Abstract: Objective. To synthesize a zirconia toughened alumina (ZTA) composite with 70% aluminareinforced by 30% zirconia for dental applications and to characterize its microstructureand optical properties for comparison with the isolated counterpart materials and a first-generation 3Y-TZP.Methods. Disc-shaped specimens were divided in four groups (n = 70/material): (1) 3YSB-E(first generation 3Y-TZP), (2) Zpex (second generation 3Y-TZP), (3) alumina, and (4) ZTA-Zpex70/30. After synthesis, ceramic powders were pressed, and green-body samples sinteredfollowing a predetermined protocol. Specimens were polished to obtain a mirror surfacefinish. Apparent density was measured by Archimedes principle. X-ray diffraction (XRD)and scanning electron microscope (SEM) were used to characterize the crystalline contentand microstructure. Reflectance tests were performed to determine the contrast-ratio (CR)and translucency-parameter (TP). Mechanical properties were assessed by biaxial flexuralstrength (BFS) test. All analyses were conducted before and after artificial aging (20 h, 134◦C, 2.2 bar). Optical parameters were evaluated through repeated-measures analysis of variance and Tukey tests (p < 0.05). BFS data were analyzed using Weibull statistics (95% CI). Results. High density values (95–99%) were found for all ceramic materials and SEM images exhibited a dense microstructure. While XRD patterns revealed the preservation of crys- talline content in the ZTA composite, an increase in the monoclinic peak was observed for pure zirconias after aging. Significantly higher CR and lower TP values were observed for the ZTA composite, followed by alumina, 3YSB-E, and Zpex. The highest characteristic stress was recorded for 3YSB-E, followed by intermediate values between ZTA and Zpex, and the lowest for alumina. Aging affected the optical and mechanical properties of both zirconias, while remained stable for ZTA composite and alumina. Significance. The synthesis of experimental 70−30% ZTA composite was successful and its relevance for dental applications relies on its higher masking ability, aging resistance, and strength similar to zirconia.

Palavras-Chave: composite materials; zirconium oxides; aluminium oxides; mechanical properties; optical properties; microstructure; dentistry; prostheses

JALKH, ERNESTO B.B.; MONTEIRO, KELLI N.; CESAR, PAULO F.; GENOVA, LUIS A.; BERGAMO, EDMARA T.P.; LOPES, ADOLFO C. de O.; LIMA, ERICK; LISBOA-FILHO, PAULO N.; CAMPOS, TIAGO M.B.; WITEK, LUKASZ; COELHO, PAULO G.; BORGES, ANA F.S.; BONFANTE, ESTEVAM A. Aging resistant ZTA composite for dental applications: microstructural, optical and mechanical characterization. Dental Materials, v. 36, n. 9, p. 1190-1200, 2020. DOI: 10.1016/j.dental.2020.05.011. Disponível em: http://repositorio.ipen.br/handle/123456789/31789. Acesso em: $DATA.

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Abstract: Objeticve. The aim of this study was to develop a composite material with antibacterial activ-ity using MMT loaded with clorhexidine (CHX). For that it was used a BisGMA/TEGDMAmatrix and added low concentration of MMT/CHX. The aim was to evaluate the drug releasecapacity of MMT, and not to provide reinforcement.Methods. Six experimental composites were made with organic matrix of BisGMA/TEGDMAin equal proportions by weight. The composites received organophlizated montmorillonitewith or without CHX. The concentrations were 2,5; 5 or 10% by weight. Degree of conversion(DC) was evaluated using FTIR (peak 6165 cm-1; n = 5). Specimens for flexural properties(10×2×1 mm) were immediate tested (24h). Elastic modulus(E) and flexural strength (FS)was measured using the three point bending test (n = 10). Inibition halo was used to test theantibacterial activity against Staphylococcus aureus, Streptococcus mutans, and Porphyromonasgingivalis (n = 5 for each bacteria). The inhibition of biofilm formation (BF) was evaluated byinserting polymerized disc of composite in to a culture media colonized with Streptococcusmutans (n = 10). The release of CHX was measured using ultraviolet (255 nm) for 10 days(n = 5). The data of degree of conversion was analysed using Kruskal–Wallis/ Mann–Whitney,and the other variables using two-way ANOVA/Tukey, always considering a global level ofsignificance of 5%.Results. DC ranged from 71% to 74%. E ranged from 5.7 to 8.1 GPa. FS ranged from 61.4 to74.7 MPa. There were no statistical differences among the groups for all the variables. Forthe three bacteria tested the composites with CHX loaded presented inhibition of growthfor all concentration, except for 2,5% that did not inihibited the growth of P. gingivalis. BFwas lower for the groups with 10% MMT/CHX, all groups presented BF, even those withoutCHX loaded. All concentrations presented release off CHX during all the 28 days analyzed. Conclusions. Within the limitation of this study it can be concluded that: all concentrations tested presented release of CHX and reduced BF. All concentration presented antibacterial activity for the three bacteria tested, except for 2,5% that did not inhibit the growth of P. gingivalis. The presence of MMT with CHX loaded did not interfere in the properties evaluated.

Palavras-Chave: composite materials; germicides; dentistry; manganese compounds; chlorine compounds; bacteria; staphylococcus; streptococcus; antimicrobial agents; resins

BOARO, LETICIA C.C.; CAMPOS, LUIZA M.; VARCA, GUSTAVO H.C.; SANTOS, TAMIRIS M.R. dos; MARQUES, PAMELA A.; SUGII, MARI M.; SALDANHA, NATHALIA R.; COGO-MULLER, KARINA; BRANDT, WILLIAM C.; BRAGA, ROBERTO R.; PARRA, DUCLERC F. Antibacterial resin-based composite containing chlorhexidine for dental applications. Dental Materials, v. 35, n. 6, p. 909-918, 2019. DOI: 10.1016/j.dental.2019.03.004. Disponível em: http://repositorio.ipen.br/handle/123456789/29927. Acesso em: $DATA.

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Abstract: Objective. The aims of this study were: 1) to evaluate the effect of sintering temperatureon microstructure, density and flexural strength of a 3Y-TZP/TiO2composite containing12.5 wt% of TiO2compared to 3Y-TZP specimens (control); 2) to compare 3Y-TZP with theexperimental 3Y-TZP/TiO2composite, both sintered at 1400°C, with respect to the followingparameters: optical properties, characteristic strength, Weibull modulus, fatigue behavior,induction of osteoblasts proliferation and differentiation (mineralization nodules forma-tion).Methods. The 3Y-TZP and 3Y-TZP/TiO2powders were uniaxially pressed and sintered at 1200°C, 1300°C, 1400°C or 1500°C for one hour in a furnace. The microstructural analysis con-sisted of X-ray diffraction and scanning electron microscopy. The density was measured bythe Archimedes’ principle and the flexural strength was obtained by the biaxial flexure test.The optical properties were measured using a spectrophotometer operating in the visiblelight wavelength range. The step-stress accelerated life testing was performed by the pneu-matic mechanical cycler and the biological behavior achieved by using osteoblast-like cells(Osteo-1 cell line).Results. Tetragonal zirconia was identified in all groups and cubic zirconia was identified onlyat 3Y-TZP group. The addition of TiO2decreased the values of density and flexural strength ofthe composite 3Y-TZP/TiO2in relation to 3Y-TZP regardless of the sintering temperature. Thecolor difference between the two materials was not significant regarding L*a*b* parameters.The composite showed higher probability of failure, and induced higher proliferation anddifferentiation than control. Significance. The composite developed have good aesthetic and biologics properties. However, its microstructure and mechanical properties need to be improved for future dental implant applications.

Palavras-Chave: nanotubes; titanium oxides; dentistry; implants; yttrium oxides; zirconium oxides; sintering; behavior; biological effects; optical properties; mechanical properties; composite materials; mineralization

MIRANDA, RANULFO B. de P.; LEITE, TAYNA P.; PEDRONI, ANA C.F.; MARQUES, MARCIA M.; LIMA, NELSON B. de; MARCHI, JULIANA; CESAR, PAULO F. Effect of titania addition and sintering temperature on the microstructure, optical, mechanical and biological properties of the Y-TZP/TiO2 composite. Dental Materials, v. 36, n. 11, p. 1418-1429, 2020. DOI: 10.1016/j.dental.2020.08.014. Disponível em: http://200.136.52.105/handle/123456789/31605. Acesso em: $DATA.

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Abstract: Objective. To evaluate the effect of aging on the microstructural, mechanical, and optical properties of an experimental zirconia-toughened alumina composite with 80%Al2O3 and 20%ZrO2 (ZTA Zpex) compared to a translucent zirconia (Zpex) and Alumina. Methods. Disc-shaped specimens were obtained by uniaxial and isostatic pressing the synthesized powders (n = 70/material). After sintering and polishing, half of the specimens underwent aging (20 h, 134 °C, 2.2 bar). Crystalline content and microstructure were evaluated using X-ray diffraction and scanning electron microscopy, respectively. Specimens underwent biaxial flexural strength testing to determine the characteristic stress, Weibull modulus, and reliability. Translucency parameter (TP) and Contrast ratio (CR) were calculated to characterize optical properties. Results. ZTA Zpex demonstrated a compact surface with a uniform dispersion of zirconia particles within the alumina matrix, and typical alumina and zirconia crystalline content. ZTA Zpex and alumina exhibited higher CR and lower TP than Zpex. ZTA Zpex and Zpex showed significantly higher characteristic stress relative to alumina. While aging did not affect optical and mechanical properties of ZTA Zpex and alumina, Zpex demonstrated a significant increase in translucency, as well as a in characteristic stress. Alumina reliability was significantly lower than others at 300 MPa, ZTA Zpex and Zpex reliability decreased at 800 MPa, except for aged Zpex. Significance. While aging did not affect the mechanical nor the optical properties of ZTA Zpex and alumina, it did alter both properties of Zpex. The results encourage further investigations to engineer ZTA as a framework material for long span fixed dental prostheses specially where darkened substrates, such as titanium implant abutments or endodontically treated teeth, demand masking.

Palavras-Chave: microstructure; zirconium oxides; aluminium oxides; mechanical properties; optical properties; polycrystals; sintering

LOPES, A.C.O.; COELHO, P.G.; WITEK, L.; BENALCAZAR JALKH, E.B.; GENOVA, L.A.; MONTEIRO, K.N.; CESAR, P.F.; LISBOA-FILHO, P.N.; BERGAMO, E.T.G.; RAMALHO, I.S.; CAMPOS, T.M.B.; BONFANTE, E.A. Microstructural, mechanical, and optical characterization of an experimental aging-resistant zirconia-toughened alumina (ZTA) composite. Dental Materials, v. 36, n. 12, p. e365-e374, 2020. DOI: 10.1016/j.dental.2020.08.010. Disponível em: http://repositorio.ipen.br/handle/123456789/31790. Acesso em: $DATA.

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Abstract: Objective. To quantify the volumetric polymerization shrinkage (VPS) of different conventional and bulk fill resin composites, through micro-computed tomography (μCT), and qualitative comparison of gap formation through optical coherence tomography (OCT). Methods. Box-shaped class I cavities were prepared in 30 third-molars and divided into 5 groups (n = 6): G1- Filtek Z100 (Z100); G2- Tetric Evoceram Bulk Fill (TEC); G3- Tetric EvoFlow Bulk fill (TEF); G4- Filtek Bulk fill (FBU); and G5- Filtek Bulk fill Flowable (FBF). All groups were treated with Adper Single Bond Plus adhesive and light cured (Bluephase 20i). Each tooth was scanned three times using a μCT apparatus: after cavity preparation (empty scan); after cavity filling (uncured scan) and after light curing of the restorations (cured scan). The μCT images were imported into a three-dimensional rendering software, and volumetric polymerization shrinkage percentage was calculated (%) for each sample. In the same images, interfacial gaps in the pulpal floor were qualitatively evaluated. After μCT evaluation, the pulpal floor from each tooth was polished until a thin tooth structure was obtained and OCT images were obtained by scanning the pulpal portion. Gap formation was observed and qualitatively compared to the μCT images.

Palavras-Chave: polymerization; shrinkage; volumetric analysis; computerized tomography; optical systems; optical modes; coherence length; resins; composite materials; biological recovery

SAMPAIO, CAMILA S.; ARIAS, JESSICA F.; ATRIA, PABLO J.; CACERES, EDUARDO; DIAZ, CAROLINA P.; FREITAS, ANDERSON Z.; HIRATA, RONALDO. Volumetric polymerization shrinkage and its comparison to internal adaptation in bulk fill and conventional composites: A μCT and OCT in vitroanalysis. Dental Materials, v. 35, n. 11, p. 1568-1575, 2019. DOI: 10.1016/j.dental.2019.07.025. Disponível em: http://repositorio.ipen.br/handle/123456789/30853. Acesso em: $DATA.

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