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| No. | Author, year | Type of magnets | Type of attractive force gauge; cross head speed; measurement of each sample | Treatment in research | Main outcomes |
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| 1 | Yiu et al. 2004 [5] | Nonencapsulated:
(i) NdFeB
(ii) Prototype iron-platinum (FePt) | Instron testing machine
2 mm/min of speed
3 times of measurement | Immersion in 3 media, namely, 1% lactic acid solution (pH 2.7), 0.1% sodium sulphide solution (pH 12), and adjusted artificial saliva (pH 6.8) were compared after 28-day and 60-day periods. | NdFeB magnet has poor corrosion resistance in artificial saliva, 1% lactic acid, and 0.1% sodium sulphide.
FePt magnet has improved corrosion resistance compared to NdFeB in both artificial saliva and 1% lactic acid. |
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| 2 | Chao et al.2005 [14] | Keepers (Magnedisc 800) | Universal testing machine (AG-10TA; Shimadzu)
5 mm/min of speed
6 times of measurement | 3 groups of treatment: casted dowel keeper, laser-welded dowel-keeper, and control group.
The alloy used is Ni-Cr. | Vertical magnetic retentive force of the control group is higher (5.6 ± 0.3 N) than the laser welded (4.2 ± 0.2 N) and casted dowel keeper groups (3.8 ± 0.3 N).
Vertical magnetic retentive force of the laser-welded dowel-keepers was significantly higher than the casted dowel keeper group. Laser welding had less influence on the magnetic retentive forces than casting. |
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| 3 | Ohashi et al. 2007 [15] | NdFeB:
(i) Hicorex slim 3013 cup yoke type
(ii) Magfit EX400 Sandwich yoke type | Digital force gauge (FGC-1)
(Speed and measurement were not mentioned) | 6 groups of treatment (Hicorex and Magfit):
Untreatment/control group, heated, cast bonded with Ag-Pd alloy, cast bonded with Ag-Pd alloy and polished, cast bonded with type 3 gold alloy, and cast bonded with type 3 gold alloy and polished. | The attractive force of the Hicorex system was reduced by cast bonding.
Attractive force of the Magfit system was reduced by both heating and cast bonding.
Attractive force of both systems was recovered through the polishing process. |
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| 4 | Huang et al. 2008 [16] | NdFeB:
Magfit DX400 | YS-31D dial tension gauge
10 times of measurement
Speed was not mentioned | Repeated gliding motion over a 5 mm distance was applied on each specimen until 30,000, 50,000, or 90,000 cycles. | Retentive force of the magnet did not change significantly after 90000 gliding cycles. |
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| 5 | Boeckler et al. 2009 [17] | NdFeB, closed field, mono system:
(i) Magfit dome type
(ii) Magfit flat type
(iii) Magna cap
NdFeB, open field, mono system:
(iv) WR Magnet
SmCo, Open field, duo system:
(v) Titan magnetics | Universal test machine (Z005)
20 mm/min of speed
10 times of measurement | All magnets were sterilized for 10 minutes at 134°C in a dental steam autoclave. | Autoclave sterilization caused a nonsignificant reduction in the magnetic attractive force of 0.04–14.6%. |
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| 6 | Akin et al. 2011 [18] | NdFeB, closed field: Hilop, Hicorex
NdFeB, Open field: Dyna
SmCo, Open field: Steco | Universal testing machine (Lloyd LF Plus)
50 mm/min of speed
10 times of measurement | All of magnetic attachments were measured in a universal testing machine. | NdFeB and closed field magnets produce significantly greater attractive forces than SmCo or open field magnets.
The strongest attractive force was found with the Hilop system (9.2 N), and the lowest force was found with the Steco system (2.3 N). |
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| 7 | Hasegawa et al. 2011 [19] | Gigauss D400, D600, D800, D1000
NdFeB magnets
Closed magnetic circuit | Universal testing machine (EZ-Test, Shimadzu)
5 mm/min of speed
5 times of measurement | Measuring magnetic force on a combination of 6 different sizes of the keeper and assemblies:
The D400 keeper was tested in combination with D400, D600, and D800 assemblies.
The D600 keeper was tested in combination with D600, D800, and D1000 assemblies. | The retentive force was the highest when the same-sized magnetic assembly and keeper were used. The larger the size difference between the keeper and the magnetic assembly, the greater the decrease in the retentive force. |
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| 8 | Yang et al. 2011 [20] | Magfit flat type and Magfit SX2 | Universal testing machine (SV-52 NA)
1 mm/sec of speed
10 times of measurement | Implant inclination: 0°, 15°,30°, 45° | The retentive force decreases with an increase in implant inclination, but the changes in the retentive force were minimal. |
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| 9 | Chung et al. 2011 [21] | NdFeB:
(i) Magnedisc 800
(ii) Neomagnet | Instron
50 mm/min of speed
Measurement was not mentioned | Repeated insertion and removal of the overdenture for 5400 cycles and the cyclic loading test (0–78 N) for 100,000 loading cycles. | No significant changes in the retentive force after repeated dislodging or cyclic loading. |
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| 10 | Akin et al. 2013 [9] | NdFeB, closed field:
Hilop, Hicorex
NdFeB, Open field: Dyna
SmCo, Open field: Steco | Universal testing machine (Lloyd LF Plus)
50 mm/min of speed
10 times of measurement | 3 groups of treatment:
(i) magnetic attachments were immersed in lactic acid 1% pH 2.3 and NaCl 0,9% pH 7,3.
(ii) magnetic attachments were put through 10,000 thermal cycles (5°C/55°C). | Magnetic attachments showed lower attractive force after immersion in corrosive environments.
Closed-field systems were not affected by the thermocycling procedures and were more resistant than open-field systems. |
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| 11 | Hao et al. 2014 [22] | Closed field system
Magfit EX 600 W | Universal testing machine (Instron)
5 mm/min of speed
5 times of measurement | Measuring the retentive force after 5000, 10,000, and 20,000 insertion and removal cycles (vertical direction). | The initial maximum retentive force of Magfit EX 600 W was 3.3 N.
The mean retentive force decreased significantly after 5000 (2.7 N), 10 000 (2.1 N), and 20 000 (1.9 N) insertion-removal cycles. |
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| 12 | Lee et al. 2017 [23] | Closed field system
DX 600
SX-L | Instron testing machine
50 mm/min of speed
10 times of measurement | Experimental groups were designed by number (2 and 4 implants) and the type of magnetic attachment (flat and cushion type).
Three directions of tensile force: vertical, oblique, and anterior-posterior were applied to measure the retentive force. | The more implant placed, the greater retentive force obtained, regardless of the type of the magnetic attachment.
In all groups, the anterior-posterior retentive force is the lowest among 3 different directions of the dislodging force.
The flat type of the magnetic attachment is more retentive than the cushion type of the magnetic attachment when oblique direction of the dislodging force is applied. |
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| 13 | Kang et al. 2019 [24] (Materials, 2019; 12:1–12) | NdFeB:
Magfit SX-L | Universal testing machine (Instron)
5 mm/min of speed
5 times of measurement | (i) Insertion-removal cycles in an artificial oral environment (standard artificial saliva at (37° ± 2°) C, a cyclic rate of 20 cycle/min.
(ii) Measurement of retention at 0, 750, 1500, and 2250 cycles. | Average loss in retention 3,38% (0–2250 cycles). No significant differences in the retentive forces of the magnetic attachments before and after insertion-removal cycles. |
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| 14 | Kang et al. 2019 [25] (J Magn, 2019; 24 : 733–8) | Magden | Universal Tester
(i) Instron 5900:
5 mm/min of speed
50 mm/min of speed
(ii) Instron 5940:
3 mm/min of speed
5 times of measurement | 3 groups of treatments:
Measure the retentive force
(i) at a different size of assembly diameter.
(ii) at a different crosshead speed (5 and 50 mm/min).
(iii) at 1500 cycles of repeated detachments (immersed in artificial saliva 37° ± 2°C). | (i) The retentive force increases as the diameter of the magnetic attachment increases and decreases as the crosshead speed increases.
(ii) The retentive force increases after 1500 detachment cycles. |
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| 15 | Kusumadewi et al. 2021 [26] | NdFeB, stainless steel encapsulated:
Magfit DX 600 | Universal Testing Machine (Llyod LRX-Plus 5 kN)
50 mm/min of speed
10 times of measurement | 4 groups of treatment:
Magnetic attachments were immersed in acid solutions with a pH of 3.8 and 5.8 in 7 and 14 days of immersions. | Immersion of magnetic attachments in both acidic solutions and time of immersions caused surface corrosion, reduces magnetic attraction, and results in dissolution of Fe ions. The highest reduction in the magnetic force (25.15%) occurred at a pH of 3.8 with time of immersion of 14 days. |
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