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

Avaliação de dois métodos de registro da relação central em desdentados totais

Objective: to compare, in the horizontal plane, the mandibular positions determined by two methods for registering the centric relation(CR): inclination of the head backward (IHB) and unstrained hinging movement (UHM), in edentulous patients. The mull hypothesis was that there is not difference between the two methods. Material and Methods: Twenty edentulous subjects were selecred for this study (n = 20). All patients were manipulated to CR position using the methods IHB and UHM. The CR measure of each method was registered in one extraoral devide, which was fixed as the maxillary and mandibular record bases. For each patient, the two CR positions were registered in the same extraoral devide. To measure the anteroposterior and lateral linear variations between the points registered for each technique, it was used a profile projector (Model 6C, Nikon/USA). The data (um) were statiscally analyzed using the Tukey test (p,0.05) and Pearson correlation test. Results: The difference between CR position obtained by the methods in anteroposterior position differed statically from zero (p = 0.001) and that there was no significant difference (p = 0.479) when compared the Cr positions with the medium line: UHM (0,56+_0,35um) and IHB (0,65+0.52um). It wasn´t observed Pearson linear correlation between the anteroposterior and lateral linear measures of the methods (r = 0.26; p = 0.268.0.05). Conclusion: It can be conclude that the method UHM presented a higher mandibular retrusion that the method IHBObjetivo: Comparar, no plano horizontal, as posições mandibulares determinadas por dois métodos de registro para determinação da posição de relação central (RC): inclinação da cabeça para trás (IC) os métodos guiado não forçado (GNF), em pacientes edêntulos. A hipótese nula é de que não haverá diferença entre os dois métodos. Material e Método: 20 pacientes desdentados totais foram selecionados para este estudo (n=20). Todos pacientes foram manipulados para posição de RC utilizando os métodos IC e GNF. A mensuração da posição de RC determinada por cada método foi registrada em um dispositivo extra-oral, cujas componentes foram fixados nos planos de orientação maxilar e mandibular. Para cada paciente, as duas posições de RC foram registradas no mesmo dispositivo extra-oral. Para mensurar as variações ântero-posteriores e laterais entre os pontos registrados por cada técnica, foi utilizado um projetor de perfil (Modelo 6C, Nikon/USA). Os dados (mm) foram analisados estatisticamente utilizando o teste T (pResultados: A diferença entre a posição de RC obtida pelos métodos na posição ântero-posterior diferiu estatisticamente de zero (p=0.001) e que não houve diferença significante (p=0,479) quando comparada as posições de RC em relação à linha média: UHM (0,56±0,35mm) e IHB (0,65±0,52mm). Não foi observada correlação linear de Pearson entre as medidas lineares antero-posteriores e laterais dos métodos estudados (r=0,26; p=0,2680,05). Conclusão: Pode-se concluir que método GNF gerou uma retrusão mandibular maior que o método IC

Avaliação do tipo de carregamento, pela análise de elementos finitos, sobre a resistência de união ao cisalhamento da interface metal/porcelana (Ni-Cr/vita omega 900)

The purpose of this study was to compare the devices influence piston, stainless steel strip and chisel, used in shear bond tests to verify the resistance in the metal/porcelain interface. The values depend on a complex tensions combination and resultants produced during the application of the forces in the specimens and the variations in the methodologies of the tests result in differents resistances values to shear bond strength, what complicates the standardization and the direct comparison between different researchers. They were used 36 specimens (Ni-Cr, Wiron 99 – Bego and porcelain Vita Omega 900 - Vita ) divided into three groups (n = 12). The specimens were submitted to the shear bond strength in a universal testing machine EMIC (model DL-2000, São José dos Pinhais – PR), with a crosshead speed of 0,5 mm/min. After, the representative sets of each group were examined in scanning electronic microscopy for the observation of the failures. The finite elements analysis was used to verifiy the tensions distribution on the specimens. The results were submitted to the analysis of variance and to Tukey's Test in the level of 5%, it was verified that there was significant statistically difference between the three devices used. The present study showed that the piston device obtained better results than the conventional method ISO 11405 and stripO propósito deste estudo foi comparar a influência dos dispositivos de carregamento pistão, fita de aço inoxidável e cinzel, usados em ensaios de união ao cisalhamento, para verificar a resistência na interface material restaurador/metal. Os valores dependem de uma complexa combinação de tensões e resultantes produzidas durante a aplicação das forças nas amostras sendo que as variações nas metodologias dos testes resultam em diferentes valores de resistência ao cisalhamento, o que dificulta a padronização e a comparação direta entre diferentes pesquisadores. Foram utilizados 36 corpos-de-prova (Ni-Cr, Wiron 99 – Bego e porcelana Vita Omega 900 - Vita ) divididos em 3 grupos (n = 12). Os corpos-de-prova foram submetidos aos ensaios de resistência ao cisalhamento em uma máquina de ensaio universal EMIC (modelo DL-2000, São José dos Pinhais – PR), com velocidade constante de 0,5 mm/min. Em seguida, os corpos-de-prova representativos de cada grupo foram examinados em microscopia eletrônica de varredura para a observação dos modos de falhas. A análise de elementos finitos foi utilizada para a verificação da distribuição de tensões sobre os corpos-de-prova. Os resultados foram submetidos à análise de variância e ao teste de Tukey em nível de 5% de significância, verificou-se que houve diferença estatisticamente significante entre os três dispositivos usados. O presente estudo mostrou que o dispositivo pistão obteve melhores resultados que o método convencional ISO 11405 e fitaCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Extensometria: avaliação de implantes de sextavado externo posicionados na configuração linear e compensada (offset), sob carregamento axial

O objetivo deste estudo foi avaliar, por meio da extensometria, a distribuição de tensões ao redor de implantes em função dos diferentes locais para carregamento, tipo de coifa (plástica ou usinada) e configuração (linear e compensada). Para tanto, em um bloco de poliuretano, foram posicionados paralelos entre si e com uma configuração linear, implantes auto-rosqueáveis de hexágono externo, com dimensões de 3,75 X 13mm, a uma distancia de 7mm, de centro a centro. Em um outro bloco a fixação do meio foi deslocada em 2mm para gerar uma configuração compensada (offset). Pilares protéticos Micro-unit, com 3mm de cinta foram instalados sobre as fixações. Com duas matrizes em aço inoxidável foram confeccionados 10 enceramentos para cada bloco, distribuídos da seguinte forma: 5 para coifa plástica e 5 para coifas usinadas (n=5). A seguir esses padrões foram fundidos com uma liga de Co-Cr. Quatro extensômetros (strain gauges) foram colados na superfície superior de cada bloco tangenciando a plataforma de cada fixação. Um carregamento de 30kg durante 10s foi feito em cinco posições (A, B, C, D, E), sendo repetido três vezes para aquisição dos dados (em με) pela aparelho condicionador de sinais. Os dados obtidos foram submetidos a análise de variância (ANOVA) e teste de Tukey (p<0,05). Como conclusão da análise dos resultados obtidos pudemos observar que não houve diferença na utilização de coifas plásticas e usinadas, que não houve diferença entre as configurações linear e compensada; havendo diferença estatisticamente significante para os locais de carregamentoThe aim of this study was to evaluate, using strain gauge, the load distribution surround the implants according differents loading sites, coping types (plastic and machined) and configuration (linear and offset). In one polyurethane block, three cylindrical implants with external hexagon (3.75mm x 13mm) were fixed parallel with 7mm between their centers in a linear configuration. In another block the midle implant was positioned in a 2mm offset. Micro-units abutments with 3mm of metallic neck were fixed. With two metallics matrix, it was manufactured 10 wax patterns for each block, distributed in the following form: 5 for plastic copings and 5 for machined copings (n=5). After, patterns were casted in cobalt-chromium alloy. Four strain gauges were positioned on the upper surface of each polyurethane model around the implants. An axial load of 30kg within 10 seconds in five positions (A, B, C, D, E), with three repetead measurements for data aquisition (in με) by the multichanel bridge machine. The datas were submitted to ANOVA and Tukey test (p<0.05). Such as conclusion from the obtained data treatment: there was no difference between the plastic and machined copings, there was no difference between the linear and offset configuration; there was statiscal significance only with the differents loading sites.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Screw Spreading: Technical Considerations and Case Report

The spreading system is an alternative technique to the Summers osteotome. The crest expansion technique is a less invasive procedure in which the facial wall expands after the medullary bone is compressed against the cortical wall. It improves the density of the maxillary bone, which allows for greater initial stability of implants. A specific screw instrument, the "spreader," achieved a controlled and standardized dilation of the bone horizontally. The use of spreaders to enhance the dental implant site is a highly predictable procedure. (Int J Periodontics Restorative Dent 2011;31:141-147.

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

PROTESIS PARCIAL FIJA POR LA TÉCNICA DE ELECTRODEPOSICIÓN CON ORO: RELATO DE CASO CLÍNICO

Electrodeposici&oacute;n es la deposici&oacute;n galv&aacute;nica de la aleaci&oacute;n de oro con 99% de pureza (24K) para el uso odontol&oacute;gico, teniendo como principio la electr&oacute;lisis. Este sistema de electrodeposici&oacute;n permite la confeci&oacute;n de una cofia de oro con una excelente adaptaci&oacute;n marginal. Puede ser fabricado con un espesor m&iacute;nimo de 0,2mm haciendo posible realizar un desgaste menor en la preparaci&oacute;n de pilares, y sobre esa fina infraestructura se puede aplicar una capa mayor de cer&aacute;mica optimizando la est&eacute;tica cuando se compara con la fundici&oacute;n de estructuras convencionales. Hace posible la confecci&oacute;n de coronas y pr&oacute;tesis parciales fijas. Las coronas metal-cer&aacute;micas confeccionadas por la t&eacute;cnica de electrodeposici&oacute;n otorgan una est&eacute;tica satisfactoria, debido a una apariencia mas natural y mejor calidad del color. Adicionalmente presenta caracter&iacute;sticas ventajosas como ausencia de corrosi&oacute;n y una excelente biocompatibilidad con los tejidos periodontales. Este trabajo muestra la confecci&oacute;n de coronas metalocer&aacute;micas totales hechas con cofias por electrodeposici&oacute;n, teniendo como objetivo presentar una alternativa en pr&oacute;tesis parcial fija para los profesionales.SUMMARYElectrodeposition is the galvanic deposition of the gold alloy with 99% of purity (24K) for the dentistry use, having like principle electrolysis. This electrodeposition system allows the preparation of pure gold coping with an excellent marginal fit. It can be made with a minimum thickness of 0,2mm doing possible to make a less teeth reduction, and on that fine infrastructure can be applied to a greater layer of ceramics optimizing the aesthetic when it is compared with the cast conventional copings. It is possible the preparation of unitary and fixed partial prostheses. The metal-ceramics crowns made by the electrodeposition technique present an aesthetic satisfactory, due to a natural appearance and better quality of the color. Additionally, it presents advantageous characteristics as corrosion absence and an excellent biocompatibility with periodontal tissues. This work shows the preparation of complete metalceramics crowns made with copings by electrodeposition, having as objective present an alternative in fixed partial prosthetics for the professionals

Adhesion of substrate–adherent combinations for early composite repairs: Effect of intermediate adhesive resin application

This study evaluated the effect of intermediate adhesive resin application (IAR) on tensile bond strength (TBS) for early composite repairs in situations where substrate and repair composite bonded together were once of the same kind with the substrate (similar) and once other than the substrate material (dissimilar). Specimens from three types of composites (TPH Spectrum (TPH), Charisma (CHA) and Filtek Z250 (Z250)) were fabricated. The specimens in each composite group (n=72) were randomly divided into six subgroups (n=12). In each composite group, the similar and two dissimilar composites were bonded onto the substrates once using an IAR (Adper Single Bond Plus) and once without. After water storage for I week at 37 degrees C, substrate-adherent combinations were submitted to tensile test. Data were analyzed with three-way ANOVA and Tukey's tests (alpha=0.05). The substrate-adherent combination (p=0.0001), adherent (repair) composite (p=0.0001), and application of IAR (p=0.0001) significantly affected the results. Utilization of IAR improved the repair bond strength for all composite combinations. (C) 2013 Elsevier Ltd. All rights reserved