Abstract: Purpose: To synthesize a zirconia-toughened alumina (ZTA) composite with 85% alumina matrix reinforced by 15% zirconia and to characterize its optical and mechanical properties before and after artificial aging, to be compared with a conventional dental zirconia (3Y-TZP). Material and methods: After syntheses, ZTA and 3Y-TZP powders were uniaxially and isostatically pressed. Greenbody samples were sintered and polished to obtain 80 disc-shaped specimens per group (12 x 1 mm, ISO 6872:2015). The crystalline content and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Optical properties were determined by the calculation of contrast ratio (CR) and translucency parameter (TP) using reflectance data. Mechanical properties were assessed by Vickers hardness, fracture toughness and biaxial flexural strength test (BFS). All analyses were conducted before and after artificial aging (20h, 134 °C, 0.22 MPa). Optical parameters and microhardness differences were evaluated through repeated-measures analysis of variance (p < 0.05). BFS data were analyzed using Weibull statistics (95% CI). Results: The synthesis of the experimental ZTA composite was successful, with 98% of theoretical density, as shown in the SEM images. XRD patterns revealed typical zirconia and alumina crystalline phases. ZTA optical properties parameters showed no effect of aging, with a high CR and low TP values denoting a high maskingability. 3Y-TZP presented lower masking-ability and aging significantly affected its optical properties. ZTA Vickers hardness, fracture toughness and Weibull parameters, including characteristic stress and Weibull modulus were not influenced by aging, while 3Y-TZP presented a significant decrease in characteristic stress and increase in fracture toughness after aging. The ZTA probability of survival for missions of 300 and 500 MPa was estimated at ~99% validating its use for 3-unit posterior fixed dental prostheses (FDP), and no different from conventional 3Y-TZP. At high-stress mission (800 MPa) a significant decrease in probability of survival was observed for aged 3Y-TZP (84%) and for immediate and aged ZTA (73 and 82% respectively). Conclusion: The ZTA composite presented a dense microstructure, with preservation of the crystalline content, optical and mechanical properties after artificial aging, which encourages future research to validate its potential use for large span FDP.

Palavras-Chave: aluminium oxides; zirconium oxides; aging; ceramics; microstructure; optical properties; optical microscopes

BENALCAZAR JALKH, E.B.; BERGAMO, E.T.P.; MONTEIRO, K.N.; CESAR, P.F.; GENOVA, L.A.; LOPES, A.C.O.; LISBOA FILHO, P.N.; COELHO, P.G.; SANTOS, C.F.; BORTOLIN, F.; PIZA, M.M.T.; BONFANTE, E.A. Aging resistance of an experimental zirconia-toughened alumina composite for large span dental prostheses: optical and mechanical characterization. Journal of the Mechanical Behavior of Biomedical Materials, v. 104, p. 1-9, 2020. DOI: 10.1016/j.jmbbm.2020.103659. Disponível em: http://repositorio.ipen.br/handle/123456789/31390. Acesso em: $DATA.

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Abstract: Objective: to verify the effect of the addition of dicalcium phosphate dihydrate (DCPD) particles functionalized with di- or triethylene glycol dimethacrylate (DEGDMA or TEGDMA) on the degree of conversion (DC), post-gel shrinkage (PS), mechanical properties, and ion release of experimental composites. Methods: Four composites were prepared containing a BisGMA/TEGDMA matrix and 60 vol% of fillers. The positive control contained only barium glass fillers, while in the other composites 15 vol% of the barium was replaced by DCPD. Besides the functionalized particles, non-functionalized DCPD was also tested. DC after 24 h (n=3) was determined by FTIR spectroscopy. The strain gage method was used to obtain PS 5 min after photoactivation (n=5). Flexural strength and modulus (n=10) were calculated based on the biaxial flexural test results, after specimen storage for 24 h or 60 days in water. The same storage times were used for fracture toughness testing (FT, n=10). Calcium and phosphate release up to 60 days was quantified by ICP-OES (n=3). Data were analyzed by ANOVA/Tukey test (alpha: 5%). Results: Composites containing functionalized DCPD presented higher DC than the control (p < 0.001). The material containing DEGDMA-functionalized particles showed higher PS than the other composites (p < 0.001). After 60 days, only the composite with DEGDMA-functionalized DCPD presented fracture strength similar to the control, while for flexural modulus only the composite with TEGDMA-functionalized particles was lower than the control (p < 0.001). FT of all composites containing DCPD was higher than the control after 60 days (p < 0.005). Calcium release was higher for the composite with non-functionalized DCPD at 15 days and no significant reductions were observed for composites with functionalized DCPD during the observation period (p < 0.001). For all the tested composites, phosphate release was higher at 15 days than in the subsequent periods, and no difference among them was recorded at 45 and 60 days (p < 0.001). Conclusions: DCPD functionalization affected all the studied variables. The composite with DEGDMA-functionalized particles was the only material with strength similar to the control after 60 days in water; however, it also presented the highest shrinkage. The presence of DCPD improved FT, regardless of functionalization. DCPD functionalization reduced ion release only during the first 15 days.

Palavras-Chave: composite materials; calcium phosphates; phosphates; spectroscopy; fourier transformation; infrared spectra; dentistry

NATALE, LIVIA C.; RODRIGUES, MARCELA C.; ALANIA, YVETTE; CHIARI, MARINA D.S.; BOARO, LETICIA C.C.; COTRIM, MARYCEL; VEGA, OSCAR; BRAGA, ROBERTO R. Mechanical characterization and ion release of bioactive dental composites containing calcium phosphate particles. Journal of the Mechanical Behavior of Biomedical Materials, v. 84, p. 161-167, 2018. DOI: 10.1016/j.jmbbm.2018.05.022. Disponível em: http://repositorio.ipen.br/handle/123456789/29253. Acesso em: $DATA.

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Abstract: Titanium scaffolds with non-toxic β stabilizing elements (Nb and Sn), Ti–34Nb–6Sn (TNS), and with magnesium as spacer (TNS/M), were processed by powder metallurgy, and sintered at 800 ◦C. The X-ray diffraction (XRD) pattern showed that materials are biphasic alloys, presenting 45 to 42% (wt %) in hcp (α-phase) and the rest is bcc (β-phase), and the presence of a slight peak relating to TiO2 in both materials. Pores of approximately 50 μm for TNS and 300 μm to TNS/M were observed in the micrographic analysis by scanning electron microscopy (SEM). The wettability was higher for TNS/M compared to TNS. The elastic modulus was higher for TNS compared to TNS/M. Stem cells derived from equine bone marrow (BMMSCs) were used for in vitro assays. The morphologic and adhesion evaluation after 72 h, carried out by direct contact assay with the materials showed that the BMMSCs were anchored and adhered to the porous scaffolds, in the way the cytoplasmic extension was observed. The cellular migration, using the “wound healing” method, was significant for the groups treated with conditioned medium with materials in 24 h. Osteogenic differentiation of BMMSCs, assessed by calcium deposition and staining with Alizarin Red, was greater in the conditioned medium with TNS/M in 10 days of culture. Since the biological effects was good and the elastic modulus decreased in the system with magnesium is a promising new content titanium alloy for biomedical application.

Palavras-Chave: titanium; magnesium; powder metallurgy; corrosion; biological materials; prostheses; sintering

ROSSI, MARIANA C.; BAYERLEIN, DANIEL L.; BRANDAO, JAQUELINE de S.; PFEIFER, JOAO P.H.; ROSA, GUSTAVO dos S.; SILVA, WILLIAM de M.; MARTINEZ, LUIS G.; SAEKI, MARGARIDA J.; ALVES, ANA L.G. Physical and biological characterizations of TiNbSn/(Mg) system produced by powder metallurgy for use as prostheses material. Journal of the Mechanical Behavior of Biomedical Materials, v. 115, p. 1-10, 2021. DOI: 10.1016/j.jmbbm.2020.104260. Disponível em: http://repositorio.ipen.br/handle/123456789/31979. Acesso em: $DATA.

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Abstract: Objectives: To evaluate biocorrosion and eccentric occlusal loading interplay in marginal quality of cervical restorations. Methods: Cervical wedge-shaped cavities were prepared in extracted premolars and restored with a composite. Premolars underwent either an erosive challenge (E: 1% citric acid/10 min), eccentric occlusal loading (EOL: 150 N/2.5 Hz/106 cycles), E before EOL (E + EOL), E intermediate to EOL (EOL/E/EOL), E after EOL (EOL + E), or no E or EOL (C: control). Marginal quality was analyzed based on a series of Optical Coherence Tomography images. Each of the margins was assigned a gap score (0, 1, 2, or 3) and measurement (μm). For each margin, scores data were analyzed with Kruskall Wallis and Dunn tests, and μm data, with Kruskall Wallis. Overall and for each group, the different margins were compared using Wilcoxon signed-rank test, and the correlation between scores and μm, Spearman’s correlation coefficient (α = 0.05). Results: E and EOL, even if associated, did not influence enamel marginal quality. EOL/E/EOL impaired dentin/ cementum marginal quality only in the case of scores and compared to E. E + EOL, EOL + E or EOL and even C, without differences between each other, did not influence results differently from E or EOL/E/EOL. Margins in dentin/cementum always showed lengthier gaps. Except for C, E and EOL + E cervical margin, there was a strong positive correlation between scores and μm. Conclusions: Eccentric occlusal loading and/or biocorrosion cannot be assumed as causes of marginal failure of cervical restorations in wedge-shaped cavities. A relevant concern may still be the establishment of adhesive interfaces in dentin/cementum. Clinical significance: Although non-carious cervical lesions are strongly being recognized multifactorial and their respective restorations not always behave as expected, biocorrosion and eccentric occlusal loading interplay cannot serve as an explanation for marginal gaps they often present.

Palavras-Chave: dentistry; caries; teeth; biological recovery; stress corrosion

ORDONEZ-AGUILERA, JUAN F.; LANDMAYER, KARIN; SHIMOKAWA, CARLOS A.K.; LIBERATTI, GIOVANNI A.; FREITAS, ANDERSON Z. de; TURBINO, MIRIAM L.; HONORIO, HEITOR M.; FRANCISCONI-DOS-RIOS, LUCIANA F. Role of non-carious cervical lesions multicausality in the behavior of respective restorations. Journal of the Mechanical Behavior of Biomedical Materials, v. 131, p. 1-9, 2022. DOI: 10.1016/j.jmbbm.2022.105232. Disponível em: http://repositorio.ipen.br/handle/123456789/33191. Acesso em: $DATA.

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