In recent years, the numbers of the patients troubled with poor retention
of their dentures are increasing. To solve this problem, it is necessary
to develop a new effective retainer of removable partial denture exhibiting
high retentive force and lengthening the life of abutment teeth. In addition,
the retainer should be low cost and easy manipulation in dental technique.
This in vitro study evaluated a trial magnetic attachment applying
ready-made conic crown telescope system. The retentive force of this single attachment was compared with
normal magnetic attachment. Moreover, removable partial denture including these
attachments was fabricated on maxillary model and measured the retentive force
of this denture.
As results, the retentive force of the single trial magnetic telescope attachment
showed higher than that of normal one. Removable partial denture with these
attachments exhibited higher retentive performance compared with traditional
magnetic attachment denture. Another trial magnetic telescope with half of the height was also effective
in tensile testing at 30 degree direction.
The purpose of this study was to evaluate the measurements of the retentive
force of magnetic attachment using the Dental Magnet TesterⓇ（Aichi Microinteligence）in
vitro experiments : influence of examiner, mutual magnet assemblies and
immersion to denture cleansers, and to investigate chronological change
of retentive force of magnetic attachment in our dental hospital. The retentive
force of Dental Magnet TesterⓇ was influenced somewhat by examiners. The
retentive force was influenced much by the close of adjacent magnet assembly.
The retentive force was influenced less by immersion to denture cleansers.
The retentive force of magnet assembly, which were placed in the dentures
wore, varied less with time. The magnet with decrease of the retentive
force had a history in which the magnet was picked up from an old denture.
Magnetic attachment is a clinical tool retaining a denture to abutment tooth using attractive force of a permanent magnet. In recent years, the clinical use of dentures using magnetic attachment has been increasing due to its benefits. However, transformation and abrasion develop at the contact surface of magnetic assembly and keeper due to the long-term functional burden placed on magnetic attachment in the mouth, resulting in the destruction of magnetic attachment and decrease in the attractive force. In the present study, repeated loads(10kgf, 100,000times)were applied to the magnetic assembly and adsorption site of the keeper using repeated duster examination machine. We measured the durability of magnetic assembly and keeper, surface morphology of the adsorption site, and attractive force of the magnetic attachment, and investigated the mechanical strength required for the magnetic attachment.
A conventional magnetic attachment is an abutment generally introduced on a pulpless tooth. An extracoronal attachment developed in recent years utilizes the space of missing teeth,and therefore can be applied to a vitaltooth. The introduction of an extracoronal magnetic attachment markedly expanded the clinical application range of a magnetic attachment. However, extracoronal attachment required complicated laboratory works due to the complex shape of the abutment.
The introduction of a ready－made plastic pattern,“GIGAUSS C600EC keeper tray”enabled standardization and simplification of laboratory works.
However, minor changes of the attachment shape are frequently needed in consideration of neighboring alveolar ridge shape and opposing relations in clinical practice. In the present study,we performed stress analysis of extracoronal magnetic attachment by changing the shape in parts of a ready－made pattern. The present paper reports the summary of the analysis results.
Magnetic fields leaking out of a cup yoke type of magnetic attachment are evaluated by a FEM analysis. The field leakage is analyzed not for the attachment in normal use but for that in the special states that a magnetic assembly is moved vertically and horizontally from the normal position for a keeper. As a result of the analysis, magnetic field leakage on the surface of the attachment in normal use is about 10 mT. Also, magnetic field leakage at points a few mm away from the attachment in special states described above is less than 40mT, the guideline by ICNIRP and WHO. Therefore, the magnetic attachment is considered to be safe from a viewpoint of biological effects of static magnetic fields.
Key words: magnetic attachment, cup yoke type, magnetic field leakage, guideline on biological effects of static magnetic fields
In dentures with magnetic attachments, the magnetic assembly and keeper must be accurately positioned three dimensionally to obtain maximum attractive force. The earlier metal housings required a complex manufacturing process; hence we improved the metal housing structure and simplified the procedure. The over contour of the housing was eased by reducing the height wise diameter by about 0.5 mm and the lengthwise diameter by about 1.3 mm. In addition, resin pattern components of a single type were used to simplify the procedure. The housing was placed in the abutment tooth and secured after its fit with the denture was confirmed using a silicone test material. Setting of the denture in this position was prevented by creating a spillway. The metal housing used for relining was removed from the denture and the auto polymerizing resin was treated with polymerizing resin cleaner for removal. The metal housing was then reattached in the same way.
The use of resin and metal housings was thus effective for accurate positioning of the magnetic assembly and keeper three dimensionally.
Key words: Magnetic Attachment, Magnetic Assembly, Housing
Atypical Odontalgia is a condition where a tooth is the source of a great deal of discomfort, but fails to demonstrate any of the associated structural flaws that point toward a specific problem. The aim of this case study was to look into the possibility of using a magnetic removable denture for reconstruction of missing teeth in an Atypical Odontalgia patient.
The patient was a 55 year old female, whose chief complaint was pain in the lower premolar area and had intense difficulty chewing. Two years ago, she began to have pain in the right mandibuler area, with the situation failing to improve over the ensuing months. Following this extraction, a root canal treatment was carried out in the first premolar and the second molar, with pain returning soon after.
We decided on a treatment plan that would include the use of a denture for reconstruction of missing teeth. This approach resolved the immediate issue of chewing, but more importantly it also allowed the patient to remove the bridge if any discomfort developed.
Key words: Magnotelescopoic crown, Removable bridge, Magnetic attachment