Kinds Of Implants Research Articles

The Effects of Sinus Mucosal Removal during Orbital Wall Reconstruction in an Experimental Model

BACKGROUND: Various kinds of implants have been used for reconstruction of blowout fracture, but they have the possibility of infection. Although infection after orbital reconstruction is not common, it could leave serious sequelae to the patients. For this reason, some surgeons routinely removed the sinus mucosa during the repair of the blowout fracture. In this study, we evaluated the effect of mucosal removal to the healing process with implant and inflammatory reaction, using histopathologic analysis of the rabbit model. METHODS: Studies were performed with fifteen “New Zealand White Rabbits”. A 1.5 cm x 1.5 cm sized bone window was made at the maxillary sinus wall. One side of the maxilla was chosen randomly as an experimental group (n=15), and the other side became the control group (n=15). The sinus mucosa of the experimental group was totally strapped and that of control group was left intact. Bioabsorbable poly-L-lactide-conglydolida plate (Rapidorsorb, synthes) was inserted to cover the bony defects. Total maxillectomy including implant at 3 weeks, 6 weeks, and 9 weeks after implantation was conducted and composition of tissue was analyzed. The grade of inflammatory reaction, the proportion of woven bone, the amount of fibrovascular proliferation (b-FGF,CD31) and capsule thickness around the implant were assessed. RESULTS: The early inflammatory reactions around the implant were grade 1.13 (mean value, experimental group) and 2.2 (mean value, control group) in 3 weeks. Woven bone formation was more prevalent in the experimental group. Calculated area of woven bone formation was 16.27% in 3 weeks, 22.20% in 6 weeks, and 36.16% in 9 weeks. In the control group, more fibrotic connective tissue change rather than woven bone formation was observed (p=0.011) (Table 1). Also, the thickness of capsule around the implants were thinner in experimental group (p=0.04) (Table 2).Table 1: The proportion of woven bone formation (%).Table 2: Thickness of implant capsule (um).CONCLUSIONS: This study suggests that less inflammatory reaction not only stimulates formation of woven bone but also reduces the fibrosis around the absorbable implant. Therefore, removal of sinus mucosa during the orbital reconstruction can be accepted as an effective option to achieve faster bone healing process with less inflammatory reaction.

Effect of zinc ions on improving implant fixation in osteoporotic bone

The application of titanium (Ti) and its alloys in tooth restoration and joint replacement for aged patients with unfavorable conditions is gaining popularity. Therefore, strategies aiming at improving the fixation of Ti-based implants are worth investigating. This study was designed to observe whether modification of Ti implants by zinc (Zn) could enhance the fixation capability in osteoporotic bone. Two kinds of implants, hydroxyapatite (HA) coated Ti and Zn-incorporated HA (ZnHA) coated Ti, were inserted into the femoral metaphysis longitudinally in ovariectomized (OVX) rats. Specimens were harvested and subjected to double fluorescence labeling examination at week 6 after surgery. At week 12, samples were evaluated with histomorphometry, micro-CT (μCT) analysis and biomechanical test. Compared to the HA coated implants, ZnHA coating improved mineral apposition rate (MAR) of peri-implant bone, which was revealed by double fluorescence labeling; bone area ratio (BA) and bone-to-implant contact (BIC) were also higher for the latter group by histomorphometry. μCT images suggested that more bone mass was formed around the ZnHA coated implants as compared to the HA coated implants. Biomechanical push-out test showed that the ZnHA coated implants demonstrated higher strength of osseointegration than the HA group. The current study suggested that Zn ions could enhance bone formation and improve implant fixation in OVX rats.

Vacancy-type defect production in CLAM steel after the co-implantation of He and H ion beams studied by positron-annihilation spectroscopy

Vacancy-type defects induced by the co-implantation of He and H ions in China low activation martensitic (CLAM) steel at room temperature were investigated by variable-energy position beam Doppler broadening spectra (DBS). The co-implantation occurred in two patterns. In one pattern, He ions were implanted before H ions; the other pattern was of the opposite sequence. Both He- and H-vacancy complexes were formed for pre-implanted He and H at different fluences. He–H-vacancy complexes were formed for pre-implanted He, which caused the S parameter of the pre-implanted He to be smaller than that of H at the lowest fluence. The defect density increased with increased fluence for the two implanted patterns, and the difference between the S parameters of pre-implanted H and He decreased with increased fluence. Nanovoids containing a few He atoms were the dominating defects at high implanted fluences for the two kinds of implantation.

EXPERIMENTS AND SIMULATIONS FOR LAPAROSCOPIC VENTRAL HERNIA REPAIR IMPROVEMENT

The authors conducted a wide experimental and numerical study in order to determine effective approaches in the laparoscopic VH repair. At first the study covered identification of mechanical properties of the abdominal fascia, implants, tacks and transabdominalsutures. Basis on these data, the one and two-dimensional mathematical models were formulated and a number of numerical static and dynamic analyses were carried out. Then various physical models of the fascia-mesh system were built in many configurations, using a porcine fascia, a few kinds of implants and tacks.

Material parameters of the reindeer antler for use in dental implant biomechanics

The survival of dental implants, in particular immediately loaded implants, critically depends on the biomechanical properties of the bone bed surrounding them. In experimental animal investigations of immediately loaded implants the initial stability, implant design as well as stress and strain distributions in the surrounding bone have been extensively studied. It was the aim of this study to investigate the biomechanical properties of the reindeer antler used as a bony tissue surrounding dental implants, in particular the Young's modulus, Poisson's ratio, and further numerical parameters such as mesh density, friction models and the corresponding frictional coefficients and relative velocities for establishing a novel animal model that can be used in the numerical analyses of experimentally investigated antler specimens. The sensitivity of the investigated parameters was analysed based on the close correlation of numerical and experimental results. No obvious influence of the frictional coefficient and/or relative velocity was observed on the implant displacement using a finite element model. Moreover, nearly identical numerical and experimental results were observed for two kinds of implants concerning implant deflection in the x-axis and implant rotation around the y-axis.

Risk of Pacemaker Patients by TASER X26 Contact Mode Application

The prevalence of pacemaker patients among the general population and of conducted energy devices (CED) for law enforcement and self-defence is increasing. Consequently, the question whether cardiac pacemaker (CPM) patients are on particular risk becomes increasingly important. The risk of Taser X26 electric interference with implanted CPM has been investigated by numerical simulation at MRI-based anatomical models of CPM patients with devices implanted at conventional sites (left pectoral, right pectoral and abdominal) and with the monopolar CPM electrode placed at the ventricular apex. In spite of 10fold higher peak voltages the different coupling conditions make Taser-induced CPM interference voltages lower than those caused by external cardiac defibrillators. It is shown that electric interference considerably depends on ECD electrode orientation. The most unfavourable conditions are encountered with ECD electrodes aligned with the line from the CPM electrode tip to CPM can (EPC line). It could be shown that worst case interference voltages of monopolar pacemakers of any kind of implantation remain below the pulse immunity level as defined in safety standards of implantable cardiac pacemakers and of cardioverter defibrillators. However, interference voltages exceed CPM sensing thresholds. Therefore, capturing should be expected at Taser X26 contact mode application at any position at the upper part of the body including the abdomen, both at frontal and dorsal positions.

Experimental and numerical investigation of different types of articular cartilage replacement materials

AbstractThe aim of the presented work is to characterize the mechanical properties of different types of articular cartilage replacement materials. For this propose an elastic‐diffusion model is developed to identify the elastic and diffusion properties of the replacement materials. A set of unconfined compression tests were performed with several kinds of implants. By means of finite element simulation integrated with an user‐defined material model, the material parameters were identified. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Bone morphogenetic protein-2 in biodegradable gelatin and β-tricalcium phosphate sponges enhances the in vivo bone-forming capability of bone marrow mesenchymal stem cells

Bone marrow mesenchymal stem cells (MSCs) have been used for bone tissue engineering due to their osteogenic differentiation capability, but their application is controversial. To enhance their capability, we prepared biodegradable gelatin sponges incorporating β-tricalcium phosphate ceramics (GT sponge), which has been shown to possess excellent controlled drug-release properties. The GT sponge was used as a carrier for both rat MSCs and bone morphogenetic protein-2 (BMP-2) and osteogenic differentiation was assessed by subcutaneous implantation of four different kinds of implants, i.e. GT-alone, MSC-GT composites, BMP-GT composites and BMP-GT composites supplemented with MSCs (BMP-MSC-GT) in rats. Two weeks after implantation, histological sections showed new bone formation in the peripheral parts of the BMP-GT and in almost the total volume of the BMP-MSC-GT implants. After 4 weeks, histology as well as microCT analyses demonstrated extensive bone formation in BMP-MSC-GT implants. Gene expression and biochemical analyses of both alkaline phosphatase and bone-specific osteocalcin confirmed the histological findings. These results indicate that the combination of MSCs, GT and BMP synergistically enhances osteogenic capability and provides a rational basis for their clinical application in bone reconstruction.

The performance of bone marrow mesenchymal stem cell – Implant complexes prepared by cell sheet engineering techniques

This study investigated the hypothesis that cell sheets composed of multilayered rabbit bone marrow derived mesenchymal stem cells (MSC) could be assembled with two kinds of implants (surface-modified titanium and zirconia) for the construction of a MSC-implant. The MSC sheets were harvested from culture flasks, wrapped around implants to construct the complexes, and then cultured in osteogenic medium. The layered cell sheets integrated well with implants and remained viable, with small mineralized nodules visible on the implant surfaces for up to four weeks after culture. Cells on the implants underwent classical in vitro osteogenic differentiation with an associated elevation of alkaline phosphatase activity and bone- and vascular-related protein expression. In vivo, two kinds of cell sheet–implant complexes were transplanted under the skin of SCID mice and cultured for eight weeks. For the MSC sheet titanium implant complex, histological examination revealed that new bone tissue that formed around implants followed a predominantly endochondral pathway, exhibiting histological markers of native bone; for the MSC sheet zirconia implant complex, however, intramembranous ossification appeared to occur on the surface of the zirconia implant, as observed with typical osteocytes embedded in dense matrix and accompanied by both microvessels and marrow cavities. These findings demonstrate that MSC-implants possessing osteogenic and vascularization abilities can be produced using cell sheet engineering techniques in conjunction with routine implant materials, which provide a novel technology to modify the implant surface.

Revision Total Hip Arthroplasty Using a Fully Porous-Coated Long Stem - a Minimum 5 Years Follow up -

Purpose: We wanted to evaluate the mid-term results of revision total hip arthroplasty using a fully porous-coated long stem. Materials and Methods: A retrospective series of 20 hips in 19 patients who underwent stem revision with a fully porous-coated long stem were evaluated at a mean follow-up of 64.6 months. The causes of revision were aseptic loosening, periprosthetic fracture and infected arthroplasty. Four kinds of implants had previously been used and an additional bone graft procedure had been done in 17 cases. The Harris hip scores, thigh pain, limping and ROM were reported. Radiological changes of the radiolucent signs, subsidence, loosening and the stress shielding signs were evaluated. Results: The Harris hip score improved from an average of 56.5 to 91.9 and the ROMs were satisfactory. The only case with persistent thigh pain showed stable bony ingrowth. No signs of subsidence or loosening of the stem was found in all the cases. There were 2 cases of periprosthetic fracture. None of the patients experienced re-revision surgery. Conclusion: The mid-term results of revision hip arthroplasty using a fully porous coated long stem have demonstrated that it provides a reliable initial fixation with a propensity for stable longevity. It is relatively easy for the techniques, and there is the opportunity to restore the bone stock by bone-grafting procedures with diaphyseal fixation and bypassing a bone defect. Yet alternative techniques may be required for the femur with extensive diaphyseal bone loss. There are some concerns about the technique and the possibility of making a crack in the femur during the operation, which will cause thigh pain at the follow-up. So, only by employing great caution when performing this technique can successful results be guaranteed.

Isolation and characterization of collagen-binding domains from human von Willebrand factor

DNA fragments encoding for two collagen binding decapeptides from the human von Willebrand factor (vWF-H1 and vWF-H2) were cloned in the Escherichia coil culture. Overproducing strains of the chimeric proteins vWF(H1)-CBD and vWF(H2)-CBD consisting of the corresponding decapeptide, Gly-Ser spacer and a cellulose binding domain (CBD) from Anaerocellum thermophilum were constructed. Using one-stage purification on cellulose, the highly purified samples of vWF(H1)-CBD and vWF(H2)-CBD proteins were obtained and the ability of these proteins to bind collagen was studied. These constructions are planned to be used for development of the recombinant collagen binding proteins with different biological activities, which, in its turn, will be used for development of the new generation products and materials for medicine, such as different kinds of implants, the coats, etc.

0659: Scanning the Breast Implant

Breast implants are becoming more popular for both cosmetic augmentation and post-mastectomy reconstruction, and are increasingly encountered in practices offering breast ultrasound. This workshop will provide the sonographer with a working knowledge of the various kinds of implants which may be encountered, and their ultrasound appearances. The workshop will address the important points to consider when scanning a patient with breast implants, in order to confidently understand the findings.

The Endo-Distractor for preimplant mandibular regeneration

A simple practical device for a new technique of vertical distraction osteogenesis was developed. The Endo-Distractor Krenkel was originally intended for the anterior regeneration of highly atrophic mandibles. The Endo-Distractor features several novelties. Placement is made intraosseously in the basal cortical bone. The distraction screw length may be adapted to the depth of chin soft tissues. The quality of anchorage in the basal cortical bone guarantees the stability of the distraction vector. The endobuccal emergence is that of an artificial crown, and does not cause any patient discomfort. The device can easily be removed without secondary surgery. All kinds of implants may be placed after the retention time. This study's objective was to evaluate the use of the Endo-Distractor Krenkel in edentulous patients with highly atrophic mandibles. This new device was used on 18 patients, between January 2000 and September 2004, who were then followed-up for at least 36 months. Mandibular atrophy was measured with a lateral cephalogram, then classified according to Atwood's modified classification. The studied criteria included the amplitude of distraction, its duration, the distractor's lingual tilt, the number and outcome of implants, and complications. The sex ratio was 17 female for one male patient. The mean patient age was 56 years (43 to 66 years). The mean distraction amplitude was 11.3mm (8 to 14 mm). The mean retention time was 186.8 days (37 to 309 days). The distractor's mean lingual tilt was 4.3 degrees (0 to 23 degrees ). Two mandibular fractures occurred 6 weeks after placing the Endo-Distractor. The first one was treated medically, and the second one required removing the Endo-Distractor and osteosynthesis. An average of four interforaminal implants were placed for a total of 24 Brånemark and 51 Straumann implants. Four implants were lost in a patient due to infection. All other implants were osseointegrated. No bone loss was detected at follow-up after functional loading. These results show that alveolar distraction is possible on severely atrophic mandibles. The quality of bone and gum reconstruction is satisfactory both for functional and esthetic results. Surgical difficulty and rate of complications were lower than with conventional distraction techniques.

The Anatomy of the Acetabulum: What is Normal?

Published studies of the human hip make frequent reference to the normal pelvis and acetabulum. However, other than qualitative descriptions we found no clinically applicable published references describing a normal pelvis and acetabulum; such information is important for designing certain kinds of implants (eg, reconstruction cages). We describe a method to quantify, average, and apply data gathered from normal human specimens to create a standard representation of the ilium and ischium. One hundred healthy hemipelves from 50 human skeletons were evaluated. We measured angles and distances between major anatomic landmarks in the pelvis. The data collected were analyzed for variance and averaged to create a normal topographic map. Finally, we examined several commercially available acetabular reconstruction cages to determine the fit to the anatomically determined normal pelvis. These results provide a representation of true acetabular geometry and may serve as the basis for future acetabular reconstruction cage design.

Healing of surgically created circumferential gap around Nano‐coating surface dental implants in dogs

AbstractThe development and expanded use of dental implants has been remarkably increased. The implant stability and osseointegration are important factors in the success of treatment. Commercially pure titanium and its alloys are the most commonly used materials for endosseous dental implants. Hydroxyapatite (HA), one of the calcium phosphate, has been studied for biomedical applications since it has similarity in chemistry with inorganic components of human bone and its biocompatibility. But the use of HA coated dental implants remain still controversial, because some reports suggest that the HA coating may separate from the substructure, undergo dissolution in tissue fluids, and contribute to rapid breakdown around the implants. HA coating can be applied on metal implants by numerous methods. Of several coating methods, ion beam‐assisted deposition (IBAD) has shown to promise. This study was to compare the healing response of various nano‐coating surface implants (by IBAD) placed in surgically created circumferential gaps 12 weeks postplacement.In six mongrel dogs, all mandible premolars and the first molar were extracted and after an 8‐week healing period, four kinds of implants were placed. 2 mm circumferential coronal defects around the implants were performed surgically with a customized step drill. Groups were divided according to the fixture surfaces. The dogs were sacrificed following a 12 week healing period. Specimens were analyzed histologically and histomorphometrically.During the healing period, healing was uneventful and implants were well maintained. The bone‐to‐implant contact (BIC) for experimental groups —calcium phosphate coating implants with or without heat treatment‐ were much higher than the control group. The defect fill were also higher in the experimental groups. In the control group, the coronal part showed minimal bone fill and osseointegration.Within the scope of this study, calcium phosphate coating using IBAD may improve the bone response and the calcium phosphate coating may therefore be suitable in implant design with complex surface geometries. Copyright © 2008 John Wiley & Sons, Ltd.

Fabrication of Functionally Porous Structures by the Sheet Lamination Method

Recent trends in bio technology have resulted in the need for accurate fabrication of pore structure of sophisticated porous materials used in advanced applications such as substrates for tissue growth, and various kinds of implants. Control of pore size is important for promoting growth of blood vessels and adequate fluid flow. In the present study, an attempt has been made to fabricate functionally porous structures using titanium, including an internally controlled three-dimensional (3-D) fractal structure. A novel 3-D modeling method that combines rapid prototyping with spark plasma sintering (SPS) is proposed, which enables us to control the internal porous structure. Titanium powder-tape or sheet is sintered or cut by a pulsed Nd:YAG laser to form 2-D fractal cross-sections. These 2-D layers are temporarily laminated in a carbon mold, being then jointed by the SPS method to maintain the internal porous structure. Process parameters for the sheet lamination method have extensively been investigated.

Experimental Study of Autologous Cartilage, Acellular Cadaveric Dermis, Lyophilized Bovine Pericardium, and Irradiated Bovine Tendon

The purpose of this study was to compare the volumetric and histologic changes of the acellular cadaveric dermis, lyophilized bovine pericardium, irradiated bovine tendon, and autologous cartilage transplanted subcutaneously in the rats. Four different kinds of implants were placed in subcutaneous pockets of the dorsum of 40 Wister rats. The implants with the subcutaneous pockets were retrieved in the first, fourth, eighth, and 12th weeks after implantation. The size and histologic change of each implant were observed. The xiphoid cartilage showed the peak survival (71.0%, P = 0.247) on the 12th week, but part of the cartilage was absorbed irregularly and its shape changed unpredictably. The lyophilized bovine pericardium had a high survival rate as well (64.4%, P = 0.016). However, the size decreased significantly in the first through 12th weeks. A survival of acellular cadaveric dermis was lower (38.8%, P = 0.036) than the cartilage and pericardium, but it sustained the structure for 12 weeks and changed peripherally into the neocollagen. Irradiated bovine tendon disclosed the lowest survival rate (31.4%, P = 0.008). The structure was gradually distorted and replaced entirely by neocollagen in the 12th week after implantation. Autologous cartilage is the best choice for soft tissue and nasal tip augmentation. Although other implants than the cartilage showed significant diminution of its volume in 12 weeks, lyophilized bovine pericardium could be the next substitute to the cartilage in soft tissue augmentation.

Study of different biocomposite coatings on Ti alloy by a subsonic thermal spraying technique

A subsonic thermal spraying technique (STS) was used to make different biocomposite coatings on titanium alloys for preparing three kinds of implants: 8Ti2G, HA and 8H2B, respectively. The implants were embedded in a region of jaw of dogs whose teeth were pulled out three months previously. The dogs, in two groups, were killed 30 days and 90 days, respectively, after they were operated on. Osteointegration between the implants and host bone was investigated by x-ray, histology and the SEM technique. The results showed that the three kinds of coatings all exhibited good biocompatibility and synostosis, but their osteointegration capability showed a difference and decreased in the sequence of 8H2B, HA and 8Ti2G. The activity of coating, which promoted the reactions between implants and bone tissue, was further increased by the addition of bioglass in the 8H2B coating. Subsequently, chemical bonding was formed, and the osteointegration strength was increased. The study provided a new approach to prepare biocomposite coatings. The 8H2B implants, which formed an integral functional biocomposite coating on Ti alloys, showed a better osteointegration capability with bioactivity and pore gradient variation. A theoretical base was provided for the biocomposite coating application.

Revision Rhinoplasty Using Porous High-Density Polyethylene Implants to Reestablish Ethnic Identity

As is widely known, no ideal alloplastic material exists for augmentation or secondary rhinoplasty. This is an interesting article because it describes another attempt to achieve success managing the different problems with alloplastic materials when autologous cartilage is not available. I remark from my experience that the only justification for using these materials is that no septal or conchal cartilage was available. Besides, an important fact to mention is that the thick skin of some ethnic groups is ideal for success in augmentation rhinoplasty with alloplastic materials. In my experience, an adequate harvest of conchal cartilage leaves no deformity, and with the ‘‘tandem’’ method described by Dr. Ronald Gruber [1], it is very useful for restoration of dorsal height and regularity. The costal cartilage tends to warp, and osseus grafts resorb at a very high rate. Although there is no ideal alloplastic material, the surgeon must maximize perfection by managing the material he uses. I emphasize that when a surgeon places these kinds of implants, careful closure of incisions should be done. I believe, according to my experience with alloplastic materials, which includes more than 1,100 patients and more than 18 years of follow-up evaluation [2], that the advantages the authors mention in their article regarding the porosity of this material might represent a problem in the long term. If the material ever needs to be removed, it might be a difficult task. I agree with the importance of antibiotic prophylaxis to increase success in dealing with alloplastic materials. Finally, besides congratulating the authors for their enthusiasm, I encourage them to share with us, in the future, a long-term report with radiographic and clinical controls.

The Composition and Behavior of Capsules around Smooth and Textured Breast Implants in Pigs

The surface of the implant is one of the many factors often associated with the occurrence of capsular contracture, the etiopathogeny of which remains unclear. The purpose of this study was to analyze the behavior of capsular contracture by means of applanation tonometry and histology using a midsized animal model. Silicone breast implants were implanted into 33 pigs and observed at 30, 60, 180, and 270 postoperative days. Capsular contracture in smooth implants showed significantly greater pressure values of tonometry, and the smooth implant capsule was significantly thicker than the textured implant capsule. Both pressure and thickness of the capsules increased at each period. The collagenous layer did not show any difference considering the periods of time in which the total thickness was analyzed; on the other hand, the increase in total capsular thickness occurred by thickening of the noncollagenous layer in both smooth and textured implants. Taking into consideration both kinds of implants, histomorphometric analysis showed that thin fibers were replaced by thick fibers in later postoperatives periods (180 and 270 days). The greater incidence of capsular contracture in smooth implants was correlated with the progressive increase in total capsule thickness, due to a higher concentration of collagenous fibers, when compared with textured implants (p = 0.011; mean difference, 6.61), and a higher concentration of thick fibers (p = 0.034; average, >5.51 percentage points per field of thick fibers than the textured implants in all periods). Pigs are good animal models for studying the healing process after breast augmentation with implants.