CT images, especially in a three-dimensional (3-D) mode, give valuable information for oral implant surgery. However, image quality is often severely compromised by artifacts originating from metallic dental restorations, and an effective solution for artifacts is being sought. This study attempts to substitute the damaged areas of the jaw bone images with dental cast model images obtained by CT. The position of the dental cast images was registered to that of the jaw bone images using a devised interface that is composed of an occlusal bite made of self-curing acrylic resin and a marker plate made of gypsum. The patient adapted this interface, and CT images of the stomatognathic system were filmed. On the other hand, this interface was placed between the upper and lower cast models and filmed by CT together with the cast models. The position of the marker plate imaged with the dental casts was registered to those adapted by the patient. The error of registration was examined to be 0.25 mm, which was satisfactory for clinical application. The damaged region in the cranial bone images as an obstacle for implant surgery was removed and substituted with the trimmed images of the dental cast. In the method developed here, the images around the metallic compounds severely damaged by artifacts were successfully reconstructed, and the stomatognathic system images became clear, and this is useful for implant surgery.
Tooth preparation is an essential technique for dental treatment, but it is a skill not easily learned by a dental student. To facilitate this leaning process, a new tooth preparation support system with a parallel link mechanism was developed. This study reports the educational efficiency of this system for dental students. Dental students with no experience in clinical practice were selected and divided into two groups; one trained with this support system; and the other, with freehand preparation. They prepared axial walls in right maxillary second premolars and molars mounted in a phantom manikin with an air-turbine handpiece. Convergence angles of the axial walls and parallelisms between axes of prepared teeth were evaluated. Training with the support system led to significantly smaller convergence angles and parallelisms as compared with freehand preparation training. With the freehand preparation after training, the convergence angles and parallelisms became smaller in the group trained with the support system than those trained with freehand. The above findings suggest that training in tooth preparation utilizing the newly developed support system can be one of practical programs that are useful for dental students to achieve greater competency in tooth preparation.
Spectrophotometric or fluorometric methods with glucose oxidase (GOD)-peroxidase (POD)-chromogen(s) systems are well known as useful tools for determination of glucose. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Indicator reactions in these methods are based on oxidative formation of a colored or fluorescent substance from a chromogen(s) with H 2 O 2 , generated through GODcatalyzed oxidation of glucose, in the presence of POD. These color reactions are well-characterized chemical processes. However, the POD-dependent indicator reactions are known to be inevitably disturbed by electron donors present in biological samples such as ascorbic acid, uric acid, and bilirubin.3) Major processes of interference by these compounds are as follows: 1) reduction of oxidatively formed colored or fluorescent substance to its original chromogen(s); and 2) competition with a chromogen in reduction of H 2 O 2 . Several methodologies have been developed for elimination of such interference in glucose determination with GOD-POD-chromogen(s) systems.3) However, the most straightforward approach to glucose determination free from such interference is design of a novel indicator reaction without recourse to redox reactions coupled with H 2 O 2 and POD. To our knowledge, only a few methods with non-redox color reactions for glucose determination using only GOD have been reported. These methods utilize transformation of a vanadium(V), 16) titanium(IV) 17) or dinuclear iron(III) 18) complex to its adduct with H 2 O 2 accompanied by a bathochromic shift as a spectrophotometric indicator reaction. As expected, it was demonstrated that glucose determination with vanadium(V) and titanium(IV) complexes was not affected by various substances usually present in serum or added to test solution. 16,17) However, spectrophotometric or fluorometric determination of glucose with high accuracy should use formation of a colored or fluorescent substance from a chromogen rather than a color change of a dye as an indicator reaction.Recently, resorufin (2) was shown to be able to reoxidize a reduced form of GOD at 37°C, being transformed to a colorless dihydro derivative, although the reductive bleaching of the dye is of no use for GOD-based determination of glucose as an indicator reaction. 19) This finding prompted us to examine how resorufin derivatives such as acetyl resorufin (1) would behave in GOD-catalyzed oxidation of glucose, and it was found that 1 behaves in a manner different from 2 in the enzymatic reaction. Here, we report that deacetylation of non-fluorescent 1 to fluorescent 2 is induced by H 2 O 2 generated in GOD-catalyzed oxidation of glucose, and the transformation is promising as an indicator reaction for fluorometric determination of glucose without significant effects of ascorbic acid, uric acid, or bilirubin. ExperimentalMaterials GOD from Aspergillus niger (EC 1.1.3.4) and glucose were used as supplied from Wako Pure Chemical Industries, Ltd. Acetyl resorufin (1) [20][21][22][23] was prepared by reaction of resorufin sod...
Recently, we found that acetyl resorufin (AR) is transformed to fluorescent resorufin through deacetylation by H 2 O 2 (perhydrolysis), and hence perhydrolysis of AR can be used as a fluorometric indicator reaction for glucose determination using only glucose oxidase (GOD). 1) In the fluorometric method with GOD and AR, glucose analysis is performed without interference by ascorbic acid, uric acid or bilirubin. These compounds interfere with colorimetric determination of serum components with indicator reactions based on H 2 O 2 -dependent oxidative coupling of two chromogens in the presence of peroxidase (POD), which are represented by so called Trinder's reactions of 4-aminoantipyrine with phenolic or anilinic derivatives. 2) Thus, it was demonstrated that the fluorometric method with GOD and AR offers a more reliable and accurate tool for determination of blood glucose than the POD-dependent colorimetric method with 4-aminoantipyrine and phenol. 3) However, there is a problem to be resolved in utilizing perhydrolysis of AR as a general fluorometric indicator reaction for determination of H 2 O 2 : although AR remains intact in CH 3 CN at room temperature for more than 6 months, 3) AR undergoes spontaneous hydrolysis when its CH 3 CN solution is mixed with pH 7.4 phosphate buffer (blank solution), which prevents the fluorometric method from being employed for the measurement of glucose over a concentration range of more than two orders of magnitude.The key to success in improving the measurement range in the fluorometric method seems to be molecular design conferring the ability to resist hydrolysis of AR. The susceptibility of esters to hydrolysis can be controlled by changing steric factors of acyl groups. To our knowledge, there have been no reports of the effects of acyl groups on perhydrolysis of esters, although perhydrolysis of esters or amides has been recognized as a useful tool for generation of peroxyacids in chemical bleaching processes. 4,5) Since the molecular sizes of HOO Ϫ and HO Ϫ are quite similar, steric effects in perhydrolysis and hydrolysis must be in the same order of magnitude. Accordingly, it seemed doubtful whether judicious choice of acyl groups in AR could shift the competition between perhydrolysis and hydrolysis in a manner favorable towards H 2 O 2 -based deacetylation. However, perhydrolysis of aryl acetates is known to be much faster than their hydrolysis, i.e., the nucleophilic reactivity of HOO Ϫ toward aryl esters is markedly higher than that of HO Ϫ , 6-9) which is referred to as the a-effect: nucleophilicity is enhanced when the atom adjacent to a nucleophilic site bears a lone pair of electrons. [10][11][12] AR is a type of aryl acetate, and hence the a-effect is likely to be operative in the H 2 O 2 -dependent deacetylation of AR, which allows the fluorometric determination of glucose with the generation of resorufin as an indicator reaction even though AR undergoes hydrolysis. Taking the a-effect into consideration, it was expected that establishing reaction conditions ...
Comparative studies were made on eleven urokinase preparations commercially available. Analysis by both gel filtration and sodium dodecyl gel electrophoresis revealed the variety of molecular forms of the activator in the preparations showing molecular weight approximately 54,000 (A), 47,000 (B) and 34,000 (C). Starch gel electrophoresis at pH 8.8 indicated that (B) and (C) moved to anode whereas (A) and the active component of fresh urine slightly moved to the cathod. Proteolytic digestion of (A) produced the same component as shown by (B) and (C) on starch gel electrophoresis. Plasminogen activating activity of (B) and (C) was found to be less than that of (A) when measured by the procedure of CTA fibrinolytic method with the physiological blood level of plasminogen. The present data suggest that variety of molecular form in the preparation may be due to the difference of purification procedure in view of proteolytic degradation of the enzyme, and (A) seems to be the naturally occuring type of urokinase in urine.
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