RESUMO
When a cylinder is connected to an abutment it is expected that abutment and cylinder will be subjected to compression forces throughout their periphery because of the clamping force exerted by the screw. The deformation resultant of this compression should be measurable and uniform along the periphery of the abutment. Considering that multiple retainers connected to each other can affect the fit of a framework, as well as the use of different alloys, it is expected that the abutments will present different levels of deformation as a result of framework connection. The aim of this study was to evaluate the deformation of implant abutments after frameworks, cast either in cobalt-chromium (CoCr) or silver-palladium (AgPd) alloys, were connected. Samples (n â=â 5) simulating a typical mandibular cantilevered implant-supported prosthesis framework were fabricated in cobalt-chromium and silver-palladium alloys and screwed onto standard abutments positioned on a master-cast containing 5 implant replicas. Two linear strain gauges were fixed on the mesial and distal aspects of each abutment to capture deformation as the retention screws were tightened. A combination of compressive and tensile forces was observed on the abutments for both CoCr and AgPd frameworks. There was no evidence of significant differences in median abutment deformation levels for 9 of the 10 abutment aspects. Visually well-fit frameworks do not necessarily transmit load uniformly to abutments. The use of CoCr alloy for implant-supported prostheses frameworks may be as clinically acceptable as AgPd alloy.
Assuntos
Dente Suporte , Projeto do Implante Dentário-Pivô , Implantes Dentários , Ligas de Cromo/química , Ligas Dentárias/química , Revestimento para Fundição Odontológica/química , Adaptação Marginal Dentária , Retenção em Prótese Dentária/instrumentação , Prótese Dentária Fixada por Implante , Humanos , Teste de Materiais , Paládio/química , Prata/química , Estresse Mecânico , Propriedades de Superfície , TorqueRESUMO
PURPOSE: Nonpassive fit frameworks are believed to lead to implant overload and consequently loss of osseointegration. This is one of the most commonly reported failures of implant prostheses. In an ideal situation of passive fit, when torque is applied to bring the abutment-cylinder interface together some amount of deformation can be expected, and it should be homogeneous along the periphery of the abutment. The aim of this study was to verify the amount of abutment deformation that can be expected when a free-standing cylinder is screwed into place. This could give insight into what should be accepted as passive fit. MATERIALS AND METHODS: Strain gauges were bonded to the sides of five standard abutments that had machined palladium-silver cylinders or cobalt-chromium cast cylinders screwed into place. Measurements were taken to verify the deformation at each site. RESULTS: Values of abutment deformation after abutment screw tightening ranged from -127.70 to -590.27 microepsilon. The deformation recorded for palladium-silver prosthetic cylinder tightening ranged from 56.905 to -381.50 microepsilon (mean: 173.298 microepsilon) and from -5.62638 to -383.86 microepsilon (mean: 200.474 microepsilon) for cobalt-chromium cylinders. There was no statistically significant difference among the two groups. CONCLUSION: Both abutment screw tightening and prosthetic cylinder screw tightening result in abutment deformation, which is compressive most of the time.
Assuntos
Dente Suporte , Implantes Dentários , Ligas de Cromo/química , Ligas Dentárias/química , Materiais Dentários/química , Humanos , Teste de Materiais , Paládio/química , Pressão , Prata/química , Estresse Mecânico , Propriedades de Superfície , Titânio/química , TorqueRESUMO
OBJECTIVES: The purpose of this in vitro study was to analyze the stress distribution on components of a mandibular-cantilevered implant-supported prosthesis with frameworks cast in cobalt-chromium (Co-Cr) or palladium-silver (Pd-Ag) alloys, according to the cantilever length. MATERIAL AND METHODS: Frameworks were fabricated on (Co-Cr) and (Pd-Ag) alloys and screwed into standard abutments positioned on a master-cast containing five implant replicas. Two linear strain gauges were fixed on the mesial and distal aspects of each abutment to capture deformation. A vertical static load of 100 N was applied to the cantilever arm at the distances of 10, 15, and 20 mm from the center of the distal abutment and the absolute values of specific deformation were recorded. RESULTS: Different patterns of abutment deformation were observed according to the framework alloy. The Co-Cr alloy framework resulted in higher levels of abutment deformation than the silver-palladium alloy framework. Abutment deformation was higher with longer cantilever extensions. CONCLUSION: Physical properties of the alloys used for framework interfere with abutment deformations patterns. Excessively long cantilever extensions must be avoided.
Assuntos
Ligas Dentárias/química , Prótese Dentária Fixada por Implante , Planejamento de Dentadura , Mandíbula/cirurgia , Ligas de Cromo/química , Dente Suporte , Análise do Estresse Dentário/instrumentação , Módulo de Elasticidade , Humanos , Teste de Materiais , Paládio/química , Prata/química , Estresse Mecânico , Propriedades de SuperfícieRESUMO
OBJECTIVES: In cantilevered implant-supported complete prosthesis, the abutments' different heights represent different lever arms to which the abutments are subjected resulting in deformation of the components, which in turn transmit the load to the adjacent bone. The purpose of this in vitro study was to quantitatively assess the deformation of abutments of different heights in mandibular cantilevered implant-supported complete prosthesis. MATERIAL AND METHODS: A circular steel master cast with five perforations containing implant replicas (Theta 3.75 mm) was used. Two groups were formed according to the types of alloy of the framework (CoCr or PdAg). Three frameworks were made for each group to be tested with 4, 5.5 and 7 mm abutments. A 100 N load was applied at a point 15 mm distal to the center of the terminal implant. Readings of the deformations generated on the mesial and distal aspects of the abutments were obtained with the use of strain gauges. RESULTS: Deformation caused by tension and compression was observed in all specimens with the terminal abutment taking most of the load. An increase in deformation was observed in the terminal abutment as the height was increased. The use of an alloy of higher elastic modulus (CoCr) also caused the abutment deformation to increase. CONCLUSION: Abutment's height and framework alloy influence the deformation of abutments of mandibular cantilevered implant-supported prosthesis.
Assuntos
Dente Suporte , Ligas Dentárias/química , Implantes Dentários , Planejamento de Prótese Dentária , Prótese Dentária Fixada por Implante , Prótese Total Inferior , Fenômenos Biomecânicos , Ligas de Cromo/química , Análise do Estresse Dentário/instrumentação , Planejamento de Dentadura , Módulo de Elasticidade , Humanos , Mandíbula/fisiopatologia , Teste de Materiais , Paládio/química , Prata/química , Estresse Mecânico , Propriedades de SuperfícieRESUMO
Understanding how clinical variables affect stress distribution facilitates optimal prosthesis design and fabrication and may lead to a decrease in mechanical failures as well as improve implant longevity. In this study, the many clinical variations present in an implant-supported prosthesis were analyzed by a 3-dimensional finite-element method. The anterior segment of a human mandible treated with 5 implants supporting a curved beam was created to perform the tests. The variables introduced in the computer model were cantilever length, elastic modulus of cancellous bone, abutment length, implant length, and framework alloy (AgPd or CoCr). The computer was programmed with physical properties of the materials as derived from the literature, and a 100-N vertical load was used to simulate the occlusal force. Images with fringes of stress were obtained, and the maximum stress at each site was plotted in graphs for comparison. Stresses tended to be concentrated at the cortical bone around the neck of the implant closest to the load, whereas stresses in cancellous bone were considered low. In general, the stress distribution was better with stiffer cancellous bone, longer abutments and implants, and shorter cantilevers. The use of a CoCr alloy framework appears to contribute to a better stress distribution.
Assuntos
Implantes Dentários , Análise de Elementos Finitos , Mandíbula/fisiopatologia , Fenômenos Biomecânicos , Força de Mordida , Densidade Óssea/fisiologia , Ligas de Cromo/química , Simulação por Computador , Dente Suporte , Ligas Dentárias/química , Planejamento de Prótese Dentária , Prótese Dentária Fixada por Implante , Módulo de Elasticidade , Ligas de Ouro/química , Humanos , Imageamento Tridimensional , Modelos Biológicos , Paládio/química , Estresse Mecânico , Propriedades de SuperfícieRESUMO
Os diversos avanços ocorridos nos últimos anos tanto na Odontologia como nas Ciências de Computaçäo permitiram uma aproximaçäo entre estas duas áreas. Através de recursos computacionais tornou-se possível a análise e a soluçäo de problemas complexos encotrados no tratamento de pacientes com dentições comprometidas. Esses recursos envolvem, entre outros, a análise de fotoelasticidade, o método de elementos finitos e a extensometria. Neste artigo säo relatadas as aplicaçöes desses procedimentos naresoluçäo de carregamentos de próteses sobre implantes, bem como as potencialidades que esses recursos apresentam para a pesquisa