Air-Powder Abrasive System a new technique currently being promoted and it is aplication in dental clinic. The new polishing units are air-powered devices which use water and air pressure to deliver a stream of cleaning powder, which is mainly sodium bicarbonate. Effects and deposit removal areas are changed by varying working angles and distances, however, these differences are not yet clear. In addition, effects on enamel, dentine and cementoenamel junction or removal of stain and deposits in pits and fissures are also unknown. Therfore, we examined these points, using an Air-flow in this study.
The following results were obtained.
1. The best working angle is 60° at a distance of 5 mm from tooth surface.
2. Air-Powder Abrasive System cannot control extent of removal area.
3. In the scanning-electron microscopic observations, the enamel surface is relatively undamaged but dentine and cementoenamel junction are markedly damaged.
4. There is no effect of stiking dental plaque on enamel by using the Air-Powder Abrasive System.
5. Removal of stain and deposits in pits and fissures is limited to the surface and no removal is seen at the bottom.

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The purpose of this study was to examine the validity of EMG parameters as evaluation of the prognosis in complete denture wearers. In this study, the comparisons had been made between two groups. One group was consist of the subjects who were immidiately after the insertion of new complete dentures (group A). Another group was consist of the subjects who had good prognosis (group B). EMG signals were evoked by tapping movement and chin tap. 4 Muscles-4 Division Coordination Pattern Analysis was used, and the name of each division was follows:
B. T. C.: EMG activity of before tooth contact
S. P. L.: Silent period latency
S. P. D.: Silent period duration
A. S. P.: EMG activity of after silent period EMG signals analyzed automatically with minicomputer system and paramaters (duration and mean average of integration on each division) were investigated whether the differences were significant or not.
The results were as follows:
1) Recognition ratio of silent period of the group A showed a slightly tendency to be lower than the group B.
2) Both of tapping and chin tap, the difference between the group A and the group B was not statistically significant on each division.
3) So, it was difficult to evaluate the prognosis in complete denture on the statistical aspects.

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Distal-extension removable partial denture tends to rotate about its most distal abutments, including heavy torsional stress on. Therefore, it is important to recognize the stress distribution to supporting tissues. The purpose of this study is to analyze the stress distribution to abutments, periodontal membranes, and bone supporting removable partial dentures of rigid and non-rigid connection. Finite element method was used to analyze. In this analysis, “joint element” was used in order to simulate the conditions of the contact area between two objects.
The stress and the displacement of supporting tissues when the load was provided on artificial teeth were calculated.
The results of this analysis were followings.
1. The most distal abutment was bended to distal direction by the load.
2. The stress distribution to supporting tissues on rigid connection type was less than on non-rigid connection type.

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In order to determine the clinical significance of mucosalplasty of edentulous ridges to improve pontic adaptation, the first step was to make a cut in the mucous membrane of the edentulous ridges of dogs using a surgical scalpel, diamond point used in gingivoplasty, and an electrode tip, to observe the healing process and degree of tissue damage from a histopathologic and oralbiomicroscopic standpoint.
The results were as follows;
1) Immediate postoperative findings after the use of a surgical scalpel showed minute tissue damage, and oralbiomicroscopy after 21 days showed keratinization of the epithelial cells, and a return to normal histological structure was observed after 28 days.
2) Effect upon the wound surface immediately following the use of the diamond point showed localized degeneration, but did not appear to affect the healing process and showed the same type of healing process as those under the use of the surgical scalpel.
3) Dentoelectrosurgery caused degenereation, necrosis, and lack of normal blood supply, which resulted in a delay of the healing process. However, normal histological tissue were observed 28 days later.
4) Although the healing duration were different in the three methods, they all resulted in successful mucosalplasty of the edentulous ridge for the improvement of pontic adaptation. Findings also showed that the special features of each method should be utilized wisely in clinical application.

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Because the retainers of an adhesion bridge are adhered to the lingual and a part of the proximal tooth surface with an adhesive resin, metal for the retainer necessiates the mechanical properties which are endurable of occlusal force even if it is thin. It is suspected that an adhesion bridge made of type IV gold alloy, which has been used conventionally for crowns and bridges, results in the insufficient longevity of placement because of the shortage of its toughness.
In this study we examined the mechanical properties and adhesive strength of the trial gold alloy we developed recently, whose hardness is higher than type IV gold alloy. Panavia EX^® was used as an adhesive resin.
We obtained the result that the trial gold alloy has greater properties in elastic modulus, proof stress and fatigue strength than type IV gold alloy and other dental gold alloys.
Therefore, it is expected that the trial gold alloy has excellent rigidity as retainer metal for an adhesion bridge even if it is thin.

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The purpose of this study was to evaluate the influence of environmental temperature, humidity and methods to dry the etched enamel surface on the adhesive strength of dental adhesive resin ‘Panavia EX’. The findings were as follows:
1. Though temperature and humidity in oral cavity were higher than 30°C and 81% respectively, they were significantly different from site to site.
2. By rubber dam application, temperature and humidity in oral cavity decreased markedly. By sucking air with vacuum in addition to rubber dam application, both decreased still more.
3. When vacuum was used, there were no statistically significant differences in temperature and humidity among applications of rubber dum, mini-dam, and cotton roll with clamp.
4. The higher were both of environmental temperature and humidity, the more was the tensile adhesive strength reduced. However, since the adhesive strength was not influenced singly by temperature or by humidity, it is suggested that the adhesive strength is influenced by absolute moisture volume.
5. Drying time on the etched-enamel surface influenced the adhesive strength significantly whatever environmental temperature and humidity are. It seems that at least 15 seconds are needed to dry the etched-enamel surface sufficiently with air syringe.
6. It was hardly effective for increasing the adhesive strength to dry the etched-enamel surface with alcohol and to increase the temperature and pressure of compressed air.

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In the random position (R. P.) where the patient lies on a dental chair and the operator sits on a chair for treatment, the left upper first molar is prepared for the abutment for a full cast crown. The author compared the measurement of the form of the abutment in R.P. and the date of home position (H. P.) conducted by Kakehashi. This study has led to the following results:
1. A significant difference in the amount of reduction for the preparation of the abutment between R. P. and H. P. was noticed as to the amount of the axial reduction and subgingival reduction on the buccal surface, and the taper degrees on both axial surfaces at the center of the buccal-lingual surfaces.
2. In comparison with the time required for the preparation of the abutment between R. P. and H. P., no large difference was noticed in the time of operation of the air turbine, while the time of non-operation in R. P. was about 1/3 of that in H. P., The total time required in R. P. was about 1/2 of that in H. P.
3. R. P. was superior to H. P. in a clinically important point of the continuance of the finish line as well as in the efficiency of operation; i. e. the total time reqired.

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The anchorage by investing was practiced to make a linear 3-unit bridge for molars by the soldering method. An experiment was carried out to determine the adaptability after soldering when three factors constituting the size of the investing block; i.e. the height, the buccolingual width, and the mesial-distal width, are changed. The following results have been obtained:
1. Two of the factors constituting the invested block, the height and the buccolingual width, affected the adaptability of bridges with a significance of 1% of danger rate.
2. As to the displacement quantity, the mesial-distal displacement was largest when the height of the block was 10 mm.
3. As to distortion, the occlusal surface was bent throughout the bridge and the distortion was observed in the direction of the neck of the tooth, which was more serious when the invested block was thinner.
4. The size of the block with witch the best adaptability was obtained was 20 mm in height, 25 mm in buccolingual width and 35 mm in mesial-distal width.

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In recent years, requests by patients concerning clinical prosthesis have become increasingly diversified and sophisticated. And not only the form and arrangement of the teeth but also their color is considered particularly important.
For that reason a spectroradiometer device was used, and three main elements of the central incisor, the lateral incisor and canine in the upper and lower jaws and the chromatic differences were compared and examined.
Conclusion
1. Distribution of colors in the L*a*b* Tables was quite similar in the upper and lower jaws when the measured area was the same even in the case where different types of teeth were compared.
2. The difference according to the areas measured was either ‘slight’ or ‘noticeable’ in both the upper and lower jaws in 60-70% of all the subjects measured.
3. As for the difference in color, many teeth in the upper jaw were observed as being different in color from one another, but no marked difference was noticed among the teeth of the lower jaw.
4. In more than 80% of the subjects measured, color differences were noticed between the teeth in the upper and the lower jaws and almost all of such differences belonged to ‘noticeable’, that is, more than1.2but less than 3.3.

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For the purpose of clarifying the color of gingiva, the author applied spectroradiometry to 23 male and 20 female subjects, all in their twenties, to measure the normal gingiva. As a result, the following facts have been obtained:
1. The spectral distribution of gingiva gradually rose as short wavelength proceeded to long wavelength, and the two absorption bands were clearly observed between 540 nm and 610nm, particularly around 540 nm and 580 nm. But denture base resin drew a curve different from the above.
2. Concerning the distribution range under the standard souce D 65,
Male incisor area: L*=48.46, Cab*=26.15, Hab°=37.57,
Male canine area: L*= 46.25, Cab*=26.42, Hab°=39.71,
Female incisor area: L* = 50.23, Cab* =27.42, Hab°=38.22,
Female canine area: L* = 47.66, Cab* =25.86, Hab°= 40.98,
3. When removable partial denture is constructed for the anterior area, it is suggested that, instead of using standardized color denture base resin, brighter and fresher yellowish hue females than males, and darker and more yellowish color denture base, should be used in the canine area than in the central incisor area, considering the regional differences in color, in order to obtain the color closer to that of natural gingiva.

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The stress distribution in a tooth is analysed numerically by considering both fixed prosthetic appliance and core simultaneously. This analysis is done by use of the finite element method and by taking account of the sustaining rigidity of neighboring teeth. As result of this analysis, the following points are clarified:
1) The stress values in the dental model as an object of study decrease as a whole under the influence of the sustaining rigidity of neighboring teeth. Furthermore, these values decrease when the horizontal component of load is applied to the dental model.
2) As the position of contact with a neighboring tooth moves to the root, the stress values increase generally and the horizontal components of principal stresses become larger.
3) When core is constructed by use of rigid materials such as metal or ready-made pin, the stress values in core increase, while those in the remnaud dentine decrease. On the other hand, when core is constructed by use of soft materials such as resin, the stress values in core decrease, but those in the remnant dentine increase.

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When a dentist prepares a vital tooth, it is very important to know the distance between the prepared surface and the pulp chamber wall, and now we have developed ultrasonic diagnostic equipment which can indicate the nearness of these two boundaries by measuring the thickness of the remaining dentin.
This equipment can be used to measure the thickness of the remaining dentin between the prepared surface and the pulp chamber wall by means of a well-focused ultrasonic beam.
1. The measuring technique is very easy. The measuring method is as in the following.
1) The ultrasonic velocity in human dentin which differs according to the portions of tooth [e.g. crown: maxillary tooth 4, 039 m/s, mandibular tooth 3, 940 m/s, neck: 3, 887 m/s, root: 3, 743 m/s These are average values.-1985, MOROZUMI] is input to the microcomputer.
2) The probe which generates the ultrasonic wave is attached to the surface of the prepared tooth with the help of the existing water between the probe and the tooth's surface.
3) The reflected waves from the surface of the prepared tooth [S] and from the pulp chamber wall [B] can be observed on the CRT.
The probe position must be adjusted so as to obtain the maximum amplitude of each reflections.
4) Keeping this probe position and pushing the measuring switch on the controller, the estimated thickness of the remaining dentin is indicated digitally after 0.3 seconds.
2. The ultrasonic wave which is generated from this equipment has no effect on the human body.
3. Accordingly, this equipment is useful for measuring the thickness of the remaining dentin under dental treatment.

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The subjects were eight bimaxillary complete denture wearers who noted neither subjective nor objective speech disorders. The mechanism of speech and changes with days were investigated and concurrently compared with that of normal subjects when pronouncing |s| and |∫| by analyzing tongue-palate contacts and speech waveforms.
The results were:
1. On pronouncing CV syllables the preceding consonant duration in denture wearers delayed greatly as compared with normal subjects, but decreased on pronouncing VCV syllables, showing nealy the same value of normal subjects.
2. The following vowel duration in denture wearers was little different from that in normal subjects when pronouncing CV syllables. Although the duration decreased greatly in both groups when pronouncing VCV syllables, the tendency to decrease was greater in denture wearers than in normal subjects.
3. As with normal subjects, the duration from the start of tongue-palate contact to the onset of preceding consonant in denture wearers was short when |a| and |o| were added as preceding vowels, whereas it was relatively long when |i|, |u|, and |e| were added, especially, the duration for |i| was the longest.
4. As is the cases for normal subjects, the duration from the onset of preceding consonant to the indication of so-called standard palatograms in denture wearers became relatively short in the group having the preceding vowel of |i|, whereas it became long in the groups having other preceding vowels.
5. There were no marked changes with days in pronunciation after setting denture at three points of time; namely, at the time of setting denture, after a few days, and after approximately 10 days.

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The retention and stability of removable prosthodontic appliances are closely related to the occlusion and arrangement of artificial teeth.
The purpose of this study was to develop a clinically oriented computer aided system for analyzing the relation between residual ridge shape and artificial posterior teeth arrangement using the finite element method. The frontal section of the upper and lower alveolar residual ridge were traced on the digitizing board and the finite element model was automatically proceed.
Following conclusions were obtained.
1) Influence of artificial posterior teeth location on the displacement and stress distribution can be easily understood by using graphical outputs of this system.
2) This system was proved to have great potentialities for the clinical and educational appication.

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TMJ patients who have occlusal interferences often complain of pains in the Sternocleidomastoid muscles. The pain occurs mainly in the insertion of the muscle (SCM-I) rather than in the middle of the muscle (SCM-M). Clinical cases were reported on the patients treated effectively by the reconstruction of proper anterior guidance.
The activities of sternocleidomastoid and masticatory muscles were studied by means of EMG during functions in relation to the occlusal contact on the patients. EMG activities of temporal, masseter, SCM-I were recorded by surface electrodes.
On the patients EMG activities of the muscles were of low amplitude and low frequency with no synchronization with the chewing movement, indicating hyperactivity of the muscle.

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This histopathological study was undertaken to investigate the pulpal irritation of Super Bond C & B 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 more than half cases showed the pulpal changes directly under the cavity, however, its degree was not severe, but moderate.
2. At the 14-day and 30-day postoperative intervals few cases showed the changes. Its degree was mild with a tendency of decreasing the changes.
3. At the 60-day, 90-day and 120-day postoperative intervals many cases showed no pulpal changes. The number of the cases with reparative dentine formation was reparatively few.
4. As a result of this study, it can be considered that Super Bond C & B was less irritative to the pulp.

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This study was aimed at determining the effect of the two factors, the type and number of retaining wire, on the fitness of the bridge (Three-unit liner bridge) in the electrical soldering. The three-dimensional distortion of both abutments to the pontic was measured. The results obtained are as follows:
1. During the electrical tacking stage in which AUS and BOND were used, the abutments were displaced by about 10 microns in each direction (X, Y and Z).
2. At the soldering stage, the mesio-distal displacement is greater than the bucco-lingual and vertical displacement, regardless of the type of the retaining wire.
3. The best fitness was obtained when the retaining wire is treated with heat and made of soft stainless AUS with an approximate rate of thremal expansion to that of the soldered metal, and two pieces of wire are used each on the occulusive surface and the buccal surface of the retaining knobs set on the buccal side and the lingual side.
4. The fitness of the bridge was almost the same as in the case of the investing method, and further the time taken for technical operation was largely shortened. Therefore, it has been shown that this method is extremely useful for clinical application.

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