RESUMO
Because many mechanical variables are present in the oral cavity, the proper load transfer between the prosthesis and the bone is important for treatment planning and for the longevity of the implant-supported fixed partial denture. Objectives To verify the stress generated on the peri-implant area of cantilevered implant-supported fixed partial dentures and the potential effects of such variable. Material and Methods A U-shaped polyurethane model simulating the mandibular bone containing two implants (Ø 3.75 mm) was used. Six groups were formed according to the alloy's framework (CoCr or PdAg) and the point of load application (5 mm, 10 mm and 15 mm of cantilever arm). A 300 N load was applied in pre-determined reference points. The tension generated on the mesial, lingual, distal and buccal sides of the peri-implant regions was assessed using strain gauges. Results Two-way ANOVA and Tukey statistical tests were applied showing significant differences (p<0.05) between the groups. Pearson correlation test (p<0.05) was applied showing positive correlations between the increase of the cantilever arm and the deformation of the peri-implant area. Conclusions This report demonstrated the CoCr alloy shows larger compression values compared to the PdAg alloy for the same distances of cantilever. The point of load application influences the deformation on the peri-implant area, increasing in accordance with the increase of the lever arm.
Assuntos
Ligas Dentárias/química , Prótese Dentária Fixada por Implante/métodos , Análise do Estresse Dentário , Prótese Parcial Fixa , Análise de Variância , Ligas de Cromo/química , Força Compressiva , Planejamento de Prótese Dentária , Módulo de Elasticidade , Teste de Materiais , Paládio/química , Valores de Referência , Reprodutibilidade dos Testes , Prata/química , Estresse Mecânico , TorqueRESUMO
ABSTRACT Because many mechanical variables are present in the oral cavity, the proper load transfer between the prosthesis and the bone is important for treatment planning and for the longevity of the implant-supported fixed partial denture. Objectives To verify the stress generated on the peri-implant area of cantilevered implant-supported fixed partial dentures and the potential effects of such variable. Material and Methods A U-shaped polyurethane model simulating the mandibular bone containing two implants (Ø 3.75 mm) was used. Six groups were formed according to the alloy’s framework (CoCr or PdAg) and the point of load application (5 mm, 10 mm and 15 mm of cantilever arm). A 300 N load was applied in pre-determined reference points. The tension generated on the mesial, lingual, distal and buccal sides of the peri-implant regions was assessed using strain gauges. Results Two-way ANOVA and Tukey statistical tests were applied showing significant differences (p<0.05) between the groups. Pearson correlation test (p<0.05) was applied showing positive correlations between the increase of the cantilever arm and the deformation of the peri-implant area. Conclusions This report demonstrated the CoCr alloy shows larger compression values compared to the PdAg alloy for the same distances of cantilever. The point of load application influences the deformation on the peri-implant area, increasing in accordance with the increase of the lever arm.
Assuntos
Ligas de Cromo/química , Prótese Dentária Fixada por Implante/métodos , Ligas Dentárias/química , Análise do Estresse Dentário , Paládio/química , Valores de Referência , Prata/química , Estresse Mecânico , Teste de Materiais , Reprodutibilidade dos Testes , Análise de Variância , Planejamento de Prótese Dentária , Força Compressiva , Torque , Prótese Parcial Fixa , Módulo de ElasticidadeRESUMO
This study aimed to analyze the stress distribution in single implant system and to evaluate the compatibility of an in vitro model with finite element (FE) model. The in vitro model consisted of Brånemark implant; multiunit set abutment of 5 mm height; metal-ceramic screw-retained crown, and polyurethane simulating the bone. Deformations were recorded in the peri-implant region in the mesial and distal aspects, after an axial 300 N load application at the center of the occlusal aspect of the crown, using strain gauges. This in vitro model was scanned with micro CT to design a three-dimensional FE model and the strains in the peri-implant bone region were registered to check the compatibility between both models. The FE model was used to evaluate stress distribution in different parts of the system. The values obtained from the in vitro model (20-587 µÎµ) and the finite element analysis (81-588 µÎµ) showed agreement among them. The highest stresses because of axial and oblique load, respectively were 5.83 and 40 MPa for the cortical bone, 55 and 1200 MPa for the implant, and 80 and 470 MPa for the abutment screw. The FE method proved to be effective for evaluating the deformation around single implant. Oblique loads lead to higher stress concentrations.
Assuntos
Implantes Dentários para Um Único Dente , Análise de Elementos Finitos , Imageamento Tridimensional/métodos , Silicatos de Alumínio/química , Fenômenos Biomecânicos , Ligas de Cromo/química , Simulação por Computador , Coroas , Projeto do Implante Dentário-Pivô , Porcelana Dentária/química , Prótese Dentária Fixada por Implante , Análise do Estresse Dentário/instrumentação , Humanos , Mandíbula/fisiologia , Teste de Materiais , Ligas Metalo-Cerâmicas/química , Modelos Anatômicos , Modelos Biológicos , Compostos de Potássio/química , Estresse Mecânico , Microtomografia por Raio-X/métodosRESUMO
UNLABELLED: Knowing how stresses are dissipated on the fixed implant-supported complex allows adequate treatment planning and better choice of the materials used for prosthesis fabrication. OBJECTIVES: The aim of this study was to evaluate the deformation suffered by cantilevered implant-supported fixed prostheses frameworks cast in silver-palladium alloy and coated with two occlusal veneering materials: acrylic resin or porcelain. MATERIAL AND METHODS: Two strain gauges were bonded to the inferior surface of the silver-palladium framework and two other were bonded to the occlusal surface of the prosthesis framework covered with ceramic and acrylic resin on each of its two halves. The framework was fixed to a metallic master model and a 35.2 N compression force was applied to the cantilever at 10, 15 and 20 mm from the most distal implant. The measurements of deformation by compression and tension were obtained. The statistical 2-way ANOVA test was used for individual analysis of the experiment variables and the Tukey test was used for the interrelation between all the variables (material and distance of force application). RESULTS: The results showed that both variables had influence on the studied factors (deformation by compression and tension). CONCLUSION: The ceramic coating provided greater rigidity to the assembly and therefore less distortion compared with the uncoated framework and with the resin-coated framework. The cantilever arm length also influenced the prosthesis rigidity, causing higher deformation the farther the load was applied from the last implant.
Assuntos
Resinas Acrílicas/química , Ligas Dentárias/química , Porcelana Dentária/química , Planejamento de Prótese Dentária , Prótese Dentária Fixada por Implante , Facetas Dentárias , Análise de Variância , Força Compressiva , Técnica de Fundição Odontológica , Análise do Estresse Dentário , Teste de Materiais , Paládio/química , Valores de Referência , Reprodutibilidade dos Testes , Prata/química , Propriedades de Superfície , Resistência à Tração , Fatores de TempoRESUMO
Knowing how stresses are dissipated on the fixed implant-supported complex allows adequate treatment planning and better choice of the materials used for prosthesis fabrication. Objectives: The aim of this study was to evaluate the deformation suffered by cantilevered implant-supported fixed prostheses frameworks cast in silver-palladium alloy and coated with two occlusal veneering materials: acrylic resin or porcelain. Material and Methods: Two strain gauges were bonded to the inferior surface of the silver-palladium framework and two other were bonded to the occlusal surface of the prosthesis framework covered with ceramic and acrylic resin on each of its two halves. The framework was fixed to a metallic master model and a 35.2 N compression force was applied to the cantilever at 10, 15 and 20 mm from the most distal implant. The measurements of deformation by compression and tension were obtained. The statistical 2-way ANOVA test was used for individual analysis of the experiment variables and the Tukey test was used for the interrelation between all the variables (material and distance of force application). Results: The results showed that both variables had influence on the studied factors (deformation by compression and tension). Conclusion: The ceramic coating provided greater rigidity to the assembly and therefore less distortion compared with the uncoated framework and with the resin-coated framework. The cantilever arm length also influenced the prosthesis rigidity, causing higher deformation the farther the load was applied from the last implant. .
Assuntos
Resinas Acrílicas/química , Ligas Dentárias/química , Porcelana Dentária/química , Planejamento de Prótese Dentária , Prótese Dentária Fixada por Implante , Facetas Dentárias , Análise de Variância , Força Compressiva , Técnica de Fundição Odontológica , Análise do Estresse Dentário , Teste de Materiais , Paládio/química , Valores de Referência , Reprodutibilidade dos Testes , Prata/química , Propriedades de Superfície , Resistência à Tração , Fatores de TempoRESUMO
The aim of this study was to evaluate the effect of unilateral angular misfit of 100 µm on stress distribution of implant-supported single crowns with ceramic veneering and gold framework by three-dimensional finite element analysis. Two three-dimensional models representing a maxillary section of premolar region were constructed: group 1 (control)-crown completely adapted to the implant and group 2-crown with unilateral angular misfit of 100 µm. A vertical force of 100 N was applied on 2 centric points of the crown. The von Mises stress was used as an analysis criterion. The stress values and distribution in the main maps (204.4 MPa for group 1 and 205.0 MPa for group 2) and in the other structures (aesthetic veneering, framework, retention screw, implant, and bone tissue) were similar for both groups. The highest stress values were observed between the first and second threads of the retention screw. Considering the bone tissue, the highest stress values were exhibited in the peri-implant cortical bone. The unilateral angular misfit of 100 µm did not influence the stress distribution on the implant-supported prosthesis under static loading.
Assuntos
Coroas , Implantes Dentários , Adaptação Marginal Dentária , Prótese Dentária Fixada por Implante , Análise de Elementos Finitos , Imageamento Tridimensional/métodos , Dente Pré-Molar , Fenômenos Biomecânicos , Simulação por Computador , Dente Suporte , Porcelana Dentária/química , Planejamento de Prótese Dentária , Facetas Dentárias , Ligas de Ouro/química , Humanos , Maxila/fisiologia , Ligas Metalo-Cerâmicas/química , Modelos Biológicos , Estresse Mecânico , Propriedades de SuperfícieRESUMO
This finite element analysis study evaluated the optimal material combination for the superstructure of single implant-supported prosthesis with different fit patterns. Two models of a two-dimensional finite element analysis were constructed: group A (control), prosthesis presenting precise fit to implant; and group B, prostheses with unilateral angular misfit of 100 microm. Each group was divided into 5 subgroups according to different materials for framework (gold alloy, titanium, and zirconia) and veneering (porcelain and modified composite resin). Evaluation was performed on ANSYS software with 133-N load applied at the opposite side of misfit on the model. The load was applied with a 30-degree angulation and 2-mm off-axis. The presence of unilateral angular misfit (group B) increased the von Mises stresses in the implant (40%) and retention screw (7%) in comparison to group A. The combination of porcelain/titanium and porcelain/zirconia displayed more favorable stress distribution. When gold alloy was used as a framework material, there was no difference in stress values for both veneering materials in all groups. The use of stiffer and softer superstructures materials did not affect the stress distribution and stress values in the supporting tissue. According to the biomechanical point of view, materials with high elasticity modulus are more suitable for the superstructure of implant-supported prosthesis.
Assuntos
Implantes Dentários para Um Único Dente , Prótese Dentária Fixada por Implante/métodos , Análise do Estresse Dentário/métodos , Resinas Acrílicas , Parafusos Ósseos , Ligas Dentárias , Porcelana Dentária , Planejamento de Prótese Dentária , Facetas Dentárias , Análise de Elementos Finitos , Ouro , Teste de Materiais , Software , Titânio , ZircônioRESUMO
This study aimed to compare the influence of single-standing or connected implants on stress distribution in bone of mandibular overdentures by means of two-dimensional finite element analysis. Two finite element models were designed using software (ANSYS) for 2 situations: bar-clip (BC) group-model of an edentulous mandible supporting an overdenture over 2 connected implants with BC system, and o'ring (OR) group-model of an edentulous mandible supporting an overdenture over 2 single-standing implants with OR abutments. Axial loads (100 N) were applied on either central (L1) or lateral (L2) regions of the models. Stress distribution was concentrated mostly in the cortical bone surrounding the implants. When comparing the groups, BC (L1, 52.0 MPa and L2, 74.2 MPa) showed lower first principal stress values on supporting tissue than OR (L1, 78.4 MPa and L2, 76.7 MPa). Connected implants with BC attachment were more favorable on stress distribution over peri-implant-supporting tissue for both loading conditions.
Assuntos
Prótese Dentária Fixada por Implante , Análise do Estresse Dentário/métodos , Revestimento de Dentadura , Fenômenos Biomecânicos , Planejamento de Dentadura , Retenção de Dentadura/métodos , Análise de Elementos Finitos , Mandíbula , Teste de Materiais , Modelos Anatômicos , SoftwareRESUMO
In implant therapy, a peri-implant bone resorption has been noticed mainly in the first year after prosthesis insertion. This bone remodeling can sometimes jeopardize the outcome of the treatment, especially in areas in which short implants are used and also in aesthetic cases. To avoid this occurrence, the use of platform switching (PS) has been used. This study aimed to evaluate the biomechanical concept of PS with relation to stress distribution using two-dimensional finite element analysis. A regular matching diameter connection of abutment-implant (regular platform group [RPG]) and a PS connection (PS group [PSG]) were simulated by 2 two-dimensional finite element models that reproduced a 2-piece implant system with peri-implant bone tissue. A regular implant (prosthetic platform of 4.1 mm) and a wide implant (prosthetic platform of 5.0 mm) were used to represent the RPG and PSG, respectively, in which a regular prosthetic component of 4.1 mm was connected to represent the crown. A load of 100 N was applied on the models using ANSYS software. The RPG spreads the stress over a wider area in the peri-implant bone tissue (159 MPa) and the implant (1610 MPa), whereas the PSG seems to diminish the stress distribution on bone tissue (34 MPa) and implant (649 MPa). Within the limitation of the study, the PS presented better biomechanical behavior in relation to stress distribution on the implant but especially in the bone tissue (80% less). However, in the crown and retention screw, an increase in stress concentration was observed.
Assuntos
Implantes Dentários , Análise do Estresse Dentário/métodos , Análise de Elementos Finitos , Fenômenos Biomecânicos , Remodelação Óssea , Reabsorção Óssea , Dente Suporte , Implantação Dentária Endóssea , Planejamento de Prótese Dentária , Humanos , Teste de Materiais , Software , Estresse MecânicoRESUMO
The misfit between prostheses and implants is a clinical reality, but the level that can be accepted without causing mechanical or biologic problem is not well defined. This study investigates the effect of different levels of unilateral angular misfit prostheses in the prosthesis/implant/retaining screw system and in the surrounding bone using finite element analysis. Four models of a two-dimensional finite element were constructed: group 1 (control), prosthesis that fit the implant; groups 2 to 4, prostheses with unilateral angular misfit of 50, 100, and 200 mum, respectively. A load of 133 N was applied with a 30-degree angulation and off-axis at 2 mm from the long axis of the implant at the opposite direction of misfit on the models. Taking into account the increase of the angular misfit, the stress maps showed a gradual increase of prosthesis stress and uniform stress in the implant and trabecular bone. Concerning the displacement, an inclination of the system due to loading and misfit was observed. The decrease of the unilateral contact between prosthesis and implant leads to the displacement of the entire system, and distribution and magnitude alterations of the stress also occurred.