ABSTRACT
Objective: was to evaluate fracture resistance of zirconia monolithic restorations after aging procedures. Material and methods: Monolithic translucent zirconia 3-unit FPDs were fabricated using Cerec inLab CAD/CAM system on 2 stainless steel dies with a uniform 120 degrees circumferential deep chamfer finish line of 1 mm width. FPDs were divided into 2 groups, first group (Group A) was subjected to aging procedures in an autoclave at hydrothermal conditions 134 oC /2 bars for 5 hours. Second group (Group B) was not subjected to any aging procedures (control group). All specimens of each group were loaded compressively in a universal testing machine at cross head speed 0.5 mm/min until fracture occurred. The percentage of monoclinic (m) phase was detected by XRD device. Scanning electron microscope (SEM) was used to examine the fractured surfaces for Aged TZI (Group A) and Non-aged TZI (Group B). Student's t-test was used to compare between fracture resistances of both groups. The significance level was set at P ≤ 0.05. Results: The fracture resistance mean (SD) values of non-aged TZI (Group B) was 2406.9 ± 306.8 N which showed statistically significantly higher than that of aged group (Group A) which was 1964.5 ± 234.5 N. The percentage of monoclinic (m) phase detected by XRD device software in non-aged TZI (Group B) was nearly 0 weight % and in aged TZI (Group A) was about 42 weight %. Conclusions:Accelerated artificial aging decreases the fracture resistance of monolithic TZI FPDs. (AU)
Objetivo: Foi avaliar a resistencia à fratura de restaurações de zircônia monolítica após procedimentos de envelhecimento.Material e Métodos: 3 unidades de FPDs de zircônia monolítica translucida foram fabricadas utilizando o sistema Cerec inLab CAD/CAM com 2 matrizes de aço inoxidável com uma linha de acabamento de chanfro profundo circunferencial de 120 graus de largura de 1 mm. As FPDs foram divididos em dois grupos, primeiro grupo (Grupo A) foi submetido a procedimentos de envelhecimento em autoclave em condições hidrotérmicas de 134 °C /2 bars por 5 horas. O segundo grupo (Grupo B) não foi submetido a nenhum processo de envelhecimento (grupo controle). Todos os espécimes de cada grupo foram carregados compressivamente em uma maquina de teste universal na velocidade de 0.5 mm/min até a fratura ocorrer. A porcentagem da fase monoclínica (m) foi detectada pelo dispositivo XRD. O microscópio eletrônico de varredura (MEV) foi utilizado para examinar as superfícies fraturadas para TZI envelhecido (Grupo A) e TZI não envelhecido (Grupo B). O teste t de estudantes foi usado para comparar as resistências à fraturas de ambos os grupos. O nível de significância foi estabelecido em P ≤ 0.05. Resultados: Os valores médios de resistência à fratura (SD) do TZI não envelhecido (Grupo B) foi 2406.9±306.8 N, o qual se mostrou estatisticamente significativamente maior do que o grupo envelhecido (Grupo A), que foi 1964.5±234.5 N. A porcentagem da fase monoclínica (m) detectada pelo software do dispositivo XRD em TZI não envelhecido (Grupo B) foi próximo de 0% em peso e em TZI envelhecido (Grupo A) foi cerca de 42% em peso. Conclusão: O envelhecimento artificial acelerado diminui a resistência à fratura de FPDs TZI monolítico (AU)
Subject(s)
Microscopy, Electron, Scanning , Flexural StrengthABSTRACT
PURPOSE: The purpose of this study was to evaluate the microleakage of various types of resin-bonded fixed partial dentures (RBFPDs) after artificial aging. MATERIALS AND METHODS: Forty models with missing first molar were fabricated using artificial resin teeth and were divided into four groups: Group A, conventional RBFPDs design; Group B, modified RBFPDs design; Group C, assembled 3-piece RBFPDs design; and Group D, assembled 3-piece RBFPDs with different occlusal rest positions. Half of the specimens underwent chewing simulation process (240,000 cycles, 50 N load, 1.7 Hz) and thermocycling (temperatures 5℃~55℃, dwelling time 30 seconds) and the remaining 20 specimens didn't receive any treatment. All the specimens were immersed in 2% methylene blue solution for 24 hours to evaluate microleakage, and were sectioned at the middle part of abutment teeth. To evaluate the microleaskage, a dye penetration was calculated. RESULT: With artificial aging, cyclic loading and thermocycling, a 3-piece RBPFD and a 2-piece RBPFD using original tooth undercuts have significantly lower microleakge (P<0.05) compared to the conventional design of RBPFD and modified RBPFD. CONCLUSION: Within the limit of this experiment, the assembled RBFPDs exhibited a smaller microleakage than the conventional RBFPDs, implying that the assembled RBFPDs can be more effective for reducing the dislodgement of the RBFPDs.
Subject(s)
Aging , Denture, Partial, Fixed , Denture, Partial, Fixed, Resin-Bonded , In Vitro Techniques , Mastication , Methylene Blue , Molar , ToothABSTRACT
Effects of nine different moisture contents on vigor of Cyathula officinalis seeds and its anti-aging mechanism were studied by artificial accelerated aging through high temperature and wet. The research results showedthat seed vigor were generally decreased after artificial aging; in general, seed vigor and its anti-aging ability are relatively stronger within the scope of 6.55%-4.78% moisture content, the increase range of seed conductivity, peroxidase activity, malondialdehyde content,and reduce amplitude of activityof dehydrogenase , superoxide dismutaseare alllower as well. And when the moisture content reduced to 5.77%, all of the germination tests index of the non-aged seeds are the highest, and the activity of peroxidase the lowest,conductivity of leaching solution relatively low, activity of dehydrogenase and superoxide dismutase the highest,and catalase activityrelatively high.Therefore, in the low temperature germplasm preservation of C. officinalis seeds, the seed moisture content should be controlled close to the range of (5.70±1)% to keep higher vigor and anti-aging ability.
ABSTRACT
PURPOSE: This study evaluated the fracture load of customized zirconia abutments with titanium insert according to preparation depths, with or without 5-year artificial aging. MATERIALS AND METHODS: Thirty-six identical lithium disilicate crowns (IPS e.max press) were fabricated to replace a maxillary right central incisor and cemented to the customized zirconia abutment with titanium insert on a 4.5x10 mm titanium fixture. Abutments were fabricated with 3 preparation depths (0.5 mm, 0.7 mm, and 0.9 mm). Half of the samples were then processed using thermocycling (temperature: 5-55degrees C, dwelling time: 120s) and chewing simulation (1,200,000 cycles, 49 N load). All specimens were classified into 6 groups depending on the preparation depth and artificial aging (non-artificial aging groups: N5, N7, N9; artificial aging groups: A5, A7, A9). Static load was applied at 135 degrees to the implant axis in a universal testing machine. Statistical analyses of the results were performed using 1-way ANOVA, 2-way ANOVA, independent t-test and multiple linear regression. RESULTS: The fracture loads were 539.28 +/- 63.11 N (N5), 406.56 +/- 28.94 N (N7), 366.66 +/- 30.19 N (N9), 392.61 +/- 50.57 N (A5), 317.94 +/- 30.05 N (A7), and 292.74 +/- 37.15 N (A9). The fracture load of group N5 was significantly higher than those of group N7 and N9 (P<.017). Consequently, the fracture load of group A5 was also significantly higher than those of group A7 and A9 (P<.05). After artificial aging, the fracture load was significantly decreased in all groups with various preparation depths (P<.05). CONCLUSION: The fracture load of a single anterior implant restored with lithium disilicate crown on zirconia abutment with titanium insert differed depending on the preparation depths. After 5-year artificial aging, the fracture loads of all preparation groups decreased significantly.
Subject(s)
Aging , Axis, Cervical Vertebra , Crowns , Dental Implants , Incisor , Linear Models , Lithium , Mastication , TitaniumABSTRACT
Objective: To investigate the deterioration mechanism of Bupleurum chinense seeds from Qingchuan county, thus to study the seeds harvesting and storage characteristics, and to reveal the deterioration mechanism. Methods: Artificial aging method is used to study the seeds deterioration and to observe the changes of nutrient substance, anti-oxidase activities, and conductivity of seeds. Results: While the seeds deteriorated, their activities of anti-oxidase (POD, SOD, and CAT) decreased, and the content of soluble sugar and soluble protein reduced also as the aging time prolonged. After 3 d treatment, SOD, POD, and CAT activities decreased to a low level. Moreover, the conductivity of seeds leachate decreased. The germination ability of B. chinense seeds lost after 1 d aging treatment. Conclusion: The seeds deterioration mechanisms include the heavy oxidative injury, over consumption of nutrients, and membrane damage. The seeds long-time storage is inappropriate and the seeds storage should avoid from high temperature and humid environment.