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Anna-Maria Lutz Rüdiger Hampe Malgorzata Roos Nina Lümkemann Marlis Eichberger Bogna Stawarczyk 《The Journal of prosthetic dentistry》2019,121(1):166-172
Statement of problem
Polymeric material for 3-dimensional printing can be used to fabricate occlusal devices. However, information about fracture resistance and wear is scarce.Purpose
The purpose of this in vitro study was to investigate the fracture resistance and 2-body wear of 3-dimensional–printed (3DP) (FotoDent splint; Dreve Dentamid GmbH), milled polymethylmethacrylate (CAM) (Temp Basic; Transpa 95H16, Zirkonzahn GmbH), and conventionally fabricated polymethylmethacrylate (CAST) (Castdon; Dreve Dentamid GmbH) occlusal devices.Material and Methods
A total of 96 occlusal devices were prepared according to the 3 different manufacturing techniques 3DP, CAM, and CAST (n=32). For each manufacturing technique, specimens were further divided into initial fracture resistance tests (n=16) and artificial aging in the mastication simulator (50 N, 37°C) with 2-body wear followed by fracture resistance tests (n=16). The fracture resistance was determined using a universal testing machine (1 mm/min). The wear was measured after 20?000 and 120?000 mastication cycles with the replica technique, mapped with a laser scanner, and quantified in R software. Data were analyzed using a 2-way ANOVA followed by a 1-way ANOVA with Scheffé or Games-Howell post hoc tests, repeated measures ANOVA with corrected Greenhouse-Geisser P values, and the Levene, Mann-Whitney, and paired t tests (α=.05).Results
CAM presented higher initial fracture resistance than 3DP or CAST (P<.001). After mastication simulation, CAM followed by 3DP showed higher fracture resistance than CAST (P<.001). Mastication simulation decreased the fracture resistance for CAM and CAST (P<.001) but not for 3DP (P=.78). Three-dimensional–printed occlusal devices showed the highest material volume loss, followed by CAM and the lowest in CAST (P<.001).Conclusions
Three-dimensional–printed occlusal devices showed lower wear resistance and lower fracture resistance than those milled or conventionally fabricated. Therefore, only short-term application in the mouth is recommended. Further developments of occlusal device material for 3-dimensional printing are necessary. 相似文献2.
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The human brain is tightly coupled to the world through its sensory‐motor systems—but it also spends a lot of its metabolism talking to itself. One important function of this intrinsic activity is the establishment and updating of event models—representations of the current situation that can predictively guide perception, learning, and action control. Here, we propose that event models largely depend on the default network (DN) midline core that includes the posterior cingulate and anterior medial prefrontal cortex. An increasing body of data indeed suggests that this subnetwork can facilitate stimuli processing during both naturalistic event comprehension and cognitive tasks in which mental representations of prior situations, trials, and task rules can predictively guide attention and performance. This midline core involvement in supporting predictions through event models can make sense of an otherwise complex and conflicting pattern of results regarding the possible cognitive functions subserved by the DN. 相似文献
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Bogna Stawarczyk Mutlu ÖzcanMalgorzata Roos Albert TrottmannIrena Sailer Christoph H.F. Hämmerle 《Dental materials》2011,27(10):1045-1053
Objectives
The aim of this study was to test whether the load bearing capacity of anterior zirconia crowns veneered with overpressed or layered, is similar and to evaluate the failure types.Methods
Standardized zirconia frameworks were fabricated and randomly divided into 8 groups (N = 120, n = 15 per test group). Four groups were veneered with one of the layered veneering porcelains: Zirox, GC Initial ZR, VITA VM9 or IPS e.max Ceram and the other four groups were veneered with overpressed veneering porcelains: PressX Zr, GC Initial LF, VITA PM9 or IPS e.max ZirPress. The crowns were cemented on their corresponding CoCr abutment and the specimens were loaded at an angle of 45° in a Universal Testing Machine to determine the fracture load. Data were analyzed using one-way and two-way ANOVA, followed by a post hoc Scheffé test, t-test and Weibull analysis (alpha = 0.05).Results
Within three manufacturers of veneering porcelain, fracture load values were not statistically significant between overpressed and layered porcelain systems. Within one manufacturer of veneering porcelain, the overpressed crowns (IPS e.max ZirPress: 1519 ± 334 N) demonstrated significantly higher (p < 0.05) fracture load than that of the layered one (IPS e.max Ceram: 894 ± 160 N). Except with IPS e.max ZirPress, where exclusively only chipping of the veneering porcelain was observed, all other porcelain systems showed predominantly framework fractures together with fracture of the veneering porcelain.Conclusion
Overpressed veneering porcelains for zirconia frameworks exhibited similar or better fracture load compared with layered ones. 相似文献5.
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David Stawarczyk Christopher N. Wahlheim Joset A. Etzel Abraham Z. Snyder Jeffrey M. Zacks 《Proceedings of the National Academy of Sciences of the United States of America》2020,117(47):29346
When encountering unexpected event changes, memories of relevant past experiences must be updated to form new representations. Current models of memory updating propose that people must first generate memory-based predictions to detect and register that features of the environment have changed, then encode the new event features and integrate them with relevant memories of past experiences to form configural memory representations. Each of these steps may be impaired in older adults. Using functional MRI, we investigated these mechanisms in healthy young and older adults. In the scanner, participants first watched a movie depicting everyday activities in a day of an actor’s life. They next watched a second nearly identical movie in which some scenes ended differently. Crucially, before watching the last part of each activity, the second movie stopped, and participants were asked to mentally replay how the activity previously ended. Three days later, participants were asked to recall the activities. Neural activity pattern reinstatement in medial temporal lobe (MTL) during the replay phase of the second movie was associated with detecting changes and with better memory for the original activity features. Reinstatements in posterior medial cortex (PMC) additionally predicted better memory for changed features. Compared to young adults, older adults showed a reduced ability to detect and remember changes and weaker associations between reinstatement and memory performance. These findings suggest that PMC and MTL contribute to change processing by reinstating previous event features, and that older adults are less able to use reinstatement to update memory for changed features. 相似文献
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Mayinger Felicitas Buser Ramona Laier Maximilian Schönhoff Lisa Marie Kelch Matthias Hampe Rüdiger Stawarczyk Bogna 《Clinical oral investigations》2022,26(11):6617-6628
Clinical Oral Investigations - The aim of this study is to investigate the influence of the material and corresponding sintering protocol, layer thickness, and aging on the two-body wear (2BW) and... 相似文献
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