This survey is given of the experimental results on the instability of magnetic properties, such as, e.g., disaccommodation in soft materials, Many parts of these experiments have been carried out by the authors except the background of the research, so these are only one part of the tremendous broad variety of the field. The rate with which a magnetic system relaxes towards its thermal equilibrium may differ widely depending on the kind of relaxation mechanisms the authors shall confine themselves to those which are in some way related to inner rearrangements in the lattice of magnetic oxides, especially in YIG. These show a strong temperature dependence of the characteristic relaxation time so that the relaxation may become relatively slow at least in some temperature range. So the authors could find the new phenomena, “double peaks of photoinduced disaccommodation” in YIG in spite of the desktop experiment, which is presented here rather in detail.
This paper is a summary of my lecture entitled “Highly Diversifying Magnetic World Created by Iron Oxides” presented at the 14th Annual Meeting of the Japanese Society of magnetic Applications in Dentistry, which was held in Nihon University on November 6, 2004.
First of all, I would like to explain the history of the application of the iron oxide, which the Cromagnon man had once used and also was handed down to men of today.
Next, I would like to mention three subjects:
- the historical development of magnets in China, Europe and Japan,
- the current situation and future trend of magnets,
- the application of iron oxide magnets to dentures.
Lastly, I would like to introduce our team’s latest research development on Heat Immunotherapy for Cancer using magnetic iron oxides. In Heat Immunotherapy the immune cells are activated when the cancer cells are broken down by the heat generated by iron oxides. Hence, the cure of the original cancer leads to the cure of metastatic cancer because of the newly activated immunity.
In this study, the grindability of cast magnetic alloys (Fe-Pt-Nb magnetic alloy and magnetic stainless steel) were evaluated and compared with that of commercially pure Ti. The grindability was evaluated by the volume of metal removed per minute (grinding rate) and the volume ratio of metal removed compared to the wheel material lost (grinding ratio). The solution treated Fe-Pt-Nb magnetic alloy had a significantly higher grinding rate than the aged one at a grinding speed of 750-1500m・min-1 . There was no significant difference in the grinding rate between the solution treated and aged Fe-Pt-Nb magnetic alloys at 500m・min-1. The grinding rate of the aged Fe-Pt-Nb magnetic alloy and the stainless steel were higher than those of commercially pure Ti.
It is recommended to use a gypsum dummy to ensure specific space in attaching a magnetic assembly to a resin-based denture. In clinical use, we sometimes form an adequate space inside the denture and attach the magnetic assembly using self-curing resin. In this case, too much resin has a bad effect on the amount of polymerization contraction, which may detach the magnetic assembly from the surface of the keeper. However, no reports have been observed.
Therefore, we made samples in which space amounts were changed with GIGAUS
D400, D600, and D800 made by GC. We compared their suction power respectively
to examine the influence of resin polymerization contraction in attaching
the magnetic assembly. We would like to report the results of our examination.
Metal plate dentures using magnetic attachments are difficult to remake in accordance with the denture when the root cap and keeper separate after preparing the denture. However, because of the recent widespread use of keeper trays, it has become possible to fix the keeper on the root cap in accordance with the magnetic assembly.
I would like to report two cases. In one, I adjusted the keeper for the magnetic assembly within the oral cavity to remake the root cap. In the other, good results were achieved by using the keeper tray for the existing inner cap to improve it to magnotelescope against the decrease of retentive force of cone crown telescope.
Key words: Magnetic attachment, Metal plate denture, Repair of denture, Keeper tray
At present, magnetic attachments have been developed as retainers of partial denture, and have been applied in various cases.
About 12 years have passed since, magnetic attachments have been applied clinically, and the problems observed at initial stages have gradual been solved. They have now become recognized as safe and useful by general clinicians.
In this case, it is reported that the long-term usefulness for prognosis of the magnetic attachment without extracting the remaining teeth in bad condition, is good.
Key words: Magnetic attachment, Longitudinal prognosis, Abutment teeth
The conventional cast-bonding technique and the direct-bonding technique developed in recent years are used to fabricate copings with keepers for dental magnetic attachments. We compared the two methods from the view point of dental clinical procedure and dental laboratory procedure. As direct-bonding technique is not influenced by casting, the original surface form of the keeper is maintained. The surface of the direct-bonding keepers were flatter than those of the cast-bonding keepers. The retentive force of the direct-bonding magnetic attachment should thus closely approximate the force of the original product. Even when influences of the keepers on MRI are anticipated, removing the keepers may be a more effective means by which to avoid magnetic influence during imagery. Since the coping and keepers are bonded with adhesive resin cement, a clear cement line appears which serves as a guide for removing the keepers and makes the removal easy
Key words: Magnetic attachment Cast-bonding technique, Direct-bonding technique