The cementation is important process in crown and bridge therapy. Faulty cementation disturbs previously established margins and occlusal relationship.
In this study various devices to apply and maintain the forces used to seat complete crowns during cementation were compared with one another from the viewpoints of film thickness and stability of the mandible. Devices compared were as follows: cotton roll, wood stick, stopping and crown setter uni-and bilaterally respectively, vibration (Vibraseat), hand pressure and with no material. However, instead of dental cement a silicone impression material (injection type) was used as a luting agent.
The following results were found.
1. Vibra-seat, crown setter and stopping unilaterally respectively showed constantly very fine film thickness.
2. Unilateral Forces were more effective than bilateral ones in order to reduce film thickness.
3. Cotton roll and crown setter bilaterally respectively and wood stick uni-and bilaterally didn't show constant film thickness.
4. The mandible was the stablest in stopping and the least stable in crown setter.
5. There was no difference between uni-and bilaterally concerning the stability of the mandible.
6. Stopping was the most comfortable for the patients and the others were at any rate uncomfortable.
7. Summarily, Vibra-seat and stopping unilaterally were recommended.

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In the present study, the author addressed himself to the elucidation of such factors as temperature change and constraint of impression trays on thiokol rubber impression by an application of laser holographic technique, including manipulative conditions such the thickness of the material, times of infusion and removal as well in relation to their possible effects on impression material surfaces that would correspond to the occlusal surfaces in clinical environment.
As a result of this experimental study, the author obtained the conclusions as follows.
1. An internal temperature change of the material itself under different environmental factors registered an increase of about 3.0-4.0 degrees C in 10 minutes from the commencement of trituration at 23.0 degrees C.
When the material was triturated at 37.0 degrees C and stored under this condition for 14 minutes and then exposed to ordinary room temperatuer (23.0 degrees C), an increase of temperature by 11.0 to 12.0 degrees C took place in about 15 minutes afterward.
These maximum values showed gradual decreases and, in 80 to 100 minutes, they reverted to that of room temperature more or less.
2. Time-wise variations due to changes in environmental temperature were found to be twice as much when stored at 37.0 degrees C immediately after processing of the material as compared with room temperature environment of 23.0 degrees C.
3. Whon the presence and absence of a bonding material were compared, time-wise variations were anywhere from 7.9 to 23.9% less when a bonding material was employed.
4. Certain change was still observable in the material even after 360 minutes after the commencement of trituration.
5. Variations owing to differences in the thickness of the material and times of infusion and removal were confirmed to reveal different values respectively.
6. Within the scope of the present experimental study, the conditions that produced the minimum variations were that the thickness of the material was 1.0 mm, an infusion time of 2 minutes 30 seconds after the commencement of trituration and its subsequent removal in 26 minutes.

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In recent years, Levin has developed the lingual bladed teeth having a combined benefit of anatomic occlusal form and that of bladed teeth through an improvement of the conventional Sosin blade and their clinical effectiveness and masticatory function are reported to be quite favorable. For the purpose of elucidating possible effect of the lingual bladed teeth on the masticatory function, the author was concerned in these studies with an application of the semiconductor strain element and masticatory force measuring apparatus to measure the masticatory and antagonistic forces at swallowing, their electromyographic recordings being made at the same time. Further, the recorded masticatory force and EMG findings were subjected to integrated analyses, so that the amounts of both the masticatory and muscular activities could be obtained in a quantitative manner.
As a result of this comprehensive study, the author arrived at the following conclusions.
1. The biting force at centric occlusion was found to be about 14kg, that of lateral occlusion on the working side was about 13kg, about 8kg on the balancing side, and that of anterior occlusion was found to be about 5kg.
2. In terms of the masticatory force, peanuts required approximately 12kg, hams anywhere from 6 to 9kg, and pickled radish (takuan) anywhere from 9 to 11kg. In common with the different types of foods, the largest values were measured in the middle stage of masticatory activity.
Further, when analyzed in terms of masticatory rhythms, the duration of electric discharge was short both in 2 and 3 period in the case of peanuts, and it was short in 4 period in the cases of hams and pickled radish, the tendency of short electric discharge being observed in 5 period in common with these various types of foods.
The number of masticatory activity was the fewest on the part of peanuts followed by hams and pickled radish in order.
3. As for the masticatory rhythms of masticatory muscles, the duration of electric discharge, interval and frequency were all small in 3 period in common with the different types of foods under study.
However, the ratio of electric discharge duration in a given frequency was found to be the smallest in 5 period.
4. In terms of muscular activity, it was small in 4 period in the cases of peanuts and hams, while it was the smallest in 5 period in the case of pickled radish.
5. In common with the various types of foods, the amount of masticatory force was small in 1 period whereas it was measured to be much larger in 3 period.
6. The amount of muscular activity required per unit of mastication was small in 5 period in the case of peanuts, whereas they were small in 4 period and in 3 period in the cases of hams and pickled radish respectively.

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We are going to come an advanced aged society, I guess that the requirement of Gerodontic services corresponded to the old age people is elevated to high position.
In this situation, the full denture prosthodontics will be occupied essential position on the elevation of old ages masticatory function. It has been considerd that the vertical dimention, artificial teeth arrengement, occlusal types and forms and sizes of denture bases are the significant factors, which have direct effect masticatory function of full denture wearers. Several authors have made a study of the aspects of artificial molar teeth since oid times. And in our laboratory other authors studied on the masticatory function of the 30 degree, 0 degree, 20 degree cusp artificial posterior teeth, and lingual bladed teeth. However, there are not the study about the effect to masticatory function by difference of grinding pattern on occlusal adjustment, the key procedure of full denture service. In this study, the author analyzed and investigate about that the biting forces masticatory forces, the electromyography of masseter and temporalis and the number of masticatory times, the full denture with occlusal aspects of artificial molar teeth added excessive grinding pattern.
The outline of the discussion about theses studies as follows;
1. The biting forces in upper first molars are about 7-15kg in the several occlusal position.
2. The masticatory forces in various foods (peanuts, ham and pickled radish (Takuan)) were about 6-11kg, and were larger and constance value in the 2nd 4th period through the masticating periods. And antagonistic forces in swallowing period was smaller. The duration of masticating forces was smaller in 3rd period by peanuts and ham, and 2nd period by pickled radish than the other periods, the interval was smaller in 2nd period by peanuts and ham, and 3rd period by pickled radish, the term was smaller in 2nd period by peanuts and ham, and 3rd period by pickled radish, and the ratio of the duration during electric disch arge period was smaller in 5th period by all foods.
3. Concering the masticatory rythum in various foods, the duration was smaller in 2nd period by peanuts and 3rd period in ham and pickled radish, the interval was smaller in 2nd period by peanuts and ham and 3rd period by pickled radish, the term was smaller in 2nd period by peanuts and 3rd period by ham and pickled radish, and the ratio of the duration during electric discharge period was smaller in 5th period by all foods. Among foods, the pickled radish was smaller than the other foods in the duration, interval and the term, and the ham was smaller in the ratio of the duration during electric discharge period.
4. The integrated masticatory forces in various foods was larger in 3rd period. Among foods, the pickled radish was larger. The number of masticatory times was mors in pickled radish.
5. The activities of masticatory muscles in masticating various foods wsa smaller in 1st and 5th period, and the activities of masticatory muscles in swallowing period was larger than the masticating period. Among foods, peanuts was smaller.
6. The activities of masticatory muscles which were needed for the integrated masticatory force unit in various foods was smaller in 5th period. Among foods, peanuts was smaller.
7. It was established on the necessity that the grinding grinding performed on occlusal adjustment of full denture, is not done to excess and accords to the mandibular movement peculiar to each patients and is done properly, from these studies.

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