Accuracy, adaptation and margin quality of monolithic zirconia crowns fabricated by 3D printing versus subtractive manufacturing technique: A systematic review and meta-analysis of in vitro studies.

OBJECTIVE: The purpose of this systematic review and meta-analysis was to evaluate the accuracy (trueness and precision), marginal and internal adaptation, and margin quality of zirconia crowns made by additive manufacturing compared to subtractive manufacturing technology. METHODS: The investigation adhered to the PRISMA-ScR guidelines for systematic reviews and was registered at the Prospero database (n°CRD42023452927). Four electronic databases, including PubMed, Scopus, Embase, and Web of Science and manual search was conducted to find relevant studies published until September 2023. In vitro studies that assessed the trueness and precision, marginal and internal adaptation, and margin quality of printed crowns compared to milled ones were included. Studies on crowns over implants, pontics, temporary restorations, laminates, or exclusively experimental materials were excluded. RESULTS: A total of 9 studies were included in the descriptive reporting and 7 for meta-analysis. The global meta-analysis of the trueness (P<0.74,I2=90 %) and the margin quality (P<0.61,I2=0 %) indicated no significant difference between the root mean square of printed and milled zirconia crowns. The subgroup analysis for the printing system showed a significant effect (P<0.01). The meta-analysis of the crown areas indicated no significant difference in most of the areas, except for the marginal (favoring milled crowns) and axial (favoring printed crowns) areas. For precision and adaptation, both methods showed a clinically acceptable level. CONCLUSIONS: Additive manufacturing technology produces crowns with trueness and margin quality comparable to subtractive manufacturing. Both techniques have demonstrated the ability to produce crowns with precision levels, internal discrepancy, and marginal fit within clinically acceptable limits. CLINICAL SIGNIFICANCE: 3D printing emerges as a promising and potentially applicable alternative method for manufacturing zirconia crowns, as it shows trueness and margin quality comparable to restorations produced by the subtractive method.

Effect of ZrO2 paste, surface treatments, and storage on Weibull characteristics and resin bond strength to zirconia.

The objective is to evaluate the effect of different surface treatments and storage on the shear strength of ultratranslucent zirconia. 36 blocks of ultra-translucent zirconia were fabricated (7x7x2mm) and sintered. Then, divided into 12 groups according to the "surface treatment" (C -Primer; Al -Sandblasting with Al2O3 + Primer; Si -Silicate + Primer; Gl -Glaze + HF + Primer; Z -Zirlink; Zp -Zirlink + Primer) and "storage" factors (ST-with 150 days/37º and without). After surface treatment, five cylinders (Ø=2mm; h=2.0mm) of resin cement (n=15) were constructed in each ceramic block; at the end, the shear strength test was performed (1mm/min, 50Kgf), and analysis of surface failures. 60 additional samples (2x2x2mm) were made for extras analysis (surface roughness, MEV, and EDS). Bond strength and surface roughness data were statistically evaluated by ANOVA (2 factors/1 factor), Tukey test (5%), and Weibull analysis, respectively. ANOVA (2-way) revealed that all factors were statistically significant for bond strength. The silicatization groups (SiST: 30.47AMPa; Si: 29.21AMPa) showed the highest bond strength values, regardless of storage (Tukey's test). While the groups treated with Zirlink (ZST: 2.76FMPa; Z: 5.27EFMPa) showed the lowest values, just similar to the GlST group (5.14EFMPa). The Weibull modulus (m) showed a statistical difference between groups (p=0.000). ANOVA (1 factor) revealed that the "surface treatment" factor (p=0.0000) was statistically significant for surface roughness. Therefore, the application of Zirlink and Glaze on pre-sintered zirconia did not promote efficient adhesion of the ultratranslucent zirconia to the resin cement, even when associated with a primer containing MDP.

Effect of ZrO2 paste, surface treatments, and storage on Weibull characteristics and resin bond strength to zirconia

Abstract The objective is to evaluate the effect of different surface treatments and storage on the shear strength of ultratranslucent zirconia. 36 blocks of ultra-translucent zirconia were fabricated (7x7x2mm) and sintered. Then, divided into 12 groups according to the "surface treatment" (C -Primer; Al -Sandblasting with Al2O3 + Primer; Si -Silicate + Primer; Gl -Glaze + HF + Primer; Z -Zirlink; Zp -Zirlink + Primer) and "storage" factors (ST-with 150 days/37º and without). After surface treatment, five cylinders (Ø=2mm; h=2.0mm) of resin cement (n=15) were constructed in each ceramic block; at the end, the shear strength test was performed (1mm/min, 50Kgf), and analysis of surface failures. 60 additional samples (2x2x2mm) were made for extras analysis (surface roughness, MEV, and EDS). Bond strength and surface roughness data were statistically evaluated by ANOVA (2 factors/1 factor), Tukey test (5%), and Weibull analysis, respectively. ANOVA (2-way) revealed that all factors were statistically significant for bond strength. The silicatization groups (SiST: 30.47AMPa; Si: 29.21AMPa) showed the highest bond strength values, regardless of storage (Tukey's test). While the groups treated with Zirlink (ZST: 2.76FMPa; Z: 5.27EFMPa) showed the lowest values, just similar to the GlST group (5.14EFMPa). The Weibull modulus (m) showed a statistical difference between groups (p=0.000). ANOVA (1 factor) revealed that the "surface treatment" factor (p=0.0000) was statistically significant for surface roughness. Therefore, the application of Zirlink and Glaze on pre-sintered zirconia did not promote efficient adhesion of the ultratranslucent zirconia to the resin cement, even when associated with a primer containing MDP.

Resumo O objetivo é avaliar o efeito de diferentes tratamentos superficiais e do envelhecimento na resistência ao cisalhamento da zircônia ultratranslúcida. Foram confeccionados 36 blocos de zircônia ultratranslúcida (7x7x2mm) e sinterizados. Em seguida, divididos em 12 grupos de acordo com o "tratamento de superfície" (C-Primer; Al-Jateamento com Al2O3+Primer; Si-Silicato+Primer; Gl -Glaze+HF+Primer; Z-Zirlink; Zp-Zirlink+Primer) e fatores de "armazenamento" (ST-com, 150 dias/37º e sem). Após o tratamento superficial, foram construídos cinco cilindros (Ø=2mm; h=2,0mm) de cimento resinoso (n=15) em cada bloco cerâmico; ao final foi realizado o ensaio de resistência ao cisalhamento (1mm/min, 50Kgf) e análise de falhas superficiais. Foram confeccionadas 60 amostras adicionais (2x2x2mm) para análises extras (rugosidade superficial, MEV e EDS). Os dados de resistência de união e rugosidade superficial foram avaliados estatisticamente por ANOVA (2 fatores/1fator), teste de Tukey (5%) e análise de Weibull, respectivamente. ANOVA (2 fatores) revelou que todos os fatores foram estatisticamente significativos para a resistência de união. Os grupos de silicatização (SiST: 30,47AMPa; Si: 29,21AMPa) apresentaram os maiores valores de resistência de união, independente do armazenamento (Tukey). Enquanto os grupos tratados com Zirlink (ZST: 2,76FMPa; Z: 5,27EFMPa) apresentaram os valores mais baixos, apenas semelhantes ao grupo GlST (5,14EFMPa). O módulo de Weibull (m) apresentou diferença estatística entre os grupos (p=0,000). A ANOVA (1 fator) revelou que o fator "tratamento superficial" (p=0,0000) foi estatisticamente significativo para rugosidade superficial. Portanto, a aplicação de Zirlink e do Glaze na zircônia pré-sinterizada não promoveu adesão eficiente da zircônia ultratranslúcida ao cimento resinoso, mesmo quando associada a primer contendo MDP.

Influência do tipo de impressão, do pós processamento e do tipo de resina na resistência à flexão e na estabilidade dimensional de resinas impressas / Influence of the type of printing, post processing and type of resin on the flexural strength and dimensional stability of printed resins

Avaliar a influência de diferentes protocolos de pós processamento e do tipo de impressão 3D na resistência a flexão de três pontos () e estabilidade dimensional de diferentes resinas impressas. Metodologia: A partir da modelagem de uma barra (26 x 2,2 x 2,2mm) em software Meshmixer (Autodesk) e obtenção de arquivo STL, este foi exportado para os softwares das impressoras 3D SLA (Forms 2/Formslab) e LCD (FlashForge Foto 6.0/ FlashForge). Em seguida, 45 barras de cada tipo de resina (Pr - Provisório/Cosmos Temp, Yller; Pl - Placa oclusal/Cosmos Splint, Yller; Mo ­ Modelos/ Cosmos Model, Yller) foram impressas por cada sistema de impressão (SLA e LCD). Após a impressão, as barras de cada tipo de resina foram limpas com álcool isopropílico e distribuídas aleatoriamente (n=15) de acordo com o fator de estudo: "Protocolo de pós processamento" Controle (C: sem pós processamento); Luz Ultravioleta (UV: 15 min em forno Anycubic Wash e Cure Plus, Anycubic) e Micro-ondas (M: 15 min em forno micro-ondas/1.400W). Após, as barras foram submetidas ao teste de  (100KgF, 1mm/min) e os dados (MPa) submetidos à ANOVA 2 fatores e Tukey (5%) para cada tipo de resina. Também foram realizadas as análises complementares de estabilidade dimensional (analisados pelos testes T pareado, ANOVA 2 fatores e Tukey 5%) e MEV das superfícies e fraturas. Resultados: Para a resistência à flexão da resina de modelo, ANOVA 2 fatores indicou que os fatores "Impressora" (p<0,0001) e "Pós processamento" (p<0,0001) apresentaram significância estatística. Os grupos SLAMUV (33.80±4.82AMPa) e LCDMUV (35.93±4.47AMPa) apresentaram maiores valores de , sendo superiores estatisticamente aos grupos sem pós processamento e pós processados em micro-ondas. Para os grupos de resina de provisório, ANOVA 2 fatores revelou que os fatores "Impressora" (p=0,0044) e "Pós processamento" (p<0,0001) apresentaram significância estatística. O grupo LCDPUV apresentou maior resistência à flexão (52,06±12.40AMPa), seguido de SLAPUV (42.86±2.09BMPa) e SLAPMO (26.73±5.48CMPa). Para os grupos de placa, ANOVA 2 fatores mostrou que os fatores "Impressora" (p<0,0001) e "Pós processamento" (p<0,0001) apresentaram significância estatística. O grupo LCDPLUV (91.46±12.33AMPa) apresentou o maior valor de resistência à flexão, sendo estatisticamente superior aos demais grupos. Para estabilidade dimensional, na resina de modelo, o teste T para amostras pareadas demonstrou que apenas as amostras impressas em SLA apresentaram uma alteração significativa da largura e espessura após os métodos de pós processamento. Para o comprimento apenas as amostras pós curadas em luz ultravioleta tiveram alterações significativas (p<0,05). Já com relação a resina para placas o grupo SLAPl-UV a apresentar maiores variações nas três dimensões analisadas (largura: -55,60Aµm; espessura: -12,80Aµm; comprimento: - 93,73Aµm), e por apresentar dados negativos sugere-se expansão do material. Com relação a resina para provisório, em todas as dimensões estudadas o grupo LCDProv-UV apresentou maiores alterações dimensionais (largura: 31,46Aµm; espessura: -28,40Bµm; comprimento: - 86,53Aµm), enquanto o grupo LCDProv-MO apresentou menores alterações (largura: -7,20 Bµm; espessura: -4,40 Aµm; comprimento:18,00Bµm). Conclusão: Pôde-se concluir que o pós processamento em luz ultravioleta promoveu os melhores valores de resistência à flexão para todos os tipos de resinas avaliadas, sendo a técnica de impressão LCD a que apresentou melhores valores de () quando associada ao pós processamento em luz ultravioleta, independente do tipo de resina. A estabilidade dimensional está associada ao tipo de resina e ao pós processamento utilizado (AU).

To evaluate the influence of different post-processing protocols and the type of 3D printing of different printed resins on the three-point bending strength () and dimensional stability. Methodology: A bar was modeled (26 x 2.2 x 2.2mm) on Mishmixer software and a STL file was obtained, the it was exported to the 3D printer software SLA (Forms 2/Formslab) and LCD (FlashForge Photo 6.0/ FlashForge). Then, 45 bars of each type of resin (Pr - Provisional/Cosmos Temp, Yller; Pl - Occlusal Plate/Cosmos Splint, Yller; Mo ­ Models/ Cosmos Model, Yller) were printed by each printing system (SLA and LCD). After printing, the bars of each type of resin were cleaned with isopropyl alcohol and randomly divided (n=15) according to factors: "Post-processing protocol" Control (C: without post-processing); Ultraviolet Light (UV: 15 min in Anycubic Wash and Cure Plus, Anycubic) and Microwave (M: 15 min in microwave oven/1,400W). Thein, the bars were submitted to the  test (100KgF, 1mm/min) and data (MPa) analyzed with 2-way ANOVA and Tukey (5%). Complementary analyzes of dimensional stability (analyzed by paired T tests and 2-way ANOVA) and SEM of surfaces and fractures were also performed. Results: For the flexural strength of the model resin, 2-way ANOVA indicated that the factors "Printer" (p<0.0001) and "Post processing" (p<0.0001) showed statistical significance. The SLAMUV (33.80±4.82AMPa) and LCDMUV (35.93±4.47AMPa) groups presented higher  values, being statistically superior to the groups without post-processing and microwave-processed powders. For the provisional resin groups, 2-way ANOVA revealed that the factors "Printer" (p=0.0044) and "Post processing" (p<0.0001) were statistically significant. The LCDPUV group showed the highest flexural strength (52.06±12.40AMPa), followed by SLAPUV (42.86±2.09BMPa) and SLAPMO (26.73±5.48CMPa). For the plate groups, 2-way ANOVA showed that the factors "Printer" (p<0.0001) and "Post processing" (p<0.0001) were statistically significant. The LCDPLUV group (91.46±12.33AMPa) presented the highest flexural strength value, being statistically superior to the other groups. For dimensional stability, on the template resin, the T-test for paired samples demonstrated that only the SLA printed samples showed a significant change in width and thickness after post-processing methods. For length, only the samples post-cured in ultraviolet light had significant changes (p<0.05). Regarding the resin for plates, the SLAPlUV group presented greater variations in the three dimensions analyzed (width: -55.60Aµm; thickness: -12.80Aµm; length: -93.73Aµm), and for presenting negative data, we suggest material expansion. Regarding the resin for provisional, in all dimensions studied, the LCDProv-UV group showed greater dimensional changes (width: 31.46Aµm; thickness: - 28.40Bµm; length: -86.53Aµm), while the LCDProv-MO group presented minor changes (width: -7.20 Bµm; thickness: -4.40 Aµm; length: 18.00 Bµm). Conclusion: It could be concluded that the post processing in ultraviolet light promoted the best values of flexural strength for all types of resins evaluated, being the LCD printing technique the one that presented the best values of () when associated with post processing in ultraviolet light, regardless of the type of resin. Dimensional stability is associated with the type of resin and post-processing used (AU).