Sadamori et al.

Int Chin J Dent 2006; 6: 89-92.

Application of magnetic attachment for connecting a fixed partialdenture and a detachable gingiva: A clinical report
Shinsuke Sadamori, DDS, PhD, Seicho Makihira, DDS, PhD, Nobuyuki Nakai, DDS,PhD, and Taizo Hamada, DDS, PhD
Department of Prosthetic Dentistry, Division of Cervico-Gnathostomatology, Graduate School of
Biomedical Sciences, Hiroshima University, Hiroshima, Japan
Magnetic attachments have been applied for various prostheses. In this report, a fixed partial denture (FPD) towhich a detachable gingiva was connected by magnetic attachment was fabricated to support esthetic recovery of
the alveolar bone defect and the maxillary anterior missing teeth. Missing teeth, accompanied with an alveolarbone defect, are generally recovered with a removable denture or with a combination of surgical treatment and aconventional FPD without a detachable gingiva. However, surgical treatment was avoided by utilizing amagnetic system for connection between the FPD and the detachable gingiva. The detachable gingiva made it
possible for the patient to maintain oral hygiene by himself. Therefore, this clinical report suggests that adetachable magnetic connection is an alternative technique to avoid surgical treatment and promote oral hygienein the esthetic restoration required for remarkable alveolar bone defects. (Int Chin J Dent 2006; 6: 89-92.)
Key Words: attachment, detachable gingiva, magnet.

Introduction
Alveolar bone defect and loss of interdental papillae caused by accidents and periodontal diseases can berestored by surgical and prosthetic approaches. The surgical options are auto-connective tissue transplantation,1auto-bone graft,2 and bone substitute-transplantation.3 Soft tissue transplantations for the localized alveolar ridge
defect have been done often and are evaluated to be greatly useful. On the other hand, in the operation of
auto-bone graft to the remarkable bone defect, a great deal of pain may be caused to patients. Engineered bone,using bone marrow cells, may help the treatment of such remarkable bone defects. However, the technique of
hard tissue engineering has not yet been established. Alternatively, missing teeth and tissues can be replacedwith a detachable gingival extension connected to an implant-supported prosthesis with precision attachments.4
The implant system requires surgical treatment, but not preparation of the abutment teeth.
Prosthetic treatment is considered to be another option if patients desire to avoid surgical risks. Cura et al.
reported an excellent clinical case of the technique of esthetic connection between a fixed partial denture (FPD)
and a detachable gingival extension to compensate for an enormous alveolar bone defect.5

This usefulconnection was a custom-made precision attachment. We recovered the remarkable alveolar bone defect by adetachable gingiva connected to a FPD using magnetic attachment. This magnetic connection is also esthetic.
The concept of our magnetic method is consistent with Cura’s concept for a simple fixed prosthesis, though thesystem of each esthetic connection differs.5 The purpose of our new fabrication means that the detachable
gingival extension, as a replacement for the missing soft tissue on bone defect, helps patients to maintainhygiene around the alveolar bone defect, and to keep the FPD clean. Patients can avoid surgical treatments
possibly involving high risks. We describe here a novel application of an improved magnetic attachment for theFPD.

Clinical Report
A 28-year-old man injured his face in a traffic accident. The alveolar bone, periodontal tissues and teeth wereclinically examined. Maxillary right lateral incisor and canine teeth were extracted in the Department of Oral

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Surgery of our hospital. Pulpectomy of the maxillary central incisors was carried out because of deep caries atDepartment of Periodontology. The patient was diagnosed to have an accidentally injured remarkable bone
defect, and a loss of soft tissue, that would need an esthetic recovery (Fig. 1).

1
View of remarkable alveolar bone defect.
Fixed partial denture to which the magnet keeper was bonded.

2Fig. 1.
Fig. 2.

3
Detachable polymerized resin-gingiva in which the magnet was buried.
Fixed partial denture and removable gingival extension set in place.

4

Fig. 3.
Fig. 4.

5
Fixed partial denture with the magnet keeper in follow-up, after 2 years.
Detachable gingiva part after 2 years.

6Fig. 5.
Fig. 6.

At first, the provisional restoration made with ivory-colored resin for the missing teeth was set on theabutment teeth of the maxillary incisors and right premolars without a gingiva, since the patient desired neither aconventional partial (removable and fixed) denture with a gingiva, nor, a surgical treatment including implants.
However, this temporary fabrication was not acceptable to the patient. The patient was not pleased about nocover over the bone defect, and complained of food impaction into bone defect area. The problems werediscussed and we proposed a novel prosthesis using an improved magnetic attachment at the level of size andforce. The patient understood the expected advantages and disadvantages of the magnet system. Patient finally90

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Int Chin J Dent 2006; 6: 89-92.

preferred a simple fabrication, combined with a FPD, a removable gingival extension, and a magneticattachment.
We fabricated a porcelain-fused-to-metal FPD and a gingival extension in accordance with the manufacturer’smethod, which were detachably connected by a magnetic attachment system (Hyper Slim Direct BondingKeeper Set, J. Morita, Suita, Japan). In brief, after a metal framework was completed, Direct Bonding (DB)keeper housing pattern was set on a metal framework in order to secure a space for the magnet keeper (diameter
3.0 mm, thickness 0.8 mm, Morita), prior to build-up of the porcelain. The DB keeper housing pattern was burnt
out when the porcelain was built up and burned. The magnet keeper was bonded to the lower portion of theceramic pontic using Super-Bond C&B (Sun Medical, Moriyama, Japan) (Fig. 2). We polymerized the artificial
gingiva with the use of pink-colored denture base resin (Palapress Vario, Heraeus Kulzer, Hanau, Germany).
This polymerization was carried out in the presence of the improved magnet assembly (diameter 3.0 mm,thickness 1.3 mm, attractive force 3.9 N, Morita), resulting in the magnet being fixed on the gingival side of thethin polymerized resin-gingiva (Fig. 3). Though this patient did not desire reappearance of melanin pigments,
some efforts will be normally required to make melanin-like stain on polymerized resin-gingiva part.
The detachable function of these fabrications is theoretically permanent, by means of magnetic force (Figs.
2-4). The patient received an explanation about the nature of the magnet, and was instructed in daily use,important for maintenance. The patient understood enough how to wear them. In 2 months, the patient wasaccustomed to use of the prostheses, and described satisfaction with the magnetic connection, because he could
set the gingival extension, and remove it from the FPD by himself, at anytime, and because he had less food
impaction.
After 2 years, the patient was asked about the condition of the magnet system, and was thoroughly examined.
The patient had no complaints about a decrease in attractive force, and felt comfortable wearing the fabrications.
No obvious changes around bone defect or the abutment teeth were clinically observed in comparison with theinitial state of seating (Figs. 5 and 6).

Discussion
Cura et al. indicated a novel method to esthetically recover alveolar bone defect using a detachable gingival
extension.

They utilized a custom-made pin system (rather than intra- or extracoronal attachment) as aconnection of partial denture and detachable gingiva.5 In this case, we applied a magnetic attachment for analternative connection to combine such prostheses, suggesting that a magnetic attachment is also for connecting
a detachable gingiva and a fixed partial denture, as well as the custom-made pin system.
It is possible to fabricate magnetic attachments for dental prostheses which are comparable in holding power
to conventional mechanical precision attachments. The obvious advantage is that magnetic attachments do notneed complicated coplanar surfaces and springs which are expensive to fabricate and require frequent adjustment
or replacement with use.6 Magnet systems are not complicated, however, the size and the corrosion of magnets
are considered to be important limiting factors in the use of magnets intraorally. Magnets have been reduced toan acceptable size for intraoral use. A numbers of magnetic retentive appliances have been developed, butalmost all are rarely used, because of their low retentive force, corrosion, and large size.7,8 These problems weresolved with the magnetic attachment developed, and is a sure retainer of position for dentures.9,10 The size of theimproved magnet and keeper used here was likely acceptable, as expected, for the limited space intraorally,

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Int Chin J Dent 2006; 6: 89-92.

including the thin extended pontic and gingiva as shown in Figs. 2 and 3.
The magnet we used is made from neodymium-iron-boron and its capability is theoretically permanent.11
However, rare-earth magnets like neodymium-iron-boron, are susceptible to corrosion, and have been shown to
break down in the oral cavity.8 Various coating procedures (parylene coating, and stainless steel casing sealedwith epoxy resin, welding, or laser welding) have been employed to seal them off from the harsh intraoral
environment.12,13 In a 2-year follow up, no corrosion was observed on the surface of the magnet (Fig. 6). The
magnet was covered with the high anticorrosion stainless steel and seams were laser welding. This laser welding
was effective in protecting against corrosion.
Patients had no complaints about the reduction of magnetic force. An advantage of magnetic retainers overmechanical attachments is that they do not wear and fail within an increasing number of break-way cycles, andcan remain functional indefinitely as long as they do not corrode.6 Our case indicated that the improved magnet
had kept its force for two years intraorally, supporting the finding that our magnet treated with laser welding had
no corrosion.
In conclusion, this clinical report indicates that a detachable prosthesis by magnet is a novel technique to
avoid surgical treatment, to recover remarkable alveolar bone defects and missing teeth. Development of asmaller and more powerful magnetic attachment could be required. Magnets could possibly be applied tovarious other prostheses in the oral cavity.
Acknowledgement
This study was supported in part by a Grant-in-Aid for Scientific Research (16390617) from Japan Society for thePromotion of Science (JSPS).

References
1. Studer S, Naef R, Scharer P. Adjustment of localized alveolar ridge defects by soft tissue transplantation to improve
mucogingival esthetics: a proposal for clinical classification and an evaluation of procedures. Quintessence Int 1997; 28:785-805.
2. Buser D, Dula K, Belser UC, Hirt HP, Berthold H. Localized ridge augmentation using guided bone regeneration. II. Surgicalprocedure in the mandible. Int J Periodontics Restorative Dent 1995; 15: 10-29.
3. Gray JL, Quattlebaum JB. Correction of localized alveolar ridge defects utilizing hydroxyapatite and a "tunneling" approach: acase report. Int J Periodontics Restorative Dent 1988; 8: 72-8.
4. Brygider RM. Precision attachment-retained gingival veneers for fixed implant prostheses. J Prosthet Dent 1991; 65: 118-22.
5. Cura C, Saracoglu A, Cotert HS. Alternative method for connecting a removable gingival extension and fixed partial denture:a clinical report. J Prosthet Dent 2002; 88: 1-3.
6. Jackson TR, Healey KW. Rare earth magnetic attachments: the state of the art in removable prosthodontics. Quintessence
Int 1987; 18: 41-51.
7. Drago CJ. Tarnish and corrosion with the use of intraoral magnets. J Prosthet Dent 1991; 66: 536-40.
8. Riley MA, Williams AJ, Speight JD, Walmsley AD, Harris IR. Investigations into the failure of dental magnets. Int J
Prosthodont 1999; 12: 249-54.
9. Mizutani H, Nakamura K, Ai M. Follow-up study of removable partial denture with magnetic attachment by questionnaire todentist. J Jpn Prosthodont Soc 1997; 41: 902-9.
10. Thean HP, Khor SK, Loh PL. Viability of magnetic denture retainers: a 3-year case report. Quintessence Int 2001; 32: 517-20.
11. Vardimon AD, Graber TM, Drescher D, Bourauel C. Rare earth magnets and impaction. Am J Orthod Dentofacial Orthop
1991; 100: 494-512.
12. Walmsley AD, Brady CL, Smith PL, Frame JW. Magnet retained overdentures using the Astra dental implant system. Br Dent
J 1993; 174: 399-404.
13. Noar JH, Wahab A, Evans RD, Wojcik AG. The durability of parylene coatings on neodymium-iron-boron magnets. Eur J
Orthod 1999; 21: 685-93.

Correspondence to:Dr. Shinsuke Sadamori
Department of Prosthetic Dentistry, Division of Cervico-Gnathostomatology
Graduate School of Biomedical Sciences, Hiroshima University
1-2-3, Kasumi, Minami-ku, Hiroshima 734-8553, Japan
Fax: +81-82-257-5682 E-mail: tsada@hiroshima-u.ac.jp
Received May 17, 2006. Accepted June 3, 2006.
Copyright ©2006 by the International Chinese Journal of Dentistry.

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