309 research outputs found

    Polymerization Efficiency of Glass-Ionomer and Resin Adhesives under Molar Bands

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    Objective: To determine the degree of cure of a light-cured resin-modified glass ionomer (RMGI) under molar bands compared with a light-cured resin and a dual-cured resin. Materials and Methods: The 3 cements used were Fuji Ortho LC, Eagle Spectrum resin, and Variolink II dual-cure. Each sample was indirectly light cured for 20 seconds (10 seconds occlusally, 10 seconds cervically) under sections of molar bands, and the degree of cure was evaluated with micro-MIR FTIR spectroscopy. Results: The RMGI exhibited a significantly higher mean degree of cure (55.31%) than both of the resins (Eagle 19.23%; Variolink II, 25.42%), which did not differ significantly at α = .05 level of significance. Conclusion: Higher degree of conversion can be obtained from RMGIs under molar bands compared with composite resin adhesives provided the proper curing technique is used

    Do the Mechanical and Chemical Properties of Invisalign\u3csup\u3eTM\u3c/sup\u3e Appliances Change After Use? A Retrieval Analysis

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    Aim: To investigate the mechanical and chemical alterations of Invisalign appliances after intraoral aging. Materials and methods: Samples of Invisalign appliances (Align Technology, San Jose, California, USA) were collected following routine treatment for a mean period of 44±15 days (group INV), whereas unused aligners of the same brand were used as reference (group REF). A small sample from the central incisors region was cut from each appliance and the buccal surface was analysed by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy (n = 5). Then the appliances were cut (n = 25) and embedded in acrylic resin, ground/polished in a grinding polishing machine, and the prepared surfaces were subjected to Instrumented Indentation Testing under 4.9 N load. Force-indentation depth curves were recorded for each group and the following parameters were calculated according to ISO 14577-1; 2002 specification: indentation modulus (E IT), elastic to total work ratio also known as elastic index (ηIT), Martens Hardness (HM), and indentation creep (C IT) The mean values of the mechanical properties were statistically analysed by unpaired t-test (a = 0.05). Results: ATR-FTIR analysis confirmed the urethane based structure of the appliances, without important chemical differences attributed to the aging process. INV group showed significantly lower E IT (REF: 2466±20, INV: 2216±168MPa), HM (REF: 119±1, INV: 110±6 N mm−2) and higher ηIT (REF: 40.0±0.3, INV: 41.5±1.2%), and C IT (REF: 3.7±0.2 INV: 4.0±0.1%). The increase in ηIT indicates that INV is a more brittle than REF, whereas the increase in C IT, a decrease in creep resistance. Conclusion: Despite the lack of detectable chemical changes, intraoral aging adversely affected the mechanical properties of the Invisalign appliance

    Structure, Composition, and Mechanical Properties of Australian Orthodontic Wires

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    Objective: To investigate the surface morphology, structure, elemental composition, and key mechanical properties of various sizes and tempers of Australian wires. Materials and Methods: Three types of Australian wire were used: 0.016″ regular, 0.018″ regular+, and 0.018″ special+ (A.J. Wilcock, Whittlesea, Victoria, Australia). Each type of wire was subjected to scanning electron microscopy (SEM) analysis, x-ray energy dispersive spectroscopy (EDS) investigation, Vickers hardness testing, and tensile testing. The modulus of elasticity and ultimate tensile strength were determined. Hardness, modulus, and strength data were analyzed with one-way analysis of variance (ANOVA) and Tukey testing at the .05 level of significance. Results: All three types of Australian wire were found to possess considerably rough surfaces with striations, irregularities, and excessive porosity. All three wire types had high levels of carbon and a similar hardness, which ranged within 600 VHN (Vickers hardness number), and a similar modulus of elasticity (173 to 177 GPa). The 0.018″ special+ had a significantly lower tensile strength (1632 MPa) than the 0.016″ regular and the 0.018″ regular+ wire (2100 MPa). Conclusions: Australian wires did not show variation implied by the size or temper of the wires

    Evidence-based orthodontics: too many systematic reviews, too few trials

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    Why are there so many systematic reviews in orthodontics, and what are the negative consequences of this for our speciality as an academic discipline

    Force to Debond Brackets from High-fusing and Low-fusing Porcelain Systems

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    The purpose of this study was to test the hypothesis that porcelain surface finishing, ie, low- and high-fusing porcelain, has an effect on the amount of force required to debond orthodontic brackets. A total of 20 high-fusing and 20 low-fusing porcelain specimens were prepared, polished, and bonded with standard edgewise brackets using a suggested porcelain bonding protocol. The brackets were debonded with a universal testing machine at shear mode. Resin removal was performed using two methods: a multifluted carbide bur with and without the use of Sof-Lex polishing discs. Representative specimens were studied under a scanning electron microscope before and after debonding to assess the surface morphology and potential surface damage. Statistical analysis with a t-test revealed that there was no difference between the two porcelain treatments on the force to debond values and no qualitative differences were observed on the porcelain surface between the two resin clean-up methods. From a clinical perspective, the practitioner can bond ceramic restorations without previous knowledge of the porcelain type used

    Randomization in clinical trials in orthodontics: its significance in research design and methods to achieve it

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    Randomization is a key step in reducing selection bias during the treatment allocation phase in randomized clinical trials. The process of randomization follows specific steps, which include generation of the randomization list, allocation concealment, and implementation of randomization. The phenomenon in the dental and orthodontic literature of characterizing treatment allocation as random is frequent; however, often the randomization procedures followed are not appropriate. Randomization methods assign, at random, treatment to the trial arms without foreknowledge of allocation by either the participants or the investigators thus reducing selection bias. Randomization entails generation of random allocation, allocation concealment, and the actual methodology of implementing treatment allocation randomly and unpredictably. Most popular randomization methods include some form of restricted and/or stratified randomization. This article introduces the reasons, which make randomization an integral part of solid clinical trial methodology, and presents the main randomization schemes applicable to clinical trials in orthodontic

    Effect of Various Curing Lights on the Degree of Cure of Orthodontic Adhesives

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    Introduction: The purpose of this study was to compare the percentage degree of cure (%DC) of orthodontic adhesive resins irradiated with 3 types of light sources of various intensities: plasma arc, halogen, and light-emitting diode (LED). Methods: Twenty maxillary incisor stainless steel brackets (0.018-in slot) were divided into 4 groups of 5 brackets each. A standardized amount of composite resin was applied to each bracket base, simulating its clinical application. The brackets were light-cured with a halogen light for 20 seconds (10 seconds each from the incisal and cervical bracket edges), an LED light for 20 seconds (10 seconds per edge), a plasma light for 10 seconds (5 seconds per edge), and an LED light for 10 seconds (5 seconds per edge). The %DC was assessed by using micro-multiple internal reflectance Fourier transform infrared spectroscopy, and the results were analyzed with 1-way ANOVA. Results: Overall, the LED and the halogen lights, with the 20-second regimen, produced higher %DC. No significant difference was found in %DC between the plasma light and the 10-second LED light, whereas both showed lower %DC compared with 20 seconds of halogen or LED light. Conclusions: Significant variations in %DC are associated with the various light-curing units, which must be considered in selecting the light source and the irradiation time

    Reporting, interpretation, and extrapolation issues (SPIN) in abstracts of orthodontic meta-analyses published from 2000 to 2020

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    Summary Aim To assess the prevalence of and identify factors associated with SPIN in abstracts of orthodontic meta-analyses. Materials and methods Electronic search was performed within the contents of five orthodontic journals and the Cochrane Database of Systematic Reviews (CDSR) to identify meta-analyses of studies involving humans, from 1 January 2000 until 31 August 2020. Inclusion of SPIN in the abstract of meta-analyses, defined as misleading reporting, misleading interpretation, and inappropriate extrapolation of the findings, was documented. Extent of SPIN and associations with journal and year of publication, type of study, number of authors, continent of authorship, methodologist involvement, funding, and significance of the primary outcome were investigated. Results One hundred and nine meta-analyses were identified, with the highest proportion being published in the European Journal of Orthodontics (EJO: 31/109; 28.4%). Inclusion of SPIN, in at least one domain, was recorded in nearly half (53/109; 48.6%) of the studies, of which 30 (56.6%) included 2 or more domains of SPIN. Meta-analyses of observational studies presented 1.66 times higher risk for including SPIN in their abstracts compared with interventional ones [95% confidence intervals (CIs): 1.14, 2.40; P = 0.007], after adjusting for a number of predictors. Studies with a large number of authors (≥6) presented 1.76 times higher risk of SPIN (≥6 versus 1–3: 95% CIs: 1.04, 2.97; Wald test, P = 0.021), conditional on the pre-defined predictors. Conclusions Flaws in the reporting and interpretation of the findings of abstracts of meta-analyses, as framed by inclusion of SPIN are persistent in orthodontic research, being more prevalent in meta-analyses of observational studies. Consistent, multidirectional efforts should be endorsed to improve the quality of the disseminated research findings

    Outcomes of comprehensive fixed appliance orthodontic treatment: A systematic review with meta-analysis and methodological overview

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    OBJECTIVE: The aim of this systematic review was to assess the occlusal outcome and duration of fixed orthodontic therapy from clinical trials in humans with the Objective Grading System (OGS) proposed by the American Board of Orthodontics. METHODS: Nine databases were searched up to October 2016 for prospective/retrospective clinical trials assessing the outcomes of orthodontic therapy with fixed appliances. After duplicate study selection, data extraction, and risk of bias assessment according to the Cochrane guidelines, random-effects meta-analyses of the mean OGS score and treatment duration were performed and 95% confidence intervals (CIs) were calculated. RESULTS: A total of 34 relevant clinical trials including 6,207 patients (40% male, 60% female; average age, 18.4 years) were identified. The average OGS score after treatment was 27.9 points (95% CI, 25.3-30.6 points), while the average treatment duration was 24.9 months (95% CI, 24.6-25.1 months). There was no significant association between occlusal outcome and treatment duration, while considerable heterogeneity was identified. In addition, orthodontic treatment involving extraction of four premolars appeared to have an important effect on both outcomes and duration of treatment. Finally, only 10 (39%) of the identified studies matched compared groups by initial malocclusion severity, although meta-epidemiological evidence suggested that matching may have significantly influenced their results. CONCLUSIONS: The findings from this systematic review suggest that the occlusal outcomes of fixed appliance treatment vary considerably, with no significant association between treatment outcomes and duration. Prospective matched clinical studies that use the OGS tool are needed to compare the effectiveness of orthodontic appliances
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