The use of zeolite-based geopolymers as adsorbent for copper removal from aqueous media.

Copper has been proven to have hazardous effects on human beings depending on its concentration levels. Recently, there has been a growing interest in developing geopolymers using local industrial minerals and by-products. However, research on the adsorption of heavy metals by geopolymer based on mordenite-rich tuffs is still limited. The geopolymer adsorbents have been synthesized using natural Ecuadorian zeolite-rich tuffs containing quartz, mordenite calcite and amorphous content with 20.8%, 28.5%, 4.2% and 46.4%, respectively. The geopolymers showed a maximum compressive strength of 26.86 MPa for 28 d of curing time. In the present study, an Ecuadorian zeolite-based geopolymer's removal capacity on copper ions in aqueous solutions, varying concentration and contact time were tested. Kinetic models were developed using pseudo first-order, pseudo second-order and the Elovich model. The adsorption data, using Cu2+ concentrations from 20 to 160 ppm, at 25°C were described by the Langmuir and Freundlich isotherms. Linear coefficient of determination (R 2) results show that the Langmuir model fits the best. The attained adsorption capacity of 52.63 mg g-1 demonstrates the low-cost geopolymer's effectiveness for this study and its competitiveness compared with other studies. Adsorption kinetics follows the pseudo second-order kinetics model at the lower initial concentration of Cu2+.

A new standardized-automatic method for bone-to-implant contact histomorphometric analysis based on backscattered scanning electron microscopy images.

AIM: To establish an image analysis procedure for measuring the bone-to-implant contact (BIC) by a systematic non-subjective approach based on backscattered scanning electron microscopy (BS-SEM) images. MATERIAL AND METHODS: A total of 36 dental implants (9 mm length, Ø 4.0 mm with a SBM surface) were implanted in six beagle dog mandibles. The implants were removed after 1, 2, 4, 6, and 8 weeks and then embedded in resin and cut along their long axis. Sample observation was performed by BS-SEM, acquiring 10 to 16 images per sample. Image processing and BIC determination were performed using the Fiji image processing package. Images were stitched, filtered, and thresholded to obtain a binary image of the whole implant that finally was dilated and outlined. The length of this outline was measured as the maximum possible BIC. The regions of coincidence between this line and the bone were measured as the real BIC. RESULTS: The proposed methodology for BIC determination, based on SEM, which has a much higher resolution than optical microscopy, allows the acquisition of highly discriminative images with great contrast between implant and bone. The high resolution and high contrast in SEM images provide more accurate results than those obtained by classical methods. Furthermore, the methodology of image analysis described in this study delineates precisely and automatically the contour of the implant, which results in non-biased measurements. The average percentage of BIC was 35%, ranging from 24.7 to 45.5%. These values were similar to the results documented in the literature for implants of similar roughness in animal models. CONCLUSIONS: A novel, non-subjective, and systematic method for measuring BIC is described based on BS-SEM images. The proposed methodology minimizes the shortcomings of the results obtained by previously described methods.

Effects of smoking on periodontal tissues.

BACKGROUND/AIMS: Most studies about the association between tobacco and periodontal disease have shown that tobacco negatively affects periodontal tissues, although some authors have failed to demonstrate such association. Very few studies have tried to find out whether the effect of tobacco on periodontal tissues was similar for women and men. The aims of this investigation were to confirm the possible relationship between tobacco consumption and periodontitis, to study the correlation between intensity of smoking and disease severity, and to investigate any differences between genders related to the effects of tobacco consumption in periodontal health. MATERIAL AND METHODS: In this case-control study, 240 dental patients were selected according to previously defined criteria and were divided in two groups according to their periodontal status. Patients with established periodontitis constituted the case group. The remaining patients constituted the control group. Smoking status, probing depth, gingival recession, clinical attachment level, tooth mobility, periodontal bleeding index and plaque index were determined for each participant. Generated data were processed for statistical analysis using multiple comparisons, covariance analysis and logistic regression analysis. RESULTS: Logistic regression analysis showed that smokers had 2.7 times and former smokers 2.3 times greater probabilities to have established periodontal disease than non-smokers, independent of age, sex and plaque index. Among cases, probing depth, gingival recession and clinical attachment level were greater in smokers than in former smokers or non-smokers, whereas plaque index did not show differences. Bleeding on probing was less evident in smokers than in non-smokers. There was a dose-effect relationship between cigarette consumption and the probability of having advanced periodontal disease. The association between tobacco smoking and periodontal disease was more evident after 10 years of smoking, independent of age, gender and plaque index. Finally, it was observed that tobacco affected periodontal tissues more severely in men than in women. CONCLUSIONS: Smoking is a risk factor strongly associated with periodontitis. The effects of smoking on periodontal tissues depend on the number of cigarettes smoked daily and the duration of the habit. The effect of tobacco on periodontal tissues seems to be more pronounced in men than in women.