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Doctoral Thesis
DOI
https://doi.org/10.11606/T.25.2019.tde-05102021-142059
Document
Author
Full name
Ilana Santos Ramalho
Institute/School/College
Knowledge Area
Date of Defense
Published
Bauru, 2019
Supervisor
Committee
Bonfante, Estevam Augusto (President)
Pegoraro, Luiz Fernando
Reis, José Mauricio dos Santos Nunes
Vidotti, Hugo Alberto
Title in English
Influence of abutment fabrication method and fixation mode on the three-dimensional fit and reliability of implant-supported prostheses
Keywords in English
Computer-aided design
Dental implant-abutment designs
Dental implant-abutment interface
Dental implants
MicroCT
Reliability
Abstract in English
Objectives. To evaluate the effect of abutment fabrication method on the threedimensional fit at the implant-abutment interface and its correlation with stress at fatigue failure of prostheses. Probability of survival (reliability) and fractography to characterize failure modes were also performed for cemented and screw-retained prostheses. Methods. Central incisor crowns were milled to restore implants and divided in 3 cemented and 3 screwed-retained groups, as follows (n=21/group): [Digital-Sc]: milled one-piece monolithic abutment/crown; [TiB-Sc]: milled crowns cemented onto Ti-base abutments; [UCLA]: screw-retained crown using UCLA abutments; [Digital- Ce]: milled two-piece assembly comprised by screwed monolithic abutment and a cemented crown; [TiB-Ce]: milled coping cemented onto Ti-base abutments to receive a cemented crown; [UCLA-Ce]: UCLA abutments that received an overcast coping and a cemented crown. Volume measurements were performed to assess the internal misfit using silicone replica of the implant/abutment interface area threedimensionally reconstructed after microcomputed tomography (CT). Implant/crown systems were subjected to step-stress accelerated life testing (SSALT) in water. The use-level probability Weibull curves and reliability for a mission of 50,000 cycles at calculated stress at failure of 2,300, 3,300 and 4,300 MPa were plotted. Fractographic analysis was performed with scanning electron microscopy. Internal misfit was analyzed through one-way ANOVA following post-hoc comparisons by Tukey test (P<0.05). Correlation between misfit volume and the stress at fatigue failure was assessed by Pearson test. Results. Similar misfit volumes were observed for TiB-Sc (0.458 mm3), TiB-Ce (0.461 mm3), UCLA (0.471 mm3) and UCLA-Ce (0.480 mm3), which were significantly lower than Digital-Sc (0.676 mm3) and Digital-Ce (0.633 mm3). The mean values were: 1.68, 1.39, 1.48, 2.41, 2.27 and 0.71 for Digital-Sc, TiB-Sc, UCLA, Digital-Ce, TiB-Ce and UCLA-Ce, respectively, indicating that fatigue was an accelerating factor for failure of all groups, except for UCLA-Ce. Higher stress at failure decreased the reliability of all groups, more significantly for screw compared to cement-retained groups, especially for Digital-Sc that demonstrated the lowest reliability. The failure mode was restricted to abutment screw fracture. A negative correlation was observed between misfit values and stress at failure (r = -0.302, P=0.01). Conclusions. Ti-Base and UCLA abutments exhibited better internal fit at the implant/abutment interfaces compared to full commercial lab fabrication process (CAD-CAM custom abutments). An impairment of the mechanical resistance according to different levels of internal misfit was observed, since the higher the volume of misfit, the lower the stress at failure during fatigue. Probability of survival decreased at higher stress, especially for screw compared to cement-retained groups, and failures were confined to abutment screws
Title in Portuguese
Influência do método de fabricação de pilares e modo de fixação na adaptação tridimensional e confiabilidade de próteses sobre implantes
Keywords in Portuguese
Confiabilidade
Implantes dentários
MicroCT
Projeto Auxiliado por Computador
Abstract in Portuguese
Objetivos. Avaliar o efeito do método de fabricação de pilares sobre a adaptação tridimensional na interface implante-pilar e sua correlação com o estresse à fratura por fadiga das próteses. Probabilidade de sobrevida (confiabilidade) e fractografia para caracterizar modos de falha também foram realizadas para próteses cimentadas e parafusadas. Métodos. Coroas de incisivos centrais foram confeccionadas para restaurar implantes e divididas em seis grupos, sendo 3 grupos parafusados e 3 cimentados (n=21/grupo): [Dig-Par] coroa fresada monolítica parafusada; [TiB-Par] coroa fresada cimentada sobre pilar Ti-Base e parafusados ao implante; [UCLA] coroa fundida sobre UCLA parafusada; [Dig-Cim] pilar fresado parafusado para receber coroa fresada cimentada; [TiB-Cim] pilar fresado e cimentado sobre Ti-Base para receber coroa cimentada; [UCLA-Cim] pilar fundido sobre UCLA parafusado para receber coroa cimentada. Mensurações de volume foram realizadas para avaliar o desajuste interno usando réplica de silicone na área da interface implante/pilar reconstruída tridimensionalmente após a microtomografia computadorizada (CT). Os espécimes foram submetidos ao teste de fadiga acelerada progressiva na presença de água. As curvas de probabilidade de Weibull e a confiabilidade para missões de 50.000 ciclos a 2.300, 3.300 e 4.300 Mpa foram plotadas e calculadas em função do estresse. A análise fractográfica foi realizada com microscopia eletrônica de varredura. O desajuste interno foi analisado através de ANOVA seguida de comparações múltiplas pelo teste de Tukey (P<0,05). A correlação entre o volume de desajuste e o estresse à fratura por fadiga foi avaliada pelo teste de correlação de Pearson. Resultados. Volumes de desajuste semelhantes foram observados para TiB-Par (0,458 mm3), TiB-Cim (0,461 mm3), UCLA (0,471 mm3) e UCLA-Cim (0,480 mm3), que foram significativamente menores que Dig-Par (0,676 mm3) e Dig-Cim (0,633 mm3). Os valores médios de foram: 1,68, 1,39, 1,48, 2,41, 2,27 e 0,71 para Dig- Par, TiB-Par, UCLA, Dig-Cim, TiB-Cim e UCLA-Cim, respectivamente, indicando que o acúmulo de danos em função da fadiga foi um fator de aceleração para as falhas em todos os grupos, exceto para UCLA-Cim. Maior estresse à fratura diminuiu a confiabilidade de todos os grupos, mais significativamente para os grupos parafusados comparado aos cimentados, especialmente para o Dig-Par, que demonstrou a menor confiabilidade. O modo de falha predominante foi a fratura do parafuso do pilar. Uma correlação negativa foi observada entre os valores de desajuste e estresse à fratura (r = -0,302, P = 0,01). Conclusões. Os pilares do tipo Ti-Base e UCLA exibiram melhor ajuste interno na interface implante/pilar comparado com os pilares fresados em laboratório comercial (customizados CAD-CAM). Observou-se um comprometimento da resistência mecânica de acordo com os diferentes níveis de desajuste interno, visto que quanto maior o volume de desajuste, menor o estresse à fratura durante a fadiga. Probabilidade de sobrevivência diminuiu em nível maior de estresse, especialmente para os grupos parafusados em comparação com os cimentados, e as falhas foram confinadas aos parafusos do pilar.
 
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Release Date
2023-10-05
Publishing Date
2021-10-05
 
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