Somatometry of the head, face, body height and body weight was performed to comparatively examine the differences in Japanese and Chinese children. The subjects consisted of 1069 boys and girls (530 Japanese and 539 Chinese) ranging in age from two to six years. The Martin system was employed for the measurement. The following results were obtained:

In the frontal aspect of the face, the en-en and ex-ex distances showed no age-related differences in both the Japanese and Chinese children. In the Japanese children, the gn point was markedly developed inferiorly with age. On the other hand, the Chinese children had less inferior development of the gn point. In the lateral aspect, the t-go distance was not noticeably increased with age in the Japanese children. In the Chinese children, the t-go distance was markedly developed inferiorly. These differences began to grow pronounced from three years of age. The facial profile in the Japanese children was configurationally characterized by a remarkable anteroinferior inclination of the mandibular base and that in the Chinese children by the small gonial angle and flat mandibular base. The Japanese children had a distinct tendency of having a shorter face compared to those of 30 years ago. The body height and weight of the Japanese children were larger than those of the Chinese children at any age over three years. This seemed to be attributable to differences in the current social environment between Japan and China.

Since the frequency of intraoral reontgenography has increased, the levels of exposure to patients by a radiation dose should be taken into consideration. The dose given to the whole body by one single dental radiography is low, when compared to radiography to other organs. As to calculation of risk, however, a rather high frequency of radiography should be taken into account. Statistical data show that approximately one hundred million radiographs are taken yearly in Japan. The use of high sensitive dental films and being careful not to commit techical failure are important in reducing the radiation dose given to patients. There are many reasons why the radiographic quality can not be constantly well-kept. The use of an old developer is one of them. It is very important to know the quality of the developer in use. In this study, the subtraction masking film method was attempted to evaluate the quality of radiographs and the developer. A wedge made of Mix D (10 mm wide, 30 mm long, 0~40 mm in height) was radiographed and developed with a new solution. A subtraction masking radiograph was prepared from the radiograph of the wedge. Dental films of the wedge were also developed using weakened developing solutions. Each dental film was superimposed on the masking film prepared at first to measure the density. If the developer is effective, then the superposed films have the same transmission density at any area. If the film is developed with a weakened developer, the density is reduced. The density is decreased with an increase in the number of films developed, because the developing solution becomes weakned and undergoes chemical changes during the course of development. In this study, a decrease in transmission density was detected after development of approximately 100 films. This method is simple and useful for the evaluation of the activity level of the developer at any time after preparation.

The effects of oral and subcutaneous administration of sodium fluoride (NaF) on the monoaminergic systems at several discrete brain regions of mice were examined. The mice were sacrificed 30 min after oral or subcutaneous administration of NaF (1㎎/kg). The levels of noradrenaline (NE), dopamine (DA), serotonin (5-HT), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the seven brain regions were measured by high-performance liquid chromatography with an electrochemical detector. In the noradrenergic system, oral NaF increased the NE level in the midbrain (MB) and the MHPG levels in the hypothalamus (Hyp), stratum (Str) and MB. In the dopaminergic system, oral NaF increased the DA levels in the Str and hippocampus (Hip), and the DOPAC levels in the Hyp and Str. In the serotonergic system, oral NaF increased the 5-HIAA levels in the Hyp, Str, Hip and MB. Subcutaneous NaF increased the MHPG and DOPAC levels in the Hyp and the MHPG, DA and DOPAC levels in the Str. These results suggest that oral administration of NaF affects the activities of the monoaminergic systems over a wide area of the mouse brain. The mechanism of these actions of NaF may include the peripheral action of NaF.

Metallic plates and screws made of stainless steel, pure titanium, titanium alloy and titanium nitride were implanted in the dorsal subcutaneous tissue and femur of 64 rabbits, and elution of metallic elements and tissue reaction in surrounding tissues were comparatively investigated at the 2nd, 4th, 8th, and 12th weeks after implantation. Using an inductively coupled plasma spectrometer, the metallic elements eluted in the subcutaneous tissues were quantitatively analyzed. The amount of iron from the stainless steel decreased with time. The amount of titanium eluted from pure titanium, titanium alloy and titanium nitride, increased with time, although only slightly in all cases. However, the amount of aluminum eluted from the implanted titanium alloy was considerably higher than that of titanium. Histological examination of the reaction of subcutaneous tissue, revealed encapsulation of pure titanium, titanium alloy and titanium nitride plates by dense fibrous connective tissues from the 2nd week after implantation, whereas the stainless steel plate was encapsulated by thin fibrous tissue. Using an energy dispersed X-ray microanalysis on the metal-bone interface, it was found that the element of titanium accumulated in the bone area about 5μm from the metallic screw, but there was no such finding for titanium alloy and titanium nitride. From stainless steel, no elution of iron, chromium and nickel was detected. Histological examination of the reactions of bone tissue to pure titanium, titanium alloy and titanium nitride, showed the formation of new bone between the metallic screw and bone tissue from the 4th week, and it gained a close and dense contact with normal bone at the 12th week after implantation, All experimental materials used in this study exhibited excellent resistance to corrosion and materials of titanium had better biocompatibility compared with stainless steel. Above all, the results of this study suggest that titanium nitride is useful as a biomaterial the same as pure titanium and titanium alloy.

A calcifying odontogenic cyst that occurred in the mandible of a 40-year-old man was ultrastructurally examined with special reference to the appearance of the peculiar ghost cells (GCs) that are characteristic of this cyst. The following results were obtained: The GCs were derived from odontogenic epithelial cells following the increase in the number and width of tonofilamentous bundles in the cytoplasm, and were formed by the disruption and disappearance of nucleus and plasma membrane of the epithelial cells. This process of GCs formation closely resembled the process of hard keratinization of the nail and the hair cortex. Many needle-like or radial structural calcifications were detected in the cytoplasm of the GCs. It was suggested that the yellowish-brown granules microscopically observed in the GCs were ultrastructurally lipid droplets.