The present author examined five subjects aged from 25 to 50 (four males and one femal) for the purpose of obtaining information about their biting force and the depth of sinking of their denture bases. The method of examination he employed was a comparison of control dentures (not relined) and dentures relined, 1mm thick with two kinds of resilient reliner: Low Temperature Vulcanization vinyl sillicone (LTV silicone reliner hereafter) and Methyl Metacrylate resin system reliner (MMA reliner hereafter), the latter of which would be easily obtainable in the common market. The following are the results of his examination.
1. The biting force of the first and the second molars of the five subjects who had dentures inserted, relined by resilient reliner proved to be less than when they usednon-relined dentures.
2. The biting force of the first molar tended to be greater than that of the second molar of dentures, and this tendency was not affected when their dentures were relined by resilient reliner.
3. In the cases of the first molars, the depth of sinking of the denture bases was 0.38 mm with dentures not relined by resilient reliner, 0.44mm with those relined by LTV silicone reliner, and 0.50mm with those relined by MMA reliner. As for the second molars, the depth was 0.29min with dentures not relined by resilient reliner, 0.39mm with those relined by LTV silicone, and 0.48 mm with those relined by MMA reliner. The sinking depth of denture bases was greater when relined by MMA reliner than by LTV silicone reliner.
4. The relationship between biting force and the sinking depth of denture bases, both relined and nonrelined dentures, showed that above about 6Kg of biting force the sinking depth indicates no discrepancy between dentures relined and those not relined.
5. By applying finite element method, the following facts are obtained:
1) Stronger tensile and compression stresses inside the resin were observed in the cases of dentures relined by resilient reliner than those not relined.
2) Stresses transmitted to the cortical bones were not affected by the presence of resilient relining materials.

抄録全体を表示

Although there is a fair large literature on the reproducibility of jaw movement by a semi-adjustable articulator, researches dealing with a fully adjustable articulator are yet relatively few.
In the present study, the author was concerned with the chew-in method by use of the TMJ articular with special attention on the following three points.
i) Changes in the form corresponding to the mandibular condyle or resin. fossa when the form of central bearing plate was made into either one of flat, convex and concave planes.
ii) The degree of reproducibility of the TMJ articulator.
iii) Possible effect on a range of 2mm from the centric relation from a standpoint of functional movement.
By way of study material, 3 male students in their twenties at Nihon University School of Dentistry, who were in possession of normal arch and periodontal structure free from any defective tooth or teeth? were selectively used.
Exchangeable central bearing plates of flat, convex and concave (the last two being 2 inches in radius) forms were constructed on the mandibular resin clutch, where chew-ins were made in the subjects by keeping vertical occlusal dimension at the centric relation uniform or constant.
By repeating the procedure for three times to produce 9 chew-ins per individual subject, a total of 27 resin. fossas were prepared. Subsequently, these resin fossas were subjected to a series of three-dimensional measurements (on the left side only) for comparative analyses.
As a result of the study, the author arrived at the following conclusions:
1. Changes in the form of each central bearing plate did not influence the form of resin fossas.
2. When the form of TMJ articulator resin fossa was regarded as being functional in a range 2mm away from the centric relation, there was no appreciable influence on the part of central bearing plate.
3. The form of resin fossa between respective central bearing plates was approximately 4μ at the centric relation and, . within a range of 2mm from it, the mean value was 50μ. As the value was less than 200μ in terms of the clinical requirements, the reproducibility of the TMJ articulator could' be confirmed to be quite adequate.
4. With any form of the central bearing plates, a scatter of resin fossa forms was smaller outside the centric relation (corresponding to the working side) than inside of it (corresponding to the balancing side).
In other words, with the TMJ articular its degree of reproducibility was inferior on the balancing side rather than on the working side.
5. When condylar distance of the TMJ articulator was fixed at the innermost position, the resin fossas of individual subjects were collected in more or less similar forms.
This suggests a possibility that, by increasing the number of cases, it wll be possiblei to construct a semiadjustable articulator that has the average condylar fossa morphology.
6. From the fact that changes in the form of central bearing plates would not affect the form of glenoid fossa, it could be established that the TMJ articulator has an excellent degree of reproducibility.
On the strength of the above findings, it is to be concluded that the TMJ articulator is one which serves clinical purposes satisfactorily.

抄録全体を表示

The present study is desined to Silicone Rubber Impression materials on manipulated condition, that is impression thickness, making and remove of impression its time elapse of mixing, have influence on occulusal surface and axial surface used with Holography.
As the results of these effort, the following conclusions were obtained.
1. This study is good method used with the Holography. This method can measured deformation and infinitesimal displacement of dental materials, don't touch the object and that can observe with the bodily eye.
2. Silicone Rubber Impression materials showed various displacement volume severally on manipulated conditions.
3. Impression surface of axial surface condition that impression thickness 1, 0mm, making of impression after 75 seconds, removed after 5 minutes its time elapse of mixing showed minimum. And the state added between occulusal surface and axial surface, that condition showed minimum displacement volume too.
4. Silicone Rubber Impression materials surface keep on after 60 minutes displacement all condition that this study established.

抄録全体を表示

There is a fair amount of published literature on the positional changes of the residual teeth after substantial loss of the abjacent ones. But the majority of these studies are concerned with macroscopic observations of positional changes on the part of the residual teeth after several years of extraction by use of plaster models. They reflect difficulties in grasping accurately the positional changes of the residual teeth after extraction.
Therefore, the author and his associates earlier reported on our measurement. method and measurement apparatus. In the present study, the author was concerned with the positional changes is a selected sample of 10 Japanese dental students by an application of the above measurement method and apparatus. With these subjects, efforts were made to establish chronologically the changes of the residual teeth after extraction of the mandibular first molar on the right side.
As a result, the author arrived at the following findings: 1. Throughout the measurement period, all the subjects were found to have suffered from some kind of positional changes in the second premolar and second molar on the extracted side.
With the exception of 1 subject, the remaining 9 subjects suffered from the positional change in the first premolar.
2. With the residual teeth from the mandibular right canine to left second molar, there were found no positional changes in all the subjects.
3. With the right first, second premolars and second molar in which the positional changes were found, the amount of change was the largest in the second molar in common with all the subjects.
4. In terms of dental regions where the positional changes were found, there was a statistical difference between the time passage after extraction and the amount of changes except for the first premolar in 1 subject.
5. There were observed two different patterns in the positional change of the second molar on the extracted side. One pattern was that the amount of change was noticeably large in the initial stage of extraction, the change becoming smaller in proportion to the passage of time.
The other pattern, on the other hand, showed an opposite tendency.
6. In terms of the time passage after extraction and the amount of positional change in all the subjects, there was observed a fairly high correlation between the first, second premolars and the second molar in these items.
7. Based on the amount of positional changes obtained from all the subjects, the degree of positional change of the second molar was approximately 10 times as large as that of the first premolar, and approximately 7.5 times that of the second premolar.
8. Concerning the time-point when positional changes of the adjacent teeth would occur after dental extraction, the change took place comparatively soon in the second molar and anywhere from 15 days to one month in the second premolar. As regards the first premolar, on the other hand, the positional change occurred after that of the second premolar took place.

抄録全体を表示

Recently, as an approach to the easier and more precise casting method, re-recognized was Die Investing Technique, whose chief characteristics is the investmentof the model itself together with the wax-pattern.
The present author examined various impression materials, density of colloidal silica, and casting alloy to obtain information of their influence upon the surface of models and castings, when Die Investing Technique was employed. He further compared the surfaces of castings between Die Investing Technique (Direct Technique) and Die Pattern Technique (Indirect Technique) with a view to ascertain the clinical effect of the former.
The following are the conclusions he reached:
1) The surface roughness of models and castings was closely related in the case when Die Investing Technique was employed.
2) The surface roughness of models are under the stronginfluence of the kind of impression materials: Hydrocolloid impression materials proved to have the surface roughness two or three times as large as Rubber Base impression materials.
3) The surface roughness was not largely dependent on the density of colloidal silica, but it showed a slight decrease when the density was high.
4) The reproducibility rate of the models, evaluated by Fourier analysis, marked highest when Surflex was used as an impression material, and Flexion, Hydro-Colloid, and Algiace came in the order of the rate.
5) The comparison of castings by Cristobalite investment material and by Die investment material proved that the surface roughness and the reproducibility indicated better results in the case of the latter.
6) He concluded that Die Investing Technique may well claim high clinical effectiveness when the surface roughness of castings was considered.

抄録全体を表示

We have experienced the Epulis fissuratum in clinic. The most cases are caused by the continuous repeating mechanical stimuli due to the ill-fitting dentures.
When we observed them, we have gained the following results.
Especially about the dentures which brought the chronically mechanical irritation, we have measured the occlussal stress-concentration by means of “Prescale (FUJI FILM Co., Ltd)”.
1. The average of the age was 61.6 S.D.±8.5 years old.
2. In respect of sex, the female were 8 cases and the male was a case. The female caused more than the male.
3. The position of the proliferation located the parts of the incisor and premolar. The maxilla were 6 cases and the mandible were 3 cases. The maxilla caused more than the mandible.
4. About the growing form, the lobulated iype were 5 cases, the ridge type were 3 cases, and the mixed type was a case.
5. About the chief complaint, there were many swelling, but few pain.
6. All dentures were ill-fitting, and polished insufficiently.
7. About the histologic features, we have observed the epithelial proliferation, the proliferation of the fibrous conective tissue, and the accessory salivary glands in a few cases.
8. About the alveolar ridge and the dental arch, there were discrepancy between the maxilla and the mandible in the most cases. 9. About the occlusal stress-concentration, the result which used “Prescale (FUJI FILM Co., Ltd)” were distributed the press as the parts of the incisor as the molar.

抄録全体を表示