1,721,271 research outputs found
Halogen versus high-intensity light-curing of uncoated and pre-coated brackets: a shear bond strength study
No full textAIM:To evaluate the shear bond strengths of adhesive pre-coated brackets (APC) and conventional uncoated brackets (Victory) cured with two different light-curing units: a conventional halogen light (Visilux 2) and a micro-xenon light (Aurys).
SETTING: Ex vivo study
MATERIALS AND METHODS: Sixty freshly extracted bovine permanent mandibular incisors were randomly assigned to one of four groups, each group consisting of 15 specimens. Two groups (one for each type of bracket) were exposed to the halogen light for 20 seconds and used as controls. The remaining two groups were cured with the micro-xenon light for 2 seconds. After 24 hours, all samples were tested in a shear mode on an Instron Machine. Analysis was by two-way ANOVA with Scheffé's test for comparisons, Kaplan-Meier survival estimates, and Cox model. The Chi-square (chi(2)) test was used to determine significant differences in the ARI scores.
RESULTS: The mean shear bond strength of the uncoated brackets cured with Visilux 2 was significantly higher than those of all the other groups tested. Both groups cured with Visilux 2 produced significantly higher mean shear bond strengths than those of the corresponding groups cured with Aurys. No statistically significant differences were found between the two groups cured with Aurys.
CONCLUSIONS: Compared to halogen light-curing, the micro-xenon light enables the clinician to reduce significantly the curing time of both APC and uncoated brackets, and although significantly lower, their shear bond strengths may be clinically acceptable
Polymerization with a micro-xenon light of a resin-modified glass ionomer: a shear bond strength study 15 minutes after bonding
No full textThe purpose of this study was to evaluate the initial shear bond strength (15 minutes after bonding) of a resin-modified glass ionomer (RMGIC, Fuji Ortho LC) cured with two different light-curing units: a conventional visible light (Ortholux XT) and a microxenon light (Aurys). Seventy-five freshly extracted bovine permanent mandibular incisors were randomly assigned to one of five groups; each group consisted of 15 specimens. Group A (Transbond XT) and group B (Fuji Ortho LC) were exposed to the visible light for 20 and 40 seconds, respectively, and used as controls. The remaining three groups (C, D, and E) were bonded with Fuji Ortho LC and cured with Aurys for 10, 5, and 2 seconds, respectively. All samples were tested in a shear mode on an Instron universal testing machine 15 minutes after bonding. The shear bond strength of the control group bonded with Transbond XT was significantly higher (P = 0.000) than those of all the other groups tested. Regarding Fuji Ortho LC, no statistically significant differences were found between the bond strength of the control group cured with Ortholux XT, and those of the groups cured with Aurys for 2, 5, and 10 seconds. The present findings indicate that, compared with visible light-curing, the micro-xenon light enables the clinician to significantly reduce the curing time of RMGICs, without affecting their initial shear bond strengths
Effect of water and saliva contamination on the shear bond strength of a new light-cured cyanoacrylate adhesive
Full text linkAIM: The purpose of the study was to assess the effect of water and saliva contamination on the shear bond strength and site of bond failure of two different orthodontic adhesives (Transbond XT and cyanoacrylate Smartbond LC). MATERIALS AND METHODS: 120 bovine permanent mandibular incisors were randomly divided into 6 groups, and each group consisted of 20 specimens. Each adhesive was tested under three different enamel surface conditions: 1) dry, 2) water contamination, 3) saliva contamination. 120 stainless steel brackets (0.018-inch slot DB, Leone) were bonded in each test group with the respective adhesive. After bonding, all samples were stored in distilled water for 24 hours and subsequently tested in a shear mode on an Instron Universal Testing Machine. Shear bond strength and site of bond failure were evaluated. Kruskal-Wallis and Fisher's exact tests were applied to determine significant differences in terms of bond strength among the 6 groups. The chi-square test was used to determine significant differences in the Adhesive Remnant Index (ARI) scores. RESULTS: Transbond XT showed the highest bond strength values when it was applied onto dry enamel (P < 0.0002). No significant differences were reported when Transbond was used either on water- or saliva- contaminated enamel (P = 0.5), however the bond strength values were significantly low. For Smartbond LC no significant differences were found between dry and moist with water conditions (P = 0.3). Significantly higher bond strength values were reported when Smartbond LC was used on saliva contaminated enamel (P = 0.002). Significant differences in debond locations were found among the different groups. CONCLUSIONS: The use of a cyanoacrylate adhesive is indicated under moist conditions (particularly saliva), and when a short setting time is required. This can be considered advantageous in clinical orthodontic bonding compared to conventional composites
Effect of pulse vs continuous micro-xenon irradiation on the shear bond strength of a light-cured orthodontic composite resin
No full textThe aim of the study was to evaluate the effect of
pulse vs. continuous irradiation on the shear bond strength of a
conventional orthodontic composite resin cured with a microxenon
light (Aurys, Degre` K, Schiltigheim, France). Ninety freshly extracted bovine permanent mandibular incisors were
randomly assigned to one of six groups; each group consisting of
15 specimens. Three groups were exposed to continuous irradiation of micro-xenon light for 10, 5, and 2 s, respectively, and used as controls. The remaining three groups were exposed to pulse irradiation of the same light source for 10, 5, and 2 s,
respectively. After 24 h, all samples were tested in a shear mode
on an Instron Machine (Instron Corp., Canton, MA, USA). Analysis
was made by ANOVA with Scheffe ́ ’s test for comparisons.
The chi-square test was used to determine significant differences
in the Adhesive Remnant Index scores. The mean shear
bond strength of the brackets continuously cured for 10 s was
not statistically different from that of the brackets pulse-activated
for the same curing time. Also, no statistically significant differences were found between both groups cured for 5 s. The group pulse-activated for 5 s, however, had a significantly lower mean shear bond strength than the control group cured for 10 s.
Finally, the group pulse-activated for 2 s showed significantly
lower bond strength values than all the other groups tested.
Compared with continuous light curing, the micro-xenon pulse
activation provides similar shear bond strength values, except
when used for only 2 s; but despite lower performance characteristics, the shear bond strength may be clinically acceptable
Is mitral E/E' ratio a reliable predictor of left ventricular diastolic pressures in patients without heart failure?
No full textAim: Conflicting evidence exists as to whether the mitral E/E′ ratio can be a reliable predictor of the left ventricular enddiastolic pressure (LVEDP). Our aim was to assess the value of the mitral E/E′ ratio for the estimation of left ventricular diastolic pressures (LVDP) in patients without heart failure (HF). Methods and results: Echo-Doppler examination and left heart catheterization were carried out in 100 consecutive patients to assess the correlation between echo-Doppler parameters and the LVDP. The E/A ratio showed the best correlation with the pre-a LVDP and the LVEDP, whereas septal and mean E/E′ ratios were significantly correlated with pre-a LVDP but not with the LVEDP. No difference in the echo-Doppler parameters was found between patients with normal and elevated LVEDP. Mitral E/E′ ratio was significantly higher in patients with an ejection fraction (EF) 15. The best cut-off values identified by receiver operating characteristic curve analysis for septal, lateral, and mean E/E′ had sensitivities of 53, 68, and 54% and specificities of 66, 51, and 69% for identifying a >15 mmHg LVEDP. Conclusion: In patients without HF mitral E/E′ ratio is influenced by EF and LV volumes and is better correlated with the pre-a LVDP than with the LVEDP. The suboptimal sensitivity and specificity of E/E′ for predicting increased LVDP suggest that the mitral E/E′ ratio is of limited clinical value in patients without HF. Published on behalf of the European Society of Cardiology. All rights reserve
In-vitro fluoride release rates from 9 orthodontic bonding adhesives
Full text linkINTRODUCTION: The purpose of this study was to compare the in-vitro fluoride release rates from 9 orthodontic adhesives in distilled water. METHODS: Of the adhesives tested, 4 were bracket bonding agents (Fuji Ortho LC [GC, Leuven, Belgium], Enlight LV [Ormco, Glendora, Calif], ConTec LC [Dentaurum, Ispringen, Germany], and Transbond XT [3M Unitek, Monrovia, Calif]); the remaining 5 were molar banding cements: Fuji Ortho Band Paste Pak (GC), OptiBand (Ormco), GlasTec (Dentaurum), Multi-Cure (3M Unitek), and Transbond Plus (3M Unitek). Ten samples of each adhesive were stored in containers holding 5 mL of deionized distilled water at 37 degrees C. Fluoride release was measured with an ion-specific electrode (model 96-09BN, Orion Research, Beverly, Mass). Readings were taken periodically for a total time period of 3 months. Descriptive statistics were calculated for the fluoride release rates of each material group. The data were subjected to a general linear regression model to detect differences in fluoride ion concentration by material and time. Post-hoc test with the Bonferroni adjustment was used to further delineate group differences. RESULTS: Among the bracket bonding adhesives, statistically significant differences were found in fluoride release rates (P = .000), with Fuji Ortho LC releasing the most fluoride. Enlight LV, ConTec LC, and Transbond XT released negligible amounts of fluoride. Fuji Ortho Band Paste Pak released more fluoride (P = .000) than all remaining molar banding adhesives. Multi-Cure released more fluoride than GlasTec, Transbond Plus, and Optiband. The latter released negligible amounts of fluoride. CONCLUSIONS: Fuji Ortho Band Paste Pak released more fluoride than the other adhesives. Fuji Ortho Band Paste Pak and Fuji Ortho LC might have sufficient fluoride-release rates to reduce white spot formation, and they are recommended as suitable fluoride-releasing orthodontic adhesives
Plasma arc versus halogen light curing of orthodontic brackets: A 12-month clinical study of bond failures
Full text linkThe purpose of this randomized clinical trial was to evaluate the performance of adhesive-precoated brackets cured with 2 different light-curing units (conventional halogen light and plasma arc light). Thirty patients treated with fixed appliances were included in the investigation. Each patient's mouth was divided by the split-mouth design into 4 quadrants. In 15 randomly selected patients, the maxillary left and mandibular right quadrants were cured with the halogen light, and the remaining quadrants were cured with the plasma arc light. In the other 15 patients, the quadrants were inverted. A total of 600 adhesive precoated stainless steel brackets were examined: 300 were cured with a conventional halogen light for 20 seconds, and the others were cured with the plasma arc light for 5 seconds. The number, cause, and date of bracket failures were recorded for each light-curing unit over 12 months. Statistical analysis was performed with the Fisher exact test, Kaplan-Meier survival estimates, and the log-rank test. No statistically significant differences in bond failure rates were found between the adhesive-precoated brackets cured with the halogen light and those cured with the plasma arc light; neither were any significant differences in performance found with each light-curing unit between the maxillary and mandibular arches. Plasma arc lights can be considered an advantageous alternative to conventional light curing, because they enable the clinician to reduce the curing time of adhesive-precoated orthodontic brackets without significantly affecting their bond failure rate
The effect of bleaching on shear bond strength of brackets bonded with a resin-modified glass ionomer
Full text linkINTRODUCTION: This study assessed the effect of a 35% hydrogen peroxide bleaching gel on the shear bond strength and bond failure site of a resin-modified glass ionomer (Fuji Ortho LC, GC Europe, Leuven, Belgium). METHODS: Forty-five bovine mandibular permanent incisors were randomly divided into 3 groups; each group contained 15 teeth. Bleaching treatment was performed at 2 different times before the bonding procedure. Forty-five stainless steel brackets were bonded with the resin-modified glass ionomer. After bonding, all samples were stored in distilled water for 24 hours and then tested in shear mode on a testing machine. RESULTS: Group 1 (no bleaching) showed significantly higher shear bond strength values than groups 2 (bleaching immediately before bonding) and 3 (bleaching 1 week before bonding). No significant differences were found between groups 2 and 3. Moreover, no significant differences in debond locations were found among the 3 groups. CONCLUSIONS: Bleaching treatment before bonding significantly lowered the bond strength values of Fuji Ortho LC
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