Remediation of Toxic Metal Contaminated Sediment Using Three Types of nZVI Supported Materials.

Due to nZVI effectiveness in the removal of toxic metals as well as low-cost regarding its production, kaolinite, bentonite and carboxymethyl cellulose supported nZVI were chosen for in-situ remediation of river sediment. Small-scale laboratory studies have shown that the percentage of removed metal (Ni, Zn and Pb) ranged up to 80% depending on the nanomaterial used. The metal mobility in sediments was investigated using single extraction, which is proved to be better for quick estimation of metal mobility, and for highly contaminated sites both single and sequential extraction needs to be used. Risk assessment code indicated medium risk for Ni and high risk for Pb and Zn in untreated sediment. In-situ treatment in laboratory proved to be very effective, providing the choice of optimal doses of three different nanomaterials used towards the concentration of toxic metals in the sediment.

Removal of Ni(II) and Cu(II) from aqueous solutions using 'green' zero-valent iron nanoparticles produced by oak and mulberry leaf extracts.

The production of zero-valent iron nanoparticles, using extracts from natural products, represents a green and environmentally friendly method. Synthesis of 'green' zero-valent nanoparticles (nZVI) using oak and mulberry leaf extracts (OL-nZVI and ML-nZVI) proved to be a promising approach for Ni(II) and Cu(II) removal from aqueous solutions. Characterization of the produced green nZVI materials had been conducted previously and confirmed the formation of nanosize zero-valent iron particles within the size range of 10-30 nm, spherical with minimum agglomeration observed by transmission electron microscopy and scanning electron microscope morphology measurements. Batch experiments revealed that the adsorption kinetics followed a pseudo-second-order rate equation. The obtained adsorption isotherm data could be well described by the Freundlich model and OL-nZVI showed higher adsorption capacity for Ni(II) removal than ML-nZVI, while ML-nZVI adsorption capacity was higher for Cu(II). In addition, investigation of the pH effect showed that varying the initial pH value had a great effect on Ni(II) and Cu(II) removal. Adsorbed amounts of Ni(II) and Cu(II) increased with pH increase to pH 7.0 and 8.0. This study indicated that nZVI produced by a low-cost and non-toxic method with oak and mulberry leaf extracts could be used as a new material for remediation of water matrices contaminated with Ni(II) and Cu(II).

Changes in metal availability during sediment oxidation and the correlation with the immobilization potential.

Fractionation of metals (Pb, Cd, Ni, Zn, Cu and Cr) in severely contaminated sediment has been investigated to determine its speciation and eco-toxic potential at the beginning of the experiment and after 18 months of sediment oxidation. Pb, Ni and Zn showed a high risk, while Cu, Cd and Cr showed low to medium risk at the beginning. Oxidation yielded an increased mobility of all metals apart from cadmium. The ratio of the simultaneously extracted metals (SEM) and acid volatile sulfides (AVS) was found to be >1. Semi-dynamic and toxicity characteristic leaching tests were conducted to assess the effectiveness of solidification/stabilization (S/S) thermal treatment with clay and long-term leaching behavior of these metals. A diffusion-based model was used to elucidate the controlling leaching mechanisms. Applied S/S thermal treatment was effective in immobilizing metals, irrespective of their different availability in the untreated samples. The controlling leaching mechanism appeared to be diffusion.

A comparison of sediment quality results with acid volatile sulfide (AVS) and simultaneously extracted metals (SEM) ratio in Vojvodina (Serbia) sediments.

The acid-volatile sulfide (AVS), simultaneously extracted metals (SEM), total metals, and pore-water metal concentrations were studied in Vojvodina (Serbia) sediments. In Serbia, there are no regulations concerning sediment quality standards and sediment management. Harmonization of legislation in the domain of environmental protection with EU requirements will increase the significance of the sediment issue. Sediment quality was assessed according to Dutch standards, but the results were also compared with Canadian and USEPA (United States Environmental Protection Agency) guidelines for sediment quality. A comparison of the results based on different criteria for sediment quality assessment shows that they are sometimes contradictory. Therefore, a single approach to quality assessment may be insufficient. The Sigma[SEM]/[AVS] ratio was found to be greater than one at several locations that were already recognized as places of high risk based on Dutch standards. Some other samples had Sigma[SEM]/[AVS]<1, despite of the high risk classification based on the Dutch evaluation. However, not all sediments with Sigma[SEM]/[AVS]>1 can cause increased toxicity because there are many other metal-binding phases in sediments. Metals that are associated with AVS may be released within sediments through storms, dredging activities, oxidation, etc., and may have adverse environmental impacts. This has to be taken into account during dredging, which is for some sediments necessary because the sediment is of class 4 (Dutch evaluation), because the dredging process will certainly increase the concentration of bioavailable heavy metals and disturb the sedimentation dynamics. The obtained results will be invaluable for future activities regarding dredging and sediment management in the country.

Pollution of the Begej Canal sediment--metals, radioactivity and toxicity assessment.

The Begej Canal is one among a large number of canals in Vojvodina (Northern Province of Serbia and Montenegro). The paper describes a study of metal and radioactivity contamination of the Begej Canal sediment. It is also concerned with the evaluation of sediment acute toxicity based on standard test species Daphnia magna and simultaneously extracted metals and acid volatile sulfides. The quality of sediment was assessed according to Dutch standards, but the results were also compared with some Canadian and USEPA (United States Environmental Protection Agency) guidelines for sediment quality. The results showed severe pollution with chromium, copper, cadmium and zinc, whereby the anthropogenic origin of these contaminants was indicated. The tests of toxicity of sediment pore water to D. magna, gave no indication of the presence of substances in acutely toxic concentrations to this species. It can be speculated that, despite of high metal contents, the observed toxicity was low because of the high contents of clay and iron, as well as sulphide. Also, based on a comparison with the Danube sediment and Vojvodina soil in general, the data of the Begej sediment contamination with 238U and 137Cs. The 137Cs data were used for approximate dating of the sediment. No traces of contamination by nuclear power plants in the region were found, while the presence of technologically enhanced naturally occurring radioactive materials (TENORM) was proved. Conclusions based on different criteria for sediment quality assessment were in some cases contradictory. Study also showed that radioactivity aspects can be useful in sediment quality surveys. The obtained results will be invaluable for the future activities regarding integrated water management based on EC Water Framework Directive (2000/60/EC) in the Danube basin, and particularly in the region of crossborder water body of the Begej Canal.

The Frialit-2 implant system: five-year clinical experience in single-tooth and immediately postextraction applications.

In an observational study of 696 Frialit-2 implants in 376 patients that was carried out between 1990 and 1995, implants of varying diameters and lengths were delivered for a range of indications in the maxilla and mandible. Single-tooth replacement was performed in 42% of cases; of these, 22.4% were placed immediately following extraction. Study parameters (Plaque Index, Gingival Index, probing depth, Periotest value, and peri-implant bone loss) are reported in detail. Statistical analysis is based on a 97.6% rate of recall. The overall success rate was found to be 96% using the Kaplan-Meier statistical analysis. No difference was apparent between single-tooth applications and prosthesis restorations.

Regression coefficient analysis of neutrophil chemotaxis in periodontitis.

Micropore-filter techniques have been widely used to assess motility and chemotaxis of neutrophils. In some cases the results were impaired by inadequate methods of evaluation and failures of the test system. For clinical purposes the mode of test evaluation should be able to differentiate between failures of the test system (false-negative) and real functional defects (true-negative). A new method has been developed to check parallel assays for homogeneity. Based on earlier procedures this type of evaluation uses the comparison of regression coefficients to identify false-negative test results within the cell population of an individual. The newly developed method was used to study the chemotactic response in a group of 49 patients and 22 healthy volunteers. Intraclass correlation coefficients of the regression coefficient analysis and the leukotactic index were calculated and compared. It could be demonstrated that the regression coefficient analysis had the same sensitivity as the leukotactic index. Slight variations in the cell counts at a single plane of the chemotactic filter affecting the leukotactic index by 18% had no measurable influence on the calculated regression coefficient.

Caries risk analysis: considering caries as an individual time-dependent process.

AIM: To estimate the probability that a tooth does not develop a cavitated lesion (= end-stage caries) within time periods of interest. Additionally it was of interest to assess the heterogeneity between patients, in relation to the time periods required for their teeth to develop a cavitated lesion. DESIGN: A prospective study using patient data of a clinical pedodontic course. SAMPLE AND METHODS: Forty-one patients who had been followed for at least 3 years were selected. Before initiation of therapy, affiliation to a specific risk group was checked. Nine individuals who had belonged to a high-risk group on test were excluded. Of 1968 teeth, 1378 were eligible for data evaluation. The statistical techniques applied originate from time-to-event analysis methods, including a parametric frailty approach providing estimates of the relative caries risk for each individual to develop a cavitated lesion. RESULTS: In the selected group of patients the probability that a tooth remained free of a cavitated lesion within five years ranged from 0.89 to 0.95 applying a 95% confidence interval. In the present sample the true caries risk of the patients to develop a cavitated lesion varied considerably although such variation was not expected from the individual examinations at baseline. CONCLUSION: The frailty model accounts sufficiently for the heterogeneity of each patient. The applied time-to-event methods facilitated reliable estimation of both the probability that a tooth remains free of a cavitated lesion within a certain time and the relative caries risk of an individual to develop a cavitated lesion.

Effect of occlusal wear on bone loss and Periotest value of dental implants.

PURPOSE: Occlusal overload may contribute to the loss of osseointegration of oral implants, so some clinicians are reluctant to place implants in patients with signs of bruxism. This study evaluated the effect of occlusal wear as a probable sign of bruxism on bone loss and implant stability. MATERIALS AND METHODS: The study investigated 379 patients who had worn implant-retained or implant-supported restorations for many years. Occlusal wear, patient age and gender, time of prosthetic loading, jaw, location in the dental arch, implant diameter, prosthesis construction, occlusal material, periimplantitis, and loosening of the prosthetic construction were recorded. One implant from each patient was selected for radiographic and Periotest measurements. The implant with the highest bone resorption was chosen. A forward stepwise multiple linear regression analysis was performed to analyze the effect of the explanatory variables on Periotest value and radiographic bone loss. RESULTS: The statistical models could account for part of the variation in bone loss rate and Periotest value. Some influence of time of loading, jaw, and implant diameter on bone loss or Periotest value was formally established. Occlusal wear failed to have any statistical impact on vertical annual bone loss rate or Periotest value. CONCLUSION: This study gave no indication that implants in patients with occlusal wear have an increased bone loss rate or Periotest value.

The prevalence of radiologic TMJ findings and self-reported orofacial pain in a patient group wearing implant dentures.

PURPOSE: This study had a twofold aim: first, to gather knowledge about the prevalence of radiologic signs of temporomandibular joint osteoarthritis (TMJ-OA) and possible risk factors in patients who had worn an implant prosthesis for between 2.5 and 10 years; and second, to investigate the diagnostic value of radiologic TMJ-OA signs for orofacial pain in a non-temporomandibular disorders group. MATERIALS AND METHODS: Two hundred thirty patients (134 women, 96 men) answered a questionnaire regarding orofacial pain. In mean, they were 64 years old and wore 98 fixed and 132 removable implant dentures. The effect of age, gender, state of the dentition, time span after prosthesis placement, parafunction, and TMJ sounds on radiologic TMJ-OA signs was estimated through multiple logistic regression. The predictive values were calculated to assess the diagnostic value of severe TMJ-OA signs to predict orofacial pain. RESULTS: Prevalence of TMJ-OA signs was 70% for flattening, 23% for osteophytes, and 24% for erosion. Some effect on radiologic TMJ-OA signs of gender and state of the dentition was found. The predictive values for orofacial pain from radiologic TMJ-OA ranged from 0.22 to 0.81. CONCLUSION: Radiologic signs of TMJ-OA were common findings. The study gave no indication that long-term wearing of an implant prosthesis has a negative effect on TMJ-OA. It was not possible to predict orofacial pain from radiologic TMJ-OA signs.

Prognosis of conventional root canal treatment reconsidered.

In endodontic literature, the so-called success rate of conventional root canal treatment is reported to range between 70% and 95%. This has been calculated as the percentage of successfully treated teeth of all teeth followed up or included in the clinical trial. This approach, however, does not allow for valid assertions on the prognosis of root canal treatment as the individual observation times are not considered. This article discusses some methodological and statistical aspects of how to design a prognostic study which focuses on the outcome of endodontic therapy and of how to analyse the data appropriately. Methodologically, the response variable should preferably be the individual time required for the occurrence of an event, e.g., success or failure of endodontic therapy, which should clearly be defined on the basis of widely accepted criteria in endodontology. Event times can appropriately be analysed by the Kaplan-Meier method, which estimates the probability that the event will not occur within a fixed time. This probability, together with the approximate 95% confidence interval (CI), permits an evaluation of the prognosis of a particular treatment. Two data sets were re-analysed to clarify the rationale behind the analysis of event times. Accordingly, the probability that an endodontically induced lesion will completely heal, e.g., within the first 3 years after root canal therapy ranges between 0.87 (CI: 0.74-1.00) and 0.89 (CI: 0.80-0.98). In this situation, the simple calculation of success rates would overestimate the chance of complete periapical healing within the first years after therapy but underestimate it over longer observation periods. Another example was used to analyse the time to occurrence of periapical pathosis associated with root canal treated teeth not diseased periapically. In this case the chance of recording a successful endodontic treatment is initially underestimated by the percentage of successful cases of all teeth integrated in the study but is markedly overestimated for longer observation periods. Potential risk factors affecting the outcome of the endodontic therapy and thereby the event times can adequately be determined by applying the Cox's or Aalen's regression model.

Intra-oral storage phosphor and conventional radiography in the assessment of alveolar bone structures.

OBJECTIVES: To compare storage phosphor (SP) with conventional film radiography for accuracy of linear measurements of the marginal alveolar bone and visibility of anatomical structures. METHODS: Linear measurements were made in paired SP and conventional images of dried human mandibles with a metal pin fixed 10 mm below the alveolar crest. One observer measured the distance from the alveolar crest to the reference point on the radiographs. The difference between the measured and the true distance was calculated. Two observers rated the visibility of bony structures (periodontal ligament space, periapical bone tissue, alveolar crest) in 51 paired digital and conventional images of 21 patients on a 3-point scale. Overall agreement and Kappa index were calculated. RESULTS: Accuracy of linear measurements was higher in digital radiography (mean difference 0.17 mm) than in conventional radiography (mean difference 0.59 mm). Overall, the two observers rated visibility higher in conventional radiographs. The Kappa indices for the periodontal ligament space and periapical bone indicated fair to almost perfect agreement (kappa = 0.38 and 0.5; kappa = 0.39 and 0.84) while for the alveolar crest there was only poor or moderate agreement (kappa = 0.2 and 0.5). CONCLUSIONS: The small differences in linear measurements indicate that the Digora system is suitable for clinical assessment of periodontal and peri-implant bone loss. The visibility of dental structures depends as much on the individual features assessed, as the radiographic system.

A clinical evaluation of some factors affecting image quality in panoramic radiography.

AIM: To evaluate the suitability of panoramic radiographs obtained with two different machines for clinical use. MATERIAL AND METHODS: Three observers assessed 111 pairs of panoramic radiographs taken with the Scanora (Soredex, Orion Corp., Helsinki, Finland) programme 001, and the Orthophos Plus (Sirona, Bensheim, Germany), programme P1 respectively, for visualisation of seven anatomical structures on each side, on a 5-point scale where 1 = very good. The median values were computed and a descriptive analysis performed. Interrater and intrarater agreement were expressed as weighted kappa. RESULTS: The median values of both Scanora and Orthophos radiographs were the same, scoring 2. The intra- and inter-observer agreement was generally poor and similar for both machines. CONCLUSIONS: The two panoramic machines were both given good ratings for evaluation of anatomical structures. The differences were very small and suggest that both machines are suitable for clinical use.

[Maximal force measurements of lip and tongue pressures and their significance for the diagnosis of orofacial dyskinesias]. / Maximalkraftmessungen des Lippen- und Zungendrucks und ihre Bedeutung für die klinische Diagnostik orofazialer Dyskinesien.

The functioning of the orofacial muscular system essentially determines the shape of the jaw and of the dental arch as well as the position of the axis of the anterior teeth. Disturbances of the normal functioning can cause anomalies of the position of teeth or malformations of the bone structure. With the help of the newly developed device "Myometer 160" we now have the possibility to measure the intra- and extraoral forces. We examined 107 persons aged 8 to 37 years. The maximal force was measured by ventral tongue pressure, when the lips were pressed against each other and when a brass button was pulled. In addition clinical results as well as a functional status were ascertained in order to record orofacial dyskinesias. A significant connection between the age respectively the sex of the persons and the determined force was found. However, no clear relationship between the occlusal position respectively the functional anomaly and the results of maximal force was determined. Thus it does not seem sensible to use maximal force measurement within the framework of the determined. Thus it does not seem sensible to use maximal force measurement within the framework of the diagnosis of orofacial dyskinesias.

Reliability of electromagnetic articulography recording during speaking sequences.

For the development of malocclusions and speech disorders, major aetiological significance is attributed to orofacial malfunctions, especially of the tongue. The position of the tongue to the alveolar arch and teeth, particularly within the area of the tip of the tongue, is of special interest for orthodontists. Electromagnetic articulography is a new technique used to examine tongue function and to record its movement in the midsagittal plane. The aim of the study was to determine whether this procedure offers suitable and reliable results. Thirty-one subjects aged 14.3-37.3 years had to repeat speaking sequences five times. The German syllables they had to repeat were /asa/, /ascha/, /ata/, /ala/, /ana/, /aka/. The tongue movements were registered with an 'Articulograph AG 100'. Distances, angles and encircled planes were evaluated, and the proportion of intra-individual to overall variability was calculated in order to check the reliability of the courses of movement. Angles and distances especially showed, depending on the position of the receiver coils, strong reliability during speaking sequences, whereas area produced unfavourable results. The analysis of long trajectories and angles appeared favourable in order to describe the courses of movement. This required, however, a systematic assessment of functional movement with electromagnetic articulography.

Vital microorganisms in early supragingival dental plaque and in stimulated human saliva.

The aim of this study was to compare the percentage of vital microorganisms (= microbial vitality) of saliva with that of supragingival plaque both collected at various times during the early phases of de novo plaque formation. Between intervals of optimal oral hygiene, 14 healthy participants refrained from all oral hygiene measures for periods of 1, 4, 8 and 72 h. Stimulated whole saliva was collected at the beginning (= baseline) and the end of each period. Vestibular plaque was removed from teeth 13-16, and 23-26. Analysis of the pooled plaque (p) and saliva (s) samples comprised the total number of bacterial counts and colony-forming units to estimate the percentage of viable microorganisms (PEp; PEs). The microbial vitality (VFp; VFs) was determined by using a fluorescence staining to differentiate vital from dead bacterial cells. The bulk of the PEs values reached 5-30%. At baseline VFs ranged between 70% and 90%. The VFs values recorded at baseline or in the presence of 1 h and 4 h-old plaque, were significantly (alpha = 0.05) higher than the corresponding VFp values ranging from 5% to 30%. It was concluded that there is a considerable discrepancy between the microbial vitality of a very early dental plaque and that of whole surrounding saliva sampled at the same time. Unfavourable local environmental conditions prevailing at cervical tooth surfaces are suggested to restrain the survival of the majority of the first bacteria adhering to a particular tooth area during the early phases of supragingival plaque formation.