This study was investigated to clarify the biocompatibility of implant materials by means of MC3T3-E1 osteogenic cell line established from newborn mouse calvaria. These cells have the ability to differentiate into osteoblasts in vitro and to deposit hydroxyapatite crystals on extracellular matrix produced by them. So they seem to be more suitable than fibroblasts for the in vitro evaluation of implant materials, since the materials are mostly applied into bone. The materials used in this study are aluminium oxide (single crystal and poly crystal), titanium, zirconium, palladium-alloy, thermanox plastic cover slip (control). Disks (diameter: 10 mm, thickness: 1 mm) of these materials were placed in Φ60 mm plastic dishes. On these disks, 3, 000/disk of cells were inoculated and cultured in 5ml of α-MEM supplemented with 10% fetal bovine serum. On 2 days of culture, the cells on titanium and zirconium were thick and spindle in shape, similarly to them grown on plastic dishes.
To study the effect of implant materials on cell growth, differentiation and calcification, the cells were cultured for 17 days. The protein and DNA contents in the cells cultured on titanium and aluminium oxide were significantly greater than those on the other materials. Titanium and aluminium oxide poly crystal hastened cell growth. The values of alkaline phosphatase activity were high on titanium and zirconium. The capability of collagen synthesis has been examined using tritium proline. Zirconium was the most capable material on the proportion of collagen to protein synthesized. Titanium and zirconium accelerated cell differentiation. Ca and P contents were the highest on titanium, while they were lower on the other materials than those on control.
In conclusion, these results suggest that titanium has very well biocompatibility to the bone tissue as an implant material.

View full abstract

We investigated the jaw opening degree and jaw opening pathway on 138 normal subjects and 104 abnormal subjects to make an objective basis of the jaw opening pathway as one of the examinations of stomatognathic dysfunction. As examining the terminal hinge opening pathways we distinguished the initial phase in which the movement of the condyle was considered mainly to be rotation from the second phase in which the jaw moved to the maximal opening position after the initial phase. Then we classified jaw opening pathways of all subjects into seven patterns by the presence of the mandibular deviation in each phase described above and near the maximal opening position. As a result, half of the normal subjects belonged to pattern A, 70% of those with pain and temporomandibular joint noise to pattern B and, 50% of those with the limitation of the jaw movement showed linear opening and 30% with the limitation belonged to pattern D.

View full abstract

When a vital tooth is restored with a metal inlay or crown, a complaint that thetooth has become sensitive to cold water is sometimes heard. The same complaint can be made even after the restoration by porcelain jacket crown (a bad conductor of heat). Usually this complaint fades out when the occlusal adjustment is made properly. So it is considered that such hypersensitivity is caused by a high crown or supracontact.
In this paper treatment procedures for two patients are described and the relationship between a hypersensitive tooth and overload is discussed.
The first patient is a 40-years-old woman treated with a fixed partial denture. After cementation of prosthesis, opposite intact tooth became hypersensitive and recovered by occlusal adjustment of the prosthesis.
The second patient is a 17-years-old man with partial anodontia. His chief complaint was the hypersensitivity of existing teeth. His symptom was disappeared after insertion of a removable partial denture.

View full abstract

Temporary crowns for gum displacement were tested how they work in order to obtain subgingival tooth preparation and impression of abutment tooth accurately and without difficulty. The observation of the displaced gum revealed the following conclusions.
1. They displaced the gum so sufficiently that subgingival tooth preparation was possible without injuring or bleeding of the gum.
2. It is possible to get the impression after the preparation of the abutment tooth without any additional gum displacement due to their long effectiveness.
3. Inflammation of the sulcular epithelium which temporary crowns for gum displacement bring were proportional to the length of the set period ; only slight inflammation was recognized within less than 4 weeks and the sulcular epithelium shows clinically normal appearance especially within one or two day after the setting.

View full abstract

The purpose of this study was to establish an effective connecting method between wrought wire clasps and cast rests.
In this study, straight Co-Cr alloy wire samples connected by three different methods were evaluated with the tensile test and the bending test. The first method was the hightemperature (800°C) fusing method with Co-Cr alloy, the second one was the conventional soldering method using Ag alloy and the third was the newly developed room temperature fusing method using Co-Cr alloy.
Following results were obtained:
1) On room temperature fused samples about 80% of original wire strength were measured, while values of other were relatively small.
2) The deflection under the unit bending load was slightly smaller in room temperature fused samples and slightly larger in soldered samples than original clasp wires. High-temperature fused samples did not endure the bending stress and broke easily.
3) Mechanical properties of wrought wires hardly changed in the process of the room temperature fusing method.
From above mentioned results, the newly developed room temperature fusing method have great potentialities for clinical usage.

View full abstract

The purpose of this study was to investigate each and individual step of the construction of fixed prosthetic appliances, and its effects on the marginal gingivae. The fixed prosthetic appliances consisted of twenty porcelain fused to metal crowns and six full cast crowns of the anterior and posterior teeth respectively. The state of the marginal gingivae was determined by staining the exfoliative epithelium of the gingival sulcus, recording the gingival fluid, and measuring the gingival index and depth of the gingival sulcus.
The results of the experiment were as follows:
1. Effects upon the marginal gingivae were greatest during the preparation of the tooth abutment and slight during impression taking. Some temporary resin crowns were shown to have effect upon the marginal gingivae while others did not.
2. Based upon daily clinical procedures in making a crown, effects on the marginal gingivae could be observed in the different stages of construction. However, after setting the crown for a period to disappear.
3. No significant differences were observed in relation to crown construction and its effect on the marginal gingivae between the full cast crowns and porcelain fused to metal crowns.
4. Continual observations of the sulcular exfoliative epithelium and sulcular fluid proved to be an effective method in detecting minute and early changes of the gingival sulcus.

View full abstract

Periodical observations of the gingival tissue after a 3 year placement of fixed prosthesis was made.
The prosthetic appliances consisted of 4 full cast crowns in the molar region and 16 porcelainfused-to-metal crowns in the anterior region.
The objective of this report was to measure the amount of crevicular fluid and appearance rate of exfoliative epithelial cells of the gingival sulcus, as well as recording the gingival index and depth of the sulcus itself. To clarify the marginal fit between the prosthetic appliances to the cervical region, the replication technique was used and observed under a scanning electron microscope (SEM).
Results showed 18 cases of the cement thickness to be 50-105μm which were within clinical standards, and 2 cases which were not (280-340μm). The marginal fit region were then classified into the following 3 categories, smooth type, overhanging type, and underhanging type. Results showed a possible effect of prosthetic appliances on the gingiva, for the crevicular fluid and appearance rate of exfoliative epithelial cells which met clinical standards showed no significant statistical or periodical change, while an increase was observed in those which did not meet clinical standards.
Accurate procedures leading up to the setting of the crown can result in satisfactory placement, which in turn can be correlated to the longevity of normal marginal periodontal tissue and harmonious balance between it and the prosthetic appliance.

View full abstract

Since 1979, we have been reported that the metal bonding denture base resin had many advantages when we used in the prosthetic field. However unexpected fractures of the wire clasp were frequently observed within the shorter clinical period than commonly. Cantilever type repeating bending tests were carried out to search for whether the use of this resin caused the wire fracture or not. Two types of test pieces, straight and crank-like, were fabricated by the φ0.9 mm Co-Cr wrought wire and two heat cured resins, META-DENT and ACRON. Repeating bending stresses were loaded at 10 mm left from the fulcrum. Bending cycles required to the fracture of test pieces made of adhesive resin are one-half time as many as the conventional in both two types. It was considered that these differences caused by the space between wire and resin. Test pieces intentionally proposed 0.3 mm space between wire and resin showed remarkable resistances to the wire fracture. When the stress was loaded at 12 mm, the bending strengh also increased. Test pieces with φ1.0mm wrought wire were also tested, however the fracture resistance did not increased. It was recognized that the wire

View full abstract

The gap between a metal crown and an abutment tooth often leads to troubles suchas secondary caries, pulpitis, periodontitis and so on.
We expected that newly developed adhesive resins which adhere both dental alloy and tooth structure can minimize such troubles if they were used as setting materials of prosthetics.
In this study, the degree of marginal leakage of adhesive resins was compared with that of conventional dental cements. The results obtained were as follows:
1) The degree of marginal leakage of metal crowns was always greater in the dentin margin than in the enamel margin.
2) Adhesive resins showed much more excellent marginal closure than conventional dental cements.
3) No correlation was observed between the fitness of a metal crown and the degree of marginal leakage.
4) The degree of marginal leakage was always greater in the etched margin, especially in the etched enamel margin, than in the non-etched margin.

View full abstract

We have reported the clinical studies on adhesion bridge (acid-etched fixed partial denture). It was found that tooth movement of abutment tooth occured in this study.

View full abstract

This histopathological study was undertaken to investigate the pulpal irritation of Panavia EX in adult dogs at the intervals of 3, 7, 14, 30, 60, 90 and 120 days after filling. The results were as follows:
1. At the 3-day and 7-day postoperative intervals many cases showed the pulpal changes, however, its degree was not severe, but moderate.
2. At the 14-day and 30-day postoperative intervals few cases showed changes and yet its degree was mild. The number of the cases with reparative dentin formation was very few.
3. At the 60-day, 90-day and 120-day postoperative intervals many cases showed no pulpal changes, the number of the cases with changes gradually decreased and its degree became mild. The number of the cases with reparative dentin formation was reparatively few and also its amount was scanty.
4. As a result of this study, it can be considered that Panavia EX was less irritative to the pulp.

View full abstract

Light activated composite resin, Dentacolor, was examined on chemical composition, polymerization characteristics and bonding to a metal and adhesive resin cement in order to confirm the dental application of it. For bonding, the surface of metal, Au-Ag-Pd alloy, was treated as follows; a) retention beads added, b) retention beads+alumina sand blasting+tin electroplated+adhesive resin cement (Panavia EX), c) alumina sand blasting+tin electroplated+adhe sive resin cement.
The results were summarized as follows;
1) Dentacolor consists of 31 wt% of urethane dimethacrylate with a small amount of other methacrylate (unknown) and 69 wt% of composite filler (inorganic phase 47 wt%).
2) The surface hardness of the cured product of Dentacolor was little affected by a position of a specimen in a photo-irradiation apparatus (Dentacolor XS) and a shade of Dentacolor, however, conversion of polymerization, which was presumed by its hardness of a vertical plane, was relatively high in the center of a flask.
3) Compared with heat cured composite resin (Isosit), the surface hardness, wear resistance and solubility in water of Dentacolor were nearly equal, but the bending strength and water sorption were slightly lower than those of Isosit.
4) The bonding strength of Dentacolor when another layer was put on the surface of its cured product was comparatively high (170 kg/cm²) and its value was little affected by the irradiation time to the first layer.
5) The bonding strength of Dentacolor to the metal was increased with the surface treatment of the metal except for the method a)(170-180 kg/cm²).
6) After thermal cycling, a good improvement of marginal sealing was shown by the surface treatment of the metal except for the method a)

View full abstract

The purpose of this study was to make clear electromyographic feature of complete denture wearers. 31 edentulous patients who had no problems (complete denture group) and 15 subjects with complete dentitions (normal dentulous group) were selected. The EMG of the masseter muscles and the anterior part of temporalis muscles, elicited by Tapping movement and chin taps during maximum clench (Clench and chin tap) were divided 4 divisions as follow:
B. T. C.: before tooth contact
S. P. L.: silent period latency
S. P. D.: silent period duration
A. S. P.: after silent period
Each division was analyzed automatically with mini computer system, and mean ofduration and mean average of integration were measured. The data were compared with the normal dentulous group. The results were summarized as follows:
1. On tapping movement, S.P.L. duration extended about 1-2 ms (significant difference at P<0.01).
2. Mean average of integration during clenching was about half, especially, masseter was obvious.
3. The other parameters were similar to normal dentulous group.

View full abstract

Being associated with inflammation, the reaction of gingival fluid has been a constant source of interest and it has been the object of many studies. We have paied attention to its pH and reported the difference between in normal crevices and periodontal pockets. In the present report, the gingival fluid volume was recorded and correlated with the pH in each site.The gingival fluid volumes were measured by a Periotron and each datum was classified according to Garnick (1979). The pH was determined by the same method reported previously.
The results were as follows:
1. As the gingival fluid volumes increased, elevations of pH from 6.26 to 6.50, 6.54 to 6.71, and 6.30 to 6.49, were observed in the buccal, lingual and interproximal crevices, respectively.
2. After 1 week wearing of acrylic resin temporary crowns, elevations of both gingival fluid volumes and pH were observed.
3. Regardless of gingival fluid volumes, constant pH levels were observed in buccal and interproximal periodontal pockets.
4. In lingual periodontal pockets, decreasing pH values were observed with increasing gingival fluid volumes.

View full abstract

Tooth carving practice is very important to make students understand the anatomical forms of human teeth and to make them study the basic technique necessary to reproduce crown forms in the process of preparing prosthetic applicance.
Therefore, in the present studies the author makes out the design cut method (A), design mode technique our school adopted, and as preliminary studies purposing to improve tooth carving technique, selects Obana's (B), dessin mode one and the direct carving method (C), to be compared with our design cut method.
The author makes 30 beginners, out of the freshmen in 1985, operate, by themselves, the upper right central incisor, upper right first premolar and the upper right first molar, by the above-mentioned 3 kinds of methods, to evaluate their respective products from the overall viewpoints, and examine the dimensional errors, comparing them with the standard models. The results are as follows:
1. It proves that the products carved by the A, B and C methods are all evaluated low, less than 3 points, and that there is no remarkable difference due to the carving methods.
2. Dimensional errors prove to be 15-20% in the central incisor and premolar cases and 10% in the molar case.
3. Those carved by A and B methods shown an insufficient carving tendency, while those carved by C method show both excessive and insufficient carving tendencies.

View full abstract

A comparative study was made on the adaptability of the post core made by the dieinvesting technique and that of the post core made by the die-pattern technique. As a results, the following conclusions were obtained.
1. Vertical adaptability: As for the rising of the post at the apical portion, the die-pattern technique was found to cause a bigger rise. In other words, the length of the post tended to shorten when die-pattern technique was used. On the other hand, as for the rising of the post at the root-surface portion, no significant difference was noted between the two techniques.
2. Horizontal adaptability: As for the gap between the post and the wall at the apical portions, the die-pattern technique tended to enlarge the gap. On the other hand, as for the gap between the post and the wall at the root-surface portion, no significant difference was noted between techniques.

View full abstract

Our own checkup examination of masticatory efficiency was developed by using protein quantitative analysis.
The purpose of this report was to performance basic research about effectiveness of our checkup examination and was to research the condition of increasing surface area with mastication.
In this study, a Japanese fish cake so called “Kamaboko” was selected to test food according to a result of study on physical property of foods.
The results obtain were as follows:
1. Effectiveness of our own method demonstrated by result of preparatory experiment.
2.“Kamaboko” is so much better as test food.
3. It is necessary for to compare and to examine about masticatory efficiency to research 3 kinds of test foods thickness and better number of masticating time to reserch for masticatory efficiency is about 10 times.

View full abstract

The purpose of this study was to analyze the stress distribution of the teeth and the mandibular bone when a Konuskronen telescope denture was applied. The analysis was conducted by using the finite element method and changing the conditions such as thedirection of the load, the level of the bone supporting the abutments, and the number of the abutments. The model included canine, premolars, a distal-extension Konuskronen telescope denture, and their supporting structures.
The joint element reported at Part 1 was used in order to simulate the conditions of the contact area between outer and inner crowns of the abutments.
The results of analysis indicated the followings.
When the vertical load was applied, the stresses were distributed to the abutments and their supporting bone. However, when the load was applied 45deg; to the vertical axis, the stresses in the bone supporting the denture base were increased.
As the level of the bone supporting the abutments was reduced, the stresses increased and concentrated to the second premolar.
The stresses of two-abutment model were larger than that of the three-abutment model. This indicated that the use of more teeth for the abutments of the removable partial denture was mechanically desirable.

View full abstract

In the removable partial denture, it is very important that the denture movements are reduced and that the occlusal forces are distributed appropriately to the abutment teeth and the residual ridges. The purpose of this experimental studies are to investigate and evaluate characteristic movements of the denture bases and the abutment teeth, when the indirect retainers are altered.
The results are as follows:
(1) In the unilateral mandibular dentures, most of the occlusal forces are transmitted in the lingual direction.
(2) Both the amount of the denture movements and the harmful displacements of the primary abutment tooth are remarkably minimized, when the dentures have the indirect retainers with the positive rests, the minor connectors fitted with the subguide planes and the cross-arch stabilizations.
(3) In the case of the oblique forces to the dentures, the displacements of the denture bases and the abutment teeth are reduced when there are the cross-arch stabilizations and the indirect retainer with the positive rest in their denture frameworks.

View full abstract

The rotational path of insertion differs substantially from the conventional path or the straight path of insertion. In the use of the rotational path, one segment of the partial denture is seated first, then the remainder of the prosthesis is rotated into position. One segment of this system is the rigid retentive component with long rest and the other the conventional clasp.
This study examined the influence of point and direction of displacing force and the proximal undercut of rigid retainer on retention of this system. Then this system was applied in clinical field. The following results were obtained:
1) Retention of denture is the smallest when displacing force was applied at the conventional clasp part.
2) Direction of displacing force (± 10deg;) has no significant effect on the retention.
3) The value of retention showed a tendency to increase in order when proximal undercut of rigid retainer was 0.3, 0.7 and 1.0 mm respectively.
4) The effects of the point and direction of displacing force on retention of mesio-disto rests and reciprocal arms design are similar to those of original long rest design.
5) When a severly tilted posterior tooth is used as an abutment tooth, this system could provide adequate retention.

View full abstract