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Fixtures
Selected AbstractsClinical and Radiographic Evaluation of the 5-mm Diameter Regular-Platform Brånemark Fixture:2- to 5-Year Follow-upCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 1 2002DSc Odont, Georges Tawil DDS ABSTRACT Purpose: The purpose of this study was to report the clinical results obtained with 5-mm diameter regular-platform Brånemark implants after 2 to 5 years of follow-up. A secondary aim was to compare the clinical outcome to that of adjacently placed standard 3.75-mm fixtures in the same patients under the same operative condition and in the same prosthetic construction. Materials and Methods: Sixty patients, with a mean age of 54 years, received a total of 97 5-mm diameter regular-platform fixtures. The majority of the implants were placed at molar sites. In 41 of the patients, 53 5-mm diameter implants were placed adjacent to 62 standard 3.75-mm diameter fixtures in the same prosthetic reconstruction. All implants were submerged for an average period of 4 to 6 months. Abutment connection was done according to standard protocol. The prosthetic treatment consisted of freestanding fixed bridges. Results: The cumulative survival rate of the 5-mm diameter implants loaded for a period of 2 to 5 years was 96.9%. Only three implants failed. They were placed in type 4 bone in the posterior maxilla. Bone loss over the first year was 0.70 mm and over a 3-year period 0.81 mm. Implants placed in type 4 bone showed significantly higher bone loss. No difference in the resorption rate could be found between the maxillary and the mandibular implants or between the various implant lengths. There was no significant difference between the bone loss around the 5-mm diameter fixtures and the adjacent 3.75-mm diameter standard fixtures. Conclusion: The present study demonstrated a high predictability of 5-mm diameter regular-platform implants when placed in the posterior maxilla and mandible. [source] The Career Cycle Approach To Defining The Interior Design Profession's Body Of KnowledgeJOURNAL OF INTERIOR DESIGN, Issue 1 2004Denise A. Guerin Ph.D. ABSTRACT The purpose of this study was to define and document the interior design profession's body of knowledge at a single point in time. This was done using a career cycle approach and a health, safety, and welfare framework. The method and framework used to define the body of knowledge are presented in the article. The body of knowledge was defined from a career cycle approach using the four stages of a professional interior designer's career cycle: education, experience, examination, and legal regulation (NCIDQa, 2003). A content analysis was conducted of the written documents of the organizations that represent each stage in the cycle. Eighty-one knowledge areas were identified from this content analysis and placed into one of seven categories: Codes; Communication; Design; Furnishings, Fixtures, and Equipment; Human Needs; Interior Building Construction; and Professional Practice. These categories and knowledge areas are what defined the interior design profession's body of knowledge based on this approach. Next, each knowledge area was analyzed using a health, safety, and welfare framework to determine its benefit to the public. Finally, a review of literature was conducted to document that the knowledge areas comprise the specialized knowledge necessary for the professional interior designer to protect the public's health, safety, and welfare. The method used to define the interior design profession's body of knowledge assessed several limited bodies of knowledge that had been developed for a specific purpose, such as education or examination. While this comprehensive body of knowledge reflects a single point in time, it provides a venue for dialogue from which revision can occur and updating can continue, leading to further development of the profession. [source] Rehabilitation by means of osseointegrated implants in oral cancer patients with about four to six years follow-upJOURNAL OF ORAL REHABILITATION, Issue 3 2006J. SEKINE summary, This paper describes the reconstruction of mandibular defects in four oral cancer patients using iliac crest bone grafts and osseointegrated implants. In three patients, reconstructive surgery using a reconstruction plate and free forearm skin flap was performed following tumour and segmental mandibular resection. After 7,9 months, mandibular reconstruction with a free iliac bone graft was carried out. In one patient, reconstructive surgery was performed with vascularized iliac bone grafting with an anterolateral thigh flap at the same time as the tumour resection. Fixtures were placed in the transplanted bone, and abutments were connected 6,9 months later together with vestibuloplasty. Gingival grafts were used to replace the skin flap around abutments. All implants survived throughout the approximately 4,6 years observation time. Marginal bone loss of the graft was originally several millimetres but less than 1·5 mm. Bone loss as well as management of peri-implant soft tissue was also discussed. [source] In vitro differences of stress concentrations for internal and external hex implant,abutment connections: a short communicationJOURNAL OF ORAL REHABILITATION, Issue 1 2006Y. MAEDA summary, The aim of this study was to clarify the difference in the stress distribution patterns between implants with external-hex or internal-hex connection systems using in vitro models. Three 13 mm fixtures with external-hex and internal-hex connections were installed into an acrylic bone analogue. One piece abutments of 7 mm height was connected. Strain gauges were attached to the abutment surface, and the cervical and fixture tip areas of the bone analogue surface. Vertical and horizontal load applied was 30 N. Data were normalized for each model by obtaining values relative to the sum of the three values. Almost the same force distribution pattern was found under vertical load in both systems. Fixtures with external-hex showed an increase in strain at the cervical area under horizontal load, while in internal-hex fixtures the strain was at the fixture tip area. Within limitations of our model study, it was suggested that fixtures with internal-hex showed widely spread force distribution down to the fixture tip compared with external hex ones. [source] Malignant Tumors of the Maxilla: Virtual Planning and Real-Time Rehabilitation with Custom-Made R-zygoma Fixtures and Carbon,Graphite Fiber-Reinforced Polymer ProsthesisCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 1 2008Karl Ekstrand LDS ABSTRACT Background: Oral cancer is a mutilating disease. Because of the expanding application of computer technology in medicine, new methods are constantly evolving. This project leads into a new technology in maxillofacial reconstructive therapy using a redesigned zygoma fixture. Purpose: Previous development experiences showed that the procedure was time-consuming and painful for the patients. Frequent episodes of sedation or general anesthetics were required and the rehabilitation is costly. The aim of our new treatment goal was to allow the patients to wake up after tumor surgery with a functional rehabilitation in place. Materials and Methods: Stereolithographic models were introduced to produce a model from the three-dimensional computed tomography (CT). A guide with the proposed resection was fabricated, and the real-time maxillectomy was performed. From the postoperative CT, a second stereolithographic model was manufactured and in addition, a stent for the optimal position of the implants. Customized zygoma implants were installed (R-zygoma, Integration AB, Göteborg, Sweden). A fixed construction was fabricated by using a new material based on poly(methylacrylate) reinforced with carbon/graphite fibers and attached to the implants. On the same master cast, a separate obturator was fabricated in permanent soft silicon. Results: The result of this project showed that it was possible to create a virtual plan preoperatively to apply during surgery in order for the patient to wake up functionally rehabilitated. Conclusion: From a quality-of-life perspective, it is an advantage to be rehabilitated fast. By using new computer technology, pain and discomfort are less and the total rehabilitation is faster, which in turn reduces days in hospital and thereby total costs. [source] The Establishment of a Protocol for the Total Rehabilitation of Atrophic Maxillae Employing Four Zygomatic Fixtures in an Immediate Loading System , A 30-Month Clinical and Radiographic Follow-UpCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 4 2007Luis Rogério Duarte ABSTRACT Background:, The existing approaches to the treatment of the atrophic maxilla are difficult and involve an element of risk. Purpose:, The aim of the present study was to establish a new surgical/prosthetic protocol for the treatment of extremely atrophic maxillae using four zygomatic implants (ZIs) in an immediate loading system. Materials and Methods:, Twelve patients were treated with the surgical placement of 48 ZIs, and the totally edentulous maxillae were rehabilitated with protocol-type maxillary prostheses rigidly fixed to the ZIs in an immediate loading system. Follow-up was conducted at 6 months and again at 30 months. Results:, Of the 48 ZIs inserted, one implant failed to achieve osseointegration. The prosthetic components fitted well and no sinus pathology was detected in any of the patients. Conclusion:, The surgical/prosthetic protocol showed that it was possible to insert four ZIs in an immediate loading system and achieve stability for up to 30 months. [source] The Role of Functional Parameters for Topographical Characterization of Bone-Anchored ImplantsCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 2 2006Anna Arvidsson MSc ABSTRACT Background, The surface topographical characterization of bone-anchored implants has been recommended to be based on amplitude, spatial, and hybrid parameters. There are also functional parameters that have the potential to describe characteristics important for a specific application. Purpose, The aim of the present study was to evaluate if parameters that have been described as functional in engineering applications are also relevant in the topographical characterization of bone-anchored implants. Materials and Methods, The surface topography of threaded titanium implants with different surface roughness (Sa, Sds, and Sdr) was analyzed with an optical interferometer, and five candidating functional parameters (Sbi, Sci, Svi, Sm, and Sc) were calculated. Examples of the same parameters for five commercially available dental implants were also calculated. Results, The highest core fluid retention index (Sci) was displayed by the turned implants, followed by fixtures blasted with 250- and 25-,m particles, respectively. Fixtures blasted with 75-,m Al2O3 particles displayed the lowest Sci value. This is the inverse order of the bone biological ranking based on earlier in vivo studies with the experimental surfaces included in the present study. Conclusion, A low core fluid retention index (Sci) seems favorable for bone-anchored implants. Therefore, it is suggested to include Sci to the set of topographical parameters for bone-anchored implants to possibly predict the biological outcome. [source] Early Loading of Four or Five Astra Tech Fixtures with a Fixed Cross-Arch Restoration in the MandibleCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 3 2002Bruno Collaert DDS ABSTRACT Background: A change in implant placement has emerged recently from two-stage to one-stage surgery and to earlier and even immediate loading of the fixtures. Purpose: The aim of this study was to verify whether four or five fixtures installed in the edentulous mandible were suitable for early loading with a cross-arch fixed restoration. Materials and Methods: In 25 consecutively treated patients (28,88 yr), four or five Astra Tech fixtures (Mölndal, Sweden) were installed in edentulous mandibles. During the same surgical procedure, the abutments were connected. An impression was taken immediately after surgery. All patients received a fixed prosthetic rehabilitation of 10 to 12 teeth made of a cast metal framework and acrylic teeth/gingiva within a month. The fixtures were followed up clinically and radiographically for 7 to 24 months. Bone level was measured from the most coronal point of the vertical part of the fixture to the most apical bone level mesially or distally. Results: No fixtures were lost during follow-up. No postoperative complications occurred. Radiographic analysis showed a mean bone level of 0.6 mm after 7 to 12 months. Fixtures followed up from 13 to 18 and 19 to 24 months showed a mean bone level of 0.7 mm. Around two fixtures, the bone level was found at the first implant thread. All other fixtures showed the bone level somewhere along the vertical unthreaded part of the fixture. Conclusions: Early loading within 1 month of four or five Astra Tech fixtures in the edentulous mandible is a predictable procedure for a follow-up period of 6 to 24 months. [source] One-Year Prospective Evaluation of the Early Loading of Unsplinted Conical Brånemark Fixtures with Mandibular Overdentures Immediately following SurgeryCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 1 2001Alan G.T. Payne BDS, FCD(SA), MDent ABSTRACT Background: Prospective evaluation of the early loading of unsplinted Branemark implants with mandibular over-dentures opposing conventional dentures is not evident in the implant-related literature. Purpose: To clinically evaluate progressive and early loading of 20 unsplinted conical Brånemark implants in edentulous mandibles with overdentures. Materials and Methods: Ten edentulous patients all had two conical Brånemark implants placed in the anterior mandible with mandatory primary stability with bicortical anchorage. Ball abutment connection was performed simultaneously. Previously constructed conventional mandibular dentures were temporarily relined with tissue conditioner postoperatively and worn with moderation for the first 2 weeks to allow progressive loading. Early loading of the implants followed after 2 weeks, with inclusion of the respective matrices in the mandibular dentures, using a definitive reline procedure. Results: All patients successfully functioned with their mandibular implant overdentures from 2 to 52 weeks postoperatively. Mean marginal bone loss was within established criteria for success:0.22 mm (SD = 0.48 mm) mesially and 0.30 mm (SD = 0.39 mm) distally on the conical implants. Mobility tests using the Periotest instrument became more negative, although not at statistically significant levels. Difficulties in the management of the peri-implant mucosa between surgery and loading at 2 weeks were observed in 40% of the patients. Conclusions: These preliminary 1-year results show that successful early loading of unsplinted conical Brånemark implants with mandibular overdentures is possible. [source] Subcrestal placement of two-part implantsCLINICAL ORAL IMPLANTS RESEARCH, Issue 3 2009Maria Welander Abstract Objective: The aim of the present experiment was to study the healing around two-part implants that were placed in a subcrestal position. Material and methods: Five mongrel dogs, about 2 years old, were included. The mandibular premolars and the first, second and third maxillary premolars were extracted. Three months later two test and two control implants (OsseoSpeedÔ, 3.5 mm × 8 mm) were placed in one side of the mandible. The implants were placed in such a way that the implant margin was located 2 mm apical to the bone crest. In the test implants, the surface modification extended to the implant margin and, thus, included the shoulder part of the implant. Regular abutments with a turned surface (ZebraÔ) were connected to the control implants, while experimental abutments with a modified surface (TiOblastÔ) were connected to the test implants. A plaque control program that included cleaning of implants and teeth every second day was initiated. Four months later the dogs were euthanized and biopsies were obtained and prepared for histological analysis. Results: The marginal bone level at the test implants was identified in a more coronal position than that at the control implants. In 40% of the test implants, the bone-to-implant contact extended coronal of the abutment/fixture (A/F) border, i.e. in contact with the abutment part of the implant. The connective tissue portion of the peri-implant mucosa that was facing the test abutments contained a higher density of collagen and a smaller proportion of fibroblasts than that at the control sites. Conclusion: It is suggested that osseointegration may occur coronal to the A/F interface of two-part implants. Such a result, however, appears to depend on the surface characteristics of the implant components. [source] Comparison of forces transmitted through different EVA mouthguardsDENTAL TRAUMATOLOGY, Issue 4 2006Craig F. Duhaime Abstract,,, Athletic mouthguards have been recommended for decades with varying levels of athlete acceptance. Issues related to compliance center around the ability to breath and speak while wearing the mouthguards. Fabrication techniques have changed over time to a two-layer ethylene vinyl acetate mouthguard fabricated on a high-pressure machine. The reported ideal thickness of these mouthguards has been somewhat variable depending on the sport and anticipated level of risk. Recent research however, has identified 4 mm as the optimal thickness of EVA. In this study an acrylic dental cast was fabricated and mounted to a drop impact fixture. Mouthguards of varying ply, thickness and palatal coverage were fabricated and tested in the fixture. Strain gauges and load cells were used to evaluate the effect of ply, thickness, and palatal coverage on the ability of these mouthguards to minimize transmitted forces. The purpose of this study was to identify those variables of mouthguard construction that will minimize the overall transmitted force of impact to the anterior dentition. [source] Ankerung im Untertagebau , Entwicklungen in Theorie und PraxisGEOMECHANICS AND TUNNELLING, Issue 5 2008Stefan Kainrath-Reumayer Dipl.-Ing. Die systematische Ankerung des Gebirges stellt ein wesentliches Verfahren zur Stabilisierung unterirdischer Hohlraumbauten dar. Die geschichtliche Entwicklung verschiedener Ankersysteme wird kurz vorgestellt und Unterteilungsmöglichkeiten werden aufgezeigt. Unterschiedliche Ansätze der Systemankerungen in analytischen und numerischen Berechnungen werden mit der diskreten Modellierung des Gesamtssystems in numerischen Berechnungen mit FLAC3D verglichen. Der Einfluss von Systemankerungen auf das Systemverhalten ist von einer Reihe von Randbedingungen abhängig, der Erfolg der Anwendung oftmals von den verwendeten Ankersystemen. Extreme Spannungszustände im Gebirge stellen hohe Anforderungen an die Methodik der Gebirgsankerung in Untertagebauwerken, die mit den herkömmlichen Ankerungssystemen nur eher unzufriedenstellend zu bewältigen sind. In Abhängigkeit von den Eigenschaften des Gebirges ist unter solch hohen, die Festigkeit des intakten Gebirges meist bereits überschreitenden Spannungszuständen mit großen Verschiebungen, Stabilitätsproblemen sowie Bergschlagphänomenen zu rechnen. Um diesen Anforderungen bestmöglich gerecht zu werden, wird ein neuartiger, energieabsorbierender Ankertyp "Roofex" vorgestellt, der sowohl unter langsam kriechenden, statischen, wie auch abrupten, dynamischen Beanspruchungen einen kontrollierbaren und konstanten Widerstand entlang eines definierten Gleitwegs aufweist. Rock bolting in subsurface constructions , developments in theory and praxis The systematic bolting of rock is a key support element in NATM tunnelling. A short review on the historical development and methods of classification is presented. Different methods of implementation in analytical and numerical calculations are compared to the discrete modelling of the system via FLAC 3D. The influence of the systematic rock bolting to the system behaviour is dependent on many boundary conditions, the success often depends on the used rock bolting techniques. High rock mass stress conditions in underground excavations are serious challenges for rock bolting systems, where conventional bolting systems can only cope with in an rather unsatisfactory way. Depending on the rock mass conditions, high stresses, which mostly exceed already the intact rock mass strength, will lead to serious stability problems, high deformation rates and rockburst phenomena. To provide the mining and tunnelling industry with a rock reinforcement fixture that is better suited to mining with high stress conditions, Atlas Copco GDE designed a new, energy absorbing rock bolt "Roofex" that can accommodate both very large displacements (static yielding) and high energy release (dynamic rupture) in the rock mass by offering an accurate pre-set deformation behaviour. [source] Track three diplomacy and human rights in Southeast Asia: the Asia Pacific Coalition for East TimorGLOBAL NETWORKS, Issue 1 2002Herman Joseph S. Kraft Transnational networks of non-government organizations are increasingly becoming a fixture in international relations, particularly their contribution to traditional notions of diplomacy and its objectives. Less noticed, however, is the involvement of transnational NGO networks in alternative channels for diplomatic exchange, which have been referred to as ,track three diplomacy'. Described as a form of civil society that transcends borders and nationalities, track three networks and activities involve NGO networks that are movement based, and concerned primarily with raising public consciousness over issues. While their direct influence on formal processes of foreign policy-making has been limited, they have contributed to expanding both the scope of debate in international relations and the breadth of participation in those debates. Track three networks provide a forum for those communities marginalized by an international system that gives primacy of place to states and their officially-declared concerns. Their impact is limited, however, by their lack of institutionalization and their reluctance to cooperate with government agencies , an issue that goes towards both their effectiveness and their identity in the long-term. [source] Impact of energy efficiency upgrade retrofits on the residential energy consumption in CanadaINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2001Burak Guler Abstract The impact of various energy efficiency upgrade scenarios on the annual energy consumption of the Canadian housing stock is assessed using the Canadian Residential Energy End-use Model (CREEM). The energy efficiency upgrade scenarios that are considered include major retrofits, such as the improvement of the house envelope by adding insulation, and the replacement of the existing heating system and appliances by higher efficiency units, as well as minor retrofits, such as lighting fixture, thermostat, showerhead and aerator upgrades that reduce energy consumption. The economic feasibility of each upgrade was assessed using the indicator ,energy savings per dollar investment'. The results indicate that the energy savings potential of the retrofits is rather small, resulting in savings of 0,8 per cent of the total energy consumption of the Canadian housing stock. Copyright © 2001 John Wiley & Sons, Ltd. [source] Use of stereolithography to manufacture critical-sized 3D biodegradable scaffolds for bone ingrowth,JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2003Malcolm N. Cooke Abstract A novel approach to the manufacture of biodegradable polymeric scaffolds for tissue-engineering utilizing stereolithography (SLA) is presented. SLA is a three-dimensional (3D) printing method that uses an ultraviolet laser to photo-crosslink a liquid polymer substrate. The current generation of SLA devices provide a 3D printing resolution of 0.1 mm. The experiments utilized a biodegradable resin mixture of diethyl fumarate (DEF), poly(propylene fumarate) (PPF), and a photoinitiator, bisacylphosphine oxide (BAPO). The PPF is crosslinked with the use of the SLA's UV laser (325-nm wavelength). An SLA device was retrofitted with a custom fixture build tank enclosing an elevator-driven build table. A 3D prototype model testing the manufacturing control this device provides was created in a computer-aided-design package. The resulting geometric data were used to drive the SLA process, and a DEF/PPF prototype part was successfully manufactured. These scaffolds have application in the tissue engineering of bony substrates. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 64B: 65,69, 2002 [source] Submerged healing following surgical treatment of peri-implantitis: a case seriesJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 8 2007Ann-Marie Roos-Jansåker Abstract Objectives: The aim was to study a regenerative surgical treatment modality for peri-implantitis employing submerged healing. Material and Methods: Twelve patients, having a minimum of one osseointegrated implant with peri-implantitis, with a progressive loss of 3 threads (1.8 mm) following the first year of healing were involved in the study. After surgical exposure of the defect, granulomatous tissue was removed and the implant surface was treated using 3% hydrogen peroxide. The bone defects were filled with a bone substitute (Algipore®), a resorbable membrane (Osseoquest®) was placed over the grafted defect and a cover screw was connected to the fixture. The implant was then covered by flaps and submerged healing was allowed for 6 months. After 6 months the abutment was re-connected to the supra-structure. Results: A 1-year follow-up demonstrated clinical and radiographic improvements. Probing depth was reduced by 4.2 mm and a mean defect fill of 2.3 mm was obtained. Conclusion: Treatment of peri-implant defects using a bone graft substitute combined with a resorbable membrane and submerged healing results in defect fill and clinical healthier situations. [source] TREATMENT OF CULTIVATED HIGHBUSH BLUEBERRIES (VACCINIUM CORYMBOSUM L.) WITH ELECTRON BEAM IRRADIATION: DOSIMETRY AND PRODUCT QUALITYJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2008M.A. MORENO ABSTRACT We determined the dose distribution within a tray of highbush blueberries (Vaccinium corymbosum L.) exposed to electron beam irradiation at medium levels (1.0,3.2 kGy) using Monte Carlo and computer tomography scanning technology. We also evaluated the quality of irradiated and nonirradiated (control) fruits stored at 5C and 70% relative humidity during 14 days by a series of chemical analyses. Blueberries packed in plastic clamshell containers (trays) were irradiated using a 10-MeV linear accelerator with single-beam fixture (top only). Irradiation of blueberries at 1.1 kGy had no significant (P > 0.05) effect on the fruit quality with the exception of ascorbic acid, which decreased by 17% by the end of storage. Irradiation had an enhancing effect on the total phenolic and tannin content of all the irradiated fruits (10,20% increases). The calculated dose distribution in a pack of blueberries confirmed that the dose is not uniformly distributed within the pack because of density inhomogeneities (flesh, skin air). Dose levels at the bottom of the trays were 18 (±8%) higher than at the top. These results suggest that careful dose distribution examination must be conducted prior to setting up of an irradiation run for the packed fruits. Excellent agreement was found between measured and calculated doses at different electron beam conveyor speeds. PRACTICAL APPLICATIONS Little information is available on how electron beam irradiation penetrates a complex medium such as packed blueberries. This study presents unique results from a dose distribution calculation method using Monte Carlo simulation and computed tomography scanning techniques, which can be an effective tool for the development of proper irradiation treatment planning of packed fruits and other fresh produce. The suitability of using electron beam technology to preserve the quality characteristics and shelf life of packed blueberries was verified. [source] Stress relaxation of bone significantly affects the pull-out behavior of pedicle screwsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2004Serkan Inceoglu Abstract The initial fixation strength of pedicle screws is commonly tested using a standard pull-out test with load applied at a constant rate. This method overlooks the cyclic nature of in situ loading responsible for clinical failure. This study was undertaken to determine the effects of stress relaxation properties at the bone,screw interface on screw fixation strength. Pedicle screws were inserted into calf lumbar vertebrae using a paired testing array. After embedding and mounting in a custom fixture, axial pull-out tests were performed at the rates of 1, 5, and 25 mm/min. For each vertebra, one screw was pulled at a continuous rate. The other screw was pulled at increments of 0.5 mm, at the same rate, with 1000 s pause between increments. Peak load, energy-to-failure, displacement-to-failure, and stiffness were calculated for each screw pull-out test. Two-way ANOVA showed that the standard pull-out method yielded significantly higher peak loads (p < 0.05) at faster pull-out rates and higher stiffnesses (p < 0.05) at all rates compared to the stress relaxation pull-out protocol. These results suggest that the stress relaxation properties of bone significantly affect the pull-out behavior of pedicle screws, reducing the peak load and stiffness values observed during testing. This mode of testing may provide a better biomechanical model of screw pull-out failure and a more accurate estimate of initial fixation strength. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Effect of Implant Angulation upon Retention of Overdenture AttachmentsJOURNAL OF PROSTHODONTICS, Issue 1 2005MSEd, MSciDent, Michael P. Gulizio DMD Introduction: Overdentures supported and retained by endosteal implants depend upon mechanical components to provide retention. Ball attachments are frequently described because of simplicity and low cost, but retentive capacity of these components may be altered by a lack of implant parallelism. Purpose: The aim of this in vitro study was to investigate the retention of gold and titanium overdenture attachments when placed on ball abutments positioned off-axis. Methods and Materials: Four ball abutments were hand-tightened onto ITI dental implants and placed in an aluminum fixture that allowed positioning of the implants at 0°, 10°, 20°, and 30° from a vertical reference axis. Gold and titanium matrices were then coupled to the ball abutments at various angles and then subjected to pull tests at a rate of 2 mm/second; the peak loads of release (maximum dislodging forces) were recorded and subjected to statistical analyses. A balanced and randomized factorial experimental design testing procedure was implemented. Results: Statistically significant differences in retention of gold matrices were noted when ball abutments were positioned at 20° and 30°, but not at 0° and 10°. Statistically significant differences were noted among the titanium matrices employed for the testing procedure, as well as for the 4 ball abutments tested. Angle was not a factor affecting retention for titanium matrices. Conclusions: (1) The gold matrices employed for the testing procedures exhibited consistent values in retention compared to titanium matrices, which exhibited large variability in retention. (2) Angle had an effect upon the retention of gold matrices, but not for titanium matrices. [source] Dry Powder Deposition and Compaction for Functionally Graded CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2006Zachary N. Wing Functionally graded ceramics, with property variations realized via local compositional changes or porosity, are fabricated by powder deposition and compaction. A removable fixture is used to control the location of dry powders to produce a macroscopic powder array with 2-D or 3-D compositional variations. A new method is presented that relies on traditional powder pressing techniques to create spatial variation in composition and density. The fixture is removed before conventional powder compaction. This dry powder deposition and compaction method is capable of producing large monolithic bodies with functional gradients. This method produces designs with 3 mm discrete regions or pixels that have a normalized positional tolerance of 0.6% for a 39 mm substrate size. The method is used to realize a UHF antenna substrate with spatially variable dielectric properties. [source] Theoretical and experimental analysis of plastic response of isotropic circular plates subjected to underwater explosion loadingMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 2 2008J. Z. Ashani Abstract Dynamic response analysis of structures subjected to underwater explosion (UndEx) loading has been always an interesting field of study for ship designers and metal forming specialists. Understanding the deformation and rupture mechanism of simple structures plays an important role in successful designing of a reliable structure under this kind of loading. In this paper, first the major parameters of the UndEx phenomenon (peak overpressure, impulse per unit area, dimensionless damage parameter ,, etc.) are discussed and determined by means of available experimental relations mostly offered by R. Cole. After that, the maximum deflection of a fully clamped circular plate has been calculated using a theoretical procedure assuming two different conditions: (1) neglecting the effect of strain rate, (2) considering the strain rate sensitivity of the material. Some experiments have been conducted on 5010 aluminum circular plates, using C4 as explosive. In order to simulate reality, a fixture was designed so that the plates are loaded in air-backed condition. Plates were fixed on top of the fixture, so the fully clamped condition which was assumed as the boundary condition was achieved. The test specimens were measured, not only their maximum deflection but also their thickness at different radii were determined. The results are compared to experimental-based predictions offered by Nurick and Rajendran who has conducted similar experiments. The results show reasonable agreement with theoretical predictions, especially when strain rate effects are considered. In addition, two new material constants (D, q) for this special aluminum alloy are introduced. Theoretische und experimentelle Analyse der plastischen Umformung isotroper kreisförmiger Platten bei Unterwasser-Explosionsbelastung Die Analyse der dynamischen Reaktion einer Struktur bei einer Explosionsbelastung unter dem Wasser ist für die Konstrukteure von Schiffen und Umformspezialisten eine interessante Forschungsaufgabe. Das Verständnis der Umformung und der Bruchmechanismen einfacher Strukturen spielt eine wichtige Rolle im erfolgreichen Konstruieren einer festen Struktur gegen diese Belastungsart. In diesem Beitrag werden erstens die Hauptparameter der Explosionserscheinung unter Wasser (maximaler Druck, Impulse per Flächeneinheit, dimensionsloser zerstörender Parameter usw.) dargestellt und zweitens durch die vorhandenen Methoden, die überwiegend von R. Cole vorliegen, berechnet. Danach ist die maximale Durchbiegung einer ganz gespannten kreisförmigen Platte durch eine analytische Methode in zwei Formen bestimmt worden: (1) Vernachlässigung der Dehnungsgeschwindigkeit, (2) Berücksichtigung der Dehnungsgeschwindigkeitsempfindlichkeit des Werkstoffes. Einige Untersuchungen wurden an kreisförmigen Platten aus Aluminium 5010 mittels Sprengstoff C4 durchgeführt. Zur Praxissimulation wurde die Spannvorrichtung so konstruiert, so dass die Platten Luft-gepuffert belastet wurden. Die Platten wurden oben auf der Spannvorrichtung vollständig eingespannt, um Grenzbedingungen zu erhalten. Bei den Proben wurde nicht nur die maximale Durchbiegung sondern auch die Dicke in verschiedenen Radien ermittelt. Die Ergebnisse wurden mit den experimentellen Abschätzungen von Nurick und Rajendran, die ähnliche Versuche durchgeführt haben, verglichen. Die Ergebnisse zeigen eine gute Übereinstimmung mit den theoretischen Abschätzungen, insbesondere bei Betrachtung der Dehngeschwindigkeit. Zusätzlich wurden für diese spezielle Aluminiumlegierung zwei neue Materialkonstanten (D, q) eingeführt. [source] Numerical model for polymer electrolyte membrane fuel cells with experimental application and validationASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2009Javier Alonso Mora Abstract The aim of this paper is to present a simple 3D computational model of a polymer electrolyte membrane fuel cell (PEMFC) that simulates over time the heat distribution, energy, and mass balance of the reactant gas flows in the fuel cell including pressure drop, humidity, and liquid water. Although this theoretical model can be adapted to any type of PEMFC, for verification of the model and to present different analysis it has been adapted to a single cell test fixture. The model parameters were adjusted through a series of experimental tests and the model was experimentally validated for a well-defined range of operating conditions: H2/air O2 as reactants, flow rates of 0.5,1.5 SLPM, dew points and cell temperatures of 30,80 °C, currents 0,5 A and with/without water condensation. The model is especially suited for the analysis of liquid water condensation in the reactant channels. A key finding is that the critical current at which liquid water is formed is determined at different flows, temperatures, and humidity. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Micromotion and Stress Distribution of Immediate Loaded Implants: A Finite Element AnalysisCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 4 2009A. Fazel DDS ABSTRACT Background: Primary stability and micromotion of the implant fixture is mostly influenced by its macrodesign. Purpose: To assess and compare the peri-implant stress distribution and micromotion of two types of immediate loading implants, immediate loaded screw (ILS) Nisastan and Xive (DENTSPLY/Friadent, Monnheim, Germany), and to determine the best macrodesign of these two implants by finite element analysis. Methods: In this experimental study, the accurate pictures of two fixtures (ILS: height = 13, diameter = 4 mm and Xive: height = 13, diameter = 3.8 mm) were taken by a new digital camera (Nikon Coolpix 5700 [Nikon, Japan], resolution = 5.24 megapixel, lens = 8× optical, 4× digital zoom). Following accurate measurements, the three-dimensional finite element computer model was simulated and inserted in simulated mandibular bone (D2) in SolidWorks 2003 (SolidWork Corp., MA, USA) and Ansys 7.1 (Ansys, Inc., Canonsburg, PA, USA). After loading (500 N, 75° above horizon), the displacement was displayed and von Mises stress was recorded. Results: It was found that the primary stability of ILS was greater (152 µm) than Xive (284 µm). ILS exhibited more favorable stress distribution. Maximum stress concentration found in periapical bone around Xive (,30 MPa) was lesser than Nisastan (,37 MPa). Conclusions: Macrodesign of ILS leads to better primary stability and stress distribution. Maximum stress around Xive was less. [source] Malignant Tumors of the Maxilla: Virtual Planning and Real-Time Rehabilitation with Custom-Made R-zygoma Fixtures and Carbon,Graphite Fiber-Reinforced Polymer ProsthesisCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 1 2008Karl Ekstrand LDS ABSTRACT Background: Oral cancer is a mutilating disease. Because of the expanding application of computer technology in medicine, new methods are constantly evolving. This project leads into a new technology in maxillofacial reconstructive therapy using a redesigned zygoma fixture. Purpose: Previous development experiences showed that the procedure was time-consuming and painful for the patients. Frequent episodes of sedation or general anesthetics were required and the rehabilitation is costly. The aim of our new treatment goal was to allow the patients to wake up after tumor surgery with a functional rehabilitation in place. Materials and Methods: Stereolithographic models were introduced to produce a model from the three-dimensional computed tomography (CT). A guide with the proposed resection was fabricated, and the real-time maxillectomy was performed. From the postoperative CT, a second stereolithographic model was manufactured and in addition, a stent for the optimal position of the implants. Customized zygoma implants were installed (R-zygoma, Integration AB, Göteborg, Sweden). A fixed construction was fabricated by using a new material based on poly(methylacrylate) reinforced with carbon/graphite fibers and attached to the implants. On the same master cast, a separate obturator was fabricated in permanent soft silicon. Results: The result of this project showed that it was possible to create a virtual plan preoperatively to apply during surgery in order for the patient to wake up functionally rehabilitated. Conclusion: From a quality-of-life perspective, it is an advantage to be rehabilitated fast. By using new computer technology, pain and discomfort are less and the total rehabilitation is faster, which in turn reduces days in hospital and thereby total costs. [source] Early Loading of Four or Five Astra Tech Fixtures with a Fixed Cross-Arch Restoration in the MandibleCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 3 2002Bruno Collaert DDS ABSTRACT Background: A change in implant placement has emerged recently from two-stage to one-stage surgery and to earlier and even immediate loading of the fixtures. Purpose: The aim of this study was to verify whether four or five fixtures installed in the edentulous mandible were suitable for early loading with a cross-arch fixed restoration. Materials and Methods: In 25 consecutively treated patients (28,88 yr), four or five Astra Tech fixtures (Mölndal, Sweden) were installed in edentulous mandibles. During the same surgical procedure, the abutments were connected. An impression was taken immediately after surgery. All patients received a fixed prosthetic rehabilitation of 10 to 12 teeth made of a cast metal framework and acrylic teeth/gingiva within a month. The fixtures were followed up clinically and radiographically for 7 to 24 months. Bone level was measured from the most coronal point of the vertical part of the fixture to the most apical bone level mesially or distally. Results: No fixtures were lost during follow-up. No postoperative complications occurred. Radiographic analysis showed a mean bone level of 0.6 mm after 7 to 12 months. Fixtures followed up from 13 to 18 and 19 to 24 months showed a mean bone level of 0.7 mm. Around two fixtures, the bone level was found at the first implant thread. All other fixtures showed the bone level somewhere along the vertical unthreaded part of the fixture. Conclusions: Early loading within 1 month of four or five Astra Tech fixtures in the edentulous mandible is a predictable procedure for a follow-up period of 6 to 24 months. [source] Early Functional Loading of Brånemark Dental Implants: 5-Year Clinical Follow-up StudyCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 2 2000Ingvar Ericsson DDS ABSTRACT Background: Short-term clinical studies have indicated the possibility of one-stage surgery and early loading of machined titanium implants. However, long-term data comparing the outcome to the conventional two-stage technique are missing. Purpose: A clinical and radiographic study was performed to compare the outcome of oral rehabilitation of the endentulous mandible by fixed suprastructures connected to implants installed according to either (1) a one-stage surgical procedure and early loading (experimental group - EG) or (2) the original two-stage concept (reference group - RG). The EG and RG comprised 16 and 11 subjects, respectively. Materials and Methods: The following specific inclusion criterion were adopted: (1) all patients had to consider themselves to be in good general health, (2) the amount of bone had to enable the installation of five to six, at least 10-mm long fixtures (Mk II fixtures; Nobel Biocare AB, Göteborg, Sweden) between the mental foramina, and (3) the patients had to be available for the follow-up and maintenance program. A total of 88 implants were placed in the EG compared to 30 in the RG. In the EG, fixed appliances were connected to the implants within 20 days following implant installation while the fixed appliances in the RG were connected about 4 months following fixture installation. At delivery of the suprastructures, all patients were radiographically examined, an examination that was repeated at the 18- and 60-month follow-ups. Results: The analysis of the radiographs from the EG disclosed that during the observation period, between 18 and 60 months, the mean loss of bone support amounted to 0.2 mm (SD = 0.4). The corresponding value observed in the RG was 0.0 mm (SD = 0.5). During the 60-month observation period, no fixture was lost in any of the two groups examined. The implants under study as well as those in the reference material were at all observation intervals found to be clinically stable. Conclusions: This clinical study demonstrated that it is, at least based on a 5-year observation period, possible to successfully load via a permanent fixed rigid cross-arch suprastructure titanium dental implants soon after installation. However, such a treatment approach has to be strictly limited to the interforamina area of the endentulous mandible. Furthermore, the bone resorption was found to be within the same range around such implants as around implants installed and loaded according to the original two-stage protocal. [source] Marginal Bone Level around Implants Assessed in Digital and Film Radiographs: In Vivo Study in the DogCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 1 2000Eva Borg DDS ABSTRACT Background: One of the objectives of postoperative radiographic examinations of implants is to evaluate the marginal bone height and its changes over time. Purpose: The purpose of this study was to assess the influence of digital image processing on measurements of the marginal bone level around implants. Material and Methods: Implants in beagle dogs, used to study the development of peri-implantitis and subsequent healing following treatment, were monitored with conventional radiography and a digital image plate system. Five observers measured the distance between a reference point and the bone level. Measurements in conventional radiographs were made with the use of an x-ray viewer (2X) and a magnifying lens (7X). For the digital images, the system's built-in measuring function was used together with five image processing techniques: edge enhancement (matrixes set on 5 and 25), inverted grey scale, single color highlight, and color intensity mapping together with the brightness and contrast control. From the time of maximum breakdown and the end of the experiment, histologic values were available. Results: Differences between techniques and observers increased toward the end of the healing period. Measurements made at maximum breakdown did not differ significantly from the histologic value. Measurements made after healing all methods, except that using edge enhancement and a 25 × 25 kernel, differed significantly from the histologic value by underestimating the bone level. Conclusions: Measurements of bone level around implants from digital radiographs are as accurate and precise as those from film images. In particular cases, the use of specific image processing algorithms may improve both accuracy and precision. After healing, the histologic specimens showed an incomplete bone fill in the crater with a remaining thin layer of connective tissue in contact with the fixture, and in such situations, the morphology of the bone will give a more complicated diagnostic task. [source] Effect of conical configuration of fixture on the maintenance of marginal bone level: preliminary results at 1 year of functionCLINICAL ORAL IMPLANTS RESEARCH, Issue 4 2010Jung-Joo Kim Abstract Objectives: To evaluate and to compare the effect of the conical neck design on marginal bone loss around the fixtures, when both implants were provided with micro-threads to the top of the fixture. Materials and methods: Two types of implant, one with a straight shape (S) and the other with a conical neck design (C) provided with a retentive element to the top of the fixture, were placed adjacent to each other in the partially edentulous areas of 12 patients. Bone loss around each implant was analyzed after 1 year of functional loading. The bone losses after loading were compared using Wilcoxon's signed-rank test. Results: The mean marginal bone losses (S, 0.05±0.09 mm; C, 0.07±0.14 mm) were not statistically significant between the two groups (P=0.578). Conclusions: There was no significant difference between conical and straight neck implants in terms of marginal bone loss after 1 year of loading. To cite this article: Kim J-J, Lee D-W, Kim C-K, Park K-H, Moon I-S. Effect of conical configuration of fixture on the maintenance of marginal bone level: preliminary results at 1 year of function. Clin. Oral Impl. Res. 21, 2010; 439,444 doi: 10.1111/j.1600-0501.2009.01871.x [source] Placement of Brånemark implants in the maxillary tuber region: anatomical considerations, surgical technique and long-term resultsCLINICAL ORAL IMPLANTS RESEARCH, Issue 1 2009Arne Ridell Abstract Background: Fixture placement in the tuber area is one way to overcome the problem of insufficient bone volume for routine implant surgery in the posterior maxilla due to severe resorption of jawbone and an extensive enlargement of the maxillary sinus. However, little is known about the long-term results. Purpose: The aim of this study was to retrospectively evaluate the survival rate and marginal bone conditions at fixtures placed in the tuber region of the maxilla. Material and methods: Twenty-one patients previously treated with at least one implant in the tuber region of the maxilla were included in this retrospective analysis. A total of 23 standard Brånemark System fixtures with a turned surface had been surgically placed in the tuber regions and 71 additional implants in adjacent areas to support fixed dental bridges. All implants were allowed to heal for 6,8 months before abutment connection and following prosthetic treatment. The patients were radiographed after 1,12 years for evaluation of marginal bone levels. In addition, the relation between the apex of the fixture in the tuberosity area and the posterior border of the maxilla was measured. Results: Twenty of the 21 patients representing 22 tuber and 64 additional implants were radiographically evaluated. No implants in the tuber areas were lost during the follow-up whereas two fixtures in the anterior region had to be removed, one before loading and the other after 4 years of loading not interfering with the prosthesis stability. The mean marginal bone level at tuber implants was situated on average 1.6 mm (SD 1.1, n=22) from the abutment-fixture junction, whilst the other implants showed an average bone level of 1.9 mm (SD 0.8, n=64). The results were similar when comparing partially and totally edentulous patients. Conclusion: The present retrospective study shows good clinical outcome with standard Brånemark fixtures placed in the tuber region of the posterior maxilla using a two-stage procedure. In appropriate cases where bone of adequate volume and density is available, our data indicate that the technique can be used as an alternative to more extensive surgery and especially to the sinus lift procedure. However, prospective comparative studies are needed in order to evaluate the efficacy of the described technique for this purpose. [source] Bone reactions to longstanding functional load at implants: an experimental study in dogsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 9 2005T. Berglundh Abstract Objectives: The aims of the present investigation were (i) to study marginal bone level alterations following implant installation, abutment connection and functional loading and (ii) to analyse bone tissue reactions to functional load. Material and Methods: Six beagle dogs, about 1-year old, were used. All mandibular pre-molars were extracted. Three months later four implants of the Astra Tech Implants® Dental System were installed in one side of the mandible and four standard fixtures of the Brånemark System® were placed in the contralateral side of the mandible. Abutment connection was performed 3 months later and a plaque control programme was initiated. Three months after abutment connection fixed partial dentures (FPDs) made in gold were cemented to the maxillary canines and pre-molars. FPDs were also connected to the three posterior implants in each side of the mandible, while the mesial implant in each side was used as an unloaded control. Radiographs were obtained from all implant sites following implant installation, abutment connection and FPD placement. Ten months after the FPD placement the radiographic examination was repeated. The animals were sacrificed and biopsies from all implant sites were obtained and prepared for histological analysis. Results: The radiographic analysis revealed that largest amount of bone loss occurred following implant installation and abutment connection and that this loss was more pronounced at Brånemark than at Astra implants. The bone level alterations that were observed at implants exposed to 10 months of functional load in both implant systems were small and did not differ from control sites. The histological analysis revealed that implants exposed to functional load exhibited a higher degree of bone-to-implant contact than control implants in both implant systems. Conclusion: It is suggested that functional load at implants may enhance osseointegration and does not result in marginal bone loss. [source] | ||||||||||||||||||||||