Paper submission
Denture repair with the application of a magnetic attachment to theinner crown of a telescopic crown: A 3-year follow-up case
A. Izumida
Department of Comprehensive Dentistry, Tohoku University Hospital

Introduction
The cone crown telescope, a type of retainer developed by Korber, K.H., is a retainer representing
the so-called rigid support1). The cone crown telescope consists of a tapered frustoconical innercrown and an appropriate outer crown. The retentive force depends on the frictional force or wedge
effect due to contact between the inner and outer crowns and the metal elasticity of the outer crown,
but it can be adjusted by the cone angle of the inner crown axial surface. Although it is difficult toadjust the retentive force when making a denture using the cone crown telescope, the retentive force
is stable after adjustment. The cone crown telescope is also widely used in clinical practice because
it has excellent support and bracing functions. However, in prosthetic treatment using the conecrown telescope, troubles such as detachment of the inner crown and fracture of the abutment toothhave been observed in the course of operation. When the inner crown is detached, an attempt is often
made to rebuild it with the outer crown, but it should be noted that easy repairs may have poor
prognoses2).
On the other hand, due to their versatility, magnetic attachments are widely used in various
clinical situations, such as copings, magno-telescopic crowns (MT crowns), and extra-coronalrestorations. Therefore, it is worth considering applying a magnetic attachment even when repairinga denture. However, there have been few reports on prognoses when dentures have been repaired
using a magnetic attachment.
One of the inner crown of a cone telescope denture used for 14 years was removed from theabutment in order to treatment a root canal. As a prosthodontic treatment after a root canal, I used theabutment teeth and dentures to the fullest and repaired the dental prosthesis using the magneticattachment to the inner crown of the cone crown telescope. This case is reported three years after thedenture repair.

From the case
The circumstances from the patient’s first visit for denture repair using an MT crown are as shownin the previous report3), but the outline is described below. The patient is a 74-year-old female. InDecember 2000, the inner crowns of conical telescopic crowns on the maxillary right central incisor,left first premolar, and left second premolar were produced for three tooth defects of the central
incisor, lateral incisor, and cuspid on the maxillary left side. A removable denture equipped withouter crowns conforming to those inner crowns was then set. In November 2014, acute apicalperiodontitis occurred on the maxillary right central incisor that was one of the abutment teeth. Afterthe inner crown of the tooth was removed, a root canal treatment was performed. Following
prosthetic treatment, a magno-telescopic crown (MT crown) was fabricated for the maxillary rightcentral incisor and adapted to the corresponding outer crown. In July 2015, the dental prosthesis wasrepaired using a magnetic attachment (GIGAUSS C 300, GC, Japan) for the existing outer crown(Fig.1).

Fig.1 Intraoral view and the denture at the denture repair(2015.7.24)3)
Specifically, as a method of manufacturing the MT crown, the root canal part of the maxillaryright central incisor tooth was waxed according to the metal core production, and the approximate
shape was prepared using a room temperature polymerized resin as a pattern from the cervicalportion to the crown. Then, using the denture temporarily borrowed from the patient, the wax patternof the MT crown was fabricated while directly conforming to the inner surface of the outer crown.
At the same time, a space for mounting the magnetic attachment inside the outer crown was secured.
The keeper was manufactured by the cast-joining method. The magnetic attachment was attached atthe next medical treatment after the patient wore the MT crown. At that time, the facing hard resin of
the outer crown was removed, and it was newly built up.

Follow-up of the caseDenture repair was completed in July 2015. Thereafter, this case shifted to one of maintenanceand recall. In the meantime, as a restoration, the bridge of the maxillary right molar section wasremade due to desorption. Panoramic X-ray photographs taken three years and two months after thedenture repair are shown in Figure 2, and Figure 3 shows the periodontal pocket of the abutment
tooth at the time of wearing the denture in December 2000, repairing the denture, and three years
after the repair of the denture. While continuing to use not only the maxillary right central incisor
tooth with the MT crown attached but also the maxillary left first premolar tooth and the maxillaryleft second premolar tooth, the periodontal tissue has been generally well preserved. In addition,
there was no detachment of the magnetic attachment or the other inner crown by the room
temperature–polymerized resin in the outer crown. As of today, the patient is highly satisfied withusing the repaired denture (Fig.4).

Discussions
In this case, the right central incisor of the maxilla developed acute apical periodontitis after 14
years of wearing the denture. As the dental prosthesis was designed for three teeth defects of thecentral incisor, lateral incisor, and cuspid on the maxillary left side, only the three teeth of themaxillary right central incisor tooth, the maxillary left first premolar, and the maxillary left second
premolar tooth were set as abutment teeth. From this point of view, there was concern from thebeginning of overloading the right central incisor on the maxilla. However, the maxillary rightcentral incisor tooth and the maxillary right lateral incisor tooth are in close proximity. When themaxillary right lateral incisor tooth is included as the abutment tooth, cleaning efficiency is reduced,
and a pulpectomy is necessary for securing the parallelism between the abutment teeth. In addition,
the patient strongly requested the minimal prosthetic treatment, which led to the design in this case.
However, in manufacturing, the denture was carefully prevented from concentrating the occlusal
force transiently at the intercuspal position and lateral movement. As a result, it seems that theocclusal force kept the burden on the right central incisor of the maxilla, and microleakage at theabutment tooth caused acute apical periodontitis. However, the patient in this case seems to havefunctioned for 14 years with defects of the minority teeth, vertical stoppings of the bilateral molar
teeth, and with manufacturing considerations.
Because the patient strongly hoped to use the present denture as a prosthodontic treatment after aroot canal treatment, I presented a design that included the maxillary right lateral incisor as anabutment tooth. Therefore, the prosthetic treatment was directed to the right central incisor tooth
section of the maxillary. The method of prosthetic treatment was conceived as a method of
manufacturing the inner and outer crowns so as to be parallel with other inner and outer crowns,
cutting the maxillary right central incisor tooth of the existing denture and soldering the newly
manufactured outer crown. However, with this method, I was concerned that adjustment of theretentive force would be difficult, and the burden would be overloaded. As a method of solving thisproblem, there was some freedom with respect to the parallelism between the abutment teeth, andthe use of an MT crown was presented as a method that is less burdensome on the abutment teeth.
The patient selected this method, and I carried out subsequent prosthetic treatment.
The goal of prosthodontic treatment in this case was to make full use of existing dentures. In orderto achieve this goal, the maxillary right central incisor was replaced with an MT crown instead of theinner crown, and the magnetic attachment was attached to the outer crown. Since the maxillary rightcentral incisor tooth was originally a vital tooth, the outer crown was larger than the ideal size, so it
was easy to secure the space for the magnet structure, which worked favorably at the time ofmanufacture. By applying a magnetic attachment to only one of three abutment teeth, the MT crownand inner crown were combined in one prosthetic device. However, as of now, there has been nodetachment of the inner crown or fracture of the abutment teeth, and the periodontal tissue is also
well maintained. Since the patient also uses it without discomfort, it is considered to have been areasonable denture repair.

Conclusions
One of the inner crowns of the abutment tooth of a cone telescope denture used for 14 years wasremoved to treat acute apical periodontitis. In a subsequent prosthetic treatment, denture repair usinga magnetic attachment took maximum advantage of the existing denture. Three years have passed
since the denture repair, and regular maintenance and recall have been performed. As a result, even if
the MT crown and inner crown coexisted in one prosthetic device, a good prognosis was obtained.
Therefore, prosthodontic treatment with an MT crown is considered to be an effective method at thetime of the re-prosthesis of a cone telescope denture's inner crown repair.

References
1. The Glossary of Prosthodontic Terms 4th ed. pp38, Japan Prosthetic Society, ISHIYAKUPUBLISHERS, INC. Tokyo Japan, 2015.
2. K. Iida, M. Abe, T. Hosoi, F. Tsuchida, Y. Mizuno, T. Furuya: Repaired denture using magnetic
attachment against a telescopic inner crown was out of abutment tooth. : A case report. JJ Mag
Dent, 11(1), 26-30, 2002.
3. A. Izumida. A case report of denture repair with application of a magnetic attachment to theinner crown of a telescopic crown. JJ Mag Dent, 24(1), 78-82, 2015.