Dentistry in Japan最新文献

The precipitation of inorganic crystals from body fluid requires (A) elimination of the macromolecules that inhibit for crystal formation, (B) sufficient supersaturation of the relevant ions, and (C) local restriction of molecular movement. All of these must be accomplished within a space of several nanometers width. Such a nanospace excludes most peptides and oligosaccharides (A). The relaxation time of the outer layer of hydration water (nano second order) on the nanospace wall is 1,000 times longer than that of free water (pico second order). This means that the structure temperature of vicinal water is low, thus the solubilities of calcium ions and phosphate ions are reduced (B,C). Stable ion clusters are formed easier in the nanospace than in the bulk water. The 5-6 nm space in which 3 nm thick hydroxyapatite crystallites can exist should be called critical space. The critical space should be formed according to the fibril diameter and disposition of the fibril or by deployment into the filaments, and by microtubular and lamellar structures.

Monoclonal antibodies (MAbs) were prepared from myeloma cells and splenocytes of mice immunized with Streptococcus cricetus HS1 or Streptococcus downei MF25 cells. Various makes of immunoplates were coated with whole cells or purified polysaccharide antigens of oral streptococcal strains and tested for reactivity in enzyme immunoassay (EIA) using the Mabs. It was revealed that different immunoplates had different reactivities. It was also shown that the EIA system and MAbs were useful for the immunological study and identification of oral streptococci.

Computer simulation is an effective method for mathematical analysis of the image of rotational panoramic radiography. Conventional simulation methods have been used only for analysis of imaging factors and prediction of the characteristics of the obtained image. This paper describes a new computer simulation method that analyzes the imaging factors and produces the simulated image itself. The simulation is carried out by reproducing the actual image formation process in the computer. The head phantom for simulation, which represents the human dentomaxillofacial structures as a numerical value from 0 to 4, was constructed by scanning a real head phantom from neck to head with an X-ray CT scanner at a slice thickness of 1 mm and at 1 mm slice intervals. The diverging X-ray beam was expressed as a set of straight lines and was moved according to various parameters. The simulated image obtained was satisfactory for image analysis of rotational panoramic radiography.

To study the functional change of masticatory muscles during growth and development, frequency analyses of surface electromyogram (EMG) power spectra were carried out. The subjects were six children (five males and one female), aged 4.5 +/- 0.2 years, having full deciduous dentition (Hellman's dental age IIA) and six adults (four males and two females), aged 27.7 +/- 3.8 years, having full permanent dentition. EMG signals were recorded bilaterally by using bipolar silver-surface electrodes from the anterior temporal and masseter muscles while the subjects were chewing gum and while performing maximum clenching in the intercuspal position. A fast Fourier transform algorithm was used to obtain the power-spectral density function and the power spectra of the EMG signals. Since the total power value from 62.5 to 1000 Hz was 100 percent, the frequencies at 25, 50, 75, and 90 percent of the cumulative power were calculated. The results showed that the frequencies at every percent of the cumulative power were age-dependent and that the EMG power spectra patterns in adult muscles were shifted to significantly lower frequencies than those in child muscles. The shift was probably caused by differences in the proportion of fiber type and fiber size between muscles of children and adults.

To determine the hemodynamic effects of 40 micrograms of epinephrine in local dental anesthetics, circulatory parameters and plasma catecholamine concentrations were measured for 30 minutes after injection of 2% lidocaine with epinephrine (E-L group) or without epinephrine (L-group) in fully conscious healthy young volunteers. The plasma epinephrine concentrations significantly increased in the E-L group (320.9 +/- 47.9 pg/ml) after the injection, but did not change in the L-group. The plasma norepinephrine concentrations did not change in either group after the injection. The differences in each circulatory parameter between both groups (parameters in the E-L group minus those in the L-group) at 5 minutes after the injection were +6% in heart rate, +6% in RPP (rate pressure product), +12% in stroke volume index, +22% in cardiac index, -17% in diastoric blood pressure, -22% in total peripheral resistance, -11% in mean arterial pressure, and +/- 0% in systolic blood pressure. The significant increase in cardiac output and significant reduction in total peripheral resistance results in little change in mean arterial pressure. These results suggest that oral submucosal injection of 40 micrograms of epinephrine accelates the cardiac performance, with little change in blood pressure and heart rate.

In studies of whole-nerve recordings from the frog glossopharyngeal nerve, Kashiwagura et al. reported that Ni2+ enhances responses to MgCl2 and NaCl and that such enhanced responses are suppressed by Ca2+. In the present study, it was found that the responses to electrolytes of single water fibers of the frog glossopharyngeal nerve are enhanced by Ni2+. Ni2+ enhances the responses to MgCl2, NaCl, and CaCl2. The enhancement of the response to CaCl2 suggests that inhibition of the enhanced response by Ca2+ is not caused by the relationship between Ca2+ and Ni2+ ions on the receptor membrane. Kitada reported that, in the absence of Ni2+, Ca2+ competitively inhibits the responses to Na+ and Mg2+; and Kitada and Shimada reported that the response to Ca2+ is competitively inhibited by Na+ and Mg2+. The possibility is discussed that inhibition of the enhanced response by Ca2+ is due to competition between Ca2+ and Na+ and between Ca2+ and Mg2+ for multiple specific receptor sites.

The influence of plaque and calculus deposition on the prevalence of pocket formation was studied using cross-sectional data from 615 Japanese manual workers aged 18-49. A periodontal pocket with a depth of 4 mm or more from gingival margin to bottom of the pocket was coded as presence of pockets. The oral hygiene status at the specified site was classified into four hygiene patterns as no deposition, deposition of plaque only, deposition of calculus only and deposition of both plaque and calculus. The percentages of six specified tooth types with pocket formation were analyzed according to the local hygiene condition. The results indicate that local oral hygiene produces significant differences in the proportion of teeth with pocket formation in the examined tooth types. The frequency of site-specific hygiene condition were no deposition, deposition of plaque only and deposition of both plaque and calculus, except for the lower central incisors. The teeth without plaque and calculus show no pocket formation in most of the examined tooth types in the subjects aged 18-39, while teeth with plaque and/or calculus indicate high prevalence of pocket formation. It is also revealed that the teeth with both plaque and calculus tend to show higher percentages of pocket formation than those with plaque only. These findings suggest that promotion of a plaque free state would reduce risk for pocket formation to negligible level, and that calculus deposition increase the risk for pocket formation around the teeth with plaque.

Jaw movements and masticatory muscle activities were recorded in freely moving rabbits. During 5 hours of continuous recording, three states were recognized, namely, sleep, rhythmical jaw movements, and wake without any major jaw movements. The rhythmical jaw movements included chewing, drinking, and grooming and were similar in characteristics to those recorded in immobilized animals. During sleep, two kinds of masseter muscle behaviors with jaw movement features were recorded: one characterized by a short EMG bursts and a pause in jaw movements, considered similar to clenching, and the other characterized by cyclic bursts and lateral jaw excursion, a grinding-like movement. The latter was correlated with light sleep, thus suggesting a resemblance between the grinding-like behavior and bruxism.

External measurements of the zygomatic bone have been reported, but there are no reports on the internal structure. We studied the internal structure of the zygomatic bone and determined the changes in cortical bone width, cortical bone ratio to total cross-sectional area, and trabecular bone width through six periods of tooth growth and development. Zygomatic bone were fixed in resin and sliced, then the cross-sectional specimens were photographed with soft X-rays. The images were analyzed with an image processor. The specimens included the surrounding cortical bone and its internal spongy substance. The cortical bone width, cortical bone ratio, and trabecular bone width increased significantly from the period of deciduous dentition to the first early period of mixed dentition, but leveled off after that. This indicates that in addition to the growth and development of the zygomatic bone itself, its structure is also affected by the forces generated in the maxilla by mastication.