The effect of tooth preparation on microleakage behavior.

Many factors contribute to the microleakage of a restoration. One of the more important is the method of cavity preparation. This study compared the microleakage behavior of composite restorations placed in cavities prepared by different techniques. It also compared and correlated the microleakage data produced by an electrochemical vs a staining technique. Class V cavities were prepared in 48 premolars by four techniques: (1) tungsten carbide bur in a high-speed handpiece followed by acid etching; (2) air abrasion (27 microns Al2O3) followed by acid etching; (3) air abrasion (50 microns Al2O3) and (4) air abrasion (27 microns Al2O3), with n = 12 in each group. All teeth were restored with Prime and Bond 2.1 and Tetric Flow, then thermocycled between 5 degrees and 55 degrees C for 5000 cycles with a one minute dwell at each temperature. After thermocycling, a PVC-covered Cu wire was inserted apically into the pulp chamber of each tooth and sealed into position. Leakage was continuously followed by a conductimetric method for 75 days. The teeth then were immersed in 50% AgNO3 for two hours, rinsed in distilled water for 60 seconds, then placed in a rapid photographic developer solution for two hours, followed by rinsing and sectioning for microscopic examination. Electrochemical data were examined by ANOVA and Newman-Keuls multiple comparison tests, while Kruskal-Wallis and Rank Sum Difference tests were used on the staining evaluations. Spearman's rho test was used to correlate the two test techniques. Electrochemical data for cavities prepared with a bur or air abrasion followed by acid etching prior to restoration showed significantly less (p < or = 0.05) microleakage (mean leakage currents of 1.89 & 1.57 microA, respectively) than teeth prepared with air abrasion alone (mean leakage currents of 3.60 & 3.40 microA, respectively). Rank sum AgNO3 staining data (196 & 242 vs 371 & 368) supported these findings. The correlation between the electrochemical and staining data was significant (p < or = 0.05) for all four groups of test specimens.

[Detection of bactericidal antibody in the breast milk of a mother infected with enterohemorrhagic Escherichia coli O157:H7].

A 21 years-old pregnant woman developed diarrhea, fresh bloody stools and abdominal pain on April 6th 1997 at 32 weeks of gestation, and was admitted to the hospital on April 11th. The stool culture on admission was positive for enterohemorrhagic Escherichia coli (EHEC) O157:H7 (Stx1 and 2). Clinical laboratory data during admission showed only slight elevation of beta-microglobulin and N-acetyl glucosaminidase in the urine, and no neurological or hemolytic symptoms were seen. After the antibiotic and lactobacillus administration, all her symptoms were relieved and no abnormal findings in pregnancy were observed. She delivered a baby girl normally on May 30th. Serum (between 41 and 120 days from the onset) and milk (between 4 and 64 days post partum) samples from the mother, and serum (64 days of age) from a baby and cord blood were obtained to monitor the immune status against EHEC O157:H7 and against Shiga toxins (Stx). Anti-E. coli O157 LPS antibodies (IgA, G and M) were assayed by the ELISA method. Neutralizing anti-Stx antibodies were measured by using ACHN cell cytotoxicity assay. In the colostrum and mature milk, high levels of IgA and IgM, and no IgG antibodies against EHEC O157 LPS were detected. In one of the control colostrum samples obtained from 4 healthy mothers IgA antibody against EHEC O157 LPS was detected. To assess the potency of protection against EHEC O157:H7 by the breast milk, we monitored it by the bactericidal activity for the organism under complement-coincubation experiment, and by the neutralization test for the Stx cytotoxicity. As a result, breast milk samples (both colostrum and mature milk) from a patient were demonstrated to kill the organisms. One of 4 healthy milk samples, showed bactericidal activity though it was negative in O157-LPS antibody. This bactericidal activity seen in one healthy colostrum is possibly due to a nonspecific reaction caused by non-O157 E. coli infection. From these observations, it was suggested that the bactericidal activity was due to the IgM class antibody against EHEC O157:H7. However, the neutralizing antibody against Stx1 and 2 could not be detected in any sample. EHEC infection at late gestation did not cause adverse effects to a fetus, and breastfeeding may have advantage for the protection of a baby against EHEC infection.

Ethanol injection therapy in RBT-1 carcinoma of the rat liver evokes enhancement of metastasis.

To search for possible untoward effects of ethanol injection into a malignant tumor, a series of experiments was carried out using the model of RBT-1 carcinoma. Ten days after the inoculation of RBT-1 carcinoma into the rat liver, the animals were separated into three groups: Group A, ethanol injection during relaparotomy; group B, physiological saline injection during relaparotomy; and group C, relaparotomy alone without ethanol injection. Twenty minutes after these procedures, the tumor was surgically removed and histologically examined. The incidence of vascular permeation of liver tumor cells into the hepatic vein was significantly higher in groups A and B (P < 0.05). On the 10th day after relaparotomy, the number of metastatic nodules in the lungs was significantly increased in groups A and B, compared to the findings in group C (P < 0.05). Regarding the survival time of rats after relaparotomy, there was no statistically significant difference among the three groups. These results are taken to mean that ethanol injection into a tumor may enhance metastasis.

In vitro formation of fine fibrils with a D-periodic banding pattern from type V collagen.

Type V collagen was isolated from human placenta by limited pepsin treatment and purified by salt fractionation. A solution of type V collagen was dialyzed at 4 degrees C against phosphate-buffered saline or against 0.02 M Na2HPO4. Aggregates formed under these in vitro conditions from a pure type V collagen solution were examined by electron microscopy. The aggregates were fine flexible fibrils. The fibrils formed during incubation at 25 degrees C were of relatively uniform diameter, 34.8 +/- 9.1 nm and did not show an axial banding pattern. When the specimen was incubated at 37 degrees C, the fibrils were of slightly larger diameter, 38.2 +/- 9.1 nm and almost all the fibrils had the axial repeat pattern of 67 nm. The ability of type V collagen to form banding fibrils is discussed in relation in the localization of the collagen in tissues.