【Introduction】

Magnetic attachment is a type of stud attachment that offer the advantage of easy attachment and detachment without directional restrictions. We report a case in which magnetic attachments were applied to an elderly patient with rheumatoid arthritis and reduced finger dexterity, resulting in a high level of patient satisfaction.

【Case report】

The patient is an 82-year-old woman who visited the clinic with the chief complaint of difficulty eating due to the mobility of her maxillary bridge. The fixed bridge in the maxillary anterior region showed mobility in the abutment teeth, which also caused instability in the clasp denture fitted for the missing molar area. The patient complained of difficulty in putting on and taking off dentures due to rheumatoid arthritis. The anterior bridge was removed, and an overdenture was provided to achieve occlusal balance. Additionally, a magnetic attachment was employed, ensuring strong retention and easy handling.

【Discussion/conclusion】

For patients with rheumatoid arthritis who have difficulty inserting and removing dentures, magnetic attachments have proven to be a treatment method that achieves high patient satisfaction.

【Objective】

Two cases of postoperative complications of implant overdenture (IOD) and implant removal partial denture (IRPD) were improved by the use of magnetic attachments.

【Summary of the case】

Case 1: 76-year-old man. After an IRPD was placed in the maxilla at a private dental clinic, the patient came to our clinic with a complaint of dislocation of the artificial tooth; the IRPD had been repaired many times. Increased vertical dimension, new Co-Cr IRPD with magnetic attachments was delivered.

Case 2: 73-year-old man. A maxillary IOD with locator attachments was worn, but he requested re-make due to mastication disorder and denture fracture. Existing implants were placed without parallelism, so an IOD with a bar attachment and a magnetic attachment was fabricated.

【Results and Discussion】

In order for IODs and IRPDs to achieve good results for long term period, the characteristics of the attachments must be exactly understood and the IOD should be carefully designed and fabricated.

【Objective】

For magnetic attachments, it is important to accurately position and fix the magnetic assemble and the keeper. This report provides an overview of the hands-on seminars entitled “Mastering Magnetic Attachments: From Technological Operation to Installation” held at the 131st-133rd Annual Meeting of Japanese Prosthetic Society.

【Methods】

The hands-on seminars were consisted of a lecture on the features of magnetic attachments and how to proceed with treatment, and hands-on practice using a jaw model and overdenture replica to fix a magnetic structure to a denture.

【Results and Discussion】

The seminars were held six times, with 40 participants each year divided into two sessions of 20 participants each. Problems that occurred during installation each time included detachment of the magnetic assemble from the denture and lack of attractive force. The problems with detachment were thought to be due to the non-use of metal primer or the removal of the denture before the self -curing resin had completely polymerized. Insufficient attractive force may be due to misalignment of the magnetic assemble, such as resin intrusion onto the keeper surface or existing air gap.

Closed magnetic circuit dental magnetic attachments typically use non-magnetic stainless steel containing nickel as shield rings or spacers to form the magnetic circuit. However, nickel can cause metal allergies, prompting the demand for nickel-free products. This study aimed to develop an experimental nickel-free magnetic attachment and evaluate its retentive force.

Chromium, an antiferromagnetic material that is not magnetically attracted to magnets, was plated onto the disk yoke to serve as the shield ring. The disk yoke and cup yoke were laser-welded together, including the chromium plating, to fabricate the experimental magnetic attachment. Retentive force was measured according to ISO 13017 test procedures, including tests with the keeper laterally displaced. Hardness across the mating surface, from edge to center, was also measured. Results were compared to those of a same-sized commercial magnetic attachment, the Physio Magnet 4813.

The experimental attachment demonstrated equivalent retentive force to the conventional product. Its behavior during lateral displacement was also similar. The hardness values indicated that the chromium concentration in the shield ring was higher than that of conventional products, suggesting superior corrosion resistance. Thick chromium plating was confirmed to function effectively as a shield ring, enabling the successful development of a nickel-free dental magnetic attachment.

The purpose of this study is to examine the mechanical effects of different implant placement positions on the design of removable partial dentures using a three-dimensional finite element method. A mandibular model missing #35,#36,#45,#46, and#47 was used as the basic model. A metal-based denture was designed with RPI clasps on #34 and #44 and magnetic attachment on #37 as an overdenture abutment. Three experimental models were constructed by placing one implant in the right free-end missing corresponding to #45, #46, and #47 respectively. The stress analysis results of the experimental models compared to the basic model were as follows. Stress decreases were observed around abutment tooth #44 in all models. The stress increased as the implant placement position moved to the distal side. Decreased displacements of the denture showed in all models. In particular, the minimal displacement showed on the #46 implant placement model. These results suggest that implant placement in free-end missing area reduces stresses on the abutment teeth and surrounding tissues, decreases denture movement, and provide the support function in removable partial denture design.

In this study, we report on the accuracy of matching titanium root copings fabricated using an intraoral scanner.

The abutment tooth was a preformed epoxy artificial tooth (A50-359, NISSIN). The manufacturing procedure involved scanning an epoxy artificial tooth using an intraoral scanner (i700, Medit), modeling it using design software (Dental System, 3Shape), and then cutting it with a milling machine (GeoMill ARUM 5X-200, GeoMedi). Five specimens were tested, and the fitting accuracy of the titanium root coping was evaluated using the cement replica method.

The measurement points are the labial margin at point a, the labial cervix at point b, the labial post at point c, the tip of the post at point d, the lingual post at point e, the lingual cervix at point f, and the lingual margin at point g. The average gaps were 92.6±17.0 μm at point a, 77.8±25.0 μm at point b, 66.7±21.6 μm at point c, 95.6±42.5 μm at point d, 63.7±9.9 μm at point e, 70.4±33.1 μm at point f, and 57.8±22.2 μm at point g.

It was suggested that the titanium root coping manufactured using an intraoral scanner could be applied clinically.