1,720,985 research outputs found
Push-out bond strength of circular and oval-shaped fiber posts
No full textThis study aimed at evaluating the post-root dentin push-out bond strength of circular and oval posts luted in oval-shaped canals with two different resin cements. Twenty extracted premolars with oval-shaped canals were selected, endodontically instrumented and obturated. The teeth were divided into two groups according to the drill used for post-space preparation and to the post shape (Ellipson oval tip + post and MTwoPF + DT Light-Post). Each group was then subdivided into two subgroups according to the cement (Gradia Core and Corecem Automix). The post-dentin bond strength was evaluated with the thin-slice push-out test. The bonded surface area was calculated for each post shape with an appropriate geometric formula in order to express the retentive strength in megapascal. Push-out strength data were analyzed with the Kruskal-Wallis ANOVA. The results showed that neither the drill-post system nor the cement significantly affected the push-out strength. The means (SD) of the push-out bond strengths in the experimental subgroups were the following: 11. 79 MPa (4. 77) for Gradia Core/Ellipson tip and post, 13. 36 MPa (5. 16) for Gradia Core/MtwoPF and DT Light-Post, 11. 18 MPa (2. 58) for Corecem Automix/Ellipson tip and post, and 10. 91 MPa (3. 89) for Corecem Automix/MtwoPF and DT Light-Post. In conclusion, circular and oval posts achieved similar retentive strengths in oval canals. © 2010 Springer-Verlag
Effetto del pre-riscaldamento sull’adesione di cementi resinosi auto mordenzanti e autoadesivi
No full textPush-out Bond Strength of Fiber Posts Luted with Unfilled Resin Cement
No full textPurpose: The study evaluates the behavior of different adhesive systems and resin cements in fiber post placement, with the intent to clarify the possible role of unfilled resin as a luting material for fiber posts. Materials and Methods: Two luting agents (Dual-Link and Unfilled Resin) for cementing fiber posts into root canals were applied either with All-Bond 2 or One-Step Plus, or without an adhesive system, and challenged with the push-out test. Slices of roots restored with posts were loaded until post segment extrusion in the apical-coronal direction. Failure modes were analyzed under SEM. Results: Push-out strength was significantly influenced by the luting agent (p < 0.05), but not by the bonding strategy (p > 0.05). The best results were obtained in combination with Unfilled Resin with One-Step Plus. Dual-Link groups failed mainly cohesively within the cement, while Unfilled Resin demonstrated more adhesive fracture at the post interface. Conclusion: The results of this study support the hypothesis that adhesive unfilled resin application is essential for achieving high bond strength to radicular dentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Effect of Ethanol Application on Post Luting to Intraradicular Dentin
No full textTo examine the effect of the application of an ethanol rinse before luting fibre posts to intraradicular dentine with etch-and-rinse adhesive systems by means of push-out bond strength evaluation and scanning electron microscopic (SEM) analysis. Fibre posts were luted to single-canal premolars using Dual Link as a luting agent in combination with a three-step (All Bond 2) or a two-step (One Step Plus) etch-and-rinse adhesive system, which were applied as per manufacturers' instructions (control) or with the additional rinse of ethanol on acid-etched dentine prior to the bonding procedures (experimental). Bonded specimens were sectioned into 1-mm-thick slabs and subjected to push-out bond strength testing. In addition, specimens from each group were processed for SEM analysis. Data were analysed by Kruskal-Wallis followed by Dunn's post hoc test at P = 0.05. Push-out bond strength of All Bond 2 was significantly increased if the adhesive was applied on ethanol-saturated dentine (P 0.05) was detected amongst experimental and control groups for One Step Plus. Irrespective of the adhesive, the SEM analysis revealed good impregnation patterns when both bonding techniques were employed. The use of the additional ethanol rinse on acid-etched dentine revealed higher bond strength of All Bond 2 when compared with the control application procedure, used in combination with a resin-based cement to lute fibre posts into the dowel space. However, no bond strength improvements were detected using One Step Plus. Further investigations are needed to develop a clinically applicable ethanol/bonding/luting technique
Effect of pre-cure temperature on the bonding potential of self-etch and self-adhesive resin cements
No full textObjectives. To assess whether the pre-cure temperature of resin cements significantly influenced the bonding potential to dentin.
Methods. Forty extracted molars were randomly divided into 8 groups (n = 5): Groups (1-4) RelyX Unicem (RU, 3 M ESPE) and Groups (S-8) Panavia F 2.0 (PF, Kuraray Co.), at pre-cure temperatures of 4, 24, 37, and 60 degrees C, respectively. Cements were used in dual-cure mode for luting composite overlays (Paradigm MZ100, 3 M ESPE) to dentin. Microtensile bond strength testing and scanning electron microscope (SEM) observations of cement-dentin interfaces were performed.
Results. Group 4 had to be eliminated as RU at 60 degrees C under-went such an accelerated curing that was already set at the time of dispensing. The bond strengths (MPa) measured at refrigerator, room, and intraoral temperature were, respectively: RU 5.4 +/- 1.7, 11.4 +/- 6.1, 10.6 +/- 4.2; PF 7.4 +/- 3.7, 13.9 +/- 6.2, 12 +/- 5.2. The statistical analysis revealed that both luting agents developed a significantly weaker adhesion when used at refrigerator temperature (p 0.05). Pre-heating of PF to 60 degrees C resulted in a significant increase in bond strength (20.7 +/- 9.4 MPa; p < 0.05). SEM observations disclosed an enhanced potential of PF to form a hybrid layer as the temperature increased over 4 degrees C. RU exhibited a less porous and more homogeneous layer at intraoral than at refrigerated temperature.
Significance. It is advisable to let refrigerator-stored resin cements warm up to at least room temperature prior to clinical use. Pre-heating to 60 degrees C enhances the bonding potential of PF. (c) 2007 Academy of Dental materials. Published by Elsevier Ltd. All rights reserved
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