Immediately loaded mandibular 2-implant overdentures retained bymagnetic attachments: Marginal bone loss and survival rate
Kaidiliya Yalikun, Manabu Kanazawa, Anna Miyayasu, Yuri Omura, Shunsuke Minakuchi
Gerodontology and Oral Rehabilitation, Graduate school, Tokyo Medical and Dental University____________________________________________________________________________________________BACKGROUND
Mandibular 2-implant overdentures (2-IOD) as first choice standard of care for edentulouspatients.1Monitoring marginal bone loss around implants is regarded by numerous authors(Albrektsson et al. 1986; Roos et al. 1997; Zarb & Albrektsson1998) as the most important criterion
in determining the success of implants.2 The magnetic attachment is device useful to clinical, thenthe introduction of implant-retained overdenture prostheses has led to a paradigm shift in themanagement of complete edentulism. Therefore, the survival rate of the immediate loading of 2-IOD
using magnet attachment-retained mandibular overdentures was 86% has been recorded.3OBJECTIVE
The aim of this 1-year study was to evaluate and compare marginal bone loss and survival rate on
immediate and conventional loading of two implants mandibular overdenture with magneticattachments.
METHODS
1. The design of this clinical study was a randomized controlled clinical trial.
2. 20 mandibular edentulous patients were allocated 2 groups either the same day (immediate loadinggroup) or after 3 months of healing (conventional loading group). (Fig.1)
3. Each patient received 2 implants (Speedy Groovy , Nobel Biocare) with magnetic attachments(Magfit IP ,Aichi Japan). (Fig.2, Fig.3)
4. Marginal bone loss was recorded at the time of implant surgery, 3, 6 and 12 months after implant
placement using standardized radiographs. (Fig.4, Fig.5, Fig.6)
5. Marginal bone loss of 2 groups were compared by Student t test, and the log-rank test was used
for survival rates.

Fig.1 Allocation to immediate group or conventional groupEach patient received 2-IOD with magnetic attachments used flapless surgery.

Fig.2 Put a magnet on the implants MandibularFig.3 Pick up the magnets

In addition, peri-implant vertical and horizontal marginal bone loss were assessed in both groups
at time of implant surgery, 3, 6 and 12 months after implant placement using intra-oral long coneparalleling technique. Clinical and radiographic evaluations were performed at distal and mesial
peri-implant sites. T-test was performed between immediate and conventional group at T3, T6, T12.

Fig.4 Intra-oral long cone paralleling technique.

Fig.5 RL: Implant-abutment junction
d: Marginal bone loss

Fig.6 Recorded at the time of implant
surgery, 3, 6 and 12 months afterimplant

RESULTS AND DISCUSSION
Marginal bone loss: The average radiographic bone level change after 12 months of function was-1.02±0.87 mm and - 1.76±1.16 mm for the conventional loading and the immediate loading
implants. The immediate group is more apically than the conventional group. (Fig.7)

Fig.7 Marginal bone loss
Marginal bone loss in the immediate loading group was higher when compared withconventionally loaded implants after 1 year. While, there was no significant difference on theradiographic bone level change between 2 groups. (Fig.7)

Survival rate of the immediate loading of 2 implants using magnet attachment-retained mandibular
overdentures were 100% (20/20 implants), conventional loading were 89%(20/18 implants). (Fig.9)
One patient in the conventional loading group lost both implants within 1 month after implant
placement.(Fig.8)

Fig.8 Lost implantIn conventional loading group one patient lost 2 implants after 1 month of implant surgery. The
reason for this might be harmful stress because of position between implants and denture, ordifficulty to brush around healing abutment.
After 12 months follow up, survival rates was tested by log-rank test recorded that there was no
significant difference on implant survival rate between 2 groups. (Fig.9)

Implant
length(mm)Insertion
Torque(Ncm)
survival rats
in 1 year

10
11.5
1315
1845>

Immediate
group
02
2
14
220

Conventional
group
1
3
5*
7
2
18*

100%
(20/20)88.9%(18/20)*2 implants was lostFig.9 Survival rates

CONCLUSHION
Marginal bone loss was the highest for the immediate loading group, while no statisticallysignificant difference between 2 groups. Survival rates of the immediate loading of 2 implants using
magnet attachment-retained mandibular overdentures were 100%, conventional loading were 89%.
In addition, do not differ significantly between 2 groups on survival rates.

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