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Biomedical subjects

G Rippen

Publications and source records attributed to G Rippen.

8 recordsLinked to original sources
PubMed2001

Periodontal probing in comparison to diagnosis by CT-scan.

AIM: To compare clinical periodontal probing and the corresponding CT-evaluation of the loss of bone. METHOD: 639 measurement sites were studied on 95 periodontal sites. The measured length was the distance between the cemento-enamel junction (CEJ) and the pocket base on probing and the bone base of the pocket on the CT-analysis. Additionally, a comparison of the diagnostic potential of both methods regarding the furcation involvement was made. RESULTS: Clinical probing depths showed a mean value of 2.6+/-2.0 mm, while the CT-measurements exhibited a figure of 4.2+/-2.3 mm. In 49.5% of the measured sites, the difference between clinical and CT-measurement was 2mm or higher. The greatest differences between the measured values were found on the buccal and lingual sites (P=0.0004). The narrower the vertical bone defects in the CT (angle in coronal direction), the greater were the differences between the clinical probing depths and the measurements carried out on the CT (P=0.02). Clinically, in 31% of the cases the furcation involvement was underestimated or not identified at all. CONCLUSION: Computed tomography imaging techniques could be beneficial in the field of periodontal diagnosis. The results underscore the higher accuracy of the CT-technique, compared with clinical probing, while assessing periodontal breakdown and its marked superiority in the diagnosis of furcation areas, compared to the clinical examinations performed.

Alveolar Bone Loss↗
PubMed1986

Estimation of hexachlorobenzene pathways from the technosphere into the environment.

Since there are many different pathways from the technosphere to the environment, hexachlorobenzene (HCB) is widely distributed, supported by high mobility and high persistence. Several different assumptions were made about HCB inputs to air or water and, by simple calculations, potential HCB concentrations in water, air, sewage sludge and sediment were estimated. By comparing the results with measured environmental concentrations, maximum amounts of HCB released into the environment were estimated, and the relative importance of the water and air pathways appraised. Results showed that of the total HCB produced, the fraction that is released into the environment is substantially smaller than has been estimated. Despite the estimates of world-wide annual input of 10-100 t, it is well known that HCB is detected in relatively large amounts in most living tissues. This emphasizes the importance of the persistence of HCB, and of other environmental chemicals.

Air Pollutants↗
PubMed1984

The Environmental Model Segment Approach for estimating potential environmental concentrations. I. The model.

Global distribution models which can be used for evaluating the environmental impact of persistent chemicals are not well suited to assess the environmental impact of less persistent substances; this is due to the fact that the environmental effects caused by the latter substances--if there are any--are only local or regional (close to the emission source), but not ubiquitous. As a tool for estimating potential regional exposure concentrations, the Environmental Model Segment Approach (EMSA) is presented. This model yields information about possible concentrations in reasonable worst-case situations.

Air Pollutants↗
PubMed1984

The Environmental Model Segment Approach for estimating potential environmental concentrations. II. Application of the model to p-dichlorobenzene and trichloroethene.

The Environmental Model Segment Approach introduced in Part I (R. Frische, W. Klöpffer, G. Rippen, and K. O. Günther, 1984, Ecotoxicol. Environ. Safety 8, 352-362) is applied to estimate potential environmental concentrations of p-dichlorobenzene and trichloroethene. Environmental concentrations of these chemicals can be estimated only with difficulty by other models because of many diffuse emission sources emitting mainly into the air. By comparison of the estimated with the measured environmental concentrations it is found that the claim of the model to yield values which apply to reasonable unfavorable environmental boundary conditions is satisfied for the medium air and for the biota (fish). Soil concentrations calculated by means of the model, assuming equilibrium with high air concentrations, are higher than the measured ones, while the calculated water concentrations are lower than the values often measured for river waters. The latter fact may be attributed to direct input of the substances into water which is not being taken into account.

Air Pollutants↗
PubMed1982

A laboratory method for testing the volatility from aqueous solution: first results and comparison with theory.

The mobility of a chemical in the environment is often determined by its volatilization from aqueous solution, especially if it shows poor water solubility and/or high vapor pressure. A small laboratory apparatus is described which allows the simulation of the volatilization process from a stirred water body with well-defined wind velocities and water temperatures. In experiments with naphthalene, pentachlorophenol, trichloroethene, and di(2-ethylhexyl)phthalate, substance concentrations in the water body decrease exponentially, in accordance with theory. Half-residence times are found to be independent of wind velocity (v less than 1 m sec-1) or air humidity, but are strongly dependent on temperature. The measured substance fluxes through the water surface are comparable with theoretical values. In the case of pentachlorophenol, which partly dissociates in aqueous solution, the volatility is controlled by the pH value of the solution.

Diethylhexyl Phthalate↗
PubMed1981

[Pharmacokinetics of clonidine and chlorthalidone following subacute administration of a fixed combination compared with a sustained release formulation of clonidine alone (author's transl)].

Clonidine concentrations in urines and blood plasma samples analysed by RIA were observed over a period of 240 h in 6 male, healthy, normotensive volunteers being treated for 7 days with sustained-release formulations of 2-(2,6-dichloroanilino)-2-imidazoline (clonidine, Catapresan) alone (0.15 mg/d) and subsequently with a combination containing 0.15 mg clonidine plus 15 mg chlorthalidone. Chlorthalidone was determined in blood samples using a newly developed massfragmentographic method. The trials revealed: 1. There is no influence of chlorthalidone on the pharmacokinetics of clonidine. 2. the steady-state levels of the plasma or blood concentrations being reached on the 2nd (clonidine) and on the 5th day (chlorthalidone) were adjusted subsequently in therapeutically relevant ranges ranging between minima and maxima of 0.2 and 0.6 ng/ml (clonidine) and between 2.4 and 2.6 microgram/ml (chlorthalidone) respectively. From pharmacokinetic aspects therefore a fixed combination of two synergistic antihypertensive agents can be considered as useful. 3. Following 7 administrations of either clonidine formulation 63% of the total clonidine doses were excreted renally.

Adult↗