Effect of Thermocycling on Biaxial Flexural Strength of CAD/CAM, Bulk Fill, and Conventional Resin Composite Materials

New resin-based restorative materials have been developed, such as computer-aided design/computer-aided manufacturing (CAD/CAM) and bulk-fill composites, as an alternative to traditional layering techniques. This study evaluated the biaxial flexural strength (BFS) before and after thermocycling of five different resin composites: one hybrid resin/ceramic CAD/CAM indirect material, Lava Ultimate CAD-CAM Restorative (LU, 3M Oral Care); a conventional composite, Filtek Z350 XT (Z350, 3M Oral Care); two bulk-fill composites, Tetric N-Ceram Bulk Fill (TBF, Ivoclar Vivadent) and Filtek Bulk Fill (FBF, 3M Oral Care); and one bulk-fill flow resin composite, Filtek Bulk Fill Flow (FBFF, 3M Oral Care). Three hundred disc-shaped specimens (6.5 mm in diameter and 0.5 mm thick) were fabricated and divided into five groups (n=30 for each composite and condition). The BFS test was performed in a universal testing machine at a crosshead speed of 0.5 mm/min immediately (i, 24 hours) and after thermocycling (a, 500 thermal cycles of 5°C to 55°C with a 30-second dwell time). The Weibull modulus (m) and characteristic stress (η) were calculated, and a contour plot was used (m vs η) to detect differences between groups (95% two-sided confidence intervals). Significantly higher characteristic stress was observed for LUi (286.6 MPa) and Z350i (248.8 MPa) compared to the bulk-fill groups (FBFi=187.9 MPa, FBFFi=175.9 MPa, TBFi=149.9 MPa), with no differences between LUi and Z350i. Thermocycling significantly decreased the characteristic stress of all groups with the highest values observed for LUa (186.7 MPa) and Z350a (188.9 MPa) and the lowest for FBFFa (90.3 MPa). Intermediate values were observed for FBFa (151.6 MPa) and TBFa (122.8 MPa). The Weibull modulus decreased only for FBFa compared to FBFi. Composition and thermocycling significantly influenced the biaxial flexural strength of resin composite materials.

Análise da Retenção de Coroas CAD/CAM Cimentadas em Pilares do Tipo Ti-Base por Meio do Teste de Tração Pull-Out

Este estudo avaliou a resistência ao pull-out de coroas implantossuportadas confeccionadas em CAD/CAM e cimentadas em pilares de implante do tipo ti-base. Quarenta e cinco coroas foram fresadas para uso no pilar de implante ti-base (SIN Implante) e divididas (n15) de acordo com o material: Zircônia, Co-Cr ou Titânio. A cimentação foi realizada com cimento provisório Temp Bond NE (Kerr) ou cimento resinoso RelyX U200 (3M – Oral Care), sob carga de 50N por 10 minutos. As coroas foram submetidas ao   teste de tração em máquina de teste universal a 1,0 mm/min. Os testes foram feitos de acordo com a condição de cimentação: sem cimento (SC), cimentação provisória (CP, TempBond NE), sem cimento após a cimentação provisória (SCSP) e cimentação definitiva (CD, RelyX U200). Os resultados obtidos foram analisados por análise de variância e teste Tukey (p<0,05). Os valores médios de resistência (N) e desvio padrão foram: ZirSC (104,90/51,23) ZirCP (154,26/43,53) ZirSCCP (66,38/40,81) ZirCD (300,01/82,65) CoCrSC (72,38/43,07) CoCrCP (40,43/17,46) CoCrCD (900,35/133,63) TiSC (61,13/30,01) TiCP (158,85/22,18) TiSCCP (60,92/26,11) TiCD (566,66/75,82). Os materiais Co-Cr e titânio apresentaram maiores níveis de retenção ao pilar ti-base, na cimentação definitiva. O cimento RelyX U200 apresentou comportamento superior quando comparado ao cimento Temp Bond NE, independente do material da coroa.Palavras-chave: Implante Dentário. Cimentação. Coroa.