196,299 research outputs found
Root Injury During Interradicular Insertion is the most Common Complication Associated with Orthodontic Miniscrews
No full textArticle Title and Bibliographic Information: Complications reported with the use of orthodontic miniscrews: A systematic review. Giudice AL, Rustico L, Longo M, Oteri G, Papadopoulos MA, Nucera R. Korean J Orthod 2021 May 25;51(3):199–216. doi: 10.4041/kjod.2021.51.3.199. PMID: 33984227. Source of Funding: There is no information about funding. Type of Study/Design: Systematic review
The fractional integrated bi- parameter smooth transition autoregressive model
No full textThis paper introduces the fractionally integrated Bi-parameter smooth transition autoregressive model (FI-BSTAR model) as an extension of BSTAR model proposed by Siliverstovs (2005) and the fractionally integrated STAR model (FI-STAR model) proposed by van Dijk et al. (2002). Our FI-BSTAR model is able to simultaneously describe persistence and asymmetric smooth structural change in time series. An empirical application using monthly growth rates of the American producer price index is provided.Long Memory, Nonlinearity, Asymmetry, STAR models.
The overall seasonal integration tests under non-stationary alternatives
No full textFew authors have studied, either asymptotically or in finite samples, the size and power of seasonal unit root tests when the data generating process [DGP] is a non-stationary alternative aside from the seasonal random walk. In this respect, Ghysels, lee and Noh (1994) conducted a simulation study by considering the alternative of a non-seasonal random walk to analyze the size and power properties of some seasonal unit root tests. Analogously, Taylor (2005) completed this analysis by developing the limit theory of statistics of Dickey and Fuller Hasza [DHF] (1984) when the data are generated by a non-seasonal random walk. del Barrio Castro (2007) extended the set of non-stationary alternatives and established, for each one, the asymptotic theory of the statistics subsumed in the HEGY procedure. In this paper, I show that establishing the limit theory of F-type statistics for seasonal unit roots can be debatable in such alternatives. The problem lies in the nature of the regressors that these overall F-type tests specify.Fisher test, seasonal integration, non-stationary alternatives, Brownian motion, Monte Carlo Simulation.
Effects of fluorosed enamel on orthodontic bracket bonding: An in vitro study
No full textObjective: To investigate the effect of enamel deproteinization and air abrasion on shear bond strength (SBS), adhesive remnant index (ARI) scores, and surface topography when bonding orthodontic brackets to fluorosed enamel. Materials and methods: The sample included 90 fluorosed and 30 normal premolars divided into four groups: group I (fluorosed premolars subjected to air abrasion before acid etching), group II (fluorosed premolars subjected to deproteinization before acid etching), group III (fluorosed premolars; control for groups I and II), and group IV (normal premolars; control for group III). Bonding procedures included etching with 37% phosphoric acid, priming with TransbondTM XT primer (3M Unitek, Monrovia, CA, USA), and application of TransbondTM XT adhesive paste (composite; 3M Unitek, Monrovia, CA, USA). Air abrasion was done using 50 μm aluminum oxide particles under 0.28 MPa pressure for 5 s with the micro-etcher held at a distance of 10 mm. Deproteinization was done for 60 s with 5% sodium hypochlorite (NaOCl). Results: Fluorosed premolars subjected to deproteinization showed the lowest (median = 6.57 MPa) SBS among the four groups, followed by 8.14, 8.90, 8.14 MPa for groups I, III, and IV respectively. ARI scores were significantly different between the four groups (p = 0.006). Fluorosed enamel etched after air abrasion or deproteinization with NaOCl showed a predominance of type 4 etching pattern with some areas appearing unetched. Conclusions: Shear bond strength of all groups was within the 6–8 MPa acceptable range for orthodontic purposes. Fluorosed premolars subjected to deproteinization showed the lowest values. Further studies are recommended to scrutinize the deproteinization technique
Imaging software programs for reliable mathematical measurements in orthodontics
No full textAim: To evaluate the reliability of linear and angular measurements taken using different software programs in orthodontics. Materials and Methods: A sample of four software programs from different manufacturers, namely MicroDicom viewer, Photoshop® CS3, AutoCAD®, and Image-Pro®, were used for measuring the geometric features of four types of miniscrews from different manufacturers. Each miniscrew type presented a group: Group I, Tomas® (Dentaurum, Ispringen, Germany); Group II, HUBIT® (HUBIT, Gyeonggi-do, Korea); Group III, AbsoAnchor® (Dentos, Daegu, Korea); and Group IV, Creative (Creative, Zhejiang, China). Measurements of apical face angle, thread angle, lead angle, flank, pitch depth, and width were taken on 45 × magnification scanning electron microscope images of the shafts of the miniscrews. One assessor measured the seven geometric features for the four types of miniscrews using the four software programs twice in two sessions separated by a three week interval. Results: Pairwise comparisons, for each of the four miniscrew groups, showed that the only common result observed was the significant difference (p < 0.001) between measurements of flank taken by the four software programs. When measurements of the four types of miniscrews were pooled into one group, a high degree of intra-rater reliability (ICC range from 0.9 to 1.0) for all the seven geometric features was found with all the four software programs. The paired t-test showed insignificant difference (at p ≤ 0.05) between the first and second measurements, except for a few measurements including pitch width measured by Image-Pro® (p = 0.012), MicroDicom (p = 0.023), and Photoshop® (p = 0.001). Conclusions: Results did not give absolute superiority to one software program over the others and suggested an assessor effect. Assessor estimates could have been affected, among other factors, by the design of the miniscrews and the technical features of the software programs
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
Orthodontics: Bracket Materials, Adhesives Systems, and Their Bond Strength
No full textAdhesive interfaces influence greatly clinical success of modern dentistry. Durability of the interface can be determined by using several in vitro testing methods. Shear bond strength tests are widely used in dentistry and they are well suitable for testing orthodontic materials bonded to teeth. The first study that analyzed shear bond strength of orthodontic appliances appeared in international literature in the late 1970s [1]. Nowadays, more than one thousand reports have been conducted in order to analyze various factors influencing shear bond strength of orthodontic brackets. Precise interpretation of the shear bond strength test results should, however, take into account other types of stress which are occurring at the interface during testing.
Previous studies that evaluated bond strength analyzed different variables related to adhesive system (composite or resin-modified glass ionomer), bonding surface (enamel, ceramic, or metal), antibacterial agents (added to adhesive system), bracket material (steel, ceramic, or plastic), bracket type (conventional, self-ligating, or lingual), attachment base (with various mesh sizes and shapes), brace mesh or surface pretreatment (such as sandblasting) [2], bracket placement force, enamel conditioning (with etchants or lasers), enamel pretreatment (with protecting or bleaching agents), and enamel contaminants (such as blood or saliva). The effect of any of these factors may differ when rebonding orthodontic brackets [2–10]. Moreover, bonding studies have been applied to test not only orthodontic brackets but also other materials bonded to tooth structure during active or passive orthodontic treatment (such as customized CAD CAM bases, disinclusion buttons, and fiber reinforced composites bars and nets) [11].
During over 35 years of orthodontic bonding studies, a standardized technique has been reached, but many differences in methods among different studies still remain [12]. Due to increased ethical requirements, the human teeth used are usually wisdom teeth or first premolars (extracted for orthodontic reasons). Bovine teeth are collected in slaughterhouses in deciduous or permanent dentition. Tooth selection includes intact buccal enamel and no cracks due to extraction procedure. After extraction, teeth are stored in thymol, water, or artificial saliva, whereas formalin and alcohol are no more used in order to avoid adverse effects on bond strength measurement.
Brackets or jigs are bonded to teeth with an adhesive system and subsequently, or after artificial ageing specimens, are placed in a testing machine with the adhesion surface parallel to shearing force.
Predominantly, a shear force is applied with a steel tip with standardized crosshead speed until adhesive failure. Debonding force is recorded in newtons and then often converted into megapascals, which is the unit of stress at the interface. Special attention needs to be paid to ensure the geometry of the bonding site of the bracket allows calculation of stress. In the case of complex form of the bonding site, it is correct to report the bonding properties as debonding load. Moreover, enamel and appliance surfaces are analyzed under optic magnification and an Adhesive Remnant Index (ARI) is assigned to give information of the location of the adhesive failure [13]. ARI score is calculated evaluating the amount of adhesive left on tooth and appliance surfaces after debonding. ARI scale usually ranges from 0 to 3 (0: no resin remaining on tooth; 1: less than 50% resin remaining on tooth; 2: more than 50% resin remaining on tooth; 3: 100% resin remaining on tooth).
As it is a standard procedure in biomedical research, statistical analyses are performed with a high enough number of test specimens (i.e., teeth). Descriptive statistics (mean, standard deviation, minimum, median, and maximum values) are calculated for the groups which are compared. The normality of the data can be calculated (e.g., using the Kolmogorov-Smirnov test). Parametric (e.g., ANOVA) or nonparametric (e.g., Kruskal-Wallis) tests are then applied and parametric (e.g., Tukey) or nonparametric (e.g., Mann–Whitney) post hoc tests are used to show differences among various groups. On the other hand, for ARI scores a Chi Squared test is often applied. Significance for all statistical tests is almost always predetermined at P < 0.05.
In the literature, there are not clear guidelines about shear force limits, but in fact a good orthodontic biomaterial should allow good adhesion in order to sustain masticatory forces (with a minimum bond strength of 5–10 MPa) [14]. On the other hand, adhesion forces should not be too strong in order to avoid enamel loss after debonding (40–50 MPa) [15]. Therefore, the ideal orthodontic biomaterial should have bonding forces included in the interval of 5–50 MPa, even if these limits are mostly theoretical.
When considering ARI index, even if methods of measurement could influence score assignment results [16], ARI score is nowadays widely used in bonding studies to assess and discuss adhesive left on tooth surface after debonding. Generally, a score of “0” is often related to lower shear bond strength values and is often related to contaminants over enamel that can reduce bond strength. On the other hand, an ARI score of “3” means less risk of enamel fracture after bracket debonding but polishing procedures are longer as more adhesive remains on tooth surface [9]. Therefore, an orthodontic biomaterial should aspire to a mixed adhesion modality (ARI “1” and “2”).
In conclusion, bonding studies represent one of the first steps of materials testing and should be followed by in vivo clinical studies in order to confirm the in vitro results. Therefore, although some criticisms have been stated against bonding studies in orthodontics, bonding tests are still a valid instrument to test new brackets, adhesives, jigs, pad, and other biomaterials bonded to tooth surface.
On the basis of these considerations, the present special issue has been proposed to explore new variables of bonding studies. These new topics have been about the Er:YAG laser-recycled ceramic orthodontic brackets, the transmission of curing light through treated dental tissues, the effect of removal of enamel on rebonding strength of resin composite, the bond strength of different bonding systems on enamel and restorative materials, and the bonding of metal attachments to sandblasted porcelain and zirconia.
The Guest Editors do hope that the present special issue would be interesting for the readers of the journal and wish that the present work could encourage other researchers for future, original, interesting bond strength studies
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