Clinical Study about prognosis investigation of abutment
teeth and surrounding tissues using magnetic attachments
T. Masuda1 , H. Kumano1 , R. Kanbara1 , H. Nagai1 , Y. Nakamura1 , K. Shoji1 ,Y. Tanaka2 and J. Takebe1
12

Department of Removable Prosthodontics, School of Dentistry, Aichi Gakuin University
Aichi Gakuin University

Abstract
Magnetic attachments are universally recognized for their practical value and are being widelyused as magnetic attachment dentures in clinical dentistry. However, there are still few reports on theprognostic process of abutment teeth and surrounding tissues when using these magnetic attachments.
Given the expansion of more effective magnetic attachment adaptation, the necessity of objective
prognostic evaluation is very evident. Therefore, in carrying out integrated and objective evaluationof abutment teeth and surrounding tissues when using magnetic attachment, we aimed to analyze theevaluation methods commonly used by collaborating research institutes.
We collected prognostic data according to standard protocol using common evaluation manuals
and evaluation sheets available in collaborative research institutes.
Although the prognostic evaluation based on the evaluation sheet and protocol was very effective
in considering the adaptation of the magnetic attachment, it unfortunately confirmed that objective
evaluation of abutment teeth and surrounding tissues remains extremely difficult.

Introduction
Magnetic attachments are recognized for their practical value and are being widely used asmagnetic attachment dentures. Although this kind of investigation has previously been reported by
Hoshiai et al. 1,2), there are still few reports on the prognostic process of abutment teeth andsurrounding tissues when using magnetic attachments．Given the expansion of more effective
magnetic attachment adaptation, the necessity of objective prognostic evaluation from various
viewpoints is very evident.

Objective
The purpose of this study was to compare evaluation methods that have been created in carryingout integrated and objective evaluation of abutment teeth and surrounding tissues using magnetic
attachments which are common among collaborative research institutes.

Methods of investigation
We collected prognostic data according to standard protocol using common evaluation manuals
and evaluation sheets available in collaborative research institutes, and analyzed various problems ofthese evaluation methods.
1. The common evaluation sheet
Figure 1 shows the evaluation sheet at the time of setting magnetic attachment prosthesis.
This was created by Nagata, The Nippon Dental University, at the Clinical Evaluation Committeeof the Japanese Society of Magnetic Applications in Dentistry.
On the evaluation sheet, patient information, tooth defect type, intraoral photograph, PCR value,
subjective evaluation of the patient, abutment tooth, and state of residual tooth are input. As shownin Figure 2, in addition to the evaluation sheet at the time of setting, there is also an evaluation sheet

has an evaluation sheet at recall.
However, when the condition of the abutment teeth are input into the set time sheet, the state of
the abutment teeth are automatically reflected on the recall sheet. If there is a change such as "tooth
extraction or loss" on the abutment teeth, it is necessary to make a special effort to correct theabutment teeth information on the recall sheet.
In addition, as a precaution, "the patient identification number can be unique to each university,
but in order to make it possible to refer to the list, the responsible person in each university should
insure that there are no duplicate numbers."

Figure 1 : the evaluation sheet
Figure 2 : the evaluation sheet at recal
at the time of setting
magnetic attachment
prosthesis
2. The subjects of the magnetic attachment prognostic investigation
The subjects of the magnetic attachment prognostic investigation are as follows:
・Patients who visited Aichi Gakuin University Hospital, Department of Prosthodontics from 2013
to 2017・Patients who made prostheses using magnetic attachment
・Patients who are currently in recall
3. Applicable research subjects
There were 39 total applicable research subjects and among these 39 the following conditions andtotal numbers of incidence were observed: 1) Total magnetic attachment dentures: 50, and 2) Total
abutment teeth: 84. Of the 50 dentures, there were 15 complete overdentures (including 2 implantoverdentures), and 35 partial dentures including 6 nonmetal clasp dentures. Figure 3 shows theclassification of the magnetic attachment dentures.

Figure 3 : the classification of the magnetic attachment dentures

Results of investigation
1. The classification of the abutment teeth by tooth typeFigure 4 shows the results of the classification of the abutment teeth to be investigated by toothtype. It was found that the magnetic attachment was most adapted to both the maxillary andmandibular canine of the 84 abutment teeth we investigated. Conversely, there was little tendency toadapt to the mandibular central incisor and mandibular molar.

Figure 4 : the classification of the abutment teeth by tooth type2. The number of teeth lost
The number of teeth lost in the abutment teeth to which the magnetic attachment was applied
during the five-year investigation period is shown in Figure 5. The total number of lost teeth totaled
13. Of these, 9 were via tooth extraction and 4 via teeth keeper detachment. Regarding theseabutment teeth, it does not include continuation of recall after recreating the magnetic attachment.

Figure 5 : the number of teeth lost in the abutment teeth during the five-year investigation period
3. The 5-year survival rate
The 5-year survival rate of the abutment teeth to which the magnetic attachments were applied inthis investigation was about 85%.
In a previous prognostic investigation of Hoshiai et al.1), the exact same 5-year survival rate wasabout 95%, and the 10-year survival rate was reported to be 88%. A very similar trend to the results
obtained in this investigation was seen. Table 1 shows the comparison of 5-year survival rate of theabutment teeth between this investigation and the previous investigation of Hoshiai et al.
Results on the survival rate of the tooth type resulted in a high survival rate of the canines andpremolars and a low survival rate of the anterior teeth and molars. However, the survival rate of themolars showed a high result when limited to a complete denture.
Table 1 : the comparison of 5-year survival rate of the abutment teeth

Discussion
In this study, the prognostic investigation into magnetic attachment was conducted using commonevaluation methodology used by collaborative research institutes. The following observations weremade:Despite the fact that investigation into the loss of abutment teeth is considered to be one of themost stable and simple evaluation methods in the prognostic investigation of magnetic attachments,it was discovered through this investigation that evaluation on detachment, resetting and remaking of
the keeper, evaluation of the periodontal pocket and evaluation including the subjective factors ofpatients were very complicated and difficult.
Furthermore, the prognostic evaluation based on the evaluation sheet and protocol was very
effective in considering the adaptation of the magnetic attachment, it unfortunately confirmed that
objective evaluation of abutment teeth and surrounding tissues remains extremely difficult. In thefuture, we would like to further study the relevance of the evaluation items at the time of data
analysis.

References
1. K. Hoshiai，Y. Tanaka，N. Hasegawa et al.: Longitudinal Study on Metal Plate Dentures withMagnetic Attachments, J J Mag Dent, 13(1), 1-8, 2004.
2. K. Hoshiai，R. Ito，M. Miwata et al.: Investigation on Longitudinal Survival Rates of Magnetic
Attachments – Its relation to the probing depth of abutments - , J J Mag Dent, 20(1), 68-75, 2011.