Greater Degree Of Conversion Research Articles

Compliance and conversion in small groups: online vs. offline polarisation effects

ABSTRACT This study investigated the phenomena of group polarisation with particular attention to the differences between offline and online settings. Polarisation is a process that leads people to develop extreme ideologies. Three hundred and seven participants were recruited and randomly assigned to different experimental conditions, i.e. antisocial and prosocial polarisation, within groups of 6 people composed of four confederates, participating in discussions about a social dilemma under two different circumstances: face to face and online. The degree of polarisation was assessed considering the final decisions adopted by the participants, as well as the internal dynamics characterising their final attitudes, i.e. compliance versus conversion. Results showed that online groups appeared more susceptible to polarisation and their members reported a greater degree of conformism. In particular, within online environments, the risk of being polarised, both antisocially and prosocially, increased by around 12%. Furthermore, in an online setting, a greater degree of conversion emerged only when the members decided to adopt a pro-social behaviour, while a greater degree of compliance emerged whenever they decided to adopt antisocial behaviour.

Why ceramic? When you can use composite. Indirect restoration of tooth in a more biomimetic way using heat treated direct resin composite

Direct resin composites have a greater degree of conversion, physical properties, color, and resistance to abrasion when heat treated. So, it is best suited for indirect use as heat-treated direct resin using oven, autoclave or porcelain furnace, or microwave. We have chosen direct resin composite as a suitable material and heat-treated it for endo crown fabrication or aesthetic indirect restoration. The reason for such technique is supported by various research studies, and case reports available have shown positive results, and it is also considered as a biomimetic method.

Effect of the degree of conversion of resin-based composites on cytotoxicity, cell attachment, and gene expression

ObjectiveThis study investigated the influence of the degree of conversion (DC), resin-based composites (RBC) composition, and the effect of additional violet light from one light curing unit (LCU) on cell attachment/growth, eluate cytotoxicity, and gene expression. MethodsThe effect of different DC of RBCs on human gingival fibroblasts (HGFs) when cultured directly onto cured RBCs, and when exposed afterwards to eluates in cell culture medium was examined. Venus® (RBC-V; Bis-GMA-based) and Venus Pearl® (RBC-P; TCD-DI-HEA and UDMA-based) were cured using a single emission peak (blue) light, Translux Wave®; TW and a dual emission peak (blue-violet) light, Translux 2 Wave®; T2W. To determine the value of the additional violet light from the T2W, exposure times and distances were adjusted to deliver similar radiant exposures (RE) from the blue region of both lights at five different RE levels from 1.5 J/cm² to 28.9 J/cm². ResultsBoth RBCs light-cured with the T2W at higher REs resulted in higher DC, increased cell adhesion and decreased eluate cytotoxicity. RBC-V induced greater cell adhesion, lower mRNA levels of pro-inflammatory markers, and higher mRNA levels of a proliferation marker than RBC-P. Wettability was the same for both RBCs. Toxicity decreased with increasing number of elution cycles. The initial eluates from RBC-P had a lower toxicity than from RBC-V. SignificanceRBCs cured with T2W (delivering both blue and violet light) at higher RE had greater DCs. The greatest DC and the least cell reactions were observed when the RE was >25 J/cm².

Bisphenol A release from orthodontic adhesives and its correlation with the degree of conversion

Our objective was to quantitatively assess and compare the bisphenol A (BPA) released from an orthodontic adhesive using a light-emitting diode device (LED) or a halogen light-curing unit (HLC) at 3 tip-to-bracket distances (0, 5, and 10 mm) and varying curing times using high-performance liquid chromatography. BPA release with self-etching and moisture-insensitive primers with light-cured and chemically cured composites was also evaluated. BPA release was correlated to the corresponding degree of conversion. Our sample consisted of 598 stainless steel first premolar brackets. Of these, 520 were used for assessing BPA release and divided into 13 groups of 40 each. In groups I, II, and III, the composite was cured with the LED for 20 seconds at distances of 0, 5, and 10 mm, respectively. Groups IV, V, and VI were cured with the HLC for 40 seconds at the same 3 distances. Groups VII and VIII were cured for 5 and 10 seconds with the LED, and groups IX and X were cured for 10 and 20 seconds with the HLC at 0-mm distance. Groups XI, XII, and XIII consisted of brackets bonded with a self-etching primer and Transbond (3M Unitek, Monrovia, Calif), with a moisture-insensitive primer and Transbond, and with a chemically cured composite. The remaining 78 brackets were also divided into 13 groups and used for assessing the degree of conversion. The LED devices demonstrated significantly less BPA release and greater degrees of conversion (P <0.05). For both units, BPA release increased and the degree of conversion decreased as the tip distance increased and curing time decreased. The chemically cured group showed significantly less BPA release (P <0.05). Among the light-cured composites, those cured according to the manufacturers' recommendations (40 seconds and 0-mm distance for the HLC unit) released less BPA than did the self-etching primer and the moisture-insensitive primer. The degree of conversion was greatest for the chemically cured composite, whereas it was similar for the conventional, self-etching primer, and moisture-insensitive primer groups. However, correlations ranged from strongly negative to weakly positive between BPA release and degree of conversion. Clinicians should consider using LEDs in clinical practice and should keep the light-cure tip as close to the bracket as clinically possible. Curing time should be according to the manufacturer's recommendations. These steps will ensure less BPA release and a greater degree of conversion. Since chemically cured composites had less BPA release and a greater degree of conversion, they can be considered superior to light-cured composites in this aspect.

Effects of water content and initiator composition on photopolymerization of a model BisGMA/HEMA resin

Aims The purpose of this study was to evaluate the effects of photoinitiator type and water content on the polymerization rate ( R p) and degree of conversion (DC) of a model BisGMA/HEMA-based resin. Materials and methods The comonomer mixture consisted of BisGMA/HEMA (60/40 by weight). Different two- or three-component photoinitiator systems were incorporated. Two-component systems were 0.5% CQ (camphorquinone) and 0.5% DMAEMA (2-(dimethylamino) ethyl methacrylate) or 0.5% CQ and 0.5% 4E (ethyl 4-dimethylaminobenzoate). The three-component systems were added 1% DPIHP (diphenyliodonium hexafluorophosphate) to the above systems. Each system was tested as made, or after addition of 5, 10, 15 wt% water. When cured under a conventional dental light, the R p and DC of each formulation was determined using time-resolved attenuated total reflection (ATR)-Fourier transform infrared (FTIR) spectroscopy. Results For mixtures containing two-component initiator systems, when the hydrophobic initiator CQ was used in combination with hydrophilic DMAEMA, R ps and DCs were dramatically decreased as a function of water content. The R ps and DCs of the hydrophobic CQ/4E system were higher than those of the CQ/DMAEMA system in the presence of water. For three-component initiator systems, incorporation of DPIHP enhanced the polymerization of all mixtures in the presence of water compared to their counterpart two-component initiators. Interestingly, the CQ/DMAEMA caused greater DC and R p when DPIHP was used. Significance The hydrophobicity/hydrophilicity of photoinitiator components significantly affects both the DC as well as R p when in the presence of water. The results indicate that formulation of photoinitiator components should be based on the effectiveness of the bonding systems under both dry and wet conditions.

Degree of conversion of composites measured by DTA and FTIR

Objective. Differential thermal analysis (DTA) using a split fiber optic light source has been reported to be a convenient method of measuring the degree of conversion (DC) of light-activated composites. The purpose of this study was to compare the results by DTA and Fourier transformation infrared spectroscopy (FTIR), and evaluate the usefulness of the DTA method. Methods. Experimental 2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane-based composites containing SiO 2 filler and various amounts of triethyleneglycol dimethacrylate (TEGDMA) were prepared, and the DC of each composite was determined by DTA or FTIR with 60 s irradiation. The DC of three proprietary composites containing hybrid filler or prepolymerized resin filler were also measured by both methods with 20 or 60 s irradiation. The results were analyzed by ANOVA and Fisher's protected least significant difference test. Results. By both DTA and FTIR, the DC of experimental composites increased as the proportion of TEGDMA increased, although DTA showed 3–10% greater values ( p<0.05) than FTIR. For proprietary composites that contain hybrid filler, the values by DTA were not significantly different from those by FTIR at 20 s exposure. Longer irradiation time resulted in greater DC ( p<0.05) for both methods, and DTA showed 5–7% greater values than FTIR. However, the DC of the composite containing prepolymerized resin filler was 30% less by FTIR than by DTA, possibly due to the influence of unpolymerized species in the filler. Significance. The DC values determined by DTA and FTIR showed good agreement for most materials including model composites. In addition, DTA may be more useful than FTIR to measure the DC of composites containing prepolymerized resin filler.

Homogeneous and biphasic autoxidation of tetralin catalyzed by transition metal salts and complexes

The biphasic autoxidation of tetralin was carried out using various Co, Ni and Mn complexes as catalysts. Cobalt– N, N′-dimethylethylenediamine complex, which is amphiphilic and surface-active, was found to be most effective; it could be easily recovered in a compact emulsion layer after the reaction and could be reused with no apparent loss of activity. The biphasic reaction differs from the homogeneous counterpart in that (1) little hydroperoxide product is formed, (2) there is lesser sensitivity to product inhibition and a greater degree of conversion and (3) there is an easier catalyst recovery and substrate recycle.

Effects of two amine reducing agents on the degree of conversion and physical properties of an unfilled light-cured resin

The influence of varying concentrations of two amine reducing agents commonly used in commercial light-cured composites, N,N-dimethyl-p-toluidine (DMPT) and 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA), on the degree of conversion (DC), Knoop hardness, and compressive and transverse strengths of an unfilled light-cured resin was investigated. The DC obtained from employing two different internal standard peaks, carbonyl (C= O) at 1730 cm −1 and urethane (N-H) at 3350 cm −1, was compared. The resin consisted of 50 wt% triethyleneglycol dimethacrylate (TEGDMA) and 50 wt% 1,6-bis (methacryloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane (UDMA) activated with 0.5 mol% camphorquinone (CQ) and varying concentrations of either DMPT or DMAEMA. The DC calculated by use of either C= O or N-H absorption peak as an internal reference showed similar values. For both amines, the physical properties were directly related to DC and appeared to reach maximal values at an amine/CQ molar ratio of 4.0. The DC, however, appeared to reach a maximum at an amine/CQ molar ratio of 3.0. Generally, for the same amine/CQ molar ratios, the polymers formulated with DMAEMA, had greater DCs and better physical properties than those formulated with DMPT.

Crystallographic and transport studies on AsF5 intercalated graphite from 4.2 to 295 K. II. Effects of structural transformations and demixing on basal plane and c-axis electrical resistivity

Part I of this study has shown that first stage AsF5 intercalated graphite samples can be classified into two types of compounds, depending upon the nature of the structural modifications they undergo upon lowering the temperature from 295 to 4.2 K. These structural changes are related to demixing of the species contained within the intercalate resulting in the formation of phases rich in AsF5, AsF−6 − AsF5, or AsF3 depending on the degree to which the AsF5 has been converted into AsF−6 and AsF3. Resistivity studies have been carried out in the basal plane [ρa (T)] and along the c axis [ρc (T)]. The type 1 compounds, in which the AsF5 has undergone little conversion, manifest a ρa (T) transition related to the incommensurate-to-commensurate (I⇉C) transformation of the AsF5 in-plane unit cell and a rapid, structureless 300 to 200 K decrease in ρc (T). The type 2 compounds involving a greater degree of conversion of AsF5 into AsF3 and AsF6 yield more complex ρc (T) behavior from 300 to 200 K attributed to the more involved ordering phenomena; no anomalies are seen in ρa (T). In the case of the stage 2 compounds, changes in ρc (T) are seen down to lower temperatures in accord with structural data indicating a downshift of the I⇉C transformation by ∼ 70 K. The transport results are discussed in the light of the crystallographic data and the low-temperature results are analyzed within the framework of proposed conductivity models.