Given a passage, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.

Q: Few studies investigated the best method for removing stains from different types of resin-based composite restorations and compared them to the more recently introduced nanocomposites. This study compared the effect of four methods for stain removal from composite resins; finishing with Sof-lex disks, using pumice and brush, bleaching with 10% carbamide peroxide and 38% hydrogen peroxide.', 'Twenty disk specimens were prepared. Specimens were immersed in a staining solution for 3\xa0weeks. The stained surfaces of five specimens from each RBC material were treated with one of the treatment procedures. Colorimetric measurements were taken using spectrophotometer prior to and after staining, and then repeated after surface treatments. Color difference values were calculated.', "One-way ANOVA indicated significant differences in color change of the three composite resin materials following staining. Filtek Z250 showed the least susceptibility to discoloration followed by Renamel, Filtek Supreme was the material most prone to discoloration. Two-way ANOVA and Tukey's Post Hoc showed that all stain removing procedures except polishing with pumice, were able to return Filtek Z250 to clinically acceptable color difference. While bleaching with 38% carbamide peroxide was not effective with Renamel. Only pumice and 10% carbamide peroxide were able to return Renamel to clinically acceptable color difference.

A: Do the effectiveness of four methods for stain removal from direct resin-based composite restorative materials?
****
Q: The objective in lung transplantation is to prolong life, but the survival effect in patients with chronic obstructive pulmonary disease (COPD) or alpha1-anti-trypsin deficiency emphysema is still unresolved. This study assesses the impact of diagnosis, single-lung transplantation (SLT) vs bilateral lung transplantation (BLT) and timing of transplantation on survival in a national cohort.', 'In 219 consecutive patients accepted onto the lung transplantation waiting list in Norway, 1990 to 2003, we assessed predictors of death: (1) on the waiting list; (2) <or=90 days after transplantation; and (3) >90 days after transplantation. For each period we used Cox regression, including age, gender, diagnosis, baseline pulmonary function tests, cardiac catheterization data, exercise capacity and transplant type, as potential predictors. Survival benefit was assessed graphically by combining adjusted survival curves after transplantation with the curve for those waiting, modeling transplantation after 6, 12 or 24 months.', 'Mean patient age was 49 years (SD 10), with 55% women. High forced expiratory volume in 1 second (FEV(1)) percentage predicted death on the waiting list. Diagnoses other than COPD/emphysema and receiving SLT were associated with death <or=90 days after transplantation. Only low forced vital capacity (FVC) percentage predicted death >90 days after transplantation. In COPD/emphysema, there was no clear survival benefit from BLT or SLT. For patients in the "Other" group, the data suggest a survival benefit from BLT.

A: Is lung transplantation in patients with chronic obstructive pulmonary disease in a national cohort without obvious survival benefit?
****
Q: Genetic polymorphisms that modify the detoxifying activity of glutathione S-transferases (GSTs) can affect the level of carcinogenic metabolites created by endogenous steroid hormones and exogenous chemical substances. Although the GSTM1 null genotype has been shown to increase prostate cancer mortality in Caucasians, potential associations between GST polymorphisms and prostate cancer biochemical recurrence (BCR) have not been well studied, particularly in African-Americans.', 'We examined potential associations between the GSTM1 null, GSTT1 null and GSTP1 Ile105Val polymorphisms and BCR, after prostatectomy, in 168 African-American and 226 Caucasian patients treated at Henry Ford Hospital in Detroit, Michigan using Cox proportional hazards modeling.', 'We found that African-Americans with the GSTT1 null genotype had increased BCR risk compared to those having GSTT1 present (hazard ratio (HR) = 2.30; 95% CI = 1.01–5.18; p = 0.04); and African-Americans with the GSTT1 null genotype and high grade tumors had an even greater risk (HR = 7.82; 95% CI = 2.49–24.50; p < 0.001). In Caucasians, an increased risk was observed in those patients with high grade tumors and the GSTM1 null genotype (HR = 2.88; 95% CI = 1.16–7.14; p = 0.02). Similar associations were observed for advanced stage and more aggressive (high grade or advanced stage) disease.

A:
Do polymorphisms in glutathione S-transferase genes increase risk of prostate cancer biochemical recurrence differentially by ethnicity and disease severity?
****