Controle da alteração dimensional térmica em estruturas metálicas de próteses sobre implantes: estudo in vitro

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde. Programa de Pós-Graduação em Odontologia.Estudo in vitro que analisou a eficácia do condicionamento térmico de estruturas metálicas de próteses sobre implantes, previamente aos ciclos convencionais para cocção da cerâmica, no controle da alteração dimensional do metal.. Sete estruturas de Níquel-Cromo formaram o grupo controle, e foram tratados de maneira convencional. As outras estruturas, da mesma liga, constituíram o grupo teste, e foram submetidos a condicionamento térmico, logo após a fundição, ainda no interior do revestimento. Nos dois grupos, constatou-se a alteração dimensional estatisticamente semelhante após os ciclos térmicos para a cocção da cerâmica. Constatou-se a importância do aquecimento da liga previamente à prova em boca das estruturas metálicas, pois permite a avaliação de seu assentamento com a maior parte da alteração térmica dimensional já manifestada

Avaliação do efeito da força de aperto de parafusos de retenção na desadaptação marginal de próteses sobre implantes

OBJECTIVES: The present in vitro study was designed to compare the differences in the vertical misfit of implant-supported frameworks using three different forces for tightening the bridge locking screws: fastening by hand until first resistance, and using torque drivers with 10 and 20Ncm. METHODS: The investigation was conducted based on the results given by 9 six-unit nickel-chromium (2 abutments/ 4 pontics) screw-retained implant-supported frameworks. The structures were exposed to simulated porcelain firings. The marginal misfit measurements were made using a traveling measuring microscope at selected screw tightening forces: fastening by hand until first resistance, and using torque drivers with 10 and 20Ncm. The results were submitted to one-way ANOVA with repeated measures on one factor, and post hoc pairwise comparisons using Tukey test (5%). RESULTS: The mean marginal misfit of the frameworks, fastening the screws by hand until first resistance, was 41.56µm (SD±12.45µm). The use of torque driver devices caused a significant reduction in marginal opening (pO presente estudo avaliou o efeito da força de aperto de parafusos de retenção na desadaptação marginal de próteses sobre implantes. A investigação foi conduzida baseada em resultados fornecidos por nove estruturas metálicas implanto-suportadas de seis elementos (02 retentores e 04 pônticos), retidas por parafusos. A mensuração da desadaptação marginal foi realizada com auxílio de microscópio óptico, nos seguintes momentos: M1: aperto com chave manual até a primeira resistência do parafuso; M2: aperto utilizando torquímetro mecânico com 10Ncm e M3: aperto utilizando torquímetro mecânico com 20Ncm. As médias de desadaptação foram submetidas à análise estatística (ANOVA e Tukey). O emprego de torquímetros mecânicos, independente do valor de torque, determinou redução significativa na abertura marginal (

Effect of cast rectifiers on the marginal fit of UCLA abutments

OBJECTIVES: This study assessed the effect of cast rectifiers on the marginal misfit of cast UCLA abutments compared to premachined UCLA abutments. The influence of casting and porcelain baking on the marginal misfit of these components was also investigated. METHODS: Two groups were analyzed: test group - 10 cast UCLA abutments, finished with cast rectifier and submitted to ceramic application; control group - 10 premachined UCLA abutments, cast with noble metal alloy and submitted to ceramic application. Vertical misfit measurements were performed under light microscopy. In the test group, measurements were performed before and after the use of cast rectifiers, and after ceramic application. In the control group, measurements were performed before and after casting, and after ceramic application. Data were submitted to statistical analysis by ANOVA and Tukey's test (a= 5%). RESULTS: The use of cast rectifiers significantly reduced the marginal misfit of cast UCLA abutments (from 25.68mm to 14.83mm;

Avaliação in vitro do emprego de retificadores de cilindros fundidos na adaptação de próteses implanto suportadas

This study evaluated the fitting interface of cylinders cast in non-precious alloys to implant-supported prosthetic abutments, after utilization of rectifiers designed to reduce the marginal misfit of cast cylinders. Two groups of components were investigated, namely Esteticone (Est) and Micro-Unit (MU), cast in Ni-Cr alloy (Wiron 99) and Co-Cr (Wirobond C), by the conventional technique (torch) and by induction. Gold-machined cylinders were used as controls. Measurement of the vertical misfits of cast cylinders was performed with aid of a light microscope at two periods, before and after utilization of cylinder rectifiers. For the gold machined components, reading was performed only once, since these components were not rectified. The misfit values of the cast cylinders were submitted to statistical analysis by the three-way ANOVA and Tukey tests (5%). Comparisons between the rectified cast cylinders and machined cylinders were performed by the Student t test for non-paired samples. The reduction in misfit was considered significant (p 0,05) from the gold machined cylinders means (22,44mm). The utilization of manual rectifiers on cast cylinders led to significant reductions in marginal misfit of components cast in Ni-Cr alloy.Avaliou-se a interface de assentamento de cilindros fundidos em ligas não preciosas a pilares protéticos implanto-suportados, após o uso de retificadores desenvolvidos para reduzir a desadaptação marginal de fundições. A investigação foi realizada com dois grupos de componentes: Esteticone e Micro-Unit, fundidos em liga de Ni-Cr (Wiron 99,) e Co-Cr (Wirobond C), pela técnica convencional (maçarico) e por indução em alta freqüência. Cilindros usinados em ouro foram empregados como padrões de referência. As mensurações das desadaptações marginais dos cilindros fundidos foram realizadas com auxílio de microscópio óptico em dois momentos, antes e após o uso de retificadores de cilindros. Para os componentes usinados em ouro, a leitura foi efetuada em um único momento, pois não houve retifica destes componentes. Os valores de desadaptação dos cilindros fundidos foram submetidos à análise estatística utilizando-se ANOVA (3-fatores) e Teste de Tukey (a: 5%). Comparações entre cilindros fundidos retificados e cilindros usinados foram realizadas com Teste t de Student para amostras não pareadas. A redução da desadaptação marginal foi estatisticamente significante (p 0,05) para componentes fundidos em Ni-Cr. Para os cilindros fundidos em Co-Cr, os retificadores não determinaram importantes modificações em todos os grupos testados. Os menores valores de desajuste marginal foram registrados para componentes Micro Unit fundidos convencionalmente (maçarico) em Ni-Cr após a retífica (29,08mm). A desadaptação registrada para este grupo foi estatisticamente semelhante (p 0,05) à obtida com componentes similares usinados em ouro (22,44mm). Concluiu-se que o uso de retificadores manuais de cilindros fundidos determinou expressiva redução de desadaptação marginal em componentes fundidos, principalmente com liga metálica de Ni-Cr

In vitro evaluation of the precision of working casts for implant-supported restoration with multiple abutments

OBJECTIVE: The purpose of this study was to compare the accuracy of two working cast fabrication techniques using strain-gauge analysis. METHODS: Two working cast fabrication methods were evaluated. Based on a master model, 20 working casts were fabricated by means of an indirect impression technique using polyether after splinting the square transfer copings with acrylic resin. Specimens were assigned to 2 groups (n=10): Group A (GA): type IV dental stone was poured around the abutment analogs in the conventional way; Group B (GB), the dental stone was poured in two stages. Spacers were used over the abutment analogs (rubber tubes) and type IV dental stone was poured around the abutment analogs in the conventional way. After the stone had hardened completely, the spacers were removed and more stone was inserted in the spaces created. Six strain-gauges (Excel Ltd.), positioned in a cast bar, which was dimensionally accurate (perfect fit) to the master model, recorded the microstrains generated by each specimen. Data were analyzed statistically by the variance analysis (ANOVA) and Tukey's test (α= 5%). RESULTS: The microstrain values (µepsilon) were (mean±SD): GA: 263.7±109.07µepsilon, and GB: 193.73±78.83µepsilon. CONCLUSION: There was no statistical difference between the two methods studied

Precisão de duas técnicas de esplintagem com resina acrílica de transferentes para próteses sobre implantes

Dois métodos de esplintagem com resina acrílica de transferentes quadrados usados para moldagem em próteses sobre implantes foram avaliados. Dois implantes foram posicionados no centro de um bloco de poliuretano, e sobre eles foram instaladas pilares protéticos "microunit". Dezesseis amostras foram fabricadas neste modelo, cada uma empregando dois transferentes quadrados, rigidamente conectados com resina acrílica autopolimerizável. Metade das amostras formaram o grupo 1 (n=8). Para o grupo 2 (n=8) a outra metade das amostras foi armazenada durante 24 horas. Neste grupo a esplintagem foi seccionada e os dois segmentos foram unidos novamente. Quatro extensômetros (Excel Sensores Ltda.) posicionados ao redor dos implantes registraram as deformações geradas por cada amostra. Os sinais foram amplificados e transferidos, para então serem registrados e analisados pelo software (AqDados AqAnalysis). Para o grupo 1, as mensurações foram feitas após a polimerização do bloco de resina acrílica; para o grupo 2 foram realizadas após a nova união dos segmentos. A análise estatística foi realizada empregado-se o teste t de Student para amostras independentes (5%). Diferença significante (pTwo acrylic resin splinted techniques used for direct implant impression were assessed for accuracy in a laboratory model that simulated clinical practice. Two implants were embedded in the center of a polyurethane block. Microunit abutments were placed on the implants. Sixteen samples were fabricated on this model, using two square transfer copings rigidly connected to each other with autopolymerizing acrylic resin. Half the samples formed group 1 (n=8). For group 02 (n=8) the other half were stored at ambient conditions for 24 hours; then, the acrylic resin splint was sectioned in this group, and the segments were reconnected. Strain measurements were performed by four strain gauges (Excel Sensores Ltda.) placed on the superior surface of the polyurethane block. For group 1, measurements were made after the polymerization of the acrylic resin splint; for group 2 after the segments were reconnected. Student’s t-test for independent samples, with statistical significance at 5%, was applied to analyze the data. Significant difference (p< .05) was found between the 2 techniques. The 1-piece acrylic resin splinted technique (G1) produced significantly higher strain values (143.25 ±53.48mµ) than the other technique (G2/ 70.83mµ ±29.03mµ). It was concluded that the acrylic resin splinted technique with separation and reconnection after 24 hours was significantly more accurate than the 1-piece acrylic resin splinted technique

Disponibilidade óssea para instalação de implante na região edêntula de primeiro molar inferior

Objetivo: avaliar, com o auxílio de tomografias computadorizadas, a disponibilidade óssea para a realização de cirurgias de instalação de implantes osseointegrados em função da localização do canal mandibular. Metodologia: trinta e duas tomografias computadorizadas de mandíbulas edêntulas foram analisadas na região do primeiro molar inferior. As mensurações desconsideraram a crista do rebordo residual até que se alcançasse uma espessura óssea mínima de 5,0mm, e, a partir desse ponto foi mensurada a distância existente até o teto superior do canal mandibular. Resultados: observou-se, em média, 11,625mm de tecido ósseo, variando de 8,0 a 16,2mm, entre o teto superior do canal mandibular e a porção do rebordo alveolar residual, com espessura mínima de 5,0mm para a instalação do implante. Conclusão: na maioria dos casos avaliados, existiu osso suficiente em altura e espessura para uma adequada instalação de implantes osseointegrados. Palavras-chave: Tomografia; Implantes Dentários; Nervo Mandibular

High temperature dimensional alterations of implant supported frameworks

sent in vitro study was designed to evaluate the effect of high temperature firing cycles used for application of porcelain veneer in the misfit of implant supported frameworks, and the effect of a pre-heating treatment on the dimensional alterations of implant supported frameworks. The investigation was conducted based on the results given by 14 nickel-chromium (06 elements) metal structures. Half of the structures formed the control group and were exposed to simulated porcelain firings. The other half formed the test group, and were submitted to a pre-heating treatment with the implant frameworks embedded in investment, before the porcelain firing simulation. The marginal misfit measurements in both groups were made before and after the porcelain firing simulation, by using a scanning electron microscope. The results were submitted to statistical analysis of variance. The multiple comparisons were made by means of the Bonferroni t test. For the frameworks produced in the usual manner, without the preheating treatment (control group), misfit deteriorates during the high temperature firing cycles employed for porcelain application. In the test group, pre-heating treatment did not change the final metal distortion resulting from the porcelain firing cycles, and the greatest amount of the distortion took place before the conventional porcelain firing cycles

A microstrain comparison of passively fitting screw-retained and cemented titanium frameworks

STATEMENT OF PROBLEM An imprecise fit between frameworks and supporting dental implants in loaded protocols increases the strain transferred to the periimplant bone, which may impair healing or generate microgaps. PURPOSE The purpose of this study was to investigate the microstrain between premachined 1-piece screw-retained frameworks (group STF) and screw-retained frameworks fabricated by cementing titanium cylinders to the prefabricated framework (group CTF). This procedure was developed to correct the misfit between frameworks and loaded implants. MATERIAL AND METHODS Four internal hexagon cylindrical implants were placed 10 mm apart in a polyurethane block by using the surgical guides of the corresponding implant system. Previously fabricated titanium frameworks (n=10) were divided into 2 groups. In group STF, prefabricated machined frameworks were used (n=5), and, in group CTF, the frameworks were fabricated by using a passive fit procedure, which was developed to correct the misfit between the cast titanium frameworks and supporting dental implants (n=5). Both groups were screw-retained under torque control (10 Ncm). Six strain gauges were placed on the upper surface of the polyurethane block, and 3 strain measurements were recorded for each framework. Data were analyzed with the Student t test (α=.05). RESULTS The mean microstrain values between the framework and the implants were significantly higher for group STF (2517 mε) than for group CTF (844 mε) (P<.05). CONCLUSIONS Complete-arch implant frameworks designed for load application and fabricated by using the passive fit procedure decreased the strain between the frameworks and implants more than 1 piece prefabricated machined frameworks