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Concept: Levene's test


Abstract Objective: To test the null hypothesis that there is no difference between the effects of fan-type rapid (FRME) and rapid maxillary expansion (RME) used with an acrylic bonded expansion appliance on dentofacial structures in early occlusal stages. Materials and Methods: This was a prospective clinical trial. The FRME group had an anterior constricted maxillary width with a normal intermolar width, and the RME group had bilateral constricted maxillary width. The FRME group consisted of 20 patients (mean age, 8.96 ± 1.19 years), and the RME group consisted of 22 patients (mean age, 8.69 ± 0.66 years). Lateral and frontal cephalometric radiographs and dental casts were taken before and after expansion and 3 months after completing treatment for each patient. The data were compared using repeated-measures analysis of variance. The paired-samples t-test was used to evaluate treatment and retention effects, and the independent samples t-test was used to consider the differences between the two groups. Results: The maxilla moved downward and forward in both groups. The nasal cavity and maxillary width were expanded more in the RME group, and there were only a few relapses in this group during the retention period. There was significant labial tipping of the upper incisors in the FRME expansion group. The expansion of intercanine width was similar in both groups, but the expansion of intermolar width was significantly greater in the RME group. Conclusion: The null hypothesis was rejected. There was a difference between the effects of FRME and RME used with an acrylic bonded expansion appliance on dentofacial structures in the early occlusal stages.

Concepts: Statistics, Snake scales, Student's t-test, Normal distribution, Null hypothesis, Nasal cavity, F-test, Levene's test


The aim of this study was to compare the effect of different modes of toothbrushing education (lecture, video and pamphlet) on the dental plaque index (PI) of adolescents. The cluster randomized intervention was performed on 128 participants aged 12 years, who were allocated into four groups based on the type of intervention. Group 1: no intervention; and groups 2, 3, 4: education via lecture, video, and pamphlet, respectively (n = 32). Their plaque index was measured at the baseline, 24 h and two months later. Data were analyzed by repeated measures analysis of variance (ANOVA), one-way ANOVA, independent and paired t-test. The plaque indices of groups 2, 3, 4 at 24 h (p values < 0.001) and two months (p values < 0.001) showed a significant reduction when compared to the baseline. The lowest PI score was observed in the pamphlet, video and lecture groups at 24 h, respectively. After 2 months, the lowest score of PI was measured in lecture, video and pamphlet groups, respectively; however, these differences were non-significant. Therefore, toothbrushing education via lecture, video and pamphlet reduced the dental plaque index with the same effectiveness.

Concepts: Statistical tests, Statistics, Normal distribution, Multiple comparisons, Analysis of variance, Dental plaque, F-test, Levene's test


This study evaluated the effect of dentin pretreatment with the polyphenols quercetin and resveratrol on the resin-dentin microtensile bonding strength (μTBS) and collagen fibrils stability of the adhesive interface. Different concentrations (100, 250, 500, or 1,000 μg ml-1 ) of quercetin or resveratrol, or a mixture of quercetin and resveratrol (3:1, 1:1, 1:3; vol:vol), as well as distilled water or 2% chlorhexidine digluconate, were applied to etched dentin. Then, a two-step etch-and-rinse adhesive was applied followed by composite restoration. Measurements of resin-dentin μTBS were made after 1 and 120 d. The stability of collagen fibrils in the hybrid layer was evaluated using transmission electron microscopy. The Student’s t-test and two-way factorial anova with Tukey’s test were used to analyze the effects of dentin pretreatment and storage time on μTBS values. Comparisons between μTBS measurements made on 1 and 120 d showed that resveratrol had the best performance, with significantly higher μTBS values after 120 d for all concentrations of resveratrol tested. Quercetin pretreatment resulted in a significant rise of μTBS when used at concentrations of 100 and 500 μg ml-1 . Quercetin + resveratrol at the ratio of 1:1 performed better than when used at ratios of either 3:1 or 1:3. Resveratrol might represent a potential approach to achieve desirable bonding stability and reduce the frequent replacement of composite restorations.

Concepts: Electron, Statistical tests, Statistics, Ratio, Normal distribution, Analysis of variance, F-test, Levene's test


Huanglongbing (HLB) is the most recent and destructive bacterial disease of citrus and has no cure yet. A promising alternative to conventional methods is to use laser-induced breakdown spectroscopy (LIBS), a multi-elemental analytical technique, to identify the nutritional changes provoked by the disease to the citrus leaves and associate the mineral composition profile with its health status. The leaves were collected from adult citrus trees and identified by visual inspection as healthy, HLB-symptomatic, and HLB-asymptomatic. Laser-induced breakdown spectroscopy measurements were done in fresh leaves without sample preparation. Nutritional variations were evaluated using statistical tools, such as Student’s t-test and analysis of variance applied to LIBS spectra, and the largest were found for Ca, Mg, and K. Considering the nutritional profile changes, a classifier induced by classification via regression combined with partial least squares regression was built resulting in an accuracy of 73% for distinguishing the three categories of leaves.

Concepts: Regression analysis, Medicine, Statistics, Citrus, Normal distribution, Least squares, F-test, Levene's test


The aim of the present study was to investigate the efficacy of low-level laser therapy in conjunction with conventional facial exercise treatment on functional outcomes during the early recovery period in patients with facial paralysis. Forty-six patients (mean age 41 ± 9.7 years; 40 women and 6 men) were randomized into two groups. Patients in the first group received low-level laser treatment as well as facial exercise treatment, while patients in the second group participated in facial exercise intervention alone. Laser treatment was administered at a wavelength of 830 nm, output power of 100 Mw, and frequency of 1 KHz using a gallium-aluminum-arsenide (GaAIAs, infrared laser) diode laser. A mean energy density of 10 J/cm(2) was administered to eight points of the affected side of the face three times per week, for a total of 6 weeks. The rate of facial improvement was evaluated using the facial disability index (FDI) before, 3 weeks after, and 6 weeks after treatment. Friedman analysis of variance was performed to compare the data from the parameters repeatedly measured in the inner-group analysis. Bonferroni correction was performed to compare between groups as a post hoc test if the variance analysis test result was significant. To detect the group differences, the Bonferroni Student t test was used. The Mann-Whitney U test was used to compare numeric data between the groups. In the exercise group, although no significant difference in FDI scores was noted between the start of treatment and week 3 (p < 0.05), significant improvement was observed at week 6 (p < 0.001). In the laser group, significant improvement in FDI scores relative to baseline was observed at 3 and 6 weeks (p < 0.001). Improvements in FDI scores were significantly greater at weeks 3 and 6 in the laser group than those in the exercise group (p < 0.05). Our findings indicate that combined treatment with low-level laser therapy (LLLT) and exercise therapy is associated with significant improvements in FDI when compared with exercise therapy alone.

Concepts: Statistical tests, Statistics, Mann–Whitney U, Non-parametric statistics, Normal distribution, Analysis of variance, F-test, Levene's test


The aim of this research was to compare the condylar morphology of patients with unilateral condylar hyperplasia (UCH) and patients with a class III skeletal relationship using cone beam computed tomography (CBCT). A prospective study was conducted on patients with facial asymmetry attending the division of oral and maxillofacial surgery of the study university in Chile. Fifteen patients with UCH and 15 with a class III skeletal relationship were selected. Linear measurements of the condylar processes were obtained at a scale of 1:1 using the software Ez3D Viewer Plus. Analysis of variance (ANOVA) and the paired t-test were used, considering P<0.05. Patients with UCH presented statistical differences between the hyperplastic condyle and non-hyperplastic condyle for anteroposterior and mediolateral diameters, condylar neck length, and ramus height. Patients with a class III skeletal relationship showed no differences between the right and left sides; the morphology of their condyles was similar to the condyles with hyperplasia and presented statistical differences when compared with the non-hyperplastic condyles (one-way ANOVA, P<0.05). The condylar morphology of UCH patients could be related to the development of a class III skeletal relationship. These findings provide an insight into the possibility of some class III patients presenting bilateral condylar hyperplasia.

Concepts: Statistical tests, Statistics, Variance, Normal distribution, Analysis of variance, Oral and maxillofacial surgery, F-test, Levene's test


There is controversy about the anti- or pro-oxidative effects of the nitric oxide (NO)-donor sodium nitroprusside (SNP). Hence, the activity of the antioxidant enzyme catalase (CAT) and the status of malondialdehyde (MDA) were investigated after a 2.5 mg/kg dose of SNP had been i.p. administered to different and comparable groups of mice (n =  48). The drug was administered at two different circadian times (1 and 13 h after light onset [HALO]). There were, irrespectively of sampling time, no significant differences in the means of CAT activity and MDA status between control and SNP-treated groups, no matter the treatment time. However, CAT activity was significantly (Student’s t-test, p < 0.001) increased 1 h following SNP administration at 1 HALO, whereas the significant (p < 0.001) increase in the enzyme activity was found only 3 h after injection at 13 HALO. The drug dosing either at 1 or 13 HALO resulted in no significant differences of MDA status between control and treated groups regardless to the sampling time. Two-way analysis of variance (ANOVA) detected a significant (F0.05(7,88)= 5.3; p < 0.0006) interaction between sampling time and treatment in mice injected at 1 HALO, suggesting the influence of treatment on sampling-time-related changes in CAT activity. However, ANOVA validated no interaction between the two factors in mice treated at 13 HALO, illustrating that the sampling-time differences in enzyme activity were greater. Furthermore, two-way ANOVA revealed no interaction in the variation of MDA status in animals treated either at 1 or 13 HALO. This study indicates that SNP significantly affected the anti-oxidant system.

Concepts: Statistics, Enzyme, Variance, Normal distribution, Analysis of variance, Catalase, F-test, Levene's test


In this study, Nostoc muscorum, a native cyanobacterial species isolated from a coal mining site, was employed to remove Cu(II), Zn(II), Pb(II) and Cd(II) from aqueous solution containing these metals in the mixture. In this multicomponent study, carried out as per the statistically valid Plackett-Burman design of experiments, the results revealed a maximum removal of both Pb(II) (96.3 %) and Cu(II) (96.42 %) followed by Cd(II) (80.04 %) and Zn(II) (71.3 %) at the end of the 60-h culture period. Further, the removal of these metals was attributed to both passive biosorption and accumulation by the actively growing N. muscorum biomass. Besides, the specific removal rate of these metals by N. muscorum was negatively correlated to its specific growth rate. For a better understanding of the effect of these metals on each other’s removal by the cyanobacteria, the results were statistically analyzed in the form of analysis of variance (ANOVA) and Student’s t test. ANOVA of the metal bioremoval revealed that the main (individual) effect due to the metals was highly significant (P value <0.05) on each other's removal. Student's t test results revealed that both Zn(II) and Pb(II) strongly inhibited both Cu(II) removal (P value <0.01) and Cd(II) removal (P value <0.02). All these results not only demonstrated a very good potential of the cyanobacteria in the bioremoval of these metals but also the effect of individual metals on each other's removal in the multicomponent system.

Concepts: Cyanobacteria, Statistics, Student's t-test, Normal distribution, Analysis of variance, Heavy metal music, F-test, Levene's test


Abstract Objectives: To compare two-dimensional with three-dimensional ultrasound evaluation of the fetal nasal bone in the second trimester. Methods: A prospective, non-interventional study was conducted, in 55 singleton fetuses, between 18 and 24 weeks' gestation. Fetal nasal bone length was measured in the midsagittal plane by two-dimensional imaging and in the midsagittal and coronal plane with three-dimensional ultrasound. All three measurements were compared to one another using one-way repeated samples-measures ANOVA and paired samples t-test. Results: The average fetal nasal bone length (mean ± SD) as determined by the three methods was 7.01±0.94 mm for the two-dimensional-midsagittal, 6.96±1.34 mm for the three-dimensional-midsagittal and 6.98±1.32 mm for the three-dimensional-coronal plane; comparisons between one another were not statistically significant. Unilateral hypoplasia and bifid shape of the fetal nasal bone were detected in 8.2% and 20.4% of cases, respectively, by three-dimensional ultrasound, whereas all cases evaded detection with two-dimensional-ultrasound (p<0.001 and p = 0.001, respectively). Conclusions: Fetal nasal bone length measured with two-dimensional-ultrasound does not differ significantly from three-dimensional-measurements. However, three-dimensional-ultrasound is superior in detecting unilateral nasal bone hypoplasia or absence and in assessing fetal nasal bone shape. Hence, fetal nasal bone examination in the second trimester should include three-dimensional-ultrasound evaluation.

Concepts: Statistics, Student's t-test, Normal distribution, Coronal plane, F-test, Levene's test


SUMMARY Purpose : The aim of this study was to investigate the staining behavior of demineralized enamel infiltrated by low-viscosity resin. Methods and Materials : Bovine enamel/dentin cylindrical samples (3 × 2 mm) were assigned into four groups (n=45) according to the enamel treatment: sound enamel (control), demineralization + artificial saliva, demineralization + daily application of 0.05% NaF, demineralization + resin infiltration (Icon, DMG). Artificial white spot lesions were produced in groups with demineralization. After the treatments, color was assessed by spectrophotometry, using the CIE L*a*b* system. The specimens (n=15) were then immersed in deionized water, red wine, or coffee for 10 minutes daily for eight days. Color was measured again, and the specimens were repolished with sandpaper discs. The final color was assessed. Data were analyzed by two-way analysis of variance and Tukey tests (α=0.05). A paired t-test was used for comparison between staining and repolishing conditions. Results : There were significant differences for surface treatment and dye after staining and repolishing. Immersion in wine and coffee resulted in significantly increased color alteration (ΔE) compared with water (p=0.001). The resin-infiltrated group exhibited the highest staining values (p=0.001). The repolishing procedures resulted in significantly decreased color change. Conclusion : The exposure of specimens to colored solutions resulted in significant color alteration. The demineralized enamel treated with resin infiltration showed significantly higher staining than all other tested groups; however, the repolishing of the specimens minimized the staining effect.

Concepts: Color, Normal distribution, RGB color model, Color space, CIE 1931 color space, F-test, Lab color space, Levene's test