Our previous report appearing as Snow white (Shofu : the conventional phosphatebonded investment for casting plates) was impossible to apply to a heat-shock method because the mold would explode. In this study we tried to find suitable firing and casting conditions for this investment under a heat-shock procedure. At first we found that the decreasing temperature of heat shock could prevent the mold from expanding. Because we couldn't obtain sound castings from a mold fired at 700°C, we investigated an increase in the soaking time and the firing temperature. We were then able to successfully fabricate the sound Co-Cr full denture plates from the mold that was heat shocked at 700°C for 10 min followed by a secondary heating to 1,000°C with soaking for 30 min. We can conclude that the two-stage heat-shock procedure is available for fabricating a sound Co-Cr casting denture by using conventional phosphate-bonded investments.
The possibility of fabricating Co-Cr casting plates by using a heat-shock method with conventional phosphate-bonded investments was investigated. Commercial phosphatebonded investments (Snow white, Univest nonprecious : Shofu) were investigated. A block of a duplicated model was prepared by using each powder mixed with its specific colloidal silica solution. A sheet of wax pattern with 0.5 mm thick on the model was secondarily invested by slurry mixed with water, colloidal silica solution, and their mixture. After 30 min on investing, the mold was put into the furnace preheated at 800°C and kept there for 30 min. Only the mold prepared from Univest mixed with water was available for casting after the heat-shock treatment. Other molds exploded in the furnace or received cracks after the treatment.The Co-Cr castings obtained from the available molds were not obviously sound because of insufficient firing. These results suggested that we might fabricate Co-Cr casting plates by using a heat-shock method with conventional phosphate-bonded investments, but we need further investigations to find suitable conditions for this method.
For exerting a disinfectant effect, electrolyzed strong acidic water should maintain such properties as the oxidation-reduction potential being 970 mV or greater, the concentration of active chlorine gas 0.8 ppm or higher, and pH 2.7 or less. It was found that when fresh samples of electrolyzed strong acidic water are stored in a tightly closed container that protects them from light, no change occurred in 2 weeks and its disinfectant efficacy did not change for about 1 month if the storing temperature was kept as about 4°C. Since salivary proteins largely affect the property of electrolyzed strong acidic water in its oral use, it is necessary to minimize the weakening of the oxidation-reduction potential and the concentration of active chlorine gas by increasing frequency of mouthwashing. Despite the presence of salivary proteins at ordinary concentrations, electrolyzed strong acidic water showed excellent disinfectant effects not only on Streptococcus mutans, a bacterial species relating most closely to dental caries, but also on Candida albicans, a main fungus species forming denture plaques.
In the clinical, growth suppression in a cleft palate patient caused by postoperative scar tissue after the palatoplasty. Recently, the metabolism pattern of the normal palatal mucosa reports a difference in comparison with the scar tissue in collagen cross-link and conformer. This fact indicates the importance of leading the collagen of the scar tissue, which exists for the palate to the normal condition, to stimulate growth of the normal maxilla. However, the research that revealed metabolism activity of the collagen included for palatal mucosa and growth of the maxilla is limited, and the elucidation is urgent. It was then made that the relevance to maxilla lateral growth and collagen metabolism existing for palatal mucosa of the normal rat was clarified as the first step of purpose in this study. The retrieval was observed by the change of the gelatinase activity, which is concerned in metabolism activity of the collagen, using histological observation by morphological evaluation and H-E staining of the rat maxillary dentition, Film in situ zymography method (the FIZ method). The following was obtained after each relevance was examined. 1. With aging, the dentition width described by the increase curve equal to the body weight. Especially, it was indicated to be the growth middle point of a 15-week-old rat nearly in puberty almost. And though the start of the growth of the dentition width was later than that of the body weight, it became a similar growth rate after 11 weeks-old rat. 2. With the aging was a narrowing of the midpalatal suture division cartilage layer. 3. Gelatinase activity of the palatal mucosa was highest at either week-old in the epithelium.The high activity was recognized in the connective tissue division in nerve and blood vessel circumference. Moreover, the activity of epiphysis circumference bone in the midpalatal suture division was highest in a 4-week-old rat, and it lowered afterward time-dependent. In an 11-week-old rat it could not be recognized. These findings suggested that gelatinase activity, which is collagen metabolism activity, was changed with the growth of the maxilla, and it was proven that the change was obvious in the midpalatal suture.