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At least 145 records · Page 8Linked to original sources
PubMed2003

Effects of sealing the perforated sinus membrane with a resorbable collagen membrane: a pilot study in humans.

The effects of repairing the perforated sinus membrane with collagen membrane are unknown. The purpose of this pilot study was to clinically, histologically, and histomorphometrically evaluate the results of repairing the perforated sinus membrane with resorbable collagen membrane. A split-mouth design was followed in the current study. Five subjects requiring bilateral sinus grafting were included in the study, where one site was accidentally perforated during sinus augmentation procedures and the other site was not perforated. The perforated sites were repaired with a resorbable collagen membrane. Dental implants were placed at a second stage and biopsies were harvested from both sinuses. New bone formation was measured for all sites. Implant survival was recorded at second-stage surgery. Nonperforated sites demonstrated significantly more bone formation (34.40%) than perforated sites (12.80%) (P = .016). Implant survival at second-stage surgery was significantly inferior in perforated sites (54.5%) when compared with nonperforated sites (100%) (P = .0146). The study demonstrated that perforation and repair of the Schneiderian membrane can compromise new bone formation and implant survival rate.

Absorbable Implants↗
PubMed2001

The preliminary evaluation of HAP + TCP composite material biodegradation after implantation in muscular tissue of rats.

Ceramic biomaterials based on calcium phosphates have a special position among modern implantation material in osteosurgery. Non-reabsorbable hydroxyapatite (HAP) and reabsorbable tricalcium phosphate are the most popular calcium phosphate ceramics. The appropriate ratio of these two compounds should result in forming the gradually reabsorbable implants, overgrowing with the bone tissue which mechanical strength should not be negatively affected. The aim of this work was to evaluate a local tissue reaction and the HAP + TCP composite resorption rate as compared with HAP, after implantation in a muscle tissue of rats. On the basis of carried macroscopic and microscopic evaluations, it can be stated that the new HAP + TCP composite had high biocompatibility and were gradually reabsorbed. This enables faster overgrowing the implant with tissue.

Absorbable Implants↗
PubMed1993

[Resorbable implant materials in retinal detachment surgery. Initial animal experiment studies].

In detachment surgery after a mechanically stabile chorioretinal scar is at present full scleral indentation no longer mandatory. Following these considerations absorbable scleral implants have been developed and tested in an animal model. Cylindrical pieces of absorbable composite-material with a diameter of 5 mm were sutured as radial scleral explants in 18 rabbits. The composite material consisted of a polyglactin-polydioxanon ratio 7:1. The absorption time for polyglactin is 60 days, for polydioxanon 180 days. The explants produced initially in ultrasonographically measured buckle height between 3.2 and 4.0 mm. The clinical and ultrasonographical follow up study demonstrated a continuous decrease of buckle height. Two weeks after implantation there was a medium height of 2.0 mm after five weeks a medium elevation of 0.5 mm was found. Histopathological examinations showed incidence of a slight resorptive inflammation in the area of the buckle which was not evident after 12 weeks. No scleral infiltration or scleral thinning was found. The promising results have justified controlled clinical trials with the absorbable material which might allow to combine the advantages of silicone sponge explants (precise localization) with those of scleral buckles by inflatible balloons (reversibility).

Absorption↗
PubMed2000

Clinical biocompatibility of biodegradable orthopaedic implants for internal fixation: a review.

When the polymeric material reaches the final stages of its degradation process, biodegradable orthopaedic fixation devices elicit a local foreign-body reaction. In most cases, the symptoms of this tissue response are subclinical and pass unnoticed, but in some patients a clinically manifest inflammatory foreign-body reaction ensues. Mild clinical reactions consist of a painful erythematous papule, those of medium severity show a sinus discharging polymeric debris for up to 6 months, and in the patients affected by a severe reaction, extensive osteolytic lesions may develop at the implant tracks. The histopathologic picture is that of a non-specific foreign-body reaction. For implants made of polyglycolide, the average incidence of the manifest reactions is 5%. When slow-degrading polymers are used, the incidence is lower. The tissue responses to polyglycolide manifest themselves 11 weeks after surgery, on an average, whereas foreign-body reactions to devices made of poly-L-lactide can emerge as late as 4 or 5 yr after the original fracture fixation operation. A poorly vascularized bone section, use of a quinone dye as an additive in the polymer, and an implant geometry with large surface area each seems to be associated with an increased risk of the occurrence of a foreign-body reaction. Yet in majority of the patients affected, no known individual marker of high risk is present. Some recent laboratory experiments indicate that it may be possible to diminish the risk of an adverse tissue response by incorporating alkaline salts or antibodies to inflammatory mediators in the implants. The results of in vitro and animal experiments, however, cannot always be directly extrapolated to humans. Only large-scale long-term clinical research will ultimately show which physico-chemical characteristics of a biodegradable orthopaedic implant provide the optimal clinical biocompatibility.

Absorbable Implants↗
PubMed1999

Platelet adhesion on a bioresorbable poly(propylene fumarate-co-ethylene glycol) copolymer.

Platelet adhesion and aggregation on poly(propylene fumarate-co-ethylene glycol), P(PF-co-EG), hydrogels was examined under both static and flow conditions. Adherent platelets were quantified under static conditions using both 111Indium oxine-labeled platelets as well as a lactate dehydrogenase, LDH, assay. The radiolabeling assay showed a significant decrease in platelet attachment on the copolymer hydrogel films relative to the poly(propylene fumarate), PPF, homopolymer. In addition, there were reductions in adhesion resulting from the increase in poly(ethylene glycol), PEG, weight percent or molecular weight. There was good agreement between both assays under static conditions for the copolymer films. Platelet surface coverage was quantified under flow conditions in a parallel plate flow chamber using the LDH assay. There was a dramatic decrease in the number of adherent platelets on the copolymers relative to glass and silicone rubber controls. All of the copolymer surfaces showed minimal aggregation with no thrombus formation or platelet spreading as assessed qualitatively using scanning electron microscopy. These results suggest that P(PF-co-EG) is a good candidate for development as a cardiovascular implant.

Absorbable Implants↗
PubMed1997

Degradation characteristics of PLLA-PGA bone fixation devices.

Parietal craniotomies of the mature rabbit skull were repositioned and fixed with resorbable plate and screws made of LactoSorb (Walter Lorenz Surgical, Jacksonville, FL) poly L-lactic acid (PLLA) and polyglycolic acid (PGA) in 20 mature rabbits. Changes in the resorbable devices as well as at the tissue-implant interface were evaluated at 2, 6, 9, and 12 months postoperatively. At 2 months, no change in the size of the implants was seen with a noninflammatory layer of surrounding fibrous tissue and intense birefringence of the screws. At 6 months, substantial loss of implant size had occurred, accompanied by fibrovascular and a macrophage cellular infiltrate. At 9 months, more than 95% of the implant was resorbed, with a small amount remaining in the screw hole. Other than macrophages within the remaining material, very few giant cells were seen. By 1 year, no evidence of birefringent macromolecular polymer debris could be found. No contraindications for the clinical use of this specific PLLA-PGA copolyer could be found when implanted on craniofacial bone surface.

Absorbable Implants↗
PubMed2002

Bioabsorbable poly-L-lactic acid cages for lumbar interbody fusion: three-year follow-up radiographic, histologic, and histomorphometric analysis in goats.

STUDY DESIGN: Long-term evaluation was performed for bioabsorbable poly-L-lactic acid cages in a goat interbody fusion model. OBJECTIVE: To assess the radiographic, histologic, and histomorphometric characteristics of poly-L-lactic acid cages during 3 years of follow-up evaluation. SUMMARY OF BACKGROUND DATA: Failed cage fusions may be related to cage design and material in addition to the surgical technique used. To overcome material-related complications and to explore the potential benefits of bioabsorbable cages, poly-L-lactic acid cages have been designed. METHODS: For this study, 36 Dutch milk goats underwent a lumbar interbody fusion procedure (L3-L4). Two types of custom-made cage devices were impacted with bone graft and implanted: poly-L-lactic acid cages (n = 30) and titanium cages (n = 6). Sequential harvesting of surgically managed motion segments (intervals: 3, 6, 12, 24, and 36 months) was performed for analysis. RESULTS: In poly-L-lactic acid specimens, permanent interbody fusion could be achieved within 6 months after surgery with maintenance of cage height. Titanium specimens showed no interbody fusion within this period. Radiographic follow-up evaluation (6-36 months) showed interbody fusion in 86% (19/22) of poly-L-lactic acid specimens, as compared with 33% (2/6) of titanium specimens. After 36 months of implantation, in one half of the specimens, poly-L-lactic acid cages were completely absorbed. Bone histomorphometry showed complete bone remodeling after 2 years of follow-up evaluation. During the study period, no local or distant adverse histologic effects were observed. CONCLUSIONS: The current study showed that poly-L-lactic acid cage devices are feasible for lumbar interbody fusion. New poly-L-lactic acid cages designed for clinical practice might be a viable alternative to current nonabsorbable cage devices.

Absorbable Implants↗
PubMed1976

Scleral buckling with Bioplast fibrin in retinal detachment.

The study includes a series of 38 patients with retinal detachment of different aetiology. Scleral reduction combined with the intrascleral implantation of absorbable Bioplast fibrin scleral buckling rods was performed and reattachment achieved in 31 cases. The implant material is biocompatible and is eliminated from the eye in the course of a few weeks.

Adolescent↗
PubMed2002

A synthetic bioactive resorbable graft for predictable implant reconstruction: part one.

Animal studies were conducted to evaluate the cell response and chemical potentiality of a synthetic bioactive resorbable graft (SBRG) made of nonceramic cluster particulate of low-temperature HA material. The study evaluated bone-bridging of the SBRG particulates in 1-mm wide implant channels of 5 x 8 mm long roughened titanium interface in 6 dogs and compared results to the same implant channels left empty as controls at 6- and 12-week intervals. Resorption rate capacity and cell response were evaluated with an assessment of the chemical characterization of the synthetic nonceramic material next to the titanium implant interfaces. Results of the animal studies were compared with human histologic biopsies of the SBRG for bone quality, density, and bone growth into defect sites concurrent with resorption time of the graft. One human biopsy consisted of a graft mixture of the SBRG and dense bovine-derived HA, compared under the electron microscope, including histology by H and E staining. Part 1 of this paper presents evidence of the predictability and efficacy of the SBRG osteoconductive, particulate chemical potentiality to aid in the regeneration of lost bone anatomy next to titanium implant interfaces. Recent technological innovations in computer hardware and software have given clinicians the tools to determine 3-dimensional quality and density of bone, including anatomical discrepancies, which can aid in the diagnosis and treatment planning for grafting procedures. When teeth are extracted, the surrounding bone and soft tissue are challenged as a result of the natural resorptive process. The diminished structural foundation for prosthetic reconstruction, with or without implants, can be compromised. A synthetic bioactive resorbable graft material having osteoconductive biochemical and biomechanical qualities similar to the host bone provides the means to improve compromised bone topography for ridge preservation, ridge augmentation, or to enhance the bony site for implant placement and subsequent prosthetic rehabilitation. Part two of this paper will demonstrate clinical applications of the SBRG material for purposes of implant placement and prosthetic reconstruction.

Absorbable Implants↗
PubMed2001

Histopathological morphometric evaluation of 2 different hydroxyapatite-bone derivatives in sinus augmentation procedures: a comparative study in humans.

BACKGROUND: Xenografts to augment the maxillary sinus have been used extensively. The aim of the present study was to evaluate, qualitatively and quantitatively, two different HA derivatives of natural and synthetic sources on newly formed bone in the augmented sinus. METHODS: A bilateral sinus augmentation procedure with simultaneous (16 out of 20 sites) or subsequent implant placement was performed in 10 patients. The antrum was randomly filled with a deproteinized, bovine hydroxyapatite mineral (B-HA) on one side and a non-ceramic resorbable hydroxyapatite (NC-HA) on the other. Cylindrical specimens were harvested from the augmented core at 12 months. Decalcified specimens were sectioned at a cross-horizontal plane and stained with hematoxylin and eosin for histopathologic and histomorphometric examinations. Tissue area fractions of bone, marrow, and the grafted particles were calculated for each specimen from the lateral to the deep region, and changes in values were compared within each material and between them. RESULTS: New bone formation was evident. B-HA and NC-HA particles were observed in all specimens surrounded by newly formed bone in direct connection or by soft tissue marrow. Morphometrically in the B-HA sites, from the lateral to deeper area, bone area fraction increased from 29.8% to 54.2% (average 42.1%) and marrow area fraction decreased from 37.9% to 26.7% (average 33.3%). The mineral area fraction decreased from 32.3% to 19.1% (average 24.7%). All increasing/decreasing patterns were statistically significant (P < 0.001). In the NC-HA sites, from the lateral to deeper area, bone area fraction increased from 25% to 36.5% (average 32.3%) and marrow area fraction decreased from 51.6% to 41.9% (average 43.2%) (P <0.001). The mineral area fraction decreased from 29% to 21.7% (average 24.6%) (P = 0.038). Comparison between the two HA derivative groups showed a significant difference between the bone area fraction averages (P = 0.0053) and between the increasing patterns along the core depth (P = 0.0006). There was also a significant difference between the decreasing marrow patterns (P = 0.003), but not between their averages. Comparison between the mineral area fractions showed no differences. CONCLUSIONS: B-HA and NC-HA were proven to be biocompatible materials. Although the B-HA-augmented sites showed a higher percentage of bone formation at 12 months, both are suitable bone derivatives in sinus augmentation procedures and can accommodate osseointegrated implants.

Absorbable Implants↗
PubMed2001

Development of a model for bioresorbability of bioceramic microparticles.

Over the past decade, numerous studies have implicated wear particle debris, generated by everyday wear or ceramic implants, as the essential contributors to implant failure [3,4,5,6,7]. We investigated the interactions of ceramic particles (TCP and HA) on cell viability, cell damage, and respiratory burst in a macrophage cell line (RAW 264.7) for a duration of 24, 48, and 72 hours. The results show that cellular protein levels ranged between 0.20-0.3 mg/ml for the duration of the experiment, and there was no difference detected between or among the groups (P < 0.05). Differences in MDA levels (the amount of lipid peroxides formed at the cellular membrane) were not detected at the early time points (24-48 hours). However, with time in culture there is an increase in MDA levels in all groups. There were no differences detected in nitric oxide production between TCP and the control at all phases. The amount of nitric oxide produced by cells treated with Ha decreased slightly at 24 hours. In contrast, at 48 and 72 hours there was a significant increase when compared to the control. Morphological evaluation revealed that cells treated with TCP contained irregular membrane boundaries, and appeared to have cytoplasmic extensions. Many of the macrophages consisted of large vacuoles containing TCP particles. Cells treated with HA also contained irregular cytoplasmic borders with an increase in vacuolization. At 48 hours, the morphology of all groups remained the same, and at 72 hours, many of the cells treated with TCP and HA began to lyse. Overall, RAW 264.7 macrophage cells are capable of ingesting particles of TCP and HA, and after three days in culture the cells begin to show the effects of increased retention of ceramic particles. The results of this investigation can be used as a model for the assessment of the resorbability rate of implantable devices.

Absorbable Implants↗
PubMed1992

The tissue-implant interface during degradation of absorbable polyglycolide fracture fixation screws in the rabbit femur.

A transverse transcondylar osteotomy of the distal femur was fixed with an axially placed absorbable fracture fixation screw made of polyglycolide (PGA) in 25 rabbits. Changes at the tissue-implant interface accompanying degradation of the screw were examined histologically, histomorphometrically, and microradiographically seven, 20, 40, 80, and 250 days after implantation. At seven days postimplantation, a layer of fibroblasts was seen surrounding the implant, and new bone formation was discernible in the host tissues adjacent to this membranous structure. At 20 days postimplantation, the geometry of the screw was still intact and the tissue-implant boundary was distinct. The first signs of invasion of vascular granulation tissue into the implant were observed 40 days after implantation, at which time the osteotomies were united. The apparent walling-off response by formation of new trabecular bone outlining the PGA profile continued, with the greatest mean trabecular bone volume fraction at the interface, 23.9%, measured at 40 days. A significant decrease in the new bone volume occurred between 40 and 80 days postimplantation. The intensity of the foreign-body reaction seen was histologically moderate. The giant cell count was highest at 80 days postimplantation, when the migratory activity of phagocytic cells had transported intracellular particulate polymeric debris 400-800 microns away from the original tissue-implant boundary. At 250 days postimplantation, no birefringent polymeric material could be seen in the specimens. No contraindications for the clinical application of PGA implants emerged in this study.

Animals↗
PubMed2003

Space-providing expanded polytetrafluoroethylene devices define alveolar augmentation at dental implants induced by recombinant human bone morphogenetic protein 2 in an absorbable collagen sponge carrier.

BACKGROUND: Surgical implantation of recombinant human bone morphogenetic protein 2 (rhBMP-2) in an absorbable collagen sponge carrier (ACS) significantly enhances bone regeneration in horizontal alveolar defects; however, sufficient quantities of bone for implant dentistry are not routinely obtained. PURPOSE: The objective of this proof-of-principle study was to evaluate the potential of a space-providing macroporous expanded polytetrafluoroethylene (ePTFE) device to control volume and geometry of rhBMP-2/ACS-induced alveolar bone augmentation. MATERIALS AND METHODS: Bilateral critical-size supra-alveolar periimplant defects were created in four Hound-Labrador mongrel dogs. Two turned and one surface-etched 10 mm titanium dental implants were placed 5 mm into the surgically reduced alveolar ridge creating 5 mm supra-alveolar defects. rhBMP-2/ACS (0.4 mg rhBMP-2) was placed around the exposed dental implants. Additionally, one jaw quadrant in each animal was randomly assigned to receive the dome-shaped macroporous ePTFE device. Mucoperiosteal flaps were advanced for primary wound closure. The animals were euthanized at 8 weeks post surgery for histometric analysis. RESULTS: The space-providing macroporous ePTFE device defined the volume and geometry of rhBMP-2/ACS-induced bone formation, whereas bone formation at sites receiving rhBMP-2/ACS alone varied considerably. Vertical bone gain at turned dental implants averaged (+/-SD) 4.7 +/-0.2 mm at sites receiving rhBMP-2/ACS and the ePTFE device compared with 3.5 +/-0.9 mm at sites receiving rhBMP-2/ACS only. The corresponding values for rhBMP-2/ACS-induced bone area were 9.6 +/- 0.7 mm2 and 7.5 +/-6.2 mm2. There was a highly significant correlation between induced bone area and the space provided by the ePTFE device (p <.001). There was no difference in induced bone density or bone-implant contact between the two technologies. These observations were consistent with those observed at surface-etched dental implants. CONCLUSIONS: The data from this study suggest that a space-providing macroporous ePTFE device defines rhBMP-2/ACS-induced alveolar augmentation to provide adequate bone quantities for implant dentistry. The dental implant surface technology does not appear to substantially influence bone formation.

Absorbable Implants↗
PubMed2003

Microfabricated drug delivery systems: from particles to pores.

Microfabrication techniques which permit the creation of therapeutic delivery systems that possess a combination of structural, mechanical, and perhaps electronic features may surmount challenges associated with conventional delivery of therapy. In this review, delivery concepts are presented which capitalize on the strengths of microfabrication. Possible applications include micromachined silicon membranes to create implantable biocapsules for the immunoisolation of pancreatic islet cells-as a possible treatment for diabetes-and sustained release of injectable drugs needed over long time periods. Asymmetrical, drug-loaded microfabricated particles with specific ligands linked to the surface are proposed for improving oral bioavailability of peptide (and perhaps protein) drugs. In addition, microfabricated drug delivery systems ranging from transdermal microneedles to implantable microchips will be discussed.

Absorbable Implants↗
PubMed2001

Intraindividual comparative animal study of alpha- and beta-tricalcium phosphate degradation in conjunction with simultaneous insertion of dental implants.

An intraindividual comparative study of proximal tibial marrow defects in nine adult Goettinger miniature pigs (GMPs) was undertaken. The left side of the defect was filled with granular beta-tricalcium phosphate (TCP) ceramic ad modum Cerasorb, and the right side was filled with granular alpha-TCP ceramic ad modum Biobase alpha pore. Simultaneously, dental screw implants were inserted in each ceramic and fixed within the orthotopically replanted corticalis lids. Control defects were made in two other animals. The survival period ranged from 4 to 86 weeks (control study, 16 and 20 weeks). The reorganization and degree of bone regeneration, dynamics of ceramic degradation, and remodeling characteristics of the bone regenerate referring to osseo-integration of the dental implants were examined histomorphologically in nondecalcified specimens. The results reveal that both ceramic types were osteoconductive exclusively. Centripetally oriented angiogene bone regeneration occurred at the margins of the circular defects. Ceramic degradation was performed hydrolytically and within cells. Furthermore, it was demonstrated that decomposition of the intratrabecularly integrated ceramic residues underlies a dynamic process of degradation. Within 86 weeks, nearly 80% to 90% of the larger alpha-TCP granules, and nearly 90% to 95% of the beta-TCP granules were degraded. At this time, especially for the alpha-TCP modification, ceramic microparticles were found in the marrow, either unbound or within polynuclear macrophages. The predictable degradation of both ceramic types provides an early functional adaptation of bone regenerates and facilitates a biofunctional, anisotropic orientation of the neotrabeculae without delay. It is concluded that because of the initially pronounced accumulation of macrophages, dental implants should not be inserted simultaneously with ceramic, but after further progress of ceramic degradation (5 to 6 months after TCP implantation).

Absorbable Implants↗