Prevalencia de cristales de colesterol en granulomas perirradiculares de origen endodóntico / Prevalence of cholesterol crystals in periradicular granulomas of endodontic origin

Resumen Objetivo Comparar dos procedimientos de soldadura convencionales empleando una aleación de Cr-Co, para conectar barras coladas seccionadas a ser fijadas sobre implantes. Materiales y métodos A partir de un modelo maestro que representa un maxilar desdentado con cuatro implantes, se confeccionaron veinte (n=20) probetas seccionadas en tres partes. Se conformaron dos grupos, cada uno con diez (n=10) ejemplares. Una vez acondicionadas, fueron atornilladas al modelo maestro. Su desajuste inicial se analizó utilizando una lupa estereoscópica, con una cámara incorporada y un software. Las partes fueron soldadas empleando un procedimiento diferente para cada grupo. Las correspondientes al Grupo I se invistieron en un block refractario a base de sílico-fosfato. Las del Grupo II se montaron en una estructura metálica Clever Spider. El desajuste fue mensurado y los resultados procesados estadísticamente. El nivel de significación fue establecido en p<0,05. Resultados El Grupo I tuvo un desajuste inicial de 97,30±13,81μm y el Grupo II de 98,53±11,24μm. Luego de la soldadura, el Grupo I registró 98,53±17,17μm, 1,23μm mayor respecto al inicial. En el Grupo II se observó 103,13±17,61μm, 4,60μm por encima del original. Se analizaron mediante prueba t de Student; en ambos casos el resultado fue de p>0,05. Al comparar entre sí los grupos I y II, por medio de la prueba t y de comprobación no paramétrica de Mann-Whitney, se observaron diferencias no significativas, p=0,41 y p=0,38 respectivamente. Conclusiones Bajo las condiciones de este estudio, se observó que los dos métodos de soldadura analizados fueron confiables para unir supraestructurasos metálicas sin que se afecte su ajuste final.

Abstract Aim Compare two conventional welding procedures using a Cr-Co alloy, to connect sectioned cast bars to be fixed on implants. Materials and methods From a master model representing a toothless jaw with four implants, twenty (n=20) specimens sectioned into three parts were made. Two groups were formed, each with ten (n=10) specimens. Once conditioned, they were screwed to the master model. Its initial mismatch was analyzed using a stereoscopic magnifier, with a built-in camera and a software. The parts were welded using a different procedure for each group. Those corresponding to Group I were invested in a refractory block based on silyl-phosphate. Those of Group II were mounted on a Clever Spider metal structure. The mismatch was measured, and the results processed statistically. The level of significance was established at p<0.05. Results Group I had an initial mismatch of 97.30 ±13.81μm, and Group II of 98.53±11.24μm. After welding, Group I registered 98.53±17.17μm, 1.23μm higher than the initial one. In Group II, 103.13±17.61μm was observed, 4.60μm above the original. They were analyzed using Student's t test; in both cases the result was p>0.05. When comparing groups I and II, using the t-test and the Mann-Whitney nonparametric verification, non-significant differences were observed, p=0.41 and p=0.38 respectively. Conclusions Under the conditions of this study, it was observed that the two welding methods analyzed were reliable for joining metallic superstructures without affecting their final fit.

Estudio in vitro del ajuste de supraestructuras pasivadas sobre implantes múltiples / In vitro study of the adjustment of passivated suprastructures on multiple implants

Resumen Objetivo Comparar dos procedimientos de soldadura convencionales empleando una aleación de Cr-Co, para conectar barras coladas seccionadas a ser fijadas sobre implantes. Materiales y métodos A partir de un modelo maestro que representa un maxilar desdentado con cuatro implantes, se confeccionaron veinte (n=20) probetas seccionadas en tres partes. Se conformaron dos grupos, cada uno con diez (n=10) ejemplares. Una vez acondicionadas, fueron atornilladas al modelo maestro. Su desajuste inicial se analizó utilizando una lupa estereoscópica, con una cámara incorporada y un software. Las partes fueron soldadas empleando un procedimiento diferente para cada grupo. Las correspondientes al Grupo I se invistieron en un block refractario a base de sílico-fosfato. Las del Grupo II se montaron en una estructura metálica Clever Spider. El desajuste fue mensurado y los resultados procesados estadísticamente. El nivel de significación fue establecido en p<0,05. Resultados El Grupo I tuvo un desajuste inicial de 97,30±13,81μm y el Grupo II de 98,53±11,24μm. Luego de la soldadura, el Grupo I registró 98,53±17,17μm, 1,23μm mayor respecto al inicial. En el Grupo II se observó 103,13±17,61μm, 4,60μm por encima del original. Se analizaron mediante prueba t de Student; en ambos casos el resultado fue de p>0,05. Al comparar entre sí los grupos I y II, por medio de la prueba t y de comprobación no paramétrica de Mann-Whitney, se observaron diferencias no significativas, p=0,41 y p=0,38 respectivamente. Conclusiones Bajo las condiciones de este estudio, se observó que los dos métodos de soldadura analizados fueron confiables para unir supraestructurasos metálicas sin que se afecte su ajuste final.

Abstract Aim Compare two conventional welding procedures using a Cr-Co alloy, to connect sectioned cast bars to be fixed on implants. Materials and methods From a master model representing a toothless jaw with four implants, twenty (n=20) specimens sectioned into three parts were made. Two groups were formed, each with ten (n=10) specimens. Once conditioned, they were screwed to the master model. Its initial mismatch was analyzed using a stereoscopic magnifier, with a built-in camera and a software. The parts were welded using a different procedure for each group. Those corresponding to Group I were invested in a refractory block based on silyl-phosphate. Those of Group II were mounted on a Clever Spider metal structure. The mismatch was measured, and the results processed statistically. The level of significance was established at p<0.05. Results Group I had an initial mismatch of 97.30 ±13.81μm, and Group II of 98.53±11.24μm. After welding, Group I registered 98.53±17.17μm, 1.23μm higher than the initial one. In Group II, 103.13±17.61μm was observed, 4.60μm above the original. They were analyzed using Student's t test; in both cases the result was p>0.05. When comparing groups I and II, using the t-test and the Mann-Whitney nonparametric verification, non-significant differences were observed, p=0.41 and p=0.38 respectively. Conclusions Under the conditions of this study, it was observed that the two welding methods analyzed were reliable for joining metallic superstructures without affecting their final fit.

Effect of materials and superstructure designs on the passive fit of implant-supported fixed prostheses / 华西口腔医学杂志

OBJECTIVE@#This study aimed to compare the passive fits of implant-supported cement-retained computer aided design/computer aided manufacturing (CAD/CAM) bridges fabricated with different implant superstructure designs from zirconia and titanium.@*METHODS@#A total of 32 cubic clods with the same dimensions and with elastic modulus similar to that of mandibles were used. Each clod received two one-stage implants to simulate a partially edentulous jaw that was missing teeth between the lower left second premolar and second molar. Four linear strain gauges were bonded on the region surrounding each implant on the mesial, buccal, distal, and lingual aspects. A total of 32 identical frameworks were fabricated through CAD/CAM after scanning. The frameworks were allocated into four different groups (n=8) in accordance with material types and superstructure designs. Group A included zirconia ceramic implant-supported fixed prostheses with regular marginal designs. Group B comprised zirconia ceramic implant-supported fixed prostheses with full circumferential zirconia-collar marginal designs. Group C consisted of titanium ceramic implant-supported fixed prostheses with regular marginal designs. Group D included titanium ceramic implant-supported fixed prostheses with full circumferential titanium-collar marginal designs. Strain development before and after ceramic veneering was recorded during cement setting. Data were statistically analyzed by using SPSS software.@*RESULTS@#Before ceramic veneering, material types affected the strains of prostheses, and zirconia frameworks showed lower strain than other frameworks (P0.05). Nevertheless, the full circumferential collar marginal design reduced discrepancies among groups (P<0.01).@*CONCLUSIONS@#The passive fits of zirconia prostheses were better than those of titanium-based porcelain-fused-to-metal restorations. The full circumferential collar marginal design can help reduce fit inaccuracy, as well as the adverse effects of ceramic veneering.

Technique of Framework Cemented on Prepared Abutments to Obtain Passive Fit at Fixed Complete Denture: A 2-Year Follow-Up Report

The passive fit of implant-supported dentures is fundamental to the rehabilitation success due the absence of the periodontal ligament in osseointegrated implants. Many techniques to obtain passive fit have been reported in the literature, some inaccessible for the clinicians and dental laboratories. This case report presents a technique to fabricate fixed complete dentures aiming at obtain passive fit with reduced time and cost, but without demerit for the aesthetics, function and longevity. A 40-year-old woman was referred for treatment presenting some teeth in the maxilla and an edentulous mandible, reporting eating problems related to instability and little retention of the mandibular complete denture. Treatment based on the reverse planning was performed to guide the rehabilitation with a complete mandibular fixed complete denture and maxillary occlusal plane adjustment. The framework of the fixed complete denture was manufactured luting a cast metal bar above the prepared titanium cylinder abutments using resin cement. The aim of this technique was to obtain a fixed complete denture with passive fit presenting positive esthetic and functional outcomes after 2 years of follow-up.

A adaptação passiva de próteses implantossuportadas é fundamental para o sucesso da reabilitação devido à inexistência de ligamento periodontal em implantes osseointegrados. Inúmeras técnicas de confecção da infraestrutura destas próteses tem sido relatadas na literatura, algumas inacessíveis para os clínicos e laboratórios de prótese. Este relato de caso apresenta uma técnica para confecção de próteses totais fixas visando obtenção de adaptação passiva com tempo e custo reduzido, porém sem demérito à estética, função e longevidade. Uma paciente de 40 anos se apresentou para tratamento apresentando alguns dentes na maxila e mandíbula edêntula, relatando dificuldades na mastigação relacionados a instabilidade e falta de retenção da prótese total inferior. Foi realizado um planejamento reverso para orientar a reabilitação com prótese total mandibular fixa e adequação do plano oclusal da maxila. A infraestrutura da prótese total fixa foi confeccionada pela cimentação de uma barra metálica em cilindros de titânio preparados com cimento resinoso. O objetivo desta técnica foi obter uma prótese total fixa com adaptação passiva apresentando resultados positivos em termos de estética e função após 2 anos de acompanhamento.

Transferência anatômico-funcional de implantes / Anatomical-functional transfer of implants

Na cavidade bucal existem estruturas rígidas (dentes) e resilientes (tecidos moles) que deverão ser reproduzidas e, infelizmente, apresentam comportamentos distintos durante o contato com os materiais de moldagem: as estruturas rígidas não sofrem deformações e poderão gerar cópias precisas; as estruturas resilientes sofrerão deformações que precisarão ser convenientemente tratadas para que a prótese não gere traumatismos para os tecidos moles. É fundamental que a transferência espacial dos implantes para o modelo de trabalho gere posicionamentos precisos para os análogos e, com isso, o técnico de laboratório tenha condições de confeccionar peças protéticas que possuam adaptação apropriada em boca. Utilizamos transferentes parafusados em técnica de transferência direta. As moldagens são realizadas em duas etapas: (I) moldagem anatômica com moldeira de estoque e utilização de materiais de moldagem de diferentes consistências, em camadas; (II) moldagem funcional realizada com moldeira individual e poliéteres ou silicones de adição com distintas fluidezes, em camadas. Após a polimerização dos materiais de moldagem, os excessos extravasados devem ser removidos e os transferentes devem ser fixados à moldeira individual de resina com acrílico de baixa contração, pela técnica do pincel. Uma vez polimerizada a resina acrílica, os transferentes devem ser desparafusados e a moldagem removida da cavidade bucal. A transferência anatômico-funcional de múltiplos implantes é fundamental para que possamos obter modelos fiéis, e sobre esses construir próteses que possuam adequada adaptação sobre os implantes e apropriado contacto com os tecidos moles, não gerando traumatismos

In the oral cavity there are ridig structures (teeth) and resilient (soft tissue) to be reproduced and that unfortunately present different behaviors during the contact of impression materials: Rigid structures do not suffer deformation and can generate accurate copies; resilient structures suffer deformations that need to be conveniently performed so that the prosthesis does not create injuries to the soft tissues. It is essential that the spatial transfer of the implants for work model manages precise positioning for analogs and therefore the lab technician is able to fabricate prosthetic piecesd that have an appropriate adaptation to mouth. We use screwed transferents on direct transfer technique. The casts are performed in two steps: (I) anatomical impression with stock tray and use of impression materials of different consistencies, in layers; (II) functional impression with individual tray and polyether or addition-cured silicones of different flows, in layers.After curing the impression materials, spilled excess should be removed and the transferents should be fixed to individual acrylic tray with low shrinkage resin, using the technique of the brush. Once polymerized acrylic resin, transferents must be unscrewed and the impression removed from the oral cavity.The anatomical and functional transfer of multiple implants is essential so that we can get models faithful and build on these prostheses that have adequate fit on the implants and proper contact with soft tissues, generating no injuries.

Comparação do desajuste vertical de infraestruturas metálicas sobre implantes: fundida versus fresada / Comparison of vertical misfit between cast and CNC-milled frameworks for implant-supported prostheses

A adaptação passiva da infraestrutura da prótese sobreimplantes é um dos parâmetros mecânicos que podem interferir na longevidade das próteses. Várias complicações no tratamento com implantes osseointegrados podem ser causadas por deficiência na adaptação das infraestruturas protéticas, podendo ser agravadas pela ausência de ligamento periodontal. O objetivo deste trabalho foi comparar a desadaptação de infraestruturas metálicas em monobloco parafusadas sobreimplante, confeccionadas pelo sistema de fundição por cera perdida e fresadas por sistema CAD/CAM. Sobre um modelo mestre de alumínio foram instalados quatro análogos de minipilares. Sobre estes foram confeccionadas duas barras metálicas: uma fundida em Co-Cr e outra fresada. O desajuste vertical na interface barra/análogos foi mensurado utilizando-se um microscópio comparador. Foi calculada a média de desadaptação em cada um dos pilares (45, 43, 33 e 35) e a média final de desadaptação de cada uma das barras. Na barra metálica fresada observou-se redução nos valores da desadaptação vertical em todos os pilares. A barra metálica fundida mostrou uma desadaptação vertical média (108,6 µm) aproximadamente dez vezes maior do que a barra metálica fresada (9,6 µm).

Passive fit of an implant framework is one of the mechanical parameters that can affect treatment longevity. Several complications in dental implant treatment may be due to misfit of metallic frameworks and can be aggravated by the absence of periodontal ligament. The objective of this study is to compare the misfit of a metallic, one-piece cast and CNC-milled implant frameworks. Four implant analogues were placed in a aluminum master model to receive conical abutments. A Co-Cr alloy was used in both groups. Vertical misfits at implant-framework interface were measured with an optical microscope. Mean misft levels were registered at implant positions 45, 43, 33, and 35, as well as for the overall sample. Individual misfit levels were reduced in CNC-milled frameworks. Cast frameworks showed a mean vertical misfit level (108.6 micrometers) almost 10 times higher than in the milled frameworks (9.6 micrometers).

Comparative study on stress distribution around internal tapered connection implants according to fit of cement- and screw-retained prostheses

PURPOSE: The aim of this study was to compare the passivity of implant superstructures by assessing the strain development around the internal tapered connection implants with strain gauges. MATERIALS AND METHODS: A polyurethane resin block in which two implants were embedded served as a measurement model. Two groups of implant restorations utilized cement-retained design and internal surface of the first group was adjusted until premature contact between the restoration and the abutment completely disappeared. In the second group, only nodules detectable to the naked eye were removed. The third group employed screw-retained design and specimens were generated by computer-aided design/computer-aided manufacturing system (n=10). Four strain gauges were fixed on the measurement model mesially and distally to the implants. The strains developed in each strain gauge were recorded during fixation of specimens. To compare the difference among groups, repeated measures 2-factor analysis was performed at a level of significance of alpha=.05. RESULTS: The absolute strain values were measured to analyze the magnitude of strain. The mean absolute strain value ranged from 29.53 to 412.94 microm/m at the different strain gauge locations. According to the result of overall comparison, the cement-retained prosthesis groups exhibited significant difference. No significant difference was detected between milled screw-retained prostheses group and cement-retained prosthesis groups. CONCLUSION: Within the limitations of the study, it was concluded that the cement-retained designs do not always exhibit lower levels of stress than screw-retained designs. The internal adjustment of a cement-retained implant restoration is essential to achieve passive fit.

Intraoral framework pick-up technique to improve fit of a metal-resin implant prosthesis.

The achievement of passive fit is an important prerequisite for the prevention of complications in full-arch screw-retained implant prosthesis. With cemented prosthesis, the cementation compensates for the discrepancies in the cast framework, but the lack of retrievability seems undesirable. The aim of this paper is to propose a modified screw-retained prosthesis design for complete arch implant fixed rehabilitation. A technique for the fabrication of a full-arch metal-resin implant-supported screw-retained prosthesis is described. Cementation of the framework to the abutments intraorally improves the passivity of fit of the prosthesis on the implants. Maintenance of screw-access channels in the final prosthesis ensures retrievability. The metal-resin design allows for easy repair and maintenance. The prosthesis is cost-effective compared to conventional options and can be employed as a viable treatment alternative when considering metal-acrylic resin complete arch fixed prosthesis.

Accuracy of five implant impression technique: effect of splinting materials and methods

PURPOSE: The aim of this study was to evaluate the effect of dimensional stability of splinting material on the accuracy of master casts. MATERIALS AND METHODS: A stainless steel metal model with 6 implants embedded was used as a master model. Implant level impressions were made after square impression copings were splinted using 5 different techniques as follows. (1) Splinted with autopolymerizing resin and sectioned, reconnected to compensate polymerization shrinkage before the impression procedure. (2) Splinted with autopolymerizing resin just before impression procedure. (3) Primary impression made with impression plaster and secondary impression were made over with polyether impression material. (4) Splinted with impression plaster. (5) Splinted with VPS bite registration material. From master model, 5 impressions and 5 experimental casts, total 25 casts were made for each of 5 splinting methods. The distortion values of each splinting methods were measured using coordinate measuring machine, capable of recordings in the x-, y-, z-axes. A one-way analysis of variance (ANOVA) at a confidence level of 95% was used to evaluate the data and Tukey's studentized range test was used to determine significant differences between the groups. RESULTS: Group 1 showed best accuracy followed by Group 3 & 4. Group 2 and 5 showed relatively larger distortion value than other groups. No significant difference was found between group 3, 4, 5 in x-axis, group 2, 3, 4 in y-axis and group 1, 3, 4, 5 in z-axis (P<.0001). CONCLUSION: Both Splinting impression copings with autopolymerizing resin following compensation of polymerization shrinkage and splinting method with impression plaster can enhance the accuracy of master cast and impression plaster can be used simple and effective splinting material for implant impression procedure.

Avaliação da deformação do intermediário e região perimplantar de próteses implanto-suportada unitárias parafusada: estudo através da extensometria / Evaluation of abutment and perimplantar region deformation of implant-supported screwed prostheses: an study using strain gauges

O implante dental depende do osso de suporte para sua estabilidade e ongevidade funcional. O comportamento mecânico e a estrutura trabecular do osso afetam a interface com o implante. Tal conhecimento pode fornecer uma base para melhoramentos na função e desenho dos implantes atuais minimizando a reabsorção da crista óssea e falha na junção osso-implante. Desta forma a correta quantificação das forças que atuam sobre o sistema de implante e principalmente no osso de suporte ao qual ele está inserido é importante para o entendimento da biomecânica possibilitando que intervenções possam ser realizadas pelos profissionais visando assim à longevidade das próteses implanto-suportadas bem como dos implantes que as sustentam. Por essa razão, a proposta deste trabalho foi avaliar, com auxílio de extensômetros elétricos, se o processo laboratorial de confecção de coroas metalocerâmicas resulta em alterações das tensões no osso ao redor dos implantes. Para isto foi utilizado um modelo de poliuretano em forma de U simulando o osso mandibular com dois implantes de hexágono externo de 3,75mm de diâmetro por 13 mm de comprimento, nos quais foram fixados intermediários multi-unit. Os corpos de prova foram confeccionados com dois tipos de ligas odontológicas - Cobalto-Cromo e Paládio-Prata - e três tipos de cilindros protéticos calcinável, usinado de Cobalto-Cromo e usinado de Ouro. As leituras de deformação foram realizadas em dois momentos: 1- após a fundição das infra-estruturas e 2 após estas infra-estruturas terem recebido cobertura cerâmica. Os testes foram realizados parafusando os corpos de prova sobre os intermediários utilizando-se para isto um dispositivo eletrônico de torque com força máxima de 10 Ncm. Os resultados mostraram que, após a aplicação da cobertura cerâmica, ocorreu piora da condição de assentamento aos intermediários. O mesmo não foi detectado quando se avaliou a deformação do osso simulado, já que os valores de deformação não indicaram...

The dental implant depends on the supporting bone for its stability and functional longevity. Mechanical behavior and trabecular bone structure affect the interface with the implant. Such knowledge may provide a basis for improvements in the current implant function and design, decreasing bone crest resorption and failure at bone-implant junction. Adequate quantification of forces that act upon the implant system and mainly on the supporting bone is important for understanding the biomechanics, allowing the intervention by professionals with the purpose of achieving the longevity of implant-supported prostheses. Therefore, this work aims at evaluating, with the aid of strain gauges, whether the laboratorial process of metal ceramic crown fabrication results in changes of the tensions around the implants. A U-shaped polyurethane model simulating the mandibular bone with two 3.75-mm diameter and 13-mm length external hexagon implants were used with fixed multi-unit abutments. Specimens were prepared with two types of dental alloys - cobalt-chromium and silver-palladium - and three types of prosthetic cylinder castable plastic, prefabricated in cobalt-chromium or gold. The deformation readings were performed in two moments: 1- after framework casting and 2- after ceramic layering of the framework. The tests were performed with the framework screwed onto the abutments at 10Ncm using an electronic torque device. The results showed that the ceramic layering worsened the fit between the crowns and the abutments. The same was not detected when bone deformation was evaluated since the values were not statistically different.

Avaliação da deformação do intermediário e região perimplantar de próteses implanto-suportada unitárias parafusada: estudo através da extensometria / Evaluation of abutment and perimplantar region deformation of implant-supported screwed prostheses: an study using strain gauges

O implante dental depende do osso de suporte para sua estabilidade e ongevidade funcional. O comportamento mecânico e a estrutura trabecular do osso afetam a interface com o implante. Tal conhecimento pode fornecer uma base para melhoramentos na função e desenho dos implantes atuais minimizando a reabsorção da crista óssea e falha na junção osso-implante. Desta forma a correta quantificação das forças que atuam sobre o sistema de implante e principalmente no osso de suporte ao qual ele está inserido é importante para o entendimento da biomecânica possibilitando que intervenções possam ser realizadas pelos profissionais visando assim à longevidade das próteses implanto-suportadas bem como dos implantes que as sustentam. Por essa razão, a proposta deste trabalho foi avaliar, com auxílio de extensômetros elétricos, se o processo laboratorial de confecção de coroas metalocerâmicas resulta em alterações das tensões no osso ao redor dos implantes. Para isto foi utilizado um modelo de poliuretano em forma de U simulando o osso mandibular com dois implantes de hexágono externo de 3,75mm de diâmetro por 13 mm de comprimento, nos quais foram fixados intermediários multi-unit. Os corpos de prova foram confeccionados com dois tipos de ligas odontológicas - Cobalto-Cromo e Paládio-Prata - e três tipos de cilindros protéticos calcinável, usinado de Cobalto-Cromo e usinado de Ouro. As leituras de deformação foram realizadas em dois momentos: 1- após a fundição das infra-estruturas e 2 após estas infra-estruturas terem recebido cobertura cerâmica. Os testes foram realizados parafusando os corpos de prova sobre os intermediários utilizando-se para isto um dispositivo eletrônico de torque com força máxima de 10 Ncm. Os resultados mostraram que, após a aplicação da cobertura cerâmica, ocorreu piora da condição de assentamento aos intermediários. O mesmo não foi detectado quando se avaliou a deformação do osso simulado, já que os valores de deformação não ndicaram...

The dental implant depends on the supporting bone for its stability and functional longevity. Mechanical behavior and trabecular bone structure affect the interface with the implant. Such knowledge may provide a basis for improvements in the current implant function and design, decreasing bone crest resorption and failure at bone-implant junction. Adequate quantification of forces that act upon the implant system and mainly on the supporting bone is important for understanding the biomechanics, allowing the intervention by professionals with the purpose of achieving the longevity of implant-supported prostheses. Therefore, this work aims at evaluating, with the aid of strain gauges, whether the laboratorial process of metal ceramic crown fabrication results in changes of the tensions around the implants. A U-shaped polyurethane model simulating the mandibular bone with two 3.75-mm diameter and 13-mm length external hexagon implants were used with fixed multi-unit abutments. Specimens were prepared with two types of dental alloys - cobalt-chromium and silver-palladium - and three types of prosthetic cylinder castable plastic, prefabricated in cobalt-chromium or gold. The deformation readings were performed in two moments: 1- after framework casting and 2- after ceramic layering of the framework. The tests were performed with the framework screwed onto the abutments at 10Ncm using an electronic torque device. The results showed that the ceramic layering worsened the fit between the crowns and the abutments. The same was not detected when bone deformation was evaluated since the values were not statistically different.

Marginal fit of implant-supported fixed prosthesis frameworks with prefabricated and calcinable cylinders / Adaptação marginal de infra-estruturas de prótese fixa implanto-suportada com cilindros pré-usinados e calcináveis

Purpose: The aim of this study was to evaluate the vertical marginal misfit of the metal framework of an implant-supported prosthesis. Methods: Ten frameworks were made of cobalt-chromium alloy (Co-Cr), simulating a three-element fixed prosthesis on two implants. Five frameworks were constructed using prefabricated cylinders, and the other five were constructed using calcinable cylinders. All frameworks were cast by the induction technique and laser-welded. Marginal misfit was measured by means of scanning electron microscopy with the frameworks subjected to the single-screw test. Twenty-five measurements of marginal fit were recorded per abutment and averaged for statistical analysis (ANOVA, alpha=0.05). Results: There was no statistically significant difference in marginal fit between the groups tested. The only difference found was when comparing the abutments with and without screw. Conclusion: It was concluded that there is no difference in marginal fit between frameworks cast in Co-Cr with calcinable and prefabricated cylinders using induction casting, laser-welding, and single-screw test.

Objetivo: O objetivo deste trabalho foi avaliar o desajuste marginal vertical de infra-estruturas metálicas de prótese fixa sobre implantes. Metodologia: Foram confeccionadas 10 infra-estruturas em liga de cobalto-cromo (Co-Cr), simulando uma prótese fixa de três elementos sobre dois implantes, com o auxílio de uma matriz metálica. Cinco infra-estruturas foram confeccionadas com cilindros pré-usinados. Outras cinco foram confeccionadas com cilindros calcináveis. Todas as infra-estruturas foram fundidas pela técnica de indução e soldadas a laser. As leituras do desajuste marginal foram realizadas através de microscopia eletrônica de varredura, utilizando a técnica do parafuso único, totalizando 25 medições em cada cilindro. As médias de desajuste marginal de cada cilindro foram utilizadas para a análise estatística (ANOVA, alfa=0,05). Resultados: Não houve diferença estatística no grau de desajuste marginal entre os grupos testados. Apenas houve diferença quando comparados os cilindros com e sem parafuso. Conclusão: Foi concluído que não há diferença de adaptação marginal entre as infra-estruturas fundidas em Co-Cr com cilindros calcináveis e pré-usinados, utilizando fundição por indução, soldagem a laser e teste do parafuso único.

The dimensional change of cast implant bars after laboratory procedure / 대한치과보철학회지

STATEMENT OF PROBLEMS: The precision of fit between the bearing surfaces of implant abutments and the prosthesis framework has been considered fundamental to implant prosthodontic protocol. PURPOSE: The study aimed to investigate the effect of laboratory procedure on the dimensional accuracy of cast implant bars. MATERIAL AND METHODS: Thirty implant bars were fabricated on a metal master model. The gap distances were measured at the right implant abutment replica-gold cylinder interface after casting procedure. The bar length data of precasting and postcasting state were collected and analyzed. RESULTS: The mean gap distance found after casting was 106.3 micrometer for buccal side, 122.1 micrometer for distal side and 117.1 micrometer for the lingual side. The mean bar length was 17964.7 micrometer at precasting measurement, 17891.6 micrometer at postcasting measurement. The mean change of bar length was - 73.1 micrometer. CONCLUSION: Even though the techniques used in this study strictly followed the guidelines established in the literature, the 30 cast implant bars evaluated all yielded gap distances that were beyond acceptable accuracy. There was a statistically significant difference between precasting and postcasting bar length (P<0.01). There was a decreasing tendency in bar length after casting procedure. It was necessary to correct this dimensional change from laboratory procedure by some corrective methods.