Cholinergic mechanism and blood pressure regulation in the central nervous system

This study evaluated alveolar bone and cementum regeneration following surgical implantation of recombinant human transforming growth factor-beta1 (rhTGF-beta1) in conjunction with guided tissue regeneration (GTR). Supraalveolar, critical size, periodontal defects were surgically created around the 3rd and 4th mandibular premolar teeth in right and left jaw quadrants in 5 beagle dogs. Alternate jaw quadrants in consecutive animals received rhTGF-beta1, in a CaCO3/hydroxyethyl starch carrier with GTR, or carrier with GTR alone (control). 20 microg of rhTGF-beta1 in buffer solution was incorporated into approximately 0.8 ml of carrier for each defect scheduled to receive rhTGF-beta1. Animals were sacrificed at week 4 postsurgery and tissue blocks were harvested and processed for histometric analysis. Clinical healing was generally uneventful. Minor membrane exposures were observed. Defects with membrane exposure displayed an inflammatory infiltrate underneath the membrane. Bone regeneration of trabecular nature, apparent in all animals, was generally limited to the very apical aspect of the defects. Cementum regeneration was limited without obvious differences between experimental conditions. Comparing rhTGF-beta1, to control defects, statistically significant differences were found for area (1.8+/-0.4 and 1.3+/-0.6 mm2, respectively; p<0.05) and density (0.3+/-0.1 and 0.2+/-0.03, respectively; p<0.05) of alveolar bone regeneration. Observed differences are small and represent a clinically insignificant potential for enhanced regeneration in this preclinical model. Within the limitations of study, it may be concluded that rhTGF-beta1 has a restricted potential to enhance alveolar bone regeneration in conjunction with GTR.     

Resorption of hydroxyapatite and fluorapatite coatings in man. An experimental study in trabecular bone

The clinical use of hydroxyapatite (HA) coating is controversial especially in regard to the long-term performance of the coating and the effects of resorption. In each of 15 consenting patients we inserted two implants, coated with either HA or fluorapatite (FA) into the iliac crest. They were harvested at a mean of 13.6 +/- 0.6 months after surgery. Histological examination showed that bone ongrowth on the HA-coated implants was significantly greater (29%) than that on the FA-coated implants. When bone was present on the coating surface the HA coating was significantly thicker than the FA coating. When bone marrow was present, the HA coating was significantly thinner than the FA coating. The reduction in coating thickness when covered by bone or bone marrow was 23.1 +/- 9.7 microm for HA and 5.1 +/- 1.7 microm for FA (p < 0.01) suggesting that FA is more stable than HA against resorption by bone marrow. The findings suggest that in man the osteoconductive properties of HA coating are superior to those of FA. Resorption rates for both coatings were approximately 20% of the coating thickness per year. Bone ongrowth appears to protect against resorption whereas bone marrow seems to accelerate resorption. No adverse reaction was seen in the surrounding bone.     

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.     

Cloning, characterization, and chromosomal localization of human superillin (SVIL)

The specific aim of this study was to determine the response of alveolar bone after it was augmented vertically using distraction osteogenesis and subsequently loaded with implant restorations. Four dogs each had four implants placed horizontally into an edentulous mandibular quadrant and, after integration, a distraction osteogenesis device was fabricated in the laboratory. An osteotomy was made to allow the crest of the alveolar ridge to be distracted vertically. After 10 mm of vertical distraction, the device was stabilized with light cured resin. Following bone fill confirmation of the distraction gap at 10 weeks, two implants were placed into the ridges, one in distracted bone and one in nondistracted bone. After 4 months for implant integration, freestanding prostheses were fabricated. Crestal bone levels were evaluated throughout the period of function. Animals were sacrificed after 1 year of loading, for histologic evaluation of the bone. The vertical ridge augmentation averaged 8.85 +/- 1.05 mm after 10 weeks of healing following distraction, without change over 1 year of implant loading. Histologic examination showed that bone had formed between the distracted segments, creating an augmented ridge. The average thickness of the labial cortex in the distraction gap was significantly thinner than the lingual cortex in distracted bone and the lingual and labial nondistracted cortical bone. The presence of the dental implant did not significantly affect cortical bone thickness. Serial sections showed that implants remained integrated and functional without soft tissue inflammation. Dental implants placed into alveolar ridges augmented with the technique of distraction osteogenesis maintained bone and were functional for the length of this study.     

Effects of recombinant human transforming growth factor-beta 1 or/and interleukin-6 on growth inhibition and proto-oncogene c-myc expression in human leukemia cells

OBJECTIVE: To examine the effect of recombinant human transforming growth factor-beta 1 (rhTGF-beta 1) alone or recombinant human interleukin 6 (rhIL-6) alone or in combination on proliferation inhibition of the human leukaemia cell line. METHODS: In the present study, using the human monoblastic cell line (U937) and human promyelocytic cell line (HL60) as an in vitro model, we analyzed the effect of two cytokins on proliferation inhibition with rate of 3H-TdR incorporation, the cellular content of DNA, DNA indices, the cell cycle and the expression of c-myc mRNA. RESULTS: With administration of rhTGF-beta 1 and rhIL-6, U937 cell growth was inhibited and the rate of 3H-TdR incorporation inhibition was increased. There was a decrease in the cellular content of DNA and DNA indices. And no change in the cell cycle was observed after administration of rhTGF-beta 1 or rhIL-6. However, there was an increase in G0/G1 phase cells and a decrease in G2M + S phase cells after administration of combination of rhTGF-beta 1 and rhIL-6. It was also found that rhIL-6 could inhibit proliferative responses of HL60 cells, meanwhile the inhibition could be enhanced by rhTGF-beta 1. The rate of 3H-TdR incorporation inhibition rose up to 39.89%, and DNA index fell to 1.00 following induction by rhIL-6 plus rhTGF-beta 1. Furthermore, G0/G1 phase cells increased while G2M + S cells decreased. CONCLUSIONS: These results suggest that combination of rhTGF-beta 1 and rhIL-6 acted in synergy to inhibit proliferation of both U937 and HL60 cell lines. Molecular hybridization test show that rhTGF-beta 1 alone, rhIL-6 alone or rhTGF-beta 1 and rhIL-6 in combination can inhibit U937 and HL60 cells expression of c-myc mRNA in a time and dose dependent manner. rhTGF-beta 1 and rhIL-6 in combination synergistically inhibited c-myc expression, which may be one of the machanisms for the actions of the two cytokines.     

A multicentre study comparing cervicography and cytology in the detection of cervical intraepithelial neoplasia

The efficacy of local delivery of recombinant human transforming growth factor-beta 1 (rhTGF-beta 1) to promote bone regeneration, with or without cellular contribution from the periosteum, was evaluated in transosseous defects. Implantation of rhTGF-beta 1 into 5 mm in diameter "critical size defects" in the rat mandible resulted in a dose-dependent (0.1-20 micrograms/defect) bone bridging at both 12 and 24 days, independent of the type of delivery system [3% methyl cellulose gel, porous CaCO3 particles, or poly(lactide-co-glycolide) beads]. The bridging, however, never exceeded 24% at 12 days or 34% after 24 days. In contrast, when access of cells from the periosteum to the defect was prevented by means of microporous expanded polytetrafluoroethylene barrier membranes (GORE-TEX membrane), rhTGF-beta 1 caused a dose-dependent inhibition of bone regeneration. The bioactivity of the growth factor was confirmed by implantation of 5 or 10 micrograms rhTGF-beta 1 in 12 mm in diameter bicortical defects in rabbit calvaria, which resulted in complete bone healing within 28 days, whereas control defects displayed a bridging of 40%-50%. The findings support the concept, based on in vitro experiments by others, that TGF-beta 1 primarily has a proliferative effect on cells already committed to the osteoblastic lineage, but also imply that TGF-beta 1 may be inhibitory to induction of osteogenic cells in vivo.     

Experimental bone replacement with resorbable calcium phosphate ceramic (author's transl)

Compact cylindrical implants (5 x 15.5 mm) of seven calcium phosphate ceramics of different formulations that had been implanted for 6 weeks without fixation in the tibia of dogs were examined histologically. The tissue compatibility of the implant turned out to be dependent on the mineralogical and chemical composition of the material: the ceramic material was biocompatible at a CaO/P2O5 ratio between 2:1 and 4:1, the optimum ratio being about 3:1 (tricalcium phosphate). In addition, cylindrical tetracalcium phosphate implatns with an entirely porous structure were implanted in the same manner. After 6 months, they were resorbed to a minor extent. Implants of different calcium phosphate mixtures, on the other hand, were resorbed to a large extend after the same time. The ceramic material was replaced by mineralised bone tissue which had formed directly on the ceramic implant as well as within the pores. There were no foreign body reactions. Investigations with segment-shaped implants which were implanted in the tibia of dogs and fixed with AO-plates or splints extra-cutaneously for about 8-10 weeks, provided information abouth the maximum stress that can be borne by the implants. While implants with a porosity of 75 percent did not sustain the stress after the fixation had been removed, those with a porosity of 45 percent could be subjected to physiological stress after removal of the splints.     

Hemangiopericytoma: a 20-year single-institution experience

In this overview, which is based on selected books and reviews, the microscopic appearances of prosthesis-bone interfaces resulting from clinically relevant implantation techniques are highlighted. The following techniques are distinguished to insert and attach prostheses in the recipient bone: impaction into bone, primary mechanical interlocking, cement fixation, bone ongrowth and secondary mechanical interlocking with bioinert materials, and enhanced bone ongrowth and bone bonding to bioactive materials. The resulting typical histomorphologies of orthopedic and dental prostheses-bone interfaces are described and illustrated from the author's studies employing light, fluorescence, and backscattered electron microscopy, and corresponding microradiographs of undecalcified ground sections of bone and implants. Special emphasis is given to the mineralization-demineralization kinetics of the interfacial bone matrix interacting with specific surface reactions of some implant materials. Consequently, the distinction between bioinert and bioactive prosthetic materials is critically analyzed.     

Effects of guided bone regeneration around commercially pure titanium and hydroxyapatite-coated dental implants. II. Histologic analysis

The purpose of this study was to determine which treatment of a large osseous defect adjacent to an endosseous dental implant would produce the greatest regeneration of bone and degree of osseointegration: barrier membrane therapy plus demineralized freeze-dried bone allograft (DFDBA), membrane therapy alone, or no treatment. The current study histologically assessed changes in bone within the healed peri-implant osseous defect. In a split-mouth design, 6 implants were placed in edentulous mandibular ridges of 10 mongrel dogs after preparation of 6 cylindrical mid-crestal defects, 5 mm in depth, and 9.525 mm in diameter. An implant site was then prepared in the center of each defect to a depth of 5 mm beyond the apical extent of the defect. One mandibular quadrant received three commercially pure titanium (Ti) screw implants (3.75 x 10 mm), while the contralateral side received three hydroxyapatite (HA) coated root-form implants (3.3 x 10 mm). Consequently, the coronal 5 mm of each implant was surrounded by a circumferential defect approximately 3 mm wide and 5 mm deep. The three dental implants in each quadrant received either DFDBA (canine source) and an expanded polytetrafluoroethylene membrane (ePTFE), ePTFE membrane alone, or no treatment which served as the control. Clinically, the greatest increase in ridge height and width was seen with DFDBA/ePTFE. Histologically, statistically significant differences in defect osseointegration were seen between treatment groups (P < 0.0001: DFDBA/ePTFE > ePTFE alone > control). HA-coated implants had significantly greater osseointegration within the defect than Ti implants (P < 0.0001). Average trabeculation of newly formed bone in the defect after healing was significantly greater for HA-coated implants than for titanium (P < 0.0001), while the effect on trabeculation between treatments was not significantly different (P = 0.14). Finally, there were significantly less residual allograft particles in defect areas adjacent to HA-coated implants than Ti implants (P = 0.0355). The use of HA-coated implants in large size defects with DFDBA and ePTFE membranes produced significantly more osseointegration histologically than other treatment options and more than Ti implants with the same treatment combinations. The results of this study indicate that, although the implants appeared osseointegrated clinically after 4 months of healing, histologic data suggest that selection of both the implant type and the treatment modality is important in obtaining optimum osseointegration in large size defects.     

Histological comparison of early wound healing following dense hydroxyapatite granule grafting and barrier placement in surgically-created bone defects neighboring implants

The purpose of this study was to examine early wound healing following grafting of dense hydroxyapatite granules (HA granules) and barrier placement in surgically-created bone defects surrounding implants. Eight healthy adult dogs with an average weight of 15 kg were used in this study. Thirty-two bone defects measuring 4 mm x 4 mm were removed with a surgical bur to form continuous bucco-lingual bone defects and 32 implants (16 titanium [Ti]) and 16 hydroxyapatite-coated [HA]) were then placed into the defects. Four implant groups were created: 1) grafting HA; 2) covering with an expanded polytetrafluoroethylene (ePTFE) membrane; 3) grafting HA and covering with ePTFE membrane; and 4) control (no treatment). Animals were sacrificed 28 days after surgery. Histological sections revealed large amounts of newly-formed bone in all bone defects surrounding the implants treated with ePTFE membranes alone. Fibrous encapsulation of HA granules was observed in the defects of the HA granules grafting group. In the group with grafting of HA granules and covering with ePTFE membranes, small amounts of bone tissue were observed among HA granules, but most HA granules were surrounded with fibrous tissue. Bone defects were completely filled with connective tissue in the control group. There were no differences in the histological findings between Ti and HA-coated implants in all cases. Histomorphometric data disclosed that the presence of HA granules in the bone defects significantly arrested bone formation. Our study suggests that the grafting of dense HA into bone defects surrounding implants will result in fibrous healing during the early healing stage.     

Distraction osteogenesis for lengthening of the hard palate: Part I. A possible new treatment concept for velopharyngeal incompetence. Experimental study in dogs

Many procedures have been described to correct velopharyngeal incompetence. Significant complications can occur, and the results may not be satisfactory. If the short soft palate has satisfactory muscle function and if it could be moved toward the posterior pharyngeal wall by distraction osteogenesis of the hard palate, an entirely new concept of treatment for velopharyngeal incompetence would be available. The object of the present study was to explore the possibility of osteogenesis occurring in the hard palate in dogs after gradual distraction (callus distraction). Six adult, mix-bred dogs were anesthetized, and the palatal mucosa was elevated. A midpalatal transverse osteotomy and two lateral osteotomies were performed. Tantalum bone markers for cephalometric analysis were placed, and an individually fabricated, orthodontic-like distraction device with an expansion screw in the sagittal direction was inserted. The device was stabilized on the premolars and fixed to the palatal bone with titanium miniscrews. Gradual distraction began after a latency period of 10 to 18 days. The rate of the distraction varied from 0.25 to 0.75 mm per day. The device was left in place for 6 to 8 weeks after expansion to allow for bony consolidation. Assessment was by direct examination, cephalograms, computed tomography, and histology with bone labeling. Impressions of the jaws were taken preoperatively and after device removal to examine plaster cast changes in the dental occlusion. Cephalometric and computed tomographic scan analysis demonstrated a distraction of up to 8 mm. All gaps were filled with de novo osteogenesis. Comparison of the plaster casts revealed no change in the occlusion. At 1 month after distraction, the computed tomographic scan showed the first signs of ossification of the experimental gap from the anterior and posterior bone ends. After 4.5 months ossification was almost complete with a small translucent zone in the middle of the experimental gap. After 7 months ossification was complete.     

Trying to control MRSA causes more problems than it solves

OBJECTIVE: To determine the effect of recombinant canine somatotropin (STH) on radiographic, densitometric, and biomechanical aspects of bone healing using an unstable ostectomy gap model. STUDY DESIGN: After an ostectomy of the midshaft radius, bone healing was evaluated over an 8-week period in control dogs (n = 4) and dogs receiving recombinant canine STH (n = 4). ANIMALS OR SAMPLE POPULATION: Eight sexually intact female Beagle dogs, 4 to 5 years old. METHODS: Bone healing was evaluated by qualitative and quantitative evaluation of serial radiographs every 2 weeks. Terminal dual-energy x-ray absorptiometry and three-point bending biomechanical testing were also performed. RESULTS: Dogs receiving STH had more advanced radiographic healing of ostectomy sites. Bone area, bone mineral content, and bone density were two to five times greater at the ostectomy sites of treated dogs. Ultimate load at failure and stiffness were three and five times greater in dogs receiving STH. CONCLUSIONS: Using the ostectomy gap model, recombinant canine STH enhanced the radiographic, densitometric, and biomechanical aspects of bone healing in dogs. CLINICAL RELEVANCE: Dogs at risk for delayed healing of fractures may benefit from treatment with recombinant canine STH.     

Impairment, disability, and handicap in multiple sclerosis. A cross-sectional study in an incident cohort in M?re and Romsdal County, Norway

Non-submerged ITI Bonefit implants (ITI Dental Implant System) were inserted in edentulous lower jaws of 46 patients. The patients were provided with either a fixed prosthesis or an overdenture, and has been followed during a 2-year-period. At the 1-year examination, the suprastructures were removed permitting test of the individual implant stability. Radiographic examinations were performed in connection with the loading of the implants and at the 1-year examination. In total 216 implants were inserted. 4 implants were lost before loading and 4 during the 2nd year of function, which gives a survival rate after 1 year 98% and after 2 years of 96%. The mean marginal bone loss during the first year of function was 0.1 mm. However, the marginal bone changes had a high degree of variation and four implants showed a severe bone loss. The intention is to follow this patient group with annual examinations during 5 years.     

Sonography of the knee in normal and abused infants

Histometric evaluations as a function of time were performed with zirconium implants during the healing period in 10 Wistar rats. The implants (7 mm x 1 mm x 0.1 mm) were placed in the right tibia of the animals. Five rats were killed after 14 days and the remainder were sacrificed 30 days after implantation. The tibiae were resected, radiographed, and embedded in poly(methyl methacrylate). Three cross-sections were obtained transverse to the major axis of each tibia. Osseointegrated tissue thickness, percentage of direct bone-to-implant contact, and osseointegrated tissue volume were evaluated for each specimen. Bone formation was observed on the surface of the implanted strip that was in contact with tibia marrow. This method is proposed for the evaluation of the first stage of healing of bone in contact with different implant materials subjected to various surface treatment.     

Histological and biomechanical analysis of bone and interface reactions around hydroxyapatite-coated intramedullary implants of different stiffness: a pilot study on the goat

We hypothesized that reduced stem stiffness of orthopaedic implants contributes to a high risk of loosening, since interface stresses and relative motions may exceed a tolerable range. To study this hypothesis, three types of load-bearing implant with different stiffnesses were inserted into the tibia of the goat. Histological analysis was performed of bone repair after insertion of the implant, bone ingrowth, interface disruption and loosening. A finite element model of the configuration provided the quantitative range of interface stresses and relative motions for the present experiment. The implants were made out of stainless steel, hollow titanium and a thin titanium core covered with a polyacetal coating. The stiffness ratios of these implants were approximately 10:4:1, respectively. All implants were coated with a layer of hydroxyapatite (HA) in order to minimize the possible biological effects of the different implant materials. Irrespective of the type of implant, there was a repair phase that lasted 6-12 weeks. The stiff implants functioned well. Large areas of bone bonding to the HA layer were found after the repair phase at 12 weeks postoperatively. After 24 weeks, some signs of loosening were observed. More loosening occurred with the hollow titanium and polyacetal implants, mainly during the repair phase. Three hollow titanium and three polyacetal coated implants survived this period, and were killed after 24 weeks. The integrity of the HA layer at the bone-implant interface of the titanium implants was good. In the polyacetal implants, the repair reaction of the cortical bone was incomplete. Bone ingrowth into HA was largely lacking. In conclusion, we found significant differences in the repair and interface reactions around implants of different stiffness. Stiff implants showed favourable initial interface conditions for bone ingrowth. Intermediate and flexible implants provoked unfavourable interface conditions for initial bone ingrowth. The finite element study showed that the flexible stems produce larger micromotions and higher interface stresses at the bone-prosthesis interface than the stiff stems, indicating an explanation for the histological findings.     

Observations on 25 patients treated with ball-retained overdentures using the Astra Tech implant system

Twenty-five adult patients with fully edentulous jaws, aged from 44 to 80 years were treated with seventy-one 3.5 mm diameter Astra Tech dental implants in the parasymphseal region. The length of these implants varied from 9 mm to 15 mm. Either two or three implants were inserted, subsequently exposed after a minimum period of 3 months, abutments and ball attachments placed. Full lower dentures incorporating gold alloy housings for ball-attachments were constructed. The average time that the implants were in situ was 4 years and 2 months, ranging from 1 year 3 months to 5 years and 7 months. Of the 71 implants placed, 67 achieved osseointegration-a success rate of 94%. The main complication was that of the ball-attachments becoming loose.     

The effects of guided bone regeneration and grafting on implants placed into immediate extraction sockets. An experimental study in dogs

Guided bone regeneration (gbr) for the treatment of insufficient bone volume around implants can be performed using membranes with or without grafting materials (i.e., autogenous, allogenous, xenogenous, or alloplastic grafts). A possible way to evaluate the quality of implant osseointegration is the torque necessary to remove implants from their bony housing. The aim of this study was to compare the torques necessary to remove dental implants from implant beds reconstructed with different bone substitutes and GBR or GBR alone in 6 adult mongrel dogs. All mandibular premolars were extracted and 3 extraction sockets on each side were enlarged using a trephine bur. A 13 mm titanium screw-type dental implant (3.75 mm diameter) was placed in each enlarged extraction socket so that only the apical 3 to 4 mm were engaged in bone. The 3 defects were then randomly treated with either 1) canine demineralized freeze-dried bone allograft (DFDBA) plus GBR using an expanded polytetrafluoroethylene membrane (DFDBA+GTAM); 2) bioabsorbable hydroxyapatite and GBR (HA+GTAM); or 3) GBR (GTAM alone). After 6 months, the torque to remove the implants was measured in 4 animals and analyzed using ANOVA. There were no statistically significant differences between the 3 groups (GTAM alone: 46.37+/-16.41 Ncm; HA+GTAM: 46.00+/-16.59 Ncm; DFDBA+ GTAM: 52.15+/-29.24 Ncm). In addition, the influence of early removal of barriers on the torque values was evaluated with the t-test. Comparing exposed versus retained membranes by treatment modality, the only statistically significant difference was found in the DFDBA+GTAM group. When the torque values of all implants with exposed and retrieved membranes were compared to all those with retained membranes a significant difference could be detected. Histologic sections were prepared from the 2 dogs not included in the removal torque testing. In the histometric analysis the GTAM alone group showed a mean mineralized bone-to-implant-contact of 27.1%, the DFDBA+GTAM group of 34.6%, and the HA+GTAM of 39.3%. The mineralized bone-to-implant-contact of the HA+GTAM group was significantly higher than that of the GTAM alone group. In addition, the mineralized bone-to-implant-contact was divided into an apical and coronal part using the apical seventh thread as the dividing landmark. In the apical region, there was no significant difference between the groups regarding mineralized bone-to-implant-contact. In the coronal part the mineralized bone-to-implant-contact of the GTAM alone group was significantly lower compared to the other 2 groups. Within the limits of this investigation, it can be concluded that the type of grafting material will not influence torque removal values, but that early membrane exposure and removal will negatively influence the torque measurements. The combination of GBR with a bone substitute increased the mineralized bone-to-implant contact.     

Assessment of an experimental bone wax polymer plus TGF-beta 1 implanted into calvarial defects

The study reported describes an experimental biodegradable polymer ceramic composite with wax-like handling properties that was combined with 2.0 micrograms of recombinant human transforming growth factor beta (rhTGF-beta(1)). The polymer/rhTGF-beta(1) combination was introduced into standard-sized calvarial defects in rabbits to evaluate biodegradability, biocompatibility, hemostasis control, and bone promotion. The experimental wound model was a standard-size circular calvarial defect 8 mm in diameter. The experimental design included 24 skeletally mature New Zealand white rabbits divided evenly between two time periods (6 and 12 weeks) and among three experimental treatments (untreated defects and defects treated with polymer with or without rhTGF-beta(1)). Evaluations consisted of clinical examinations, standarized radiography, radiomorphometry, as well as histology and histomorphometry. Data were analyzed by an Analysis of Variance (ANOVA) and Fisher's Protected Least Significant Difference test at each time period (level of significance p < or = 0.05). Radiomorphometry data indicated that standard-sized defects treated with the wax-like polymer alone and the polymer plus 2.0 micrograms of TGF-beta(1) were significantly more radiopaque than control sites at both 6 and 12 weeks. Histomorphometric data revealed the amount of new bone was significantly greater at 6 weeks in the polymer plus 2.0 micrograms of TGF-beta(1) and in the control group than in the polymer alone. Moreover, at 12 weeks, there was significantly more new bone in the control than in either the polymer alone or the polymer plus 2.0 micrograms of TGF-beta(1). We speculate the incomplete biodegradation of the polymer ceramic composite contributed to the radiopacity and may have retarded osseous regeneration. It is important that the bone wax-like polymer material was biocompatible and acted as a hemostatic agent.     

Statistical research needs in mechanistic modelling for carcinogenic risk assessment

This study reports the results of implant therapy involving a sinus membrane lift as well as conventional implant therapy in 24 periodontally compromised patients who were treated during the period between June 1990 and May 1995. Patients were included on the basis of being in need of at least 2 implants, 1 of which was to be placed in the maxillary sinus region, and at least 3 mm bone height was required in the sinus region. Following fenestration of the lateral sinus wall and lifting of the sinus membrane sinus implants were inserted as described for conventional implants. Annual follow-up visits included recording of plaque, probing pocket depth and bleeding on probing, and recording of the radiographic distance from the implant shoulder to the alveolar crest in mm. The Astra, Astra sinus, ITI, and ITI sinus were observed for an average of 30.8, 29.9, 29.4 and 25.3 months, respectively. Of the 80 implants inserted 1 Astra and 2 ITI had failed at 11-12 months and 1 ITI had failed at 42 months. The Kaplan-Meier estimate of the proportion of non-failed implants at 36 months were 100%, 95%, 91%, and 86% for the Astra, Astra sinus, ITI, and ITI sinus implants, respectively. Of the Astra, Astra sinus, and ITI implants, 71-82% remained free from bone-loss > or = 1.5 mm at 36 months, whereas this was the case for only 29% of the ITI sinus implants. About 80-90% of the implants remained free from plaque; 65-86% remained free from bleeding; and 44-80% remained free from pockets > or = 4 mm. These results indicate that the sinus lift technique can be used successfully in periodontally compromised patients.     

Transfemoral endovascular aortic graft placement

PURPOSE: The purpose of this study was to develop an endovascular system for transfemoral placement of straight aortic grafts and bifurcated aortoiliac grafts. METHODS: Both types of graft consist of barbed, self-expanding stents attached to a woven polyester fabric. Survival studies of straight-graft function were performed in six large mongrel dogs. Digital subtraction fluoroscopic equipment was used to guide insertion and record angiograms at 0, 1, and 3 months. Bifurcated grafts were inserted in an additional eight dogs, four with distal stents and four without. Straight grafts were inserted into six cadaveric aortas (five atherosclerotic and one aneurysmal; age 68.7 + 5.7 years) to assess stent attachment. RESULTS: Angiograms obtained immediately after straight-graft insertion showed placement to be within 4.6 + 1.6 mm of the intended level. Follow-up angiograms at 1 and 3 months showed no migration, no leakage, and patency of all six grafts. After bifurcated graft insertion there were no angiographic signs of perigraft leakage, with or without distal stents. The mean force required to displace straight grafts 10 mm from their original position in cadaveric aortas was 1388 + 127 g. CONCLUSION: These preliminary results show that straight and bifurcated endovascular grafts can be positioned accurately and securely in the abdominal aorta.