Possible participation of isolated epicardial cell clusters in the formation of chick embryonic epicardium

The embryonic epicardium is formed by the spreading of cells derived from the extracardiac proepicardial organ over the myocardial surface after transfer to the dorsal side of the myocardium via a bridge of villous projections. Using whole-heart immunostaining for keratin, we found that the chronology and pattern of epicardial formation in the chick was basically identical to that reported previously in the quail. However, discrete epicardial islands were observed on the ventrolateral surface of the atrioventricular canal as well as in two previously reported areas. Closer examination by scanning electron microscopy demonstrated the presence of isolated, sparsely distributed epicardial cell clusters on both the dorsal and ventral surfaces of the myocardium. These cells showed a surface morphology similar to that of the epicardial cells at the advancing edge of the spreading epicardial sheet and possessed numerous well-developed filopodia, suggesting active motility. These clusters are probably seeded onto the myocardium by vesicular transport from proepicardial villi, and our findings suggest that the resulting small, localised patches of epicardial cells might accelerate, supplement and tune the epicardial formation mediated by radial spreading of the epicardial sheet in the chick embryonic heart.     

Dental treatment for the handicapped by a combination of public community, dental association and university hospital--a system of Suginoki Dental Clinic

Suginoki Dental Clinic, which is managed by Suginami Dental Association, financially supported by Suginami City, and technically assisted by the University Hospital, Tokyo Medical and Dental University, was established for dental treatment of handicapped persons living in Suginami City, Tokyo who are difficult to be treated by private practitioners. It has one full-time dentist, 12 part-time dentists, two dental hygienists, one nurse, and one clerk; one of the part-time dentists practices twice a week there. Since December 1994, 406 patients visited the clinic and the total cases was 9,273 in December 1999; 99 cases were mentally retarded, 36 autism, and 30 epileptic patients in the younger group; and 65 cases were cerebrovascular disease and 27 cardiac malfunction patients in the older group. Almost all the patients needed special care such as monitoring, intravenous sedation, nitrous oxide sedation, and general anesthesia. Four cases underwent general anesthesia, and no complication was seen among the cases. It was concluded that the clinic has been successful due to a good relationship among the Dental Association, Suginami City, and the dental hospital.     

Stimulation by low concentrations of fluoride of the proliferation and alkaline phosphatase activity of human dental pulp cells in vitro

Fluoride has been used for decades, either systemically or topically, to prevent dental caries. The purpose of this study was to clarify the effects of low concentrations of fluoride on proliferation, differentiation and extracellular-matrix synthesis in normal human dental pulp cells (DP-1 and DP-2) in vitro. The effects were compared with those on a human osteoblastic osteosarcoma cell line, TE-85. Fluoride at micromolar concentrations significantly and dose-dependently stimulated [3H]thymidine incorporation into DNA in DP-1, DP-2 and TE-85 cells, with optimal effects around 50 microM, by 127 +/- 7%, 124 +/- 0.6% and 152 +/- 13.4%, respectively. To assess the potential influence of fluoride on cell differentiation, the effects of mitogenic concentrations on alkaline phosphatase activity were measured. Fluoride significantly increased the enzyme's activity in DP-1 and TE-85 by 177 +/- 12% and 144 +/- 12.3%. To evaluate the effect on extracellular-matrix synthesis, the synthesis of type I collagen was indirectly determined by an assay of procollagen type I c-peptide production. Fluoride significantly increased that production by 150 +/- 8.7% in TE-85, but not in either DP-1 or DP-2. These observations suggest that fluoride, if used at low concentrations, could be a useful therapeutic agent where increased regeneration of dentine is desired, such as after pulp amputation, by stimulating the proliferation and differentiation of the dental pulp cells.     

Voltammetry and surface analysis of AISI 316 stainless steel in chloride-containing simulated concrete pore environment

The study of passive layers grown on AISI 316 stainless steel in solutions that simulate concrete pore environments contaminated with Cl^? is presented. Model solutions of saturated Ca(OH)₂ and cement extract (CE) with and without the addition of 5 g/L of NaCl are compared. Cyclic voltammetry (CV) shows different electrochemical responses of passive layers grown on samples immersed in these solutions under open circuit potential (ocp). A more resistive passive film was found on the samples exposed to the CE solution. The different voltammetric responses suggest differences in composition of the passive layers formed on each solution. XPS spectra confirm the dissimilarity in atomic composition. Optical microscope images and AFM images of the pits formed on the samples illustrate the differences of AISI 316 surface topography after exposure to model solutions. Because of these differences, it is recommended to use CE solution as a model solution and ocp passivation to simulate concrete environments.     

Mechanical properties and radiopacity of experimental glass-silica-metal hybrid composites.

OBJECTIVES: Experimental glass-silica-metal hybrid composites (polycomposites) were developed and tested mechanically and radiographically in this fundamental pilot study. To determine whether mechanical properties of a glass-silica filled two-paste dental composite based on a Bis-GMA/polyglycol dimethacrylate blend could be improved through the incorporation of titanium (Ti) particles (particle size ranging from 1 to 3 microm) or silver-tin-copper (Ag-Sn-Cu) particles (particle size ranging from 1 to 50 microm) we measured the diametral tensile strength, fracture toughness and radiopacity of five composites.METHODS: The five materials were: I, the original unmodified composite (control group); II, as group I but containing 5% (wt/wt) of Ti particles; III, as group II but with Ti particles treated with 4-methacryloyloxyethyl trimellitate anhydride (4-META) to promote Ti-resin bonding; IV, as group I but containing 5% (wt/wt) of Ag-Sn-Cu particles; and V, as group IV but with the metal particles treated with 4-META. Ten specimens of each group were tested in a standard diametral tensile strength test and a fracture toughness test using a single-edge notched sample design and five specimens of each group were tested using a radiopacity test.RESULTS: The diametral tensile strength increased statistically significantly after incorporation of Ti treated with 4-META, as tested by ANOVA (P=0.004) and Fisher's LSD test. A statistically significant increase of fracture toughness was observed between the control group and groups II, III and V as tested by ANOVA (P=0.003) and Fisher's LSD test. All other groups showed no statistically significant increase in diametral tensile strength and fracture toughness respectively when compared to their control groups. No statistically significant increase in radiopacity was found between the control group and the Ti filled composite, whereas a statistically significant increase in radiopacity was found between the control group and the Ag-Sn-Cu filled composite as tested by ANOVA (P=0.000) and Fisher's LSD procedure.SIGNIFICANCE: The introduction of titanium and silver-tin-copper fillers has potential as added components in composites to provide increased mechanical strength and radiopacity, for example for use in core materials.     

Quantitative longitudinal study of alveolar bone tissue in man

This investigation concerns the reaction of alveolar interdental tissue to periodontal surgery as observed from radiopacity changes in the region studied. The radiopacity of the tissue was determined with the aid of an Iodine¹²⁵ apparatus for intraoral measurements. The radiation source is small and the energy is 27.4 keV. The precision of the method was tested over the period of investigation and found to be high. Seven flap operations were performed on four patients with periodontal disease. The radiopacity of the alveolar tissue after operation seems to bedependent on changes caused by the postoperative edema of the soft tissue, resulting in an increase in radiopacity, and changes caused by mineralization processes in the alveolar bone. A demineralization of the interdental bone is observed from about two weeks after operation and reaching its lowest value within six weeks after operation. Thereafter a secondary increase in radiopacity is recorded. This is interpreted as a remineralization of the alveolar bone.