1,721,130 research outputs found
Travel beyond Clinical Uses of Fiber Reinforced Composites (FRCs) in Dentistry: A Review of Past Employments, Present Applications, and Future Perspectives
No full textThe reinforcementof resins with shortor long fibershasmultiple applications invariousengineering andbiomedical fields.The useoffiberreinforcedcomposites(FRCs)indentistryhasbeendescribedintheliteraturefrommorethan40years.Invitrostudies evaluatedmechanicalpropertiessuchasflexuralstrength,fatigueresistance,fracturestrength,layerthickness,bacterialadhesion, bondingcharacteristicswithlongfibers,wovenfibers,andFRC posts.Also,multiple clinicalapplicationssuchasreplacementof missing teethby resin-bonded adhesive fixed dental prostheses of various kinds, reinforcementelementsof denturesor pontics, anddirectconstructionofpostsandcoreshavebeeninvestigated.Inorthodontics,FRCshavebeenusedalsoforactiveandpassive orthodontic applications, such as anchorage units, en-masse movement units, and postorthodontic tooth retention. FRCs have been extensively testedin the literature,but todaythe advances in newtechnologies involving the introductionof nanofillers or newfibersalongwithunderstandingthedesignprinciplesofFRCdevicesopennewfieldsofresearchforthesematerialsbothin vitroandinvivo.ThepresentreviewdescribespastandpresentapplicationsofFRCsandintroducessomefutureperspectiveson theuseofthesematerials
Force levels of fiber-reinforced composites and orthodontic stainless steel wires: a 3-point bending test.
Full text linkThe purpose of this study was to evaluate the force levels of 2 sizes (diameters, 0.6 and 1.2 mm) of fiber-reinforced composites (FRCs) (Ever Stick; Stick Teck Ltd, Turku, Finland) compared with orthodontic stainless steel wires (sections, 0.016, 0.018, 0.017 x 0.025, and 0.019 x 0.026 in) under the same testing conditions. The samples were divided into 12 groups, each consisting of 10 specimens. Each sample was evaluated with a 3-point bending test on a universal testing machine. The FRC groups were light-cured by hand with a halogen curing unit (Optilux 501; SDS Kerr, Danbury, Conn) for 40 seconds. Groups 1 through 6 were tested at 1-mm deflection, and groups 7 through 12 at 2-mm deflection. The results of ANOVA indicated significant differences among the various groups (P = .000). The post-hoc test showed that the 2-mm deflection groups had significantly higher load values than the 1-mm deflection groups (P = .000). The highest force levels were recorded with the 1.2-mm FRCs, followed by the 0.019 x 0.026-in stainless steel wires. No significant differences were found between the 0.6-mm FRCs and the 0.017 x 0.025-in wires. The lowest load values were reported with the 0.016-in stainless steel wires. The 1.2-mm FRCs showed higher load values than the other stainless steel wires and the FRCs, whereas no significant difference was found between the 0.6-mm FRCs and the 0.017 x 0.025-in stainless steel wires. Thus, FRCs can be considered a viable esthetic alternative to full-size stainless steel wires to rigidly join dental segments to form anchorage units or units for active tooth movement
Flexural strengths of fiber-reinforced composites polymerized with conventional light-curing and additional postcuring
Full text linkINTRODUCTION: The purpose of this study was to evaluate the effect of hand light-curing (Optilux 501; SDS Kerr, Danbury, Conn) and secondary oven polymerization (Liculite; Dentsply, Dreieich, Germany) on the mechanical properties of 2 sizes (diameters, 0.6 and 1.2 mm) of fiber-reinforced composites
(FRCs) (Ever Stick; Stick Tech, Turku, Finland). METHODS: The FRC samples were divided into 8 groups. Each group consisted of 10 specimens. Each FRC sample was evaluated with a 3-point bending test with a universal testing machine. Groups 1,
3, 5, and 7 were hand light-cured with a halogen curing unit for 40 seconds. Groups 2, 4, 6, and 8 were light-cured with the same curing unit for 40 seconds, followed by polymerization for 15 minutes in a light-curing oven. Groups 1 through 4 were tested at 1-mm deflection, and groups 5 through 8 at 2-mmdeflection. RESULTS: The results of ANOVA indicated significant differences among the various groups (P = .000). The post-hoc test showed that the 2-mm deflection groups had significantly higher flexural strengths than the 1-mm deflection groups (P = .000). Moreover, the 1.2-mm FRCs showed significantly higher flexural
strength than the 0.6-mm FRCs (P = .000). No significant differences (P >.05) were found between the hand light-cured and the oven-polymerized groups.
CONCLUSIONS: This investigation demonstrated that oven postcuring does not increase the flexural strength values of 0.6- and 1.2-mm FRCs compared with conventional hand light-curing. Thus, hand light-curing of FRCs is recommended
directly in the mouth for orthodontic purposes
Effects of nanofillers on mechanical properties of fiber-reinforced composites polymerized with light-curing and additional postcuring
No full textThe purpose of the present study was to evaluate the effect of nanofillers on the mechanical properties of 2 sizes (diameters 0.6 and 0.9 mm) of conventional and nanofilled fiber-reinforced composites (FRCs) polymerized with conventional light-curing and additional postcuring.
METHODS:
The FRCs samples were divided into 8 groups (10 specimens each). Conventional FRCs with glass fibers preimpregnated with polymethyl methacrylate (groups 1, 2, 3 and 4) and FRCs with impregnating solution containing 32% nanofilled resin (groups 5, 6, 7 and 8) were tested in 2 different sections (0.6 and 0.9 mm in diameter). Two different polymerizations were analyzed: hand light-curing for 40 seconds with an halogen light, and additional postcuring for 25 minutes in a light-curing oven. Each sample was evaluated with a 3-point bending test on a universal testing machine, after 48 hours of dry storage. All of the data were statistically analyzed.
RESULTS:
After oven postcuring, nanofilled FRCs exhibited significantly higher load values than conventional FRCs. No significant differences were found when comparing conventional and nanofilled FRCs after hand light-curing. Moreover, 0.6-mm FRCs showed significantly lower load values than 0.9-mm FRCs, both for conventional and nanofilled FRCs.
CONCLUSIONS:
Nanofilled FRCs showed higher load values after additional oven postcuring
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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