Marginal bone loss and survival rate of immediately loaded
mandibular 2-implant overdentures retained by magnetic
attachments: 3 years follow-up
Miyayasu A1, Kanazawa M1, Shimada R1, Iwaki M2, Sato Y1, Minakuchi S1
1Gerodontology and Oral Rehabilitation, Tokyo Medical and Dental University

2

General Dentistry, Tokyo Medical and Dental University

Introduction
In these days, several studies have shown that IOD provide adequate denture stability andretention and improve patients’ quality of life (QoL) and lead to higher denture satisfaction, including
better function, speech, and comfort [1]. The McGill consensus suggested that a two-implant
overdenture (2-IOD) should become the first choice of treatment for the edentulous mandible [2].
Immediate loading of IOD treatment has been attempted to shorten the healing period and to allow
earlier use of dentures than conventional loading.
Objective
The aim of this study was to compare marginal bone loss and survival rate, between
immediately and conventionally loaded mandibular two-implant overdentures retained by magnetic
attachments.
Materials and Methods
Fig1 shows the clinical procedures of this trial. This study was a randomized unblindedparallel-group trial to compare immediately loaded mandibular 2-IODs retained by magnetic
attachments with conventionally loaded mandibular 2-IODs. Participants with a completely edentulous

mandible and any opposing maxillary

Random allocation

remaining

toothcondition

wererecruited, and randomly assigned
Conventional group

Immediate groupequallyinto

twogroups:

theimmediate loading group (immediate

Received a new mandibularcomplete denture / relinedgroup) and the conventional loadinggroup (conventional group).
EachPlanningreceived

twoimplants in the interforaminal region
withflaplesssurgery.

In

theimmediate group, each implant wasImplant insertion surgery
Set magnetic
attachments

participant

connected to each keeper and loaded

Set healing abutments
and relieve denturewith mandibular overdentures on thesame day as implant placement. In
the conventional group, the implants
were connected to healing abutments.
The inner aspects of the denture base

After 3-montharound the healing abutments wereSet magnetic
attachments

relieved. 3 months after surgery, thehealing abutments were replaced
withObservation

keepers

andloadedwithoverdentures.
Digital X-rays were taken

Fig1 Clinical proceduresat immediate, 6-month, 1-year, 2year and 3-year after implant placement. The marginal bone loss was measured by the difference ofmarginal bone level between immediate after implant placement and each observation period. To
compare the marginal bone loss of two groups, MannWhitney U test was performed. To compare the survival
rate of two groups, log-rank test was performed to the 3(+)

year accumulate survival rate.
The study protocol was approved by the Ethics
Committee at Tokyo Medical and Dental University(Number: 693) and registered with the UMIN Center(-)

Maginal boneloss (MBL)(UMIN-CTR Clinical Trial, Unique trial Number:UMIN000009889).

Fig2

Reference
Point

Marginal bone Level

Measurement of marginal bone loss

Results
The

participants

wererandomlyRandom allocation (n=19)

allocated into the immediate group (n= 10) and the conventional group (n =9). One patient in the conventionalgroupwithdrew

implants

1

placement

monthafterbecauseof

Conventional group(n=9)

Immediate group(n=10)

Implant insertion surgery
Implant failure(n=1)

implant failure.
6-monthFig4 shows the results of marginal
bone loss. The medians of 3-year

1-yearmarginal bone loss are 1.17mm for
immediate group, and 1.43mm forconventional group. There is no
significantly

difference

between2-yearDrop out(n=1)
3-yearmarginal bone loss at every evaluation
Immediate group(n=10)

time. One patient in the conventional
group

withdrew

implants

1

placement

month

after

becauseofConventional group(n=9)

Analysis

implant failure. Therefore the 3-year

Fig3 Study flowaccumulate survival rate is 100% and89% for immediate group and conventional group respectively [Fig5], and there is no significantly
difference between the groups.

Marginal bone loss (MBL) (mm)Immediate

6-mon

1-yr

2-yr

Conventional

3-yr

6-mon

1-yr

Fig4 Marginal bone loss (MBL)

2-yr

3-yr

Discussions
Elsyad et al. concluded that immediately loaded two implants supporting a ball-retained
mandibular overdenture are associated with more marginal bone resorption when compared withconventionally loaded implants after 3 years. [3] On the other hand, in this study, significant
difference of marginal bone loss was not observed. This might be because, with regard to retention
mechanisms, magnetic attachments appear to reduce lateral force to the implants.
Conclusions
However the tendency to have more marginal bone loss could be observed in immediateloaded group, there is no significantly difference in both marginal bone loss and survival rate between
two groups.
References[1] Thomason JM, Heydecke G, Feine JS, Ellis JS. How do patients perceive the benefit ofreconstructive dentistry with regard to oral health-related quality of life and patient satisfaction? A
systematic review. Clin Oral Implants Res 2007;18:168–88.
[2] Feine JS, Carlsson GE, Awad MA et al. The McGill consensus statement on overdentures.
Mandibular two-implant overdentures as first choice standard of care for edentulous patients. Montreal,Quebec, May 24–25, 2002. Int J Oral Maxillofac Implants 2002;17:601–2.
[3] Elsyad MA, Al-Mahdy YF, Fouad MM. Marginal bone loss adjacent to conventional and immediateloaded two implants supporting a ball-retained mandibular overdenture: a 3-year randomized clinical
trial. Clin Oral Implants Res 2012;23:496–503.