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Difference in the color stability of direct and indirect resin composites
Lee, Yong-Keun;Yu, Bin;Lim, Ho-Nam;Lim, Jin Ik;
Journal of Applied Oral Science , 2011, DOI: 10.1590/S1678-77572011000200012
Abstract: indirect resin composites are generally regarded to have better color stability than direct resin composites since they possess higher conversion degree. objective: the present study aimed at comparing the changes in color (δe) and color coordinates (δl, δa and δb) of one direct (estelite sigma: 16 shades) and 2 indirect resin composites (belleglass ng: 16 shades; sinfony: 26 shades) after thermocycling. material and methods: resins were packed into a mold and light cured; post-curing was performed on indirect resins. changes in color and color coordinates of 1-mm-thick specimens were determined after 5,000 cycles of thermocycling on a spectrophotometer. results: δe values were in the range of 0.3 to 1.2 units for direct resins, and 0.3 to 1.5 units for indirect resins, which were clinically acceptable (δe<3.3). based on t-test, δe values were not signifcantly different by the type of resins (p>0.05), while δl, δa and δb values were signifcantly different by the type of resins (p<0.05). for indirect resins, δe values were infuenced by the brand, shade group and shade designation based on three-way anova (p<0.05). conclusion: direct and indirect resin composites showed similar color stability after 5,000 cycles of thermocycling; however, their changes in the color coordinates were different.
Flexural strength and hardness of direct and indirect composites
Borba, Márcia;Della Bona, álvaro;Cecchetti, Dileta;
Brazilian Oral Research , 2009, DOI: 10.1590/S1806-83242009000100002
Abstract: the objective of this study was to evaluate the flexural strength (σf) and hardness (h) of direct and indirect composites, testing the hypotheses that direct resin composites produce higher σf and h values than indirect composites and that these properties are positively related. ten bar-shaped specimens (25 mm x 2 mm x 2 mm) were fabricated for each direct [d250 - filtek z250 (3m-espe) and d350 - filtek z350 (3m-espe)] and indirect [isin - sinfony (3m-espe) and ivm - vitavm lc (vita zahnfabrik)] materials, according to the manufacturer's instructions and iso4049 specifications. the σf was tested in three-point bending using a universal testing machine (emic dl 2000) at a crosshead speed of 0.5 mm/min (iso4049). knoop hardness (h) was measured on the specimens' fragments resultant from the σf test and calculated as h = 14.2p/l2, where p is the applied load (0.1 kg; dwell time = 15 s) and l is the longest diagonal of the diamond shaped indent (astm e384). the data were statistically analyzed using anova and tukey tests (α = 0.05). the mean σf and standard deviation values (mpa) and statistical grouping were: d250 - 135.4 ± 17.6a; d350 - 123.7 ± 11.1b; isin - 98.4 ± 6.4c; ivm - 73.1 ± 4.9d. the mean h and standard deviation values (kg/mm2) and statistical grouping were: d250 - 98.12 ± 1.8a; d350 - 86.5 ± 1.9b; isin - 28.3 ± 0.9c; ivm - 30.8 ± 1.0c. the direct composite systems examined produce higher mean σf and h values than the indirect composites, and the mean values of these properties were positively correlated (r = 0.91), confirming the study hypotheses.
Fracture resistance of teeth restored with packable and hybrid composites
Ghavam M,Ataee M,Fallahzade F
Journal of Dental Medicine , 2006,
Abstract: Background and Aim: With recent introduction of packable composites, it is claimed that they apply less stress on tooth structure because of reduced polymerization shrinkage, and similarity of coefficient of thermal expansion to tooth structure. However, the high viscosity may in turn cause less adaptation, so it is not clearly known whether these materials strengthen tooth structure or not. The aim of this study was to evaluate fracture resistance of maxillary premolars, receiving hybrid or packable composite restorations with different methods of application and curing. Materials and Methods: In this experimental study, seventy five intact premolars were randomly assigned to five groups of 15 teeth each. One group was maintained intact as the control group. Similar MOD cavities were prepared in the other teeth. The teeth in group two were restored with Spectrum in incremental layers and light cured with 500 mw/cm2 intensity. The third group were filled with Surefil and cured with light intensity of 500 mw/cm2. The groups four and five were restored with Surefil in bulk technique with two different modes: 500 mw/cm2 intensity and a ramp mode (100-900 mw/cm2) respectively. After thermocycling, force to fracture was assessed and degree of conversion (DC) at the bottom of cavities was evaluated for different modes and methods. The curing and placement methods in groups tested for DC (A to D) were the same as fracture resistance groups (2 to 5). Data were analyzed using one way ANOVA and Tukey HSD tests with p<0.05 as the limit of significance. Results: All the restored groups showed significantly less fracture resistance than the control group, but had no significant difference among themselves. DC of Spectrum was higher than Surefil. Bulk method with 500 mw/cm2 light intensity, significantly decreased DC. DC in bulk method with high light intensity was not significantly different from incremental method with 500 mw/cm2 light intensity. Conclusion: Placement techniques, light intensity and type of composite had no influence on the fracture resistance. The use of packable composite with bulk technique and 500 mw/cm2 intensity or less is not recommended in 4 mm depth cavities due to insufficient DC.
Comparison of chemical composition of packable resin composites by scanning electron microscopy
Silva, Ana Amélia Bianchi e;Veeck, Elaine Bauer;Oliveira, José Pedro Peixoto de;Souza, Paulo Henrique Couto;
Journal of Applied Oral Science , 2005, DOI: 10.1590/S1678-77572005000100014
Abstract: objectives: the purpose of this study was to compare the chemical composition of four different shades (incisal/extra-light, a2, a3 and b3) of two packable resin composites (solitaire?, and prodigy condensabletm). methods and materials: the specimens measured 4mm in diameter and 4mm in thickness. five specimens were made for each shade of the materials. they were light cured for 40 seconds at a power of 600mw/cm2. subsequently, the specimens were removed from the plates and ground to powder and then pressed into holes measuring 4mm in diameter in a teflon matrix, using the plates of the same material as base and cover. specimens were evaluated under sem with an x-ray detector for the spectroscopic test by energy dispersing. results: the chemical components found in both materials were practically the same, but in different proportions. carbon, oxygen, aluminum, silica, fluoride and barium were found. conclusions: the chemical composition of each same material varied according to each shade analyzed.
Indirect resin composites  [cached]
Nandini Suresh
Journal of Conservative Dentistry , 2010,
Abstract: Aesthetic dentistry continues to evolve through innovations in bonding agents, restorative materials, and conservative preparation techniques. The use of direct composite restoration in posterior teeth is limited to relatively small cavities due to polymerization stresses. Indirect composites offer an esthetic alternative to ceramics for posterior teeth. This review article focuses on the material aspect of the newer generation of composites. This review was based on a PubMed database search which we limited to peer-reviewed articles in English that were published between 1990 and 2010 in dental journals. The key words used were ′indirect resin composites,′ composite inlays,′ and ′fiber-reinforced composites.′
In vitro toothbrushing abrasion of dental resin composites: packable, microhybrid, nanohybrid and microfilled materials
Moraes, Rafael Ratto de;Ribeiro, Daiane dos Santos;Klumb, Mirian Margarete;Brandt, William Cunha;Correr-Sobrinho, Louren?o;Bueno, Márcia;
Brazilian Oral Research , 2008, DOI: 10.1590/S1806-83242008000200004
Abstract: this study evaluated weight loss and surface roughening after toothbrushing of different resin composites: one packable (solitaire 2, heraeus kulzer), one microhybrid (charisma, heraeus kulzer), one nanohybrid (simile, pentron) and one microfilled (durafill vs, heraeus kulzer). cylindrical specimens (n = 20) were prepared. half of the samples were submitted to 60,000 strokes, at 4 hz, with a dentifrice-water slurry. control samples (n = 10) remained stored at 37°c. pre- and post-abrasion parameters for weight (mg) and surface roughness (ra, μm) were determined on an analytical balance and a surface profilometer. data were separately submitted to repeated measures anova and tukey's test (a = 0.05). percentages of weight loss were analyzed by anova and tukey's test (a = 0.05). the relationship between both evaluations was assessed by pearson's test (a = 0.05). the means (%) for weight loss (standard deviation) were 0.65(0.2), 0.93(0.2), 1.25(0.6) and 1.25(0.4) for simile, durafill, charisma and solitaire, respectively. baseline roughness means ranged from 0.065(0.01), 0.071(0.01), 0.066(0.02) and 0.074(0.01) for simile, durafill, charisma and solitaire, respectively, to 0.105(0.04), 0.117(0.03), 0.161(0.03) and 0.214(0.07) after testing. the composites with larger fillers presented higher weight loss and roughening than the finer materials (p < 0.05). for both evaluations, control specimens showed no significant alteration. no significant relationship between loss of weight and roughness alteration was detected (r = 0.322, p = 0.429).
Image Quality of Digital Direct Flat-Panel Mammography Versus an Indirect Small-Field CCD Technique Using a High-Contrast Phantom  [PDF]
Kathrin Barbara Krug,Hartmut Stützer,Peter Frommolt,Julia Boecker,Henning Bovenschulte,Volker Sendler,Klaus Lackner
International Journal of Breast Cancer , 2011, DOI: 10.4061/2011/701054
Abstract: Objective. To compare the detection of microcalcifications on mammograms of an anthropomorphic breast phantom acquired by a direct digital flat-panel detector mammography system (FPM) versus a stereotactic breast biopsy system utilizing CCD (charge-coupled device) technology with either a 1024 or 512 acquisition matrix (1024 CCD and 512 CCD). Materials and Methods. Randomly distributed silica beads (diameter 100–1400? m) and anthropomorphic scatter bodies were applied to 48 transparent films. The test specimens were radiographed on a direct digital FPM and by the indirect 1024 CCD and 512 CCD techniques. Four radiologists rated the monitor-displayed images independently of each other in random order. Results. The rate of correct positive readings for the “number of detectable microcalcifications” for silica beads of 100–199? m in diameter was 54.2%, 50.0% and 45.8% by FPM, 1024 CCD and 512 CCD, respectively. The inter-rater variability was most pronounced for silica beads of 100–199? m in diameter. The greatest agreement with the gold standard was observed for beads 400? m in diameter across all methods. Conclusion. Stereotactic spot images taken by 1024 matrix CCD technique are diagnostically equivalent to direct digital flat-panel mammograms for visualizing simulated microcalcifications 400? m in diameter. 1. Introduction X-ray stereotactic, ultrasound, or MRI-guided biopsies of the breast have essentially replaced explorative surgical tissue excisions of the breast when findings suspected to be cancer need histological verification. According to the interdisciplinary S3 (level 3) guidelines on the diagnosis, therapy and followup care of the breast cancer issued by the German Cancer Society and its affiliated medical and scientific societies and by the European Commission on quality assurance in screening and diagnosis of breast cancer, the percentage of explorative tissue excisions during screening and diagnostic mammography is reported to be less than 5% [1, 2]. As stated in the guidelines, biopsies should be guided by the technique that in each specific case best visualizes suspiciously malignant findings. In most cases, when diagnostic examinations and percutaneous biopsies are performed by ultrasound and MRI mammography, the same system is used, but only with additional stereotactic equipment. Radiologically, by contrast, different systems are usually employed, respectively, for diagnostic imaging and stereotactic biopsy. Before a representative tissue sample can be biopsied for proper pathological testing, the pathological mammographic finding
Direct and indirect detection of WIMPs  [PDF]
O. Martineau,for the EDELWEISS collaboration
Physics , 2001,
Abstract: We present here the principles of detection of Weakly Interacting Massive Particles, which could represent a large contribution to Dark Matter. A status of the experimental situation is given both for indirect and direct detection. In particular, the DAMA claim for a WIMP signal is confronted to the recent results of the CDMS and EDELWEISS experiments. We conclude by comparing direct and indirect search sensitivities.
Direct and Indirect Effects  [PDF]
Judea Pearl
Computer Science , 2013,
Abstract: The direct effect of one eventon another can be defined and measured byholding constant all intermediate variables between the two.Indirect effects present conceptual andpractical difficulties (in nonlinear models), because they cannot be isolated by holding certain variablesconstant. This paper shows a way of defining any path-specific effectthat does not invoke blocking the remainingpaths.This permits the assessment of a more naturaltype of direct and indirect effects, one thatis applicable in both linear and nonlinear models. The paper establishesconditions under which such assessments can be estimated consistentlyfrom experimental and nonexperimental data,and thus extends path-analytic techniques tononlinear and nonparametric models.
Marginal Adaptation of Nanofilled, Packable and Hybrid Dental Composite Resins Stored in Artificial Saliva
American Journal of Biomedical Engineering , 2012, DOI: 10.5923/j.ajbe.20120203.03
Abstract: Resin based composites are possibly the most universal material available in dentistry as they are used in a huge variety of clinical applications, ranging from filling material, luting agent, indirect restorations and metal facing for endodontic posts and cores. The growth of bacteria on the composite resin surfaces, secondary caries and pulp damage or marginal imperfections may occur at the site of gap formation. In this study, marginal adaptation of three composites were measured and compared. A total of sixty human mandibular first molars were used. The teeth were divided into three main groups (20 teeth each) according to the composite resins that were used. In group I, Surefil (packable composite) was used as the restorative material. In group II, Esthet-X-improved (nanofilled composite) was used, while in group III Glacier (hybrid composite) was used. Each group was subdivided into four subgroups (five teeth each) according to the storage intervals (24 hours, one week, two weeks, and three weeks). In each group, occlusomesial cavities were prepared with diamond burs and restored with the composite, according to manufacturer's instructions. In all specimens, composite was applied to the cavity using incremental technique. All the restored teeth were subjected to in vitro thermal cycling and mechanical loading simulating a total of six months in vivo function. Marginal adaptation was evaluated using Measurescope-10 and the results were confirmed with scanning electron microscope. These specimens were dried, sputter coated with gold-palladium and then photographed with SEM at 1500x. A highly significant difference in marginal adaptation was found between the used composites. After specimen storage in artificial saliva, there was a gradual improvement in the marginal adaptability of the specimens. It can be concluded that the marginal adaptation of the nanofilled composite was the best when compared to the other composites.
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