the last 20 years on the surgical treatment of intrabony defects. Treatments include open flap debridement alone (OFD); OFD plus demineralized freeze-dried bone allograft (DFDBA), freeze-dried bone allografts (FDBA), or autogenous bone; and guided tissue regeneration (GTR). The review includes only studies that presented baseline and final data on probing depths, intrabony defect depths as measured during surgery, clinical attachment level (CAL) gain, and/or bone fill. Some reports were case studies and some controlled studies comparing different treatments. In order to assess what can be accomplished in terms of pocket reduction, clinical attachment level gain, and bone fill with the various treatment modalities, data from studies of each treatment category were pooled for meta-analysis in which the data from and power of each study were weighted according to the number of defects treated. In addition, where there were data for each individual defect treated, these were used for simple regression analysis evaluating the influence of intrabony defect depth on treatment outcome in terms of CAL gain and bone fill. This was done in an effort to assess some predictability of the outcome of the various treatments. OFD alone resulted in limited pocket reduction, CAL gain averaged 1.5 mm and bone fill 1.1 mm. Bone fill, but not CAL gain, correlated significantly to the depth of the defect (R=0.3; P < 0.001), but the regression coefficient was only 0.25. OFD plus bone graft resulted in limited pocket reduction. CAL gain and bone fill averaged 2.1 mm. Bone fill showed a somewhat stronger correlation to defect depth than following OFD alone (R=0.43; P < 0.001) with a regression coefficient of 0.37. GTR resulted in significant pocket reduction, CAL gain of 4.2 mm, and bone fill averaging 3.2 mm. CAL gain and bone fill correlated significantly (P < 0.001) to defect depth (R=0.52 and 0.53 respectively) with the largest regression coefficients (0.54 and 0.58 respectively) among the three treatment modalities. By comparing outcomes following the various treatments it became obvious that to benefit from GTR procedures, the intrabony defect has to be at least 4 mm deep.     

Experimental cranioplasty and skeletal augmentation using an alpha-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide cement: a preliminary short-term experiment in rabbits

Calcium phosphate cement consisting of alpha-tricalcium phosphate (alpha-TCP), dicalcium phosphate dibasic (DCPD) and tetracalcium phosphate monoxide (TeCP) was implanted into surgically created full-thickness defects in the cranial bone (bone defect experiment) and directly onto the cranial bone under the periosteum (augmentation experiment). Three months after the implantation, the implants were retrieved with the surrounding tissues and studied histologically and micrographically to evaluate if the cement can be used as a cranioplasty and skeletal augmentation material. In the bone defect experiment, successful reconstruction of the defect was seen in 8 out of 12 specimens. Four specimens, where bleeding control was difficult at the time of implantation, showed partial loss of the cement. Histological and microradiographic studies of the successfully implanted cement revealed that new bone surrounded the implant nearly completely and united directly with the cement surface. In the augmentation experiment, the augmented area maintained the hemispherical shape and was connected tightly with the host bone. Histology and microradiography demonstrated that new bone formation was seen in the gap between the cement and the host bone, and on the outer surface (periosteum side) of the cement at the edge of the implant. From this preliminary short-term study, it could be concluded that the cement is a promising material for cranioplasty and skeletal augmentation with indications that it has good osteoconductivity.     

An experiment study of the guided bone regeneration

BMP is one of important factors in the pathophysiology of bone regeneration. Fifteen New Zealand rabbits were used in this experiment. We studied the distribution and effectiveness of endogenic BMP on a 10 mm bone defect of radius, by utilizing immunohistochemistry of BMP and quantitative computer imaging system. On the 3rd day, death of osteocytes and BMP positive blood clot were observed. The mesenchymal cells from periosteum and endoosteum, and osteoblast were also BMP positive. By quantitative study, we found there was a gradient distribution of BMP in bone defect, i.e, the value of BMP decreased gradually along the distance from the fracture ends. The maximal value of BMP was noted at the 1st week postoperation. In conclusion, two sources of endogenic BMP were found, one was from the absorption of necrotic tissue of fracture ends, the other was from the secretion of osteogenic mesenchymal cells during the process of bone regeneration. Nonunion of bone defect was caused in part by the gradient distribution of BMP. Accordingly, the concept of effective quantity of endogenic BMP was drawn rosen. It might be a new method in the treatment of bone defect by increasing the concentration of endogenic BMP and improving its distribution.     

Giant neurofibroma of the occipital scalp associated with lambda defect-case report (author's transl)

Calvarial bone defect associated with a hugh neurofibroma in the region of the lambdoid suture was reported in a 42-year-old man with v. Recklinghausen's neurofibromatosis. An enlarging occipital tumor was first noted at age 4 similar to or approximately 5, and an operation was performed at age 12. Lambda defect was noted at that time, but the operative diagnosis was, apparently, "meningocele". Available literature was reviewed, and the significance of calvarial bone defect in the region of the lambdoid suture as a manifestation of v. Recklinghausen's disease was stressed. Lambda defect witn no sclerosing margin, particularly if associated with hypoplasia of the ipsilateral mastoid cells, has been known to represent the primary nature of the bone defect due to mesodermal dysplasia. In the present case, plain radiographs of the skull revealed abnormal sclerotic change around the bone defect. It is suggested that such an osteoblastic change may well indicate the secondary nature of the bone defect due to the presence of overlying neurogenic tumor.     

Differential giant cell epulis diagnosis--malignant melanoma of the mouth mucosa]

Between 1990 and 1996, 16 cases of bone defects were treated by vascularised bone grafting by the authors. Free vascularised fibula was used in 10 cases and one free iliac crest graft was used for upper extremity bone defects. Four vascular pedicled first metacarpal bone and one radial styloid bone were used for scaphoid nonunion. Average follow-up was 26 months (6-78 months) and success rate was 94%. We recommend vascularised bone grafts in the upper extremity when there is risk of infection; the defect is greater than five centimeters when the forearm rotation is unlimited. The avascularity of the scaphoid pseudarthrosis must be verified radiologically or through magnetic resonance imaging. This technique should only be used when other reconstructive techniques are unlikely to succeed.     

Human herpesvirus-6 and human herpesvirus-7 infections in bone marrow transplant recipients

Tricalcium phosphate (TCP) was combined with amylopectin to form a deliverable carrier paste for recombinant human transforming growth factor beta 1 (rhTGF-beta 1) intended for bone repair applications. Approximately 80% of rhTGF-beta 1 was released from the carrier within 24 h following in vitro incubation in serum. Full biological activity was maintained, suggesting the growth factor was stable in this formulation before and after in vitro release. In vivo efficacy also was assessed, in comparison to a sham control group and a placebo-treated group, using a rabbit unilateral segmental defect model (1 cm). Radiographs of defect sites taken at scheduled intervals and the mechanical testing of treated limbs at 56 days demonstrated a higher incidence of radiographic bone union, in concert with a stronger torque strength, in the rhTGF-beta 1-treated group compared to the placebo group. The short duration of the study and the fact that the model used was not a critical defect may account for the lack of superiority of the rhTGF-beta 1-treated group over the healing of the sham control. The in vivo pharmacokinetics of the growth factor evaluated in the same rabbit model suggested that rhTGF-beta 1 persisted intact at the defect site for more than 21 days. Gamma imaging and radioactivity recovery at defects administered to [131I]- and [125I]-labeled rhTGF-beta 1, respectively, estimated the half-life of rhTGF-beta 1 eliminated from the applied site to be 4-6 days. The present report substantiates the potential of rhTGF-beta 1 and its carrier for treatment of bone defects.     

Anatomic reconstruction of the posterolateral cranial base with titanium micromesh for combined transpetrosal approach: technical note

OBJECTIVE: We describe a new technique for the anatomic closure of the posterior petrosectomy defect after the combined supra-infratentorial transpetrosal approach for petroclival lesions. METHODS: With this technique, a titanium micromesh, tailored according to the defect of the drilled petrous bone and contoured to the outer appearance of the posterolateral cranial base, is used to cover the petrosectomy area. The mesh is fixed to the cranium and to the repositioned bone flap with titanium microscrews. RESULTS AND CONCLUSION: To date, this technique has proven to be simple and rapid and has been used in 10 patients who were operated on for various tumorous and vascular lesions of the petroclival region. Excellent cosmetic results were achieved, and no technique-related complications occurred.     

Iatrogenic arachnoid cyst with distinct clinical picture as a result of bone defect in the floor of the middle cranial fossa: case report

OBJECTIVE AND IMPORTANCE: This kind of arachnoid cyst has not previously been described as a complication of a cranial base bone defect. Recognition of this rare complication may be delayed, because clinicians are unaware of its possibility. CLINICAL PRESENTATION: A 22-year-old man presented with severe headache and increasing difficulty in breathing and swallowing. A physical examination revealed a pulsatile mass in the oral cavity, arising from the parapharyngeal area. A cystic mass that protruded into the oral cavity, through a dural and bony defect in the left middle fossa, was detected on neuroimages. INTERVENTION: A left frontotemporal craniotomy was made, and the cyst was decompressed. Duraplasty was performed with lyophilized dura. The bone defect was managed with a calvarial free bone graft and a pedicled myofacial flap. Serial neuroimaging studies performed postoperatively showed that the cyst had decreased in size. CONCLUSION: This report describes an unusual complication of a cranial base bone defect. Although not all bone defects in the cranial base require reconstruction, management of the large bone defect, particularly in the middle fossa, should preferably be accomplished with the help of a bone graft to support the dural graft.     

Nonunion using a canine model

The investigation involved a search for a model of atrophic nonunion. Fifty-two mature, adult, mongrel dogs were used to study the repair after creating a 0.5-cm bone defect in the mid-diaphysis of the radius. In addition, a 2-cm wide strip of periosteum was circumferentially resected from each osteotomy extremity. No immobilization was used thereafter. The reparative process was assessed by X-rays, histology, vascular injection, and scintigraphy. The dogs we distributed into three groups according to the time of follow-up (1, 3, and 6 months). Two kinds of repair were recognized after 3 months and were well-established after 6 months: disturbed healing with much callus (54%) and disturbed healing with absent or scanty callus (46%). In the first instance, the periosteum had regenerated and produced the external callus. The bone ends were capped with fibrocartilage; the vascularization around the defect was increased and displayed a well-defined vascular picture. In the healing pattern with absent external callus (atrophic nonunion), the bone defect was enlarged and filled with fibrous tissue, but there was no deficient vascularization in and around the osteotomy. Radioactivity counting showed an increased uptake around the osteotomy site in both types of repair, which persisted over time but was higher in the 1-month group. It was concluded that the present model yields a consistent pattern of a disturbed reparative process that mimics human cases of atrophic or hypertrophic nonunion. The differences between the two kinds of repair seemed to be related to the periosteal capacity of regeneration.     

An experimental and clinical study of Ossocol, a compound of hydroxylapatite and collagen]

Experiments on white rats revealed that introduction of Ossocol, a sponge with a composition of hydroxyl apatite with collagen, into a removed tooth well prevented mandibular atrophy and was conducive to a more smooth defect filling with better compact bone tissue. Ossocol use in 214 patients with bone tissue defects developing after tooth removal, of odontogenic cysts, sequestra, and after radical surgery for periodontal diseases demonstrated a positive effect of this agent on the course of the postoperative period: the defect was more rapidly replaced by bone tissue. No unfavorable local or general reactions to Ossocol implantation were observed.     

Resorbable versus nonresorbable membranes in combination with Bio-Oss for guided bone regeneration

The purpose of this clinical investigation was to compare the new resorbable collagen membrane, Bio-Gide, to the conventional expanded polytetrafluoroethylene material (Gore-Tex) for guided bone regeneration in situations involving exposed implant surfaces. Over a 2-year period, 25 split-mouth patients were treated randomly: one defect site was treated with Bio-Gide and the other defect site with Gore-Tex; all 84 defects were filled with Bio-Oss and covered with the respective membrane. The defect types, their dimensions, and their morphology were measured in detail initially and at re-entry to allow for calculation of the exposed implant surface. Changes in defect surface for both types of membranes were statistically significant (P < .0001); however, no statistical significance (P > .94) could be detected between the two membranes. The mean average percentage of bone fill was 92% for Bio-Gide and 78% for Gore-Tex sites. In the latter group, 44% wound dehiscences and/or premature membrane removal occurred. The resorbable membrane, Bio-Gide, in combination with a bone graft, can be a useful alternative to the well-established expanded polytetrafluoroethylene membranes.     

Bony healing of large cranial and mandibular defects protected from soft-tissue interposition: A comparative study of spontaneous bone regeneration, osteoconduction, and cancellous autografting in dogs

The purpose of this study was to compare spontaneous bone regeneration, osteoconduction, and bone autografting in critical size calvarial and mandibular defects (defects which do not heal spontaneously during the lifetime of the animal) that were protected from soft-tissue interposition. Eighteen adult mongrel dogs underwent osteotomies to create a unilateral 30-mm segmental defect in the midbody of the edentulated right mandible and bilateral 15-mm x 20-mm full-thickness window defects in the parietal bones. The defects were either left empty, implanted with coralline hydroxyapatite (HA) blocks, or autografted with iliac cancellous bone. All defects were protected with a macroporous titanium mesh and the segmental mandibular defects were additionally stabilized by internal plate fixation. Specimens were retrieved after 2 and 4 months and three undecalcified longitudinal central sections including the osteotomy interfaces were prepared from each specimen for histometry and histology. Sections were analyzed for volume fractions of bone, soft tissue, and implant using scanning electron microscopy, backscatter electron imaging and histometric computer software. In the mandibular model, the empty defects exhibited the greatest amount of bone formation after 4 months (47.3 percent), which was greater than the amount of bone in the autografted group (34.8 percent) and significantly greater than the amount of bone within the hydroxyapatite implants (19.0 percent, p < 0.05). In the cranial defects, the autografted specimens demonstrated the greatest volume fraction of bone after 4 months (27.3 percent), which was significantly greater than within both the empty defects (18.2 percent, p < 0.05) and the hydroxyapatite implants (18.2 percent, p < 0.05). New bone formation in the mandibular defects united the cut ends at 4 months regardless of treatment and originated predominantly from the periosteum which remained present only along the alveolar border after surgical closure. In the calvarial defects, periosteum was not preserved and bone regenerated centripetally, originating from the diplo? without any evidence of dural osteogenesis. Bone bridging was incomplete in the empty cranial defects at 4 months. In both the mandibular and cranial specimens, new bone at 2 months was a mixture of woven and parallel fibered bone. At 4 months, the new bone had remodeled almost entirely into mature Haversian bone. This study demonstrated a remarkable ability of defect protection with a macroporous protective sheet to facilitate bone regeneration in critical size mandibular and cranial bone defects. When active osteogenic periosteum was present, as in our mandibular model, we concluded that defect protection alone was sufficient to allow for healing even of critical size defects. When periosteum was absent as in our cranial defects, the limited spontaneous bone formation benefited from the added contributions of cancellous grafting and osteoconductive implants, both of which promoted bone bridging across the defects. We suggest that in the future a resorbable macroporous protective sheet would be advantageous in comparison to a titanium mesh to facilitate bone regeneration by preventing soft-tissue prolapse and allowing the migration of mesenchymal cells and the proliferation of blood vessels from the adjacent soft tissues into the bone defect. Finally, this study identified the need to differentiate critical size defects into those with and without defect protection and periosteum.     

Helicobacter pylori and socioeconomic factors in Russia

Transforming growth factor beta 1 (TGF-beta 1) is a polyfunctional regulatory cytokine that has been shown to have roles in extracellular matrix interactions, soft tissue healing, and osteogenesis. Twenty-five microL of recombinant human TGF-beta 1 was added to guanidine-extracted demineralized bone matrix carrier and the implants were used to fill a 14-mm osteoperiosteal critical calvarial defect in New Zealand white rabbit model. The defects were allowed to heal over 4 weeks and the degree of new bone formation was assess by radiodensitometry and undecalcified bone histomorphometry techniques. Implants with TGF-beta 1 showed complete bridging of the gap with new bone in all cases, while the controls showed fibrous tissue repair of the gap with little or no new bone formation. These results demonstrate the ability of TGF-beta 1 to induce new bone in a brief time period in an inactive carrier.