Background: The golden standard for single unit crowns has for long been porcelain fused to metal (PFM). However, demands for improved esthetic materials has driven the development of zirconia which has increased in popularity due to its eminent mechanical and esthetic properties. Long term follow-up of zirconia is lacking and no consensus regarding which luting agent to use has yet been established. Aim: The aim of the present study was to evaluate the longevity of single unit crowns in relation to luting cements used and to investigate if any shift in the choice of crown materials could be seen over time. Methods: A retrospective journal survey with inclusion criteria being patients treated with tooth supported single crowns at the students’ clinic at the Umea University School of Dentistry. Extracted data were focused on 8 factors regarding information about the patient and materials used in the crown treatment. Statistical analyses were made with GraphPad.com and Microsoft Excel 2010. Results: Core reinforced zirconia crowns luted with RelyX showed a statistically significant higher success rate (95%) compared to crowns luted with zinc oxide phosphate (60%) (p<0.05). The most common complications were loss of retention and chipping of the veneering porcelain. Conclusion: The choice of luting agent seems to be of importance for core reinforced zirconia crowns. No statistically significant difference in success rate could be seen for PFM and monolithic zirconia. A shift in the choice of crown material could be seen. Monolithic ZR had increased, while PFM and ZR core had decreased.

The aim of this study was to verify the behavior of five brands of NiCr alloys, indicated to porcelain fused to metal restorations, comparing the castability with the ability of reproducing the thin edges of restoration margins. The samples were divided in five groups, each one for one brand, with ten repetitions for castability test and ten for edge reproduction, in a total of 100 specimens. A carbon free phosphate bonded investment was used for all casting procedures. Optical microscopy was used to investigate the microstructure of the specimens obtained with two of the alloys, those which have shown better results. Statistical analysis stated that the commercial brand Tilite showed both better castability and edge reproduction. / O objetivo desta pesquisa foi verificar o desempenho de cinco ligas de níquel-cromo para restaurações de metalocerâmicas, comparando a fluidez com a capacidade de cópia da borda fina das restaurações. Os corpos-de-prova foram divididos em 5 grupos um para cada liga, sendo realizado dez corpos-de-prova para o teste de fluidez e dez corpos-de-prova para o teste da cópia da borda, totalizando 100 corpos-de-prova. Um revestimento de fosfato sem carbono foi usado para todas as inclusões e fundições. Em seguida foram submetidos a microscopia óptica, para se observar a microestrutura das duas ligas que obtiveram os melhores desempenhos. Os resultados, após análise estatística, demonstraram que a liga Tilite apresentou a melhor fluidez e melhor cópia da borda.

O estudo comparativo da distribuição de tensões de von Mises em dente endodonticamente tratado, com dois formatos de retentores intra-radiculares, pré-fabricado cilíndrico/escalonado e fundido cônico, foi realizado pelo método dos elementos finitos em modelos tridimensionais de caninos superiores com geometria axi-simétrica e restaurados com coroas metalocerâmicas, aplicando-se uma carga oblíqua de 100N com 45 º de inclinação em relação ao seu longo eixo. Os resultados indicaram uma discreta diferença nos dois modelos (formatos) de retentores. O pino escalonado neutralizou mais as cargas no sentido corono-apical e no pino cônico ficou evidenciado o efeito de cunha. / The aim of this study was to compare the von Mises stress distribution on a human canine teeth endodontically treated and restored with two types of post and core. The analysis was made using the three dimensional Finite Element Analysis method. For the analysis was created and axy-simetric structure of the teeth, including a porcelain fused to metal crown, a cement layer, and the periodontal structures. The model was analyzed when a 100N load was applied on the surface of the crown with 45º angulation with the long axis of the teeth. The results showed that both models exhibit little difference, the “stair shape" post system neutralized the axial loads, and the conical shape post showed a wedge effect on the apical third of the root.

O estudo comparativo da distribuição de tensões de von Mises em dente endodonticamente tratado, com dois formatos de retentores intra-radiculares, pré-fabricado cilíndrico/escalonado e fundido cônico, foi realizado pelo método dos elementos finitos em modelos tridimensionais de caninos superiores com geometria axi-simétrica e restaurados com coroas metalocerâmicas, aplicando-se uma carga oblíqua de 100N com 45 º de inclinação em relação ao seu longo eixo. Os resultados indicaram uma discreta diferença nos dois modelos (formatos) de retentores. O pino escalonado neutralizou mais as cargas no sentido corono-apical e no pino cônico ficou evidenciado o efeito de cunha. / The aim of this study was to compare the von Mises stress distribution on a human canine teeth endodontically treated and restored with two types of post and core. The analysis was made using the three dimensional Finite Element Analysis method. For the analysis was created and axy-simetric structure of the teeth, including a porcelain fused to metal crown, a cement layer, and the periodontal structures. The model was analyzed when a 100N load was applied on the surface of the crown with 45º angulation with the long axis of the teeth. The results showed that both models exhibit little difference, the “stair shape” post system neutralized the axial loads, and the conical shape post showed a wedge effect on the apical third of the root.