Microradiographic study on the effects of salivary proteins on in vitro demineralization of bovine enamel

The aim of this investigation was to evaluate the effects of various proteins on in vitro demineralization of bovine enamel. From each of 100 bovine incisors two samples were prepared. The specimens were embedded in epoxy resin and polished up to 4000 grit. Subsequently, the specimens' surfaces were partly covered with nail varnish, thus serving as control of sound enamel. The specimens were divided randomly into five groups (n = 40) and demineralized in a solution of constant composition (pH 5.0; 10 days). For each subgroup of specimens (n = 10) 4 L were taken and either low (50% of medium conc.), medium, or high (150%) concentrations of the proteins [human albumin (100% conc. = 7 mg L(-1)), mucin (577.5 mg L(-1)), immunoglobulin G (IgG) (46 mg L(-1)), casein isolated from bovine milk (1.2 g L(-1))] or amino acid [l-Proline (7 mg L(-1))] were added to 1 L of the demineralizing solution, whereas 1 L served as control. Mineral loss and lesion depth (LD) were evaluated from microradiographs of thin sections (110 mum) by a dedicated software package (TMR 1.24). No differences were found between the five control groups (P > 0.05; ANOVA). Albumin, l-Proline, and IgG did not affect enamel demineralization, whereas the addition of both casein and mucin resulted in significant reductions of both mineral loss and LDs (P < 0.01; Tukey's test). Within the limitations of an in vitro study, the present investigation indicates that casein and mucin seem to affect enamel demineralization significantly. Thus, these proteins might be helpful as an additive to saliva substitutes or mouthwashes if the quality of saliva is altered.

Initial in situ secondary caries formation: effect of various fluoride-containing restorative materials

This study evaluated the effects of various restorative materials (Ariston pHc; Dyract; Vitremer; Tetric Ceram; Compoglass F, F2000; Hytac and Ketac Molar) on initial secondary caries formation in situ. Eighty-eight enamel slabs from sound human molars were sterilized (ethylene dioxide) and embedded in epoxy resin. Standardized tooth preparations were filled with the various restorative materials according to manufacturers' recommendations. One specimen from each group was inserted into one of two buccal aspects of an intraoral appliance worn by 11 volunteers for four weeks, day and night. Oral hygiene was performed without additional fluoride application. During meals and oral hygiene procedures, the appliances were stored in sucrose solution (10%). After in situ exposure, the samples were prepared for microradiographic assessment. Mineral content and lesion depth were evaluated by a dedicated software package (TMR 1.24). Lesion depth and mineral loss of the carious lesions close to Ariston pHc was significantly lower when compared to distant parts of the same lesions (p < 0.05; t-test, Bonferroni-Holm correction). All other materials containing fluoride showed no caries protective effect on surrounding enamel (p > 0.05; t-test, Bonferroni-Holm correction). A hydroxyl-, calcium- and fluoride-containing restorative material hampers demineralization next to the restoration, whereas, fluoride release of various fluoride-containing restorative materials does not affect demineralization of adjacent enamel in situ.

Plasma concentrations of methadone during postoperative patient-controlled extradural analgesia

Plasma concentrations of methadone were measured by gas chromatography in 16 patients receiving extradural methadone by continuous infusion for relief of postoperative pain. Venous blood samples were taken after a loading dose of extradural methadone 2 mg and during infusion of 0.46 mg h-1 plus patient-controlled increments of 0.2-1 mg. Mean (SD) plasma concentration of methadone was 9.8 (2.1) ng ml-1 at 15 min; this did not change significantly during the first 2 h, after which it increased gradually to 32.2 (4.6) ng ml-1 (P less than 0.001) at the end of 24 h. The mean quantity of extradural methadone required to produce effective analgesia was 10.3 (1.8) mg during the first 12 h after operation and 6 (1.0) mg for the subsequent 12 h. The mean amount of methadone for effective analgesia on the second day was 7.6 (1.1) mg. No adverse effects were detected during the 2-3 days of methadone therapy. Plasma concentration of methadone increased significantly during patient-controlled infusion of extradural methadone in the first 24 h after operation, suggesting rapid vascular uptake. Systemic activity of the drug contributes to the analgesic effect of extradural methadone.