RESUMO

PURPOSE: To evaluate the fatigue survival, fracture loads and failure modes of monolithic lithium disilicate screw-retained crowns, attached to titanium insert, and cement-retained crowns. MATERIALS AND METHODS: Internal tapered connection implants, embedded in acrylic resin at 30° inclination, were restored with lithium disilicate restorations, simulating a maxillary premolar (n = 20), with different designs: screw-retained titanium base abutment-crowns, and cement-retained crowns. The specimens were submitted to cyclic mechanical loading (1.2 × 106 cycles with a load of 0-250 N at 2 Hz). Surviving specimens were subjected to single load to fracture in a universal testing machine and failure modes were determined with the aid of an optical microscope. Maximum load values were analyzed statistically using the t-test and differences in failure modes were analyzed using the chi-squared test (α = 0.05). RESULTS: All specimens survived the cyclic mechanical loading. Fracture load was significantly higher for screw-retained crowns (821.69 ±196.71 N) than the cement-retained crowns (577.03 ± 137.75 N) (p = 0.005). Ceramic failure was the predominant mode, with no statistical difference between groups. CONCLUSIONS: Screw-retained and cement-retained lithium disilicate crowns survived the cyclic mechanical loading. The use of titanium inserts to support a monolithic restoration enhances the fracture strength of the crown/abutment system.

Assuntos

RESUMO

AIM: The aim of this meta analysis was to evaluate the influence of the processing method on the marginal and internal gaps of lithium disilicate inlays/onlays. SETTINGS AND DESIGN: A systematic literature review was conducted using the PubMed/Medline, Embase, Scopus, and Cochrane Library databases. This review was registered on the PROSPERO platform. MATERIALS AND METHODS: The studies were selected according to the marginal and internal gaps of two different fabrication methods for lithium disilicate (milled and pressed). STATISTICAL ANALYSIS USED: The meta analysis was performed based on the Mantel-Haenszel and inverse variance methods, using the random effects model and a 95% confidence interval. RESULTS: From all databases, 127 studies were identified. Four in vitro studies were included in the qualitative analysis and three in the meta analysis. Moreover, 197 restorations were evaluated (103 pressed and 94 milled). During the evaluation of only the internal gap, there was a statistically significant difference favoring the pressed technique (P = 0.002). There was no statistically significant difference in the analyses of the marginal gap (P = 0.530) and the total gap (P = 0.450). CONCLUSION: Both the techniques provided acceptable marginal and total gaps, although the pressed technique revealed a more favorable internal adaptation than the milled onlays/inlays.

RESUMO

Afirmação do problema. A integridade marginal de coroas monolíticas é um fator essencial para sua longevidade. Devido a ampla aplicação dos sistemas CAD-CAM disponíveis, a avaliação da precisão de sua produção é de grande interesse clínico. Finalidade. Avaliação do lascamento marginal de coroas monolíticas de dissilicato de lítio produzidas por quatro sistemas CAD-CAM diferentes. Material e métodos. Foram selecionados quatro sitemas CAD-CAM: Ceramill (Ceramill Motion 2), Cerec (Cerec inLab MC XL), EDG (CAM5-S1 SmartDent) e Zirkonzahn (M5 Heavy). Um primeiro molar inferior artificial foi preparado para coroa total, duplicado em gesso, digitalizado e a coroa foi projetada seguindo parâmetros padronizados. Dez coroas de dissilicato de lítio (IPS e.max CAD) foram fresadas por grupo. Para cada grupo o sistema foi utilizado em sua totalidade: scanner, software do design e unidade de fresagem. Imagens foram obtidas usando o estereomicroscópio Stemi 2000-C (Zeiss), sobrepostas (programa Adobe Photoshop CS6) e medidas do perímetro marginal e área de lascamento foram realizadas (programa ImageJ). Para avaliar o grau de lascamento da margem, o Fator de Lascamento (FL) de cada coroa foi calculado e os dados foram submetidos ao teste de Kruskal-Wallis, seguido pelo método de Dunn (p < 0,05). Resultados. Com base nos valores médios absolutos e DP, o FL dos grupos Ceramill (14,5 ± 8,3) e Cerec (13,4 ± 9,4) foram estatisticamente maiores do que os grupos EDG (3,4 ± 1,2) e Zirkonzahn (2,8 ± 1,3). Conclusão. Os dados demonstraram a influência dos parâmetros selecionados durante o design, das configurações e ferramentas de confecção dos sistemas CAD / CAM sobre a integridade marginal das coroas monolíticas.(AU)

Statement of the problem. The marginal integrity of monolithic crowns is an essential factor for longevity. Due to the wide application of CAD/CAM systems, evaluation of production accuracy is of great clinical interest. Purpose. Evaluating the marginal chipping of monolithic lithium disilicate crowns produced by four different CAD-CAM systems. Material and methods. Four CAD-CAM systems were selected: Ceramill (Ceramill Motion 2), Cerec (Cerec inLab MC XL), EDG (CAM5-S1 SmartDent) and Zirkonzahn (M5 Heavy). An artificial lower first molar was prepared for a full crown, duplicated in plaster, scanned and a crown was designed following standardized parameters. Ten lithium disilicate crowns (IPS e.max CAD) per group were milled. Images were obtained using a scanning stereomicroscope Stemi 2000-C (Zeiss), overlapped (Adobe Photoshop CS6 software) and measurents of the marginal perimeter and chipping area were performed (ImageJ software). To evaluate the degree of marginal chipping, the Chipping Factor (CF) of each crown was calculated and the data were subjected to Kruskal-Wallis One-way test followed by Dunn's method (p< 0.05). Results. Based on SD and absolute mean values, the CF of Ceramill (14,5 ± 8,3) and Cerec (13,4 ± 9,4) groups was statistically higher than EDG (3,4 ± 1,2) and Zirkonzahn (2,8 ± 1,3). Conclusion. The data demonstrated the influence of selected parameters during the design, parameters settings and manufacturing tools of CAD/CAM systems on the marginal integrity of monolithic crowns.(AU)

Assuntos