新しいBis-GMA類似体を基調としたコンポジットレジンペースト性質と特徴

The relationship between filler type, filler content, and matrix resin composition and viscosity, and the flow characteristics of composite formulations were investigated. The structures of three newly synthesized monomers, i.e., 3F Bis-GMA, 6F Bis-GMA (Bis-GMA analogues) and IP AGDM (based on phthalic acid) were analyzed to determine their viscosity and polymerization shrinkage. Viscosities were determined with a cone and plate viscometer and shrinkages were determined gravimetrically. All three experimental monomers required less dilution than Bis-GMA, and they exhibited remarkable reductions in polymerization shrinkage relative to Bis-GMA. Bis-GMA and 4 experimental Bis-GMA analogues were also evaluated. For each monomer-filler combination, increasing filler contents resulted in monotonic plasticities. The maximum filler contents appeared to be an attribute of the particular filler rather than a matrix resin characteristic. Plasticity differences existed, unexpectedly, even at constant filler contents and matrix viscosities. Evidence was found that the plasticity varied with the base monomer composition and the amount of TEGDMA present

6自由度顎運動測定装置の試用

The purpose of this study was to quantitatively analyze the mandibular movement by the Jaw tracking system with six degree of freedom (MM-JI-E). Displacements of the condyles under maximum clenching with successive loss of mandibular supporting zones were measured. The patient, a 29-year-old man, had been treated at an orthodontic clinic between 1994 and 1997, and temporary full coverage crowns were fabricated on four molars of the lower jaw. He showed no signs of abnormality of stomatognathic function. We measured the jaw movements with MM-JI-E, removing the crowns from the distal end of molars to the mesial. The condylar displacement values were displayed and calculated by the measurement of mandibular movement. When the supporting zones were reduced successively, both condyles moved upwards and slightly forwards (87-117°). The maximal condylar displacement values was 700μm without any support in the molars. We compared the measurements of MM-JI-E with those obtained with another jaw movement tracking system (Bio Pack), with three degree of freedom. The maximum opening paths in sagittal border movement were compared for the two measurement systems. The Bio Pack showed the deflection of the path of anterior maximum opening due to electronic error

純チタンの鋳造性に関する研究(第4報)通気性の低い鋳型への鋳造

The purpose of this study was to evaluate the influence of casting molds with low permeability on the castability of pure titanium with an all directional pressured type casting machine. Two types of phosphate bonded casting molds were used, T-INVEST and T-INVEST C&B. We reported high performance of castability of pure titanium with an all directional pressured type casting machine, if the permeability of the investment was lower as possible. Specially prepared metal sealed rings to decrease gas permeability of casting mold were used. Two sizes of sprue condition were prepared, 1.26 and 1.48mm, under a casting pressure of 8kgf/cm^2. Five sizes of casting molds were prepared with mold diameters of 25, 35,45,55 and 65mm. The following results were obtained: A high percentage of castability was gained in T-INVEST using a high gas permeability casting mold with the sealed ring. A low percentage of castability was gained in T-INVEST C&B using a low gas permeability casting mold with the sealed ring. Back pressure action in the casting mold of T-INVEST C&B seemed to produce negative effects regarding the castability. These results indicated that the sealed ring was effective to promote pure titanium castability with a mold of high permeability

純チタンの鋳造性に関する研究(第3報)鋳造圧およびスプルー径がチタンの鋳込率に及ぼす影響について

We analyzed the external defects of castings with mesh grid patterns with 3 different kinds of phosphate bonded casting molds with 2 parameters (sprue diameter and casting pressure). Castability with pure titanium was affected by the parameters of sprue diameter, and casting pressure with different casting molds. The sprue condition was the most affective casting condition in the all directional pressure type casting machine. In 2 types of casting molds, one was strongly affected by the casting pressure in castability and the other was scarcely affected by the casting pressure. The former type of casting mold had a low permeability

チタン鋳造における鋳型温度の影響

The purpose of this study was to evaluate the titanium castability with a vacuum pressured type casting machine. We tested ethyl-silicate bonded investment "TITAVESTPS" of metal frame work. Four different mold temperatures (room temperature, 300℃, 600℃, and 900℃) were prepared for the present study, and casting was done in five times in each condition. When the mold temperature increased, high percentage of castability was gained. Mold temperature showed a highly significant (p<0.001) correlation on the castability. These results indicate that high performance of castability on the titanium was achieved when the mold temperature increased by using vacuum pressured type casting machine

Porphyromonas gingivalis SOD における活性中心近傍に局在するアミノ酸残基の金属特異的活性における関与：Leu ₇2 Trp およびLeu ₇6 Phe の2残基変異による検討

The role of superoxide dismutase (SOD) as a radical scavenger in Porphyromonas gingivalis is well documented. P. gingivalis SOD (Pg SOD), which is characterized by a metal–tolerant activity, can use either iron or manganese as a cofactor. Leu ₇2 and Leu ₇6, located near the active–site metal, are characteristic amino acid sequences of Pg SOD proteins, although they are substituted to Trp in the ₇2 position and Phe in the ₇6 position in most iron–containing SOD (Fe–SOD) proteins. In the present study, we constructed a mutant of the enzyme with changes from Leu ₇2 to Trp and Leu ₇6 to Phe. This mutant SOD was examined with respect to its metal–dependent activity and structural characterization. We herein conclude the integrity of Leu ₇2 and Leu ₇6 is a necessary requisite for the metal–tolerant activity of Pg SOD

Porphyromonas gingivalis スーパーオキシドジスムターゼの構造における72位Leu をTrp に置換した影響

Porphyromonas gingivalis contains a single constitutive superoxide dismutase (SOD) that is active with either iron or manganese at the active site. The aim of this work was to evaluate the effect of the Leu ₇2 to Trp mutation on the structure of P. gingivalis SOD (Pg SOD) using lectrophoretic characterization. Leu ₇2, which is located near the active site metal, is substituted with Trp in aligned amino acid sequences of iron–containing SOD. The results of electrophoretic characterization and the expressed activity of mutant SOD suggest that mutant SOD have the same gross structure as wild–type SOD. We herein conclude that the integrity of Leu ₇2 is a necessary requisite for the metal–tolerant activity of Pg SOD

Surveys of full–coverage restorations made of titanium at Matsumoto Dental University Hospital

Considering the presence of metal allergies and the sharp rise in the prices of precious metals, full–coverage restorations made of titanium have been covered by Japanese insurance since June 1, 2020. The clinical application of these restorations is expected to increase in the future. However, due to its high melting point and high affinity to oxygen at high temperatures, titanium has not been widely used in prosthetic clinical practice. This study aimed to survey the actual use of full–coverage metal restorations at Matsumoto Dental University Hospital. Patients who had full–coverage metal restorations placed on their molars from June 1 to December 28, 2020, were consecutively enrolled, and data on the type of metal, placement site, and time were recorded. Besides, the dentists who used titanium restorations (Ti–Rs) were given a questionnaire. We asked them to rate their impressions of Ti–Rs in comparison with full–coverage restorations made of Ag–Pd–Cu–Au alloy (Pd–R) in six categories, including occlusal adjustment, polishing, and luting operations. In all, 338 molars received full–coverage metal restorations. Ti–R was used in 33 cases and Pd–R in 305 cases; 14 upper and 19 lower, 12 first molars, 18 second molars, and 3 third molars received Ti–Rs, while 137 upper and 168 lower, 174 first molars, 174 second molars, and 3 third molars received Pd–Rs. Seven dentists responded to the questionnaire survey. Many dentists stated that Ti–R was more challenging to use than Pd–R for occlusal adjustment, polishing, and adjustment time. On the other hand, most of them stated that the luting process was similar for both. Besides, Ti–R was favorably evaluated in terms of metal allergy. The number of patients who received Ti–Rs increased during the study period, suggesting that Ti–Rs will be a commonly used metal allergy–friendly prosthetic in the future. We plan to continue the survey and study the prognosis

Simulating the carbon balance of a temperate larch forest under various meteorological conditions

<p>Abstract</p> <p>Background</p> <p>Changes in the timing of phenological events may cause the annual carbon budget of deciduous forests to change. Therefore, one should take such events into account when evaluating the effects of global warming on deciduous forests. In this article, we report on the results of numerical experiments done with a model that includes a phenological module simulating the timing of bud burst and other phenological events and estimating maximum leaf area index.</p> <p>Results</p> <p>This study suggests that the negative effects of warming on tree productivity (net primary production) outweigh the positive effects of a prolonged growing season. An increase in air temperature by 3°C (5°C) reduces cumulative net primary production by 21.3% (34.2%). Similarly, cumulative net ecosystem production (the difference between cumulative net primary production and heterotrophic respiration) decreases by 43.5% (64.5%) when temperatures are increased by 3°C (5°C). However, the positive effects of CO₂enrichment (2 × CO₂) outweigh the negative effects of warming (<5°C).</p> <p>Conclusion</p> <p>Although the model was calibrated and validated for a specific forest ecosystem, the implications of the study may be extrapolated to deciduous forests in cool-temperate zones. These forests share common features, and it can be conjectured that carbon stocks would increase in such forests in the face of doubled CO₂and increased temperatures as long as the increase in temperature does not exceed 5°C.</p

Effects of the development changes in dentition on the retention of mouthguards

Summary The use of mouthguards is one of the main strategies that are considered effective in preventing sports–related trauma.Although mouthguards are recommended for use in children during sports activities,little is known as to how growth and developmental changes in the oral cavity, jaw, and dentition affect the retention of mouthguards. In the present study, we designed mouthguards for primary,mixed(4 types),and permanent detention stages and performed tensile testing to determine the effects of dental growth and development on their retention.We also designed mouthguards for the left maxillary second milk molar,left maxillary second premolar, and left maxillary first molar to determine how the shape of the teeth affects their retention.Data was analyzed statistically,and the following results were obtained:1.Mouthguards for permanent detention stage had a significantly higher level of retention than those for primary and mixed detention stages.2.Mouthguards for primary detention stage had a significantly lower level of retention than those for mixed and permanent detention stages. 3.The retention of mixed detention stage mouthguards became poorer with the number of teeth requiring relief.4.Differences in the shape of the teeth(left maxillary second milk molar, left maxillary second premolar, left maxillary first molar)had no significant effect on the retention of mouthguards.These findings indicate that the level of mouthguard retention is lower in children at primary and mixed detention stages than in adults and children with complete eruption of central incisor to second molar.This difference may be attributed to the differences in the coverage areas of mouthguard