1,720,962 research outputs found
In vitro evaluation of bonding effectiveness to dentin of all-in-one adhesives
No full textObjectives: The study was aimed at assessing the bonding potential of all-in-one adhesives to dentin.
Methods: The microtensile bond strength of the all-in-one adhesives Bond Force (Tokuyama), AdheSE One (Ivoclar-Vivadent), and Xeno V (Dentsply) was measured in comparison with the etch-and-rinse system XP Bond (Dentsply). The ultrastructural characteristics of dentin-adhesive interface were observed under scanning electron microscope (SEM). Twenty human extracted third molars had their mid-coronal dentin exposed and ground with wet 600-grit SiC paper in order to create a standardized smear layer. Bonding procedures were performed according to the manufacturers' instructions and microtensile beams were obtained with the "non-trimming" technique. The bond strengths in MPa were statistically analyzed including pre-test failures as "zero" values (Kolmogorov-Smirnov test, Levene's test, One-Way ANOVA, Tukey's test p < 0.05).
Results. The following bond strengths were recorded in MPa (mean standard deviation): AdheSE One 31.7 +/- 21.3; Xeno V 42.8 +/- 26.4; Bond Force 43.3 +/- 22.1; XP Bond 51.9 +/- 18.6. The statistical analysis demonstrated that the bond strengths achieved by Bond Force and Xeno V were similar to that of the etch-and-rinse adhesive, whereas the bond strength of AdheSE One was significantly lower. A distinct hybrid layer with resin tags was seen only in XP Bond specimens. All-in-one adhesives demonstrated a rather superficial interaction with the dentin substrate.
Conclusions: Although the strongest bond to dentin was established by the etch-and-rinse system, however the all-in-one adhesives containing organic solvents reached bond strength levels that were comparable from a statistical point of view. (C) 2009 Elsevier Ltd. All rights reserved
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
Microtensile vs microshear bond strength of all-in-one adhesives to unground enamel
No full textPURPOSE:
to determine the bond strength to unground enamel of all-in-one adhesives in comparison with an etch-andrinse system and to compare the reliability of microtensile and microshear methods in providing such measurements.
MATERIALS AND METHODS:
the bonding procedure was performed on enamel of 64 extracted molars. The tested all-inone adhesives were: Bond Force (Tokuyama), AdheSE One (Ivoclar-Vivadent), and Xeno V (Dentsply). Prime&Bond NT (Dentsply) served as control. Microtensile specimens were obtained from 4 teeth per group. Twelve teeth per group were used for microshear testing. Microtensile specimens that failed prior to testing were included in statistical calculations; they were assigned the lowest value measured in the respective group. Failure modes were observed under light microscope and classified (cohesive within substrates, adhesive, mixed). Statistically significant differences in bond strength were assessed among the adhesives within each testing method and between microshear and microtensile data for each adhesive. Failure mode distributions were compared using the chi-square test.
RESULTS:
all-in-one adhesives had similar microshear and microtensile bond strengths. In both testing methods, the etch-and-rinse system achieved the strongest bond. For all adhesives, significantly higher bond strengths were measured with the microshear test. In microtensile testing, specimens bonded with the etch-and-rinse adhesive exhibited a significantly different distribution of failure modes. The coefficients of variation were extremely high for microtensile bond strength data, particularly of all-in-one adhesives.
CONCLUSION:
the adhesive potential to intact enamel of recently introduced all-in-one adhesives was inferior to that of an etch-and-rinse system. When testing bond strength to enamel of all-in-one adhesives, microshear testing may be a more accurate method than microtensile
Shear bond strength to enamel and flexural strength of different fiber-reinforced composites
No full textPurpose: To assess the shear bond strength to unground human enamel (ESBS) and flexural strength (FS) of different reinforcing fibers used in combination with a flowable composite resin. Materials and Methods: For ESBS testing, 90 human molars were selected and randomly divided into 9 groups (n = 10) according to the reinforcing fiber to be tested: 1. RTD Quartz Splint additionally impregnated at chairside with Quartz Splint Resin (RTD); 2. RTD Quartz Splint without additional impregnation; 3. Ribbond-THM (Ribbond) impregnated with OptiBond FL Adhesive; 4: Ribbond Triaxial (Ribbond) impregnated with OptiBond FL Adhesive; 5. Connect (Kerr) impregnated with OptiBond FL Adhesive; 6. Construct (Kerr) impregnated with Opti-Bond FL Adhesive; 7. everStick PERIO (Stick Tech); 8. everStick C&B (Stick Tech); 9. nonreinforced composite Premise flowable (Kerr). Cylinders of flowable composite reinforced with the fibers were bonded to the intact buccal surface of the teeth. After 24 h of storage, shear loading was performed until failure occurred. FS was assessed performing three-point bending test according to ISO Standard 4049/2000. ESBS and FS data were analyzed using one-way ANOVA, followed by Tukey’s HSD test for post-hoc comparisons (p < 0.05). Results: For each group, the ESBS and FS, respectively, in MPa were: 1. 17.07 ± 4.52 and 472.69 ± 30.49; 2. 14.98 ± 3.92 and 441.77 ± 61.43; 3. 18.59 ± 5.67 and 186.89 ± 43.89; 4. 16.74 ± 6.27 and 314.41 ± 148.52; 5. 14.38 ± 4.14 and 223.80 ± 77.35; 6. 16.00 ± 5.55 and 287.62 ± 85.91; 7. 16.42 ± 3.67 and 285.35 ± 39.68; 8. 23.24 ± 5.81 and 370.46 ± 29.26; 9. 12.58 ± 4.76 and 87.75 ± 22.87. For most fibers, no significant difference in ESBS was found compared to the control group, except for everStick C&B, which yielded higher ESBS. Nonreinforced composite exhibited the lowest FS, while all fibers positively affected the FS. Conclusions: Fiber reinforcement of flowable composite does not affect its ESBS. The flexural strength of FRCs is significantly influenced by fiber composition and pattern. © 2013 by Quintessence Publishing Co Inc
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
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