Two-body and three-body wear of glass ionomer cements.

OBJECTIVES: Glass ionomer cements (GIC) have been modified in an attempt to improve their mechanical properties. The objective of the present paper was to compare the two-body and three-body wear of four modified GIC. The tested materials were Fuji IX (GC Corporation), Hi-Fi (Shofu) and Ketac Molar Aplicap (3M/ESPE). The cermet cement Ketac Silver Maxicap (3M/ESPE) was used as reference material. METHODS: Two-body wear tests were carried out in the computer controlled 'artificial mouth' of the Munich Dental School, three-body wear was tested with the ACTA wear machine. RESULTS: The resulting average two-body wear rates (in microm) were: Fuji IX 327 (SD +/- 82) < Ketac Molar 379 (SD +/- 94) < Hi-Fi 376 (SD +/- 90) < Ketac silver 449 (SD +/- 127). The differences between the materials were significant (P < 0.05, ANOVA, modified LSD-test) with the exception of Ketac Molar and Hi-Fi. The average three-body wear rates (in microm) were: Hi-Fi 30 (SD +/- 10) < Ketac Molar +/- 42 (SD +/- 12) < Fuji IX 49 (SD +/- 14) < Ketac silver 73 (SD +/- 23). The difference between Ketac silver and the three other materials was significant (P < 0.05, ANOVA, modified LSD-test). No significant difference was calculated between Hi-Fi, Ketac Molar and Fuji IX. CONCLUSIONS: As Ketac Molar, Hi-Fi and Fuji IX show better wear resistance compared to Ketac silver both in occlusal-contact and contact-free areas, it may be assumed that the wear resistance of a glass ionomer cement may be improved more by changing the powder: liquid ratio than by incorporating silver particles into the glass powder.

[Right ventricular thrombus after pacemaker implantation in a patient with secondary antiphospholipid syndrome]. / Rechtsventrikulärer Thrombus nach Schrittmacherimplantation bei sekundärem Antiphospholipid-Syndrom.

HISTORY AND ADMISSION FINDINGS: An 85-year-old woman was admitted because of frequent syncopes. She also reported slight weight loss, cough and dyspnoea. Chest auscultation revealed slight stridor and a cardiac arrhythmia, with an irregular ventricular rate between 120 and 140 beats/min. INVESTIGATIONS: She had a thrombocytopenia (96 platelets/nl), and the ECG and long-term monitoring showed a tachyarrhythmia with atrial fibrillation, a bifascicular block (left anterior hemiblock and right bundle branch block), as well typical signs of sick-sinus syndrome with short periods of bradycardic sinus rhythm and pauses of up to 6 s on rhythm change. Echocardiography indicated moderately reduced left ventricular function. Chest radiogram revealed tracheal narrowing by a retrosternal goitre. No evidence of tumour was found on bronchoscopy. DIAGNOSIS, TREATMENT AND COURSE: A VVI pacemaker was implanted. When the platelet count dropped to 30/nl idiopathic thrombocytopenic purpura was suspected, but administration of high doses of corticoids and immunoglobulin was without effect. Another echocardiogram, performed because of chest pain suspicious of pulmonary embolism, revealed a large bowl-shaped right ventricular thrombus with floating parts. Demonstration of anticardiolipin antibodies established the diagnosis of antiphospholipid syndrome (APLS), thought to be secondary to thyroid cancer suspected from the computed tomography. The patient died 2 months later from recurrent pulmonary embolism and progressive liver failure. Autopsy revealed a not previously diagnosed tracheal carcinoma with metastases to the thyroid, as well as haematogenous metastatic foci within the right ventricular thrombus. INTERPRETATION: In case of thrombocytopenia of uncertain aetiology APLS should be included in the differential diagnosis, even in the absence of any early or acute thrombosis. If anticardiolipin antibodies and/or lupus anticoagulant are demonstrated, malignant neoplasm should be considered in addition to autoimmune disease.

Splenectomy for suspected malignant lymphoma in two patients with loiasis.

Intrasplenic lesions can cause diagnostic difficulties because malignant diseases can be excluded only by histologic examination. We present the cases of two patients with splenic manifestations of loiasis. Both patients had visited central Africa. Several years later, intrasplenic lesions were found during routine examinations (for chest trauma and employment, respectively). Both patients underwent splenectomies because malignant lymphoma was suspected. In both cases, histologic examination of the spleen showed eosinophilic granulomata with multiple Loa loa microfilariae.

Modifying effects of disulfiram on DNA adduct formation and persistence of benzaldehyde in N-nitroso-N-methyl-benzylamine-induced carcinogenesis in rats.

Whereas disulfiram (DSF) is known to inhibit tumor formation resulting from a number of chemical carcinogens, such inhibition does not apply to nitrosamines. In the present study, biochemical and morphological findings were examined to elucidate the effect of DSF on long-term application of N-nitroso-N-methylbenzylamine (NMBA). HPLC and fluorescence detection were used to determine O6-methylguanine (O6-MG) in DNA obtained from the respiratory tract of rats subjected to long-term simultaneous application of DSF and NMBA. After 2 days of treatment, more O6-MG was detected in the proximal portion of the respiratory tract, including the trachea and main bronchi, than in the distal portion. The findings were reversed after 10 and 30 days, at which time formation of the DNA adduct was substantially higher in the distal portion of the respiratory tract, despite increases in both portions. The biochemical results corresponded to morphological findings. Initially, increased numbers of metabolizing goblet cells appeared in mucous cell hyperplasia in the proximal respiratory tract. Subsequently, the hyperplasia migrated to distal regions of the respiratory tract; at this stage, the goblet cells disappeared from the proximal portion, which now revealed toxic degeneration, atrophy and subsequent squamous metaplasia of the mucous lining and squamous papillomas. At various times during a 40-day period, 2 to 7 times more O6-MG in pulmonary DNA was detected in rats treated with DSF and NMBA, than with NMBA alone, whereby distinct amounts of O6-MG were found in the latter animals. In contrast to the above-mentioned morphological findings, no morphological alterations occurred in the respiratory tract of the animals treated with NMBA alone. It is therefore conceivable that the above pathological lesions resulted not merely from the presence of DNA adducts, but also from an additional, previously unspecified effect. As benzaldehyde (BA) is formed in equimolar amounts in NMBA metabolism and DSF has been demonstrated to inhibit aldehyde metabolism, this aldehyde is a possible candidate for such an effect. In the present study, rats were therefore treated with BA, DSF, or NMBA, or combinations thereof. Histomorphological evaluation of these experiments revealed that long-term application of BA alone led to the following alterations in the respiratory tract: goblet cell hyperplasia, hyperplasia of the peribronchial lymphatic system, mucous epithelial atrophy and accompanying perivasculitis--the same alterations seen under long-term application of NMBA and DSF.(ABSTRACT TRUNCATED AT 400 WORDS)

Nitrite: a co-carcinogen?

The concurrent administration of N-nitroso-N-methylbenzylamine (NMBA) (10 mg/l drinking water) and sodium nitrite (5 g or 1 g/kg basic diet) induces enhanced progression of esophageal tumors. Pathologic changes of the respiratory system, which do not occur with administration of NMBA alone, are also observed. These findings call for re-evaluation of the toxicological significance of nitrite.

Effect of disulfiram on N-nitroso-N-methylbenzylamine metabolism. Biochemical aspects.

The present biochemical experiments show that disulfiram inhibits N-nitroso-N-methylbenzylamine metabolism in the rat. More N-nitroso-N-methylbenzylamine may therefore reach extrahepatic tissues. The pathological lesions observed in the lungs in the present system can be explained by the finding that alkylation of lung DNA is increased and repair processes are impaired by enhanced cell proliferation in this organ.

Role of the respiratory system in metabolism of N-nitrosamines after simultaneous application of disulfiram.

Subsequent to modification of N-nitrosamine metabolism by disulfiram, mucus-producing cells and Clara cells in the respiratory tract are involved increasingly in detoxification as well as in bioactivation of N-nitroso-N-methylbenzylamine and N-nitrosodibutylamine. Overtaxing of these cells or local concentration of antigenic metabolites leads to cytolytic defects in tracheal, bronchial and bronchiolar epithelium, in addition to toxic degenerative lesions. The resulting continuous stimulation of proliferation leads to basal-cell hyperplasia, squamous-cell metaplasia and squamous papillomas. In areas with insufficient differentiation, due to cell proliferation, there is an increased probability that focal mutation, subsequent to alkylation of purine bases, will be passed from one cell generation to the next, with subsequent formation of tumours in the bronchiolo-alveolar region.

[Differential effect of bleomycin on squamous epithelium at various sites]. / Unterschiedliche Bleomycin-Wirkung auf Plattenepithel verschiedener Lokalisation.

By autoradiographic methods it was examined, whether a specific local effect on squamous epithelium can be proved in a animal model. For this purpose the proliferatory activity was considered in the epithelium of the murine tongue, of esophagus, of the skin in the area of foot and of tail as long as 72 hours after a single application of bleomycin. The result shows, that the proliferatory activity is impaired to a greater extent in the epithelium of the tongue and the esophagus in comparison on the squamous epithelium of foot and tail skin.

[Tissue specificity of the action of bleomycin. Autoradiographic studies]. / Gewebsspezifität der Bleomycinwirkung. Autoradiographische Untersuchungen.

The proliferative activity of different types of murine tissue up to 72 h after a single dose of bleomycin was studied via histoautoradiography to determine whether bleomycin has a tissue-specific effect. Bleomycin apparently not only has a general cytotoxic and/or cytostatic action, the strongest being on tissue with a high proliferation rate, but also, as a comparison of the effect of bleomycin on the proliferative activity of squamous epithelium (plantar region, tail, skin, esophagus, tongue) and of mucosal epithelium (stomach, ileum, colon) has indicated, the proliferative activity of squamous epithelium is impaired to a greater extent. This, therefore, distinguishes bleomycin from many other substances used in tumor therapy.

The effect of disulfiram on the carcinogenicity of nitrosamines.

The effect of orally administered disulfiram (DSF) (200 mg/kg diet) on the carcinogenic action of N-nitrosodibutylamine (NDBA) (750 mg/1 drinking water) was investigated in rats. DSF had no effect on the amount of NDBA metabolites in the urine and did not influence the frequency and rate of formation of oesophageal and urinary bladder tumours. While 4 of 25 animals in the group fed only NDBA developed liver tumours, no liver tumours were observed after concurrent application of NDBA and DSF. On the other hand, only the combined application of NDBA and DSF led to the formation of lung tumours (8/27; P = 0.01).