Correlation of wear in vivo and six laboratory wear methods.

OBJECTIVE: We examined the correlation between clinical wear rates of restorative materials and enamel (TRAC Research Foundation, Provo, USA) and the results of six laboratory test methods (ACTA, Alabama (generalized, localized), Ivoclar (vertical, volumetric), Munich, OHSU (abrasion, attrition), Zurich). METHODS: Individual clinical wear data were available from clinical trials that were conducted by TRAC Research Foundation (formerly CRA) together with general practitioners. For each of the n=28 materials (21 composite resins for intra-coronal restorations [20 direct and 1 indirect], 5 resin materials for crowns, 1 amalgam, enamel) a minimum of 30 restorations had been placed in posterior teeth, mainly molars. The recall intervals were up to 5 years with the majority of materials (n=27) being monitored, however, only for up to 2 years. For the laboratory data, the databases MEDLINE and IADR abstracts were searched for wear data on materials which were also clinically tested by TRAC Research Foundation. Only those data for which the same test parameters (e.g. number of cycles, loading force, type of antagonist) had been published were included in the study. A different quantity of data was available for each laboratory method: Ivoclar (n=22), Zurich (n=20), Alabama (n=17), OHSU and ACTA (n=12), Munich (n=7). The clinical results were summed up in an index and a linear mixed model was fitted to the log wear measurements including the following factors: material, time (0.5, 1, 2 and 3 years), tooth (premolar/molar) and gender (male/female) as fixed effects, and patient as random effect. Relative ranks were created for each material and method; the same was performed with the clinical results. RESULTS: The mean age of the subjects was 40 (±12) years. The materials had been mostly applied in molars (81%) and 95% of the intracoronal restorations were Class II restorations. The mean number of individual wear data per material was 25 (range 14-42). The mean coefficient of variation of clinical wear data was 53%. The only significant correlation was reached by OHSU (abrasion) with a Spearman r of 0.86 (p=0.001). Zurich, ACTA, Alabama generalized wear and Ivoclar (volume) had correlation coefficients between 0.3 and 0.4. For Zurich, Alabama generalized wear and Munich, the correlation coefficient improved if only composites for direct use were taken into consideration. The combination of different laboratory methods did not significantly improve the correlation. SIGNIFICANCE: The clinical wear of composite resins is mainly dependent on differences between patients and less on the differences between materials. Laboratory methods to test conventional resins for wear are therefore less important, especially since most of them do not reflect the clinical wear.

A highly sensitive LC-tandem MS assay for the measurement in plasma and in urine of salbutamol administered by nebulization during mechanical ventilation in healthy volunteers.

The new-generation nebulizers are commonly used for the administration of salbutamol in mechanically ventilated patients. The different modes of administration and new devices have not been compared. We developed a liquid chromatography-tandem mass spectrometry method for the determination of concentrations as low as 0.05 ng/mL of salbutamol, corresponding to the desired plasma concentration after inhalation. Salbutamol quantification was performed by reverse-phase HPLC. Analyte quantification was performed by electrospray ionization-triple quadrupole mass spectrometry using selected reaction monitoring detection ESI in the positive mode. The method was validated over concentrations ranging from 0.05 to 100 ng/mL in plasma and from 0.18 to 135 ng/mL in urine. The method is precise, with mean inter-day coefficient of variation (CV%) within 3.1-8.3% in plasma and 1.3-3.9% in urine, as well as accurate. The proposed method was found to reach the required sensitivity for the evaluation of different nebulizers as well as nebulization modes. The present assay was applied to examine whether salbutamol urine levels, normalized with the creatinine levels, correlated with the plasma concentrations. A suitable, convenient and noninvasive method of monitoring patients receiving salbutamol by mechanical ventilation could be implemented. Copyright © 2011 John Wiley & Sons, Ltd.

Skin permeation and metabolism of di(2-ethylhexyl) phthalate (DEHP).

Phthalates are suspected to be endocrine disruptors. Di(2-ethylhexyl) phthalate (DEHP) is assumed to have low dermal absorption; however, previous in vitro skin permeation studies have shown large permeation differences. Our aims were to determine DEHP permeation parameters and assess extent of skin DEHP metabolism among workers highly exposed to these lipophilic, low volatile substances. Surgically removed skin from patients undergoing abdominoplasty was immediately dermatomed (800 μm) and mounted on flow-through diffusion cells (1.77 cm(2)) operating at 32°C with cell culture media (aqueous solution) as the reservoir liquid. The cells were dosed either with neat DEHP or emulsified in aqueous solution (166 μg/ml). Samples were analysed by HPLC-MS/MS. DEHP permeated human viable skin only as the metabolite MEHP (100%) after 8h of exposure. Human skin was able to further oxidize MEHP to 5-oxo-MEHP. Neat DEHP applied to the skin hardly permeated skin while the aqueous solution readily permeated skin measured in both cases as concentration of MEHP in the receptor liquid. DEHP pass through human skin, detected as MEHP only when emulsified in aqueous solution, and to a far lesser degree when applied neat to the skin. Using results from older in vitro skin permeation studies with non-viable skin may underestimate skin exposures. Our results are in overall agreement with newer phthalate skin permeation studies.