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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Computational Stress and Deformation Analysis of Mammary Prosthesis

Potter, Tavis L. 08 April 2003 (has links)
A linear and non-linear material model for the breast implants was developed through axial tension testing, while linear and non-linear breast tissue models were assumed based on smooth muscle. These material models were to develop axisymmetric finite element models to determine the stresses in the implant walls under tissue loading. The non-linear material models were used to more accurately model the complex nature of the implant stresses. After analysis it was found that the implants were under compressive loading which meant that local buckling in the implant might be possible. For accurate stress prediction in the implant walls and to fully characterize implant buckling a more accurate non-linear breast tissue material model needs to be developed. Having this material model would allow for a full three-dimensional finite element model can be developed. With the development of a three-dimensional FEA model the implant buckling and implant stresses could be fully characterized. Ultimately allowing for accurate implant stress estimation and fatigue life calculation using the Palmgren-Miner rule, S-N curves, and an external load spectra. / Master of Science
2

Mätning av Mikroläckage i Dentala Implantat

Löfgren, Jonas, Karlsson, Maria January 2007 (has links)
<p>Osseointegrated titanium implants have become a commonly used method in edentulous jaws and today there are success rates in the magnitude of 82 % in the lower jaw and 98 % in the upper. During first year after implantation a fully normal marginal bone loss of 1-2 mm occurs. If the bone loss continues there is a risk of implant failure. High tensions in bone and inflammation caused by bacteria are possible reasons for this problem. It has been shown that a leakage of bacterias occurs between the parts of the implant and there are theories that this has effects on the marginal bone loss.</p><p>The aim of this thesis has been to increase the knowledge about microbial leakage with help of in vitro tests and virtual simulations. The goal was to create a test method to measure differences of microbial leakage in two implant systems.</p><p>The developed test method includes an in vitro test of six implants and Finite Element Analysis. The test method is the product of a process with several small tests. The final test method measures leakage of a coloured fluid with a spectrophotometer. The results are then compared with the virtual simulations to draw conclusions and find explanations how the implants are functioning.</p><p>The result of test on six implants, four Ospol and two Nobel Replace, indicates that there are differences in the magnitude of microleakage in different implant systems in due to the implant-abutment interface. No conclusions can be drawn before the test method is refined and more implants are tested.</p>
3

Mätning av Mikroläckage i Dentala Implantat

Löfgren, Jonas, Karlsson, Maria January 2007 (has links)
Osseointegrated titanium implants have become a commonly used method in edentulous jaws and today there are success rates in the magnitude of 82 % in the lower jaw and 98 % in the upper. During first year after implantation a fully normal marginal bone loss of 1-2 mm occurs. If the bone loss continues there is a risk of implant failure. High tensions in bone and inflammation caused by bacteria are possible reasons for this problem. It has been shown that a leakage of bacterias occurs between the parts of the implant and there are theories that this has effects on the marginal bone loss. The aim of this thesis has been to increase the knowledge about microbial leakage with help of in vitro tests and virtual simulations. The goal was to create a test method to measure differences of microbial leakage in two implant systems. The developed test method includes an in vitro test of six implants and Finite Element Analysis. The test method is the product of a process with several small tests. The final test method measures leakage of a coloured fluid with a spectrophotometer. The results are then compared with the virtual simulations to draw conclusions and find explanations how the implants are functioning. The result of test on six implants, four Ospol and two Nobel Replace, indicates that there are differences in the magnitude of microleakage in different implant systems in due to the implant-abutment interface. No conclusions can be drawn before the test method is refined and more implants are tested.
4

Corrosion behaviour of implant alloys

Wright, A. R. January 1988 (has links)
No description available.
5

An investigation into the effects of two bioceramics on rat mandibular bone

McCord, J. Fraser January 1986 (has links)
No description available.
6

Comparison of osseointegration in piezoimplants versus cylindrical implants

Fujinaka, Trevor 10 July 2019 (has links)
BACKGROUND: Dental implants have been successful for the restoration of edentulous areas, but current techniques are inadequate in areas lacking sufficient bone volume. Piezoelectric surgery has shown encouraging effects on both osseous healing. A new wedge-shaped titanium PiezoImplant requires piezoelectric osteotomy. This study compares PiezoImplants to conventional threaded cylindrical shaped implants by microcomputed tomography and histology to assess osseointegration, tissue response, and alveolar ridge changes. METHODS: After 3 months post-extraction, 18 conventional cylindrical implants and 18 wedge-shaped PiezoImplants were placed using a split-mouth design in 3 adult mini pigs. The cylindrical implant sites were prepared for osteotomy with rotary instrumentation while the PiezoImplant sites were prepared with piezoelectric surgical inserts. One animal was sacrificed at 4, 8, and 12 weeks post operation. Quantitative µCT and histological analysis evaluated bone volume, osseointegration, and post-operative cellular events. RESULTS: The results of a multivariable linear regression model demonstrated that the PiezoImplants, arch location, and time were significant factors on higher BV/TV percentage. Bone to implant contact (BIC) analysis by high resolution microscopy and histomorphometry indicated osseointegration though intimate contact between implants and adjacent alveolar bone in both groups. The tissue response displayed no evidence of abnormal healing and the PiezoImplant was classified as a non-irritant. CONCLUSION: The combination of piezoelectric osteotomy and newly designed PiezoImplants had favorable effects on wound healing and osseointegration compared to conventional cylindrical implants. These novel wedge-shaped implants may be beneficial for narrow ridge spaces without additional ridge augmentation. Further research is needed to establish clinical validity.
7

Casting distortion of five-fixture supported implant frameworks fabricated on master casts

Mitha, Tasneem 23 October 2008 (has links)
Statement of the problem: Conventional techniques for implant framework fabrication have been shown to produce errors that are inconsistent with the passive-fit requirement for osseointegrated implant frameworks. Purpose: The aim of this study was to assess the three-dimensional distortion inherent in casting of full arch, screw-retained titanium implant frameworks. Materials and methods: A conventional commercial laboratory one-piece casting, using the lost-wax technique was used. Five wax patterns were fabricated on a die-stone cast poured from a plaster impression of a five-fixture brass analogue. A reflex microscope was used to determine the three-dimensional casting error, by measuring horizontal and vertical distances for each wax pattern and its corresponding cast titanium framework, as well as offset distances from the horizontal reference plane. Results: Significant differences were found in the amount of distortion between wax patterns and cast frameworks, with the castings being approximately 416 μm to 477 μm larger than the wax frameworks. The greatest amount of distortion occurred at the terminal implant abutments, and in the vertical dimension. However, there was inconsistency in these differences, indicating the three-dimensional nature of the overall distortion of the cast frameworks. Conclusions: It is doubtful whether any conventionally cast framework can be made to the degree of accuracy required to fit passively on its abutments because of the multiple variables inherent in this process. It is therefore recommended that all full-arch, cast titanium frameworks be cast in sections, or alternatively be sectioned, indexed and soldered before being seated intraorally.
8

Ceramic orbital implant: a study of the efficacy, acceptability and safety of a locally produced hydroxyapatite orbital implant for the anophthalmic socket

Levitz, Mark Lewis 04 June 2008 (has links)
ABSTRACT A novel locally manufactured and developed porous hydroxyapatite orbital implant has been investigated and found to be as safe as commercially available implants. Objective To describe and analyze the results of twenty orbital implants implanted into patients in one arm of a multicentre trial. Methods A porous hydroxyapatite orbital implant with a smooth cap was developed and implanted into twenty patients. These patients were followed up for a period of four months. Patients were examined for signs of infection or extrusion of the implants. The amount of post-operative pain, chemosis, granuloma formation and vascularity was also assessed. Results None of the twenty patients had any signs of extrusion or infection at the termination of the study. There was very little pain or chemosis noted and no granuloma formation. Conclusion The locally developed implants were safe in anophthalmic eyes when reviewed after a four month follow-up period.
9

Bisphosphonate-loaded hydroxyapatite-coated implant surfaces : physico-chemical characterisation and bone cell culture studies

McLeod, Kate January 2007 (has links)
This thesis investigates bisphosphonate adsorption onto plasma sprayed HA (PS-HA) and simulated body fluid-grown HA (SBF-HA) coatings commonly used for orthopaedic implants. Bisphosphonates exhibit high binding affinity for the calcium present in HA and hence can be adsorbed onto HA-coated implants to exploit their beneficial properties for improved bone growth at the implant interface.
10

Electrode-tissue interface: development and findings of an in vitro model

Newbold, Carrie January 2006 (has links) (PDF)
In the period immediately following the implantation of a cochlear implant electrode array within the cochlear environment, the power required to stimulate the auditory nerve at preset current levels increases. This rise is due to increases in electrode impedance which in turn is suggested to be a result of tissue growth around the electrode array. The foreign body response initiated by the immune system encapsulates the array in a matrix of fibrous tissue, separating the electrode array from the rest of the body. A second change in electrode impedance occurs with the onset of electrical stimulation. A transitory reduction in impedance has been recorded in animals and humans after stimulation of electrodes. Impedance returns to pre-stimulation levels following the cessation of stimulation. It was suggested that these changes in impedance with stimulation were also related to the tissue growth around the electrode array. A more thorough understanding of the interface was required to ascertain these concepts.

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