Mechanical testing of four-unit implant-supported prostheses with extensive pink gingiva porcelain: The dentogingival prostheses proof of concept.

OBJECTIVE: To investigate the probability of survival and failure modes of four-unit implant-supported porcelain fused to metal (PFM) dentogingival prostheses subjected to step-stress accelerated life testing (SSALT). MATERIALS AND METHODS: Eighteen implant-supported PFM dentogingival prostheses with thin metallic infrastructures, which provided minimal ceramic support and improved esthetics were fabricated over external hexagonal connection UCLA abutments. SSALT was performed until specimen failure. Use level probability Weibull curve and reliability were calculated and plotted. Weibull modulus (m) and characteristic strength (η) were also calculated. Polarized light microscope and scanning electron microscope were used to characterize fractures. RESULTS: Failures were dictated by material strength rather than fatigue damage accumulation. The probability of survival for loads reaching 100 and 150 N in 100,000 cycles was 92 and 61%, respectively. No cracks or fractures were identified in the veneered porcelain, whereas abutment fixation screw fracture was the chief failure mode. CONCLUSION: Implant-supported PFM four-unit dentogingival prostheses with minimum metal framework dimensions presented favorable lifetime prediction under fatigue testing. Fractures were restricted to fixation screws. CLINICAL SIGNIFICANCE: In-vitro fatigue testing and failure mode analyses evidenced favorable lifetime prediction for 4-unit implant-supported dentogingival prostheses with minimum metal frameworks. Abutment fixation screw fracture might be the most frequent clinical complication. Since this proof of concept has been tested in-vitro, further studies including different restorative materials, as well as long-term clinical trials are warranted.

Influência do tipo de conexão pilar/implante na manutenção da pré-carga de parafusos de retenção e na desadaptação vertical da coroa protética antes e após ciclagem mecânica / Influence of abutment/implant system on pre-load maintenance of retention screws and on the vertical misfit of the implant-supported crown before and after mechanical cycling

Próteses implantossuportadas estão sujeitas a diversos tipos de falhas, sendo o afrouxamento do parafuso de retenção a complicação mais frequente, devido à perda da pré-carga inicial. A perda da pré-carga pode ser influenciada por fatores como incidência de cargas oclusais impróprias, diferentes tipos de conexões do sistema implante/prótese e desajustes entre a coroa e o implante. Sendo assim, este estudo teve como objetivo avaliar a manutenção da pré-carga de parafusos de retenção de titânio e a desadaptação vertical de coroas protéticas parafusadas, antes e após a ciclagem mecânica. Para isso, três tipos de conexões implante/pilar foram utilizados: implantes de conexão interna híbrida com pilar do tipo esteticone (grupo CIE); implantes de conexão externa com pilar o tipo esteticone (grupo CEE); e implantes de conexão externa com pilar UCLA (grupo CEU). Para cada grupo, foram confeccionadas 10 coroas metálicas fundidas em liga de CoCrMo para a composição final dos corpos-de-prova. Os parafusos de retenção protéticos receberam torque de 20N.cm nos grupos CIE e CEE e 30N.cm no grupo CEU, e, após três minutos, foi mensurado o valor de destorque inicial, com o auxílio de um torquímetro analógico. Após essa avaliação inicial, as coroas receberam novamente o torque recomendado e foram submetidas ao ensaio de ciclagem mecânica, com carga oblíqua (30°) de 130N ± 10N, a 2Hz de freqüência, totalizando 1x106 ciclos. Após a ciclagem, foi mensurado o destorque final. Além disso, antes e depois da ciclagem mecânica, foi realizada a verificação da adaptação vertical das coroas por meio de um estereomicroscópio, com as coroas parafusadas a um único implante e posicionadas em uma matriz de silicone a fim de padronizar seu posicionamento. Os dados obtidos foram tabulados e submetidos à análise de variância, teste exato de Fisher e correlação linear de Pearson (p<0,05). Todas as mensurações de destorque foram inferiores ao torque de inserção, tanto antes quanto após a ciclagem...

Implant-supported prostheses are prone to several types of fail, and the retaining screw loosening is the most frequent complication, due to the loss of its initial preload. Loss of preload may be caused by different factors such as the incidence of excessive occlusal loading, different types of implant/prosthesis connections systems and vertical misfit between crown and implant. Thus, the aim of this study was to evaluate the preload maintenance of titanium retaining screws and to measure the vertical misfit of implant-supported screwed crowns, before and after mechanical cycling. For this purpose, three types of implant/abutment systems were embedded in polyester resin: internal hybrid connection implants and Estheticone abutments (Group ICE); external connection implants with Estheticone abutments (Group ECE); and external connection implants with UCLA abutments (Group ECU). For each group, 10 metallic crowns were cast in CoCrMo alloy for the final compositions of the specimens. Retaining screws received insertion torque of 20 N.cm in groups ICE and ECE and 30N.cm in group ECU, and, after three minutes, the initial detorque was measured through an analogical torquemeter. After this initial evaluation, crowns were retightened and submitted to cyclic loading test, with an oblique loading (30°) of 130N ± 10N, at 2Hz of frequency, totalizing 1x106 cycles. After cycling, final detorque was measured. Moreover, before and after mechanical cycling, the vertical misfit of the crowns was measured through estereomicroscopy, with the crowns screwed to a single implant and positioned into a silicone matrix. The data obtained were tabulated and submitted to variance analysis, Fisher’s exact test and Pearson’s linear correlation (p<0,05). All detorque values were lower that the insertion torque, both before and after mechanical cycling. When groups were compared, there was no statistically significant difference before mechanical cycling. When groups were compared after...

Influência do tipo de conexão pilar/implante na manutenção da pré-carga de parafusos de retenção e na desadaptação vertical da coroa protética antes e após ciclagem mecânica / Influence of abutment/implant system on pre-load maintenance of retention screws and on the vertical misfit of the implant-supported crown before and after mechanical cycling

Próteses implantossuportadas estão sujeitas a diversos tipos de falhas, sendo o afrouxamento do parafuso de retenção a complicação mais frequente, devido à perda da pré-carga inicial. A perda da pré-carga pode ser influenciada por fatores como incidência de cargas oclusais impróprias, diferentes tipos de conexões do sistema implante/prótese e desajustes entre a coroa e o implante. Sendo assim, este estudo teve como objetivo avaliar a manutenção da pré-carga de parafusos de retenção de titânio e a desadaptação vertical de coroas protéticas parafusadas, antes e após a ciclagem mecânica. Para isso, três tipos de conexões implante/pilar foram utilizados: implantes de conexão interna híbrida com pilar do tipo esteticone (grupo CIE); implantes de conexão externa com pilar o tipo esteticone (grupo CEE); e implantes de conexão externa com pilar UCLA (grupo CEU). Para cada grupo, foram confeccionadas 10 coroas metálicas fundidas em liga de CoCrMo para a composição final dos corpos-de-prova. Os parafusos de retenção protéticos receberam torque de 20N.cm nos grupos CIE e CEE e 30N.cm no grupo CEU, e, após três minutos, foi mensurado o valor de destorque inicial, com o auxílio de um torquímetro analógico. Após essa avaliação inicial, as coroas receberam novamente o torque recomendado e foram submetidas ao ensaio de ciclagem mecânica, com carga oblíqua (30°) de 130N ± 10N, a 2Hz de freqüência, totalizando 1x106 ciclos. Após a ciclagem, foi mensurado o destorque final. Além disso, antes e depois da ciclagem mecânica, foi realizada a verificação da adaptação vertical das coroas por meio de um estereomicroscópio, com as coroas parafusadas a um único implante e posicionadas em uma matriz de silicone a fim de padronizar seu posicionamento. Os dados obtidos foram tabulados e submetidos à análise de variância, teste exato de Fisher e correlação linear de Pearson (p<0,05). Todas as mensurações de destorque foram inferiores ao torque de inserção, tanto antes quanto após a ciclagem...

Implant-supported prostheses are prone to several types of fail, and the retaining screw loosening is the most frequent complication, due to the loss of its initial preload. Loss of preload may be caused by different factors such as the incidence of excessive occlusal loading, different types of implant/prosthesis connections systems and vertical misfit between crown and implant. Thus, the aim of this study was to evaluate the preload maintenance of titanium retaining screws and to measure the vertical misfit of implant-supported screwed crowns, before and after mechanical cycling. For this purpose, three types of implant/abutment systems were embedded in polyester resin: internal hybrid connection implants and Estheticone abutments (Group ICE); external connection implants with Estheticone abutments (Group ECE); and external connection implants with UCLA abutments (Group ECU). For each group, 10 metallic crowns were cast in CoCrMo alloy for the final compositions of the specimens. Retaining screws received insertion torque of 20 N.cm in groups ICE and ECE and 30N.cm in group ECU, and, after three minutes, the initial detorque was measured through an analogical torquemeter. After this initial evaluation, crowns were retightened and submitted to cyclic loading test, with an oblique loading (30°) of 130N ± 10N, at 2Hz of frequency, totalizing 1x106 cycles. After cycling, final detorque was measured. Moreover, before and after mechanical cycling, the vertical misfit of the crowns was measured through estereomicroscopy, with the crowns screwed to a single implant and positioned into a silicone matrix. The data obtained were tabulated and submitted to variance analysis, Fisher’s exact test and Pearson’s linear correlation (p<0,05). All detorque values were lower that the insertion torque, both before and after mechanical cycling. When groups were compared, there was no statistically significant difference before mechanical cycling. When groups were compared after...

Evaluation of pre-tightening in abutments and prosthetic screws on different implant connections / Avaliação do pré-aparafusamento em pilares e parafusos protéticos em diferentes conexões de implante

Purpose: This study evaluated pre-tightening maintenance in abutment and prosthetic screwsof external and internal hexagon implant with straight and angled abutments. Methods: Four groups of implants and abutments were assessed combining internal andexternal hexagon and straight and angled abutments, which were retained by titanium screws tightened to 20 N.cm. Crowns were retained with gold screws tightened at 10 N.cm. A verticalline was ascribed across the implant-abutment-crown interface to verify horizontal displacement by a light microscope. The fatigue tests were performed in a servo-hydraulic machine, which delivered forces between 100 and 120 N for 250,000 cycles. The screw was removed, and the detorque value was recorded. Data were analyzed with 2-way ANOVA and Tukey's test. Results: No horizontal displacement was observed on the interface of implant-abutment or abutment and crown. It was found significant difference for prosthetic screw between implant connection types, but without interaction with abutment. However, for abutment screw, there was a difference between implant connection types and abutment with interaction between implant and abutments. The straight abutment showed significant better performance than the 17º angled abutment. Conclusion: The connection implant types or abutment affected pre-tightening maintenance. Internal and external hexed connections were effective to avoid horizontal displacement of crowns.

Objetivo: Este estudo avaliou a manutenção do pré-aparafusamento em pilar e parafuso protético de implantes com hexágono interno e externo, com pilares retos e angulados. Metodologia: Quatro grupos de implantes e pilares foram avaliados, combinando-se ohexágono interno ou externo e o pilar reto ou angulado, os quais foram retidos por parafusos de titânio aparafusados 20 N.cm. As coroas fora retidas com parafusos de ouro aparafusadosa 10 N.cm. Uma linha vertical foi delineada sobre a interface implante-pilar-coroa para verificar o deslocamento vertical com uso de microscópio ótico. Os testes de fadiga foram realizados em uma máquina servo-hidráulica, que promoveu forças entre 100 e 120 N por 250.000 ciclos. O parafuso foi removido e o valor de detorque for registrado. Os dadosforam analisados por ANOVA de dois fatores e teste de Tukey. Resultados: Nenhum deslocamento horizontal foi observado na interface implante-pilar oupilar-coroa. Observou-se uma diferença significativa para o parafuso protético entre os tipos de conexão do implante, mas sem interação com o pilar. Porém, para o parafuso do pilar houve diferença entre tipos de conexão e pilar, com interação entre pilar e implante. O pilar reto mostrou melhor performance que o pilar angulado a 17°. Conclusão: Os tipos de conexão do implante ou pilar afetaram a manutenção do pré aparafusamento. As conexões de hexágono interno e externo foram efetivas para evitar o deslocamento horizontal das coroas.