oral mucosa pressure caused by mandibular overdenture with different types of attachments

2.  INTRODUCTION
 AIM
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 RELATED ARTICLES
 CONCLUSION
 REFERENCES

3.  Any removable dental prosthesis that covers
and rests on one or more remaining natural
teeth, the roots of natural teeth, and/or
dental implants; a dental prosthesis that
covers and is partially supported by natural
teeth, natural tooth roots, and/or dental
implants -GPT
Over denture treatment is a notion which precludes inevitability of floating
plastic in edentulous mouth - George Zarb

4. higher levels of
patient satisfaction,
comfort and quality
of life
improved chewing
ability
less surgically
invasive
economically
reasonable
better masticatory
force
According to the 2002
McGill consensus and
2009 York consensus
2-IOD was
recommended as first-
line therapy for
edentulous mandible

5. ATTACHMENT
SYSTEM
MATRIX
RECEPTABLE
COMPONENT
MECHANICAL/FRIC
TION
FIT/MAGNETIC
CLIPS OR BARS
ADJUSTABLE/REP
LACABLE
PATRIX
FITS CLOSELY
WITHIN MATRIX
CONNECTING
BARS/FREE
STANNDING
BALL/MAGNETIC
ABUTMENTS
ONE PART-CONNECTED TO IMPLANT
OTHER PART-INCORPORATED WITHIN
UNDER SURFACE OF OVERDENTURE

6. SINGLE ELEMENTS(UN
SPLINTED)
SINGLE BALL
ABUTMENTS
SINGLE MAGNET
ABUTMENTS
INDIVIDUALLY CAST
TELESCOPIC
COPINGS
CONNECTED
ELEMENTS(SPLINTED)
EGG SHAPED
DOLDER BAR
ROUND CLIP BAR
U SHAPED BAR
CUSTOMISED
PRECISIONMILLED
BAR
STRESS
BREAKING
MECHANISM
RIGID
MECHANISM
STRESS
BREAKING
MECHANISM
RIGID
MECHANISM

7. IOD
LOCATORS
BARS
MAGNETS
BALLS

8. MORPHOLOGY
OF RESIDUAL
RIDGE
POSITION OF
IMPLANT
ANGLE OF
IMPLANT
RETENTIVE
FORCES
PATIENT’S
LIFESTYLE
PATIENT’S
ABILITY TO
CLEAN
EASE OF
MAINTENANCE

9.  To determine the appropriate attachment
and design of a denture base for mandibular
implant overdenture (IOD), the oral mucosa
pressure caused by mandibular implant
overdentures was measured using
edentulous jaw models with various
attachments.

10. An experimental mandibular edentulous jaw model
with a 1.5mm
thick artificial oral mucosa
Two dental implants (3.75 11.5 mm)
were placed at the position of the
bilateral canines, perpendicular to a
tentative occlusal plane

11. Experimental 2-IODs were fabricated
• Mainly made of acrylic resin denture base material
Each attachment was inserted
• connected to the experimental 2-IOD with chemical
cure resin material
shape of 2-IODs were similar to the record
base with occlusion rim morphology that was
made according to the standard protocol

12. • performing retentive forces 0.7 kg ,
locator abutment, Bmk RP 2.0 mm,
Nobel Biocare),
Locator
attachments with
retention discs (LA)
• ball abutment, Bmk RP 1 mm, Nobel
Biocare
Ball
attachments(BA)
• MA, MAGFIT IP-DXFL, Aichi Steel,
Aichi, Japan
Magnetic
attachments(MA)
• NobelProcera Impl Bar Overdenture Ti
2 Impl, Nobel Biocare
resilient round-bar
attachments (R-
BA)

14. 6
miniature
sensors
Buccal
premolar
region
Buccal
shelves
Lingual
molar
region
Six miniature pressure sensors were
placed to measure pressure values on the
oral mucosa when the experimental
dentures were loaded
An experimental CD without attachment
was prepared as a control

15.  The load on the experimental dentures was
set at 50 N by referring to the masticatory
force of CD wearer
• The load points were either an area
equivalent to the center of the model
which should represent equivalent
mastication on both sides
Bilateral
load
• an area equivalent to the left first molar
which should represent unilateral
mastication
Unilateral
load

16. BILATERAL LOADING UNILATERAL LOADING
A metal plate was placed on the experimental dentures

17. Precision universal
testing machine
(Instron 8874, Instron,
Norwood, MA, USA).
dynamic repetitive loads of 1 Hz were applied perpendicularly to the tentative
occlusal plane by precision universal testing machine

18. The experiments were repeated 5 times each In the CD and the
experimental 2-IOD
LA BA MA R-BA
The oral mucosa pressure values were defined as average values of the
load with the precision universal testing machine during 5 continuous
cycles.
Pressure distributions during the loading were measured with 6-channel
frequency sensors
200 Hz sampling rate
recorded via a sensor
interface

19. Example of a waveform during the dynamic
repeated load.
The oral mucosa pressure values were defined as average values of the load with the
precision universal testing machine during 5 continuous cycles

20. Differences in oral mucosa
pressure values between CD
and 2-IOD
Oral mucosa
pressure value
exerted by 2-IOD
was significantly
lower in the left
buccal premolar
region than that of
CD Under the unilateral load condition

21. On the non-
loading side, oral
mucosa pressure
values exerted by
all attachments
were extremely
low and did not
exceed 8.0 kPa
in the right buccal
premolar region
and the right
buccal shelf

22.  Changes in oral mucosa pressure values
with different attachments
•Pressure on the residual ridge exerted by CD was
compared to that of 2-IOD with various attachments.
•Oral mucosa pressure value exerted by 2-IOD was
significantly lower in all sites than that of CD

23. The oral mucosa
pressure value exerted by
R-BA was significantly
higher in the right lingual
molar region than those
of other attachments

24.  2-IOD reduced the oral mucosa pressure
value of 37– 190 kPa at the supportive site.
 The oral mucosa pressure value exerted by
2-IOD in the left lingual molar region was not
always lower than that of CD.
 The oral mucosa pressure value was
increased significantly by MA and LA, but
decreased significantly by BA

25.  Significant decrease in oral mucosa pressure
value and increase in support and bracing
ability were observed when 2-IOD was applied,
compared with CD.
 Effect of BA on the reduction of oral mucosa
pressure is greater than LA, MA and R-BA in
the supportive and bracing regions
 BA could be the first choice to reduce oral
mucosa pressure value during mastication.

26. Nobuhiro Yoda, Yoshiki Matsudate, Masaru
Abue, Guang Hong and Keiichi Sasaki

27.  to investigate how several commonly used
attachments of the IOD affect the load on the
supporting implants and the residual ridge
beneath the denture base in a model study
applying those measuring systems.

28. An acrylic resin mandibular edentulous
model was modified
Two implants were inserted in the canine
region both sides of the edentulous
residual ridge, perpendicular to the
occlusal plane of the experimental IOD
An artificial mucosa made using a silicone
impression material approximately 2-mm
thick,was affixed to the edentulous molar
area, posterior to the two supporting
implants of the mandibular model
Experiment device development

29. A film pressure distribution
measurement tactile sensor was
placed on the artificial mucosa on
the right side
The artificial mucosa was molded by
initially fixing the film sensor to the
basal surface of the experimental IOD,
followed by polymerizing the silicone
under the application of a 5-N load to
the occlusal surface of the IOD.
The experimental IOD was made using
acrylic resin for the denture base
material
The basic form of the experimental IOD
was a ready-made record base with an
occlusal rim The occlusal table of the
denture was fabricated parallel to the
occlusal plane.

30. • Piezo electric force
transducers
LOAD ON
IMPLANTS
• film pressure distribution
measurement tactile
sensor
LOAD ON
RESIDUAL
RIDGE
 Devices for simultaneous measurement of
three-dimensional (3D) loads on the
supporting implants and the load on the
residual ridge beneath the denture base
were developed.

31.  To measure the
load on the
implants, three
types of
attachments were
fabricated to be
fitted accurately
onto the
piezoelectric force
transducers:
LOCATOR
TYPE
ATTACHMENT
LA
ROUND BAR
ATTACHMENT RA
BALL TYPE
ATTACHMENT
BA

35. Loads on the implants and the residual ridge beneath the denture base were
measured when static and dynamic repeated loads of 100 N were applied vertically
to the right first molar region of the occlusal table of the denture by a universal
testing machine
The load measurement
was repeated five times
for each of the three
different attachments in
the order BA, LA, and
RA

36. • assumed to be the occlusal
force
• applied to the right first
molar area
• crosshead speed of 15
mm/s
• continued for 10 s
Static load
100N
• to simulate a masticatory
force
• Same area
• Cross head speed of 30
mm/s
• loading cycle of 2 Hz
Dynamic
repeated
load
100 N

37. Measured
pressure on
the residual
ridge
beneath the
denture was
converted to
a force and
analyzed as
the total force
on the
measuremen
t area.

38. • Lateral direction
• coincident with the occlusal surface of the IODX axis
• Antero-posterior direction
• coincident with the occlusal surface of the IODY axis
• vertical direction, which was defined to be
perpendicular to the occlusal surface of the
denture
• same in the implant inserted direction.
Z axis

39.  Regardless of the
attachment type, the
direction of the load
exerted on both
implants was
consistently in a
posterior direction.
 Force vector on the
non loading side
implant for the three
attachments occurred
in an upward direction.

40. LOADING SIDE
• BA>LA>RA
NON LOADING
SIDE
• BA>RA>LA
The horizontal
component, that
is, the resultant
force value of the
load on the
implants in the X-
and Y-axes when
a static load of
100 N was
applied,

41. LOADING SIDE
• BA>RA>LA
NON LOADING
SIDE
• Little
difference
among 3
• LA
Significantly
low
BOTH LOADING
AND NON
LOADING SITES
• BA>RA>LA

42. With all
attachments-
higher load in
the distal parts
of the sensor
area.
load centers of
the three
attachments in
similar position,
loci of the load
center were
different among
the three
attachments.
shows the typical pattern of load distribution on the residual
ridge beneath the denture under a static and dynamic repeated
load of 100 N

43. RA
LA
BA

44. load on the residual ridge
beneath the denture base
when a static load of 100
N was applied
• RA>LA>BA

45. shows an example of the
calculated 3D resultant
force data for the three
attachments when a
dynamic repeated load of
100 N was applied five
times. The three
attachments showed
different wave patterns.,
but this was
• plateau phase
between the peaks
of the waves
BA AND
RA
• not evident on the
loading side
implant.
LA

46. 1. This model experiment using piezoelectric 3D
force transducers and a tactile sheet sensor
enabled us to clarify the effects of the
attachments used in an IOD on loading to
implants and the underlying residual ridge.
2. Using RA in an IOD is effective for reducing the
load to the supporting implants.
3. The load on the residual ridge beneath the
denture in IODs can be efficiently reduced
using a BA.

47. Jin Suk Yoo, Kung-Rock Kwon, Kwantae Noh,
Hyeonjong Lee, Janghyun Paek

48.  The design of the attachment must provide
an optimum stress distribution around the
implant. In this study, for implant
overdentures with a bar/clip attachment or a
locator attachment, the stress transmitted to
the implant in accordance with the change in
the denture base length and the vertical
pressure was measured and analyzed.

49. For the strain gauge to have a tight contact with the surface of the implant, buccal and
mesial threads of the #43 implant and lingual and distal threads of the #33 implant were
properly adjusted, and flat surfaces were obtained.
model base was created with epoxy resin
Tissue-level Straumann implants were used (diameter 4.1 mm, length 10 mm,
to reproduce the implant mandibular overdentures
A ridge replication plastic model made for an actual patient was impressed with silicone.
alveolar mucosa (2 mm thick) was reproduced with a previously taken
impression and polyether impression material

50. STRAIN GAUGES were
attached to the implants
using an adhesive
In the replicated epoxy model, holes 8 mm
in diameter were made at both canine sites
and implants were placed. Resin cement
was used to represent the osseo
integration of actual implants. The
maxillary and mandibular dentures on the
replication model were fabricated in a
conventional manner, and the same
dentures were used repeatedly in the
experiment by modifying their bases.
POSITION
OF STRAIN
GAUGES
CLOSE TO
NECK OF
IMPLANT
BUCCAL
SIDE
LINGUAL
SIDE
CLOSE TO
APEX
MESIAL
SIDE
DISTAL
SIDE

51. A universal testing machine was used to exert a vertical pressure on the
mandibular implant overdenture. To measure the strain rate of the
implants placed in the replication epoxy model, a strain gauge was used.
An A/D converter was connected to a personal computer to amplify and
quantify the electrical signal from the gauge.

52. • RN synOcta abutment
• RN synOcta gold coping
• SCS occlusal screw
• CM bar
• female component of 10 mm length
BAR/CLIP
ATTACHMENT
• RN Locator abutment
• BLUE replacement male piece
LOCATOR
ATTACHMENT

53. RN synOcta gold coping
RN Locator
abutment

55. DENTURES BASED ON LENGTH OF
DENTURE BASE
GROUP 1:
pressure with no
modification (intact
denture)
GROUP 2:
pressure after
eliminating the
denture base distal
to mandibular
second molar
GROUP
3:pressure after
eliminating the
denture base distal
to the mandibular
first molar.

56.  Vertical pressure, 0.5 mm/min up to 50 N,
was placed on the three types of complete
denture
 repeated 10 times
 Whenever the attachment was replaced or
the length of the denture base was modified,
20 minutes were given for recovery
 Results measured with the four strain
gauges were analyzed statistically

58. • vertical pressure on the mandibular right
first molar (A) and the mandibular right
posterior area (B), the implants on the
working side generally showed higher
strain than those on the non-working
side
LOCATOR
ATTACHMENT
• vertical pressure on the mandibular right
first molar (A) and the mandibular right
posterior area (B), the implants on the
both non-working and working sides
showed high strain
BAR/CLIP
ATTACHMENT

59.  For the mandibular
right first molar, the
mandibular right
posterior area, and the
whole mandibular
denture base, the
strain was statistically
significantly different
between the locator
attachment and the
bar/clip attachment

61. TENSILE
FORCE
• Applied on
mesial surface
of the implant
on the working
side
COMPRESSIVE
FORCE
• applied to the
buccal surface
and on the
surfaces of the
implant on the
non-working
side
all surfaces except the
mesial surface of the
implant on the non-
working side showed a
compressive force
when applying vertical pressure at
three different areas (cases A, B,
and C), the bar/clip attachment
generally showed a higher strain
than the locator attachment
For both attachments, the shorter denture base
resulted in a higher strain on the implants

62.  For mandibular implant overdentures, locator
attachments result in lower strain on implants
than do bar/clip attachments. Longer denture
bases have the same effect. Therefore, to
minimize the strain on implants in mandibular
implant overdentures, this study may provide
the clinical implication that the use of locator
attachment would be more preferable in regard
of strain on implants than bar /clip attachment,
and the denture base needs to be extended as
much as possible.

63. Takaharu Goto, DDS, PhD, Kan Nagao,
DDS, PhD, Yuichi Ishida, DDS, PhD,
Yoritoki Tomotake, DDS, PhD, & Tetsuo
Ichikawa, DDS, PhD

64.  This in vitro study investigated the effect of
attachment installation conditions on the load
transfer and denture movements of implant
overdentures, and aims to clarify the
differences among the three types of
attachments, namely ball, Locator, and
magnet attachments.

65. Three types of attachments, namely ball,
Locator, and magnetic attachments were
used.
An acrylic resin mandibular edentulous
model with two implants placed in the
bilateral canine regions and removable
overdenture were prepared.
The two implants and bilateral molar ridges
were connected to three-axis load-cell
transducers

66. Universal testing machine was used to apply a
50N vertical force to each site of the occlusal
table in the first molar region.
Thedenturemovement was
measured using a G2 motion
sensor.
Three installation conditions, namely, the
application of 0, 50, and100 N loads were used
to install each attachment on the denture base.
The load transfer and denture movement were
then evaluated.

67. X axis-
along
length
Y axis-
along
width
Z axis-
as
vertical
direction
Twelve signals from the four
transducers and one signal from
the load cell were digitized by a
digital data recorder with 14-bit
accuracy at a rate of 50 Hz, and
then transferred to a computer
resultant force (FR) was calculated using
the following:
FR=(M2 x +M2 y +F2 z)

68. The output of the G2 motion sensor was calculated from the flexibility of
the Euler angles (i.e., the pitch, yaw, and roll) using original software
with a C-based synthesis system

69.  A 50 N static load was applied to the loading points of
the first molar regions on the right side by a universal
testing machine with a 2.0 mm/min crosshead speed.
 The magnitude of the applied load was based on the
bite force of edentulous patients with complete
dentures.
 Six complete experimental dentures were
fabricated,and six artificial mucosal materials
modified for the respective denture bases were also
prepared.
 The recording was repeated five times for each
experimental condition, allowing intervals of at least 5
minutes for recovery

70. shows the time patterns of the resultant forces acting on the implant and residual ridges
on the loading side.The time patterns were obtained by averaging the signal at the onset
of the universal testing machine measurements for each condition. The resultant force
acting on the implants on the loading side of the magnetic attachment exhibited a two-
phase pattern

71.  For the residual ridges on the loading side,
the direction of the forces for all attachments
changed to downward with increasing
installation load. Furthermore, the yaw Euler
angle increased with increasing installation
load for the magnetic attachment

72.  The resultant force acting on the implants on the loading
side for the ball and Locator attachments transmitted
homogeneous increases without a two-phase pattern.
When the attachments were installed using a 50N load,
which was the same as the resultant force acting on the
implants on the loading side, all the attachments
transmitted a homogeneous increase with out a two-phase
pattern. The increase in the resultant force acting on the
residual ridges on the loading side was greater for a 50 N
installation load than for 0 N, especially for the Locator
attachment. No distinctive pattern was observed in the
resultant force acting on the implant residual ridges on the
non loading side.

73. The resultant force on th
implants decreased with
increasing installation
load for all attachments
The resultant force
acting on the
residual ridges on
the loading side
increased with
increasing
installation load for
all the attachments.
The resultant force acting on the residual ridges on the non loading side was not
greater than that acting on the ridges on the loading side for all attachments

74. • The resultant force acting on
the implant on the nonloading
side significantly decreased
when the installation load was
increased from 0 to 50 N
BALL AND
LOCATOR
ATTACHMENT
• smaller resultant force than
the ball and Locator
attachments for all installation
loads
MAGNETIC
ATTACHMENT
• significantly
decreased when the
installation load was
increased from 0 to
50 N
Locator
attachment
• significantly
decreased when the
installation load was
increased from 50 to
100 N
Magnetic
attachment

75. • 18.1 to
23.9 N
0 N
• 4.01 to
15.9 N
50
N
• 0.44 to
11.0 N
100
N
The resultant force acting on the implants
on the loading side
The resultant force acting on the residual
ridge on the loading side
• 0.87 to
1.15 N0 N
• 1.22 to
2.21 N
50
N
• 1.65 to
2.43 N
100
N

77. Installation load
0N
BALL
ATTACHMENT
DOWNWARD
LOCATOR
ATTACHMENT
BACKWARD
AND
DOWNWARD
MAGNETIC
ATTACHMENT
FORWARD
AND
DOWNWARD
NON
LOADING
SIDE
Residual ridges
on loading
sides
Installation load
0 N
BALL
ATTACHMENT
DOWNWARD
LOCATOR AND
MAGNETIC
ATTACHMENT
DOWNWARD
TO
BACKWARD

78. ON INCREASING
INSTALLATION
LOAD
LOCATOR AND
MAGNETIC
ATTACHMENTS
DOWNWARDS
TO BACKWARDS
AND AGAIN TO
DOWNWARDS
BALL
ATTACHMENTS
DOWNWARDS
The direction of the forces of all the
attachments changed to downward with
increasing installation load.
None of the forces of
the attachments acting
on the residual ridges
on the nonloading side
had a distinctive
direction.
when the
installation load
was 0 N, the
forces of the ball
and Locator
attachments were
horizontal and
large compared to
that of the
magnetic
attachment.

80.  The magnetic attachment had a high yaw Euler
angle compared to the ball and Locator
attachments for all installation loads.
 The yaw Euler angle increased with increasing
installation load for the magnetic attachment, and
particularly increased significantly when the
installation load was increased from 50 to 100 N.
 Simultaneously, the Euler angles of pitching and
rolling slightly increased in the negative
direction.The ball and Locator attachments did not
exhibit this distinctive movement

81.  Subject to the limitations of this study, the use of
any installation load greater than 0N is
recommended for the installation of ball and
Locator attachments on a denture base. Regarding
magnetic attachments, our results also recommend
installation on a denture base using any installation
load greater than 0N, and suggest that the resultant
force acting on the implant can be decreased by
increasing the installation load; however, a large
installation load of 100 N should be avoided when
installing the attachment on the denture base to
avoid increasing the denture movement

82. AsukaHaruta, YasuyukiMatsushita,
YoshihiroTsukiyama,YoshinoriSawae,
NobuoSakai, and Kiyoshi Koyano

83.  to compare the effects of mucosal thickness
on the stress pattern around implants and
movement of implant-supported
overdentures with ball/female and three
different types of magnetic attachments.

84. Two rootform implants were inserted into
mandibular model
Surface of the model was covered with a 1.5- or
3-mm layer of impression material to simulate the
oral mucosa
removable overdentures were fabricated on each
model
A 50-N vertical force was applied to the right first
molar
the resultant stress distribution and denture
movement were measured

85. Each experiment was repeated five times under the same conditions.
Each sequence of strain data was used to calculate the axial force and the
bending moment transmitted to the implant
Loads from 0 to 50N were applied gradually
to simulate a moderate level of biting force on an implant-retained overdenture
Autograph applied a load to the occlusal surface of the right first molar region
Point to receive the load with the largest force during function

86. Experimental Mandibular Model. An
edentulous mandibular acrylic resin model
Two implants were
placed bilaterally in
the canine region
vertical to the residual
ridge.
They were set at 22
mm apart, similar to
the distance between
two natural canines.
The implants were
retained using resin
cement

87.  A 1.5-mm layer was removed from the denture-
supporting surface of the resin model and replaced
with polyvinyl siloxane impression material to
simulate the resilient edentulous ridge mucosa.
An experimental acrylic resin denture was
conventionally fabricated on the model.
 In the same way, a 3-mm layer of impression
material and a denture were fabricated on the
same mandibular model.
All experiments for the four attachments were
carried out with one model of each mucosal
thickness.

88. Four strain gauges were attached to the
mesiodistal and buccolingual sides of the
neck part of each implant to measure the
strain on the implants
The electric signals from the
strain gauges were
amplified, transmitted, and
recovered by a personal
computer following A/D
conversion
The sensor used
electromagnetic fields to
determine the position and
orientation of a remote object.
The output of the movement
sensor was input into a
computer and a mathematic
algorithm calculated the
position of the receiver
relative to the transmitter and
recorded the results.

89. denture movement at
the loading side (right
first molar region) was
measured by vertical
displacement of
Autograph .

90. The ball attachment consisted of an anchor
head and a metal female component

91. The flat type was a typical magnetic attachment,whilethedome-shaped
type had a dome-shaped surface of the magnet and keeper, and the
cushion type had a stress distributor with a magnet

94. plus-force -tensile stress
minus-force - compressed stress.

95. 1.5mmmodel3mmmodel
 the ball attachment showed a significantly
higher axial force on the implants than all the
magnetic attachments at both the loading and
non-loading sides
 ball attachment had a lower vertical force than all
the magnetic attachments at the loading side and
had a tensile stress at the non-loading side.
 dome-shaped type caused the highest axial force
at the loading side.
 no significant differences among the three
magnetic attachments in the 3-mm mucosal
model at the non-loading side.

97. 1.5mm3mm
 all the magnetic attachments showed
significantly lower bending moments on the
implants than the ball attachment at both the
loading and non-loading sides
 the magnetic attachments were higher than that of the
ball attachment at the loading side. At the non-loading
side, all the magnetic attachments showed lower
bending moments than the ball attachment. The dome-
shaped type caused the largest bending moment at the
loading side, while it caused the lowest bending
moment at the non-loading side. The flat type made a
smaller bending moment than the dome-shaped type
and cushion type at the loading side in each mucosal
model.

98. plusmovement - upward displacement
Minus movement -downward displacement

99. 1.5mmmucosalmodel3mmmucosalmodel
 denture base movements were larger on the
ball attachment at both the loading and non-
loading sides. At the loading side, the denture
movement was the lowest on the flat type. On
the other hand, at the non-loading side, the
denture movement was very small on the
magnetic attachments
 Denture base movement was larger on the
cushion type. At the non-loading side on the
3-mm mucosal model, upward movement was
shown on the magnetic attachments.

100.  In the 1.5-mm mucosal model, the magnetic
attachments showed significantly lower bending
moments than did the ball attachment.
 The denture base displacement was the lowest
on a magnetic attachment.
 In this study, use of magnetic attachments
could be advantageous for mandibular implant-
supported overdentures based on lower stress
and better denture stability especially in the thin
mucosalmodel.

101.  Within the limits of this study, the findings
indicated that the magnetic attachments were
more favorable than the ball attachment in
terms of the stress distribution and the denture
base stability on a thin mucosa. For a thick
mucosa, the flat type caused the smallest
bending moment and denture base movement
among all the attachments, suggesting that the
flat type was the most favorable for this
condition.

102.  H. Sato, et al., Oral mucosa pressure caused by
mandibular implant overdenture with different types
of attachments, J Prosthodont Res (2019)
 Goto T, Nagao K, Ishida Y, Tomotake Y, Ichikawa T.
Influence of matrix attachment installation load on
movement and resultant forces in implant
overdentures. J Prosthodont 2015;24:156–63
 Yoda N, Ogawa T, Gunji Y, Kawata T, Kuriyagawa T,
Sasaki K. The analysis of the load exerted on the
implants supporting an overdenture based on in
vivo measurement. Prosthodont Res Pract
2008;7:258–60.

103.  Yoda N, Matsudate Y, Abue M, Hong G, Sasaki K.
Effect of attachment type on load distribution to
implant abutments and the residual ridge in
mandibular implant-supported overdentures. J Dent
Biomech 2015;6:1–10
 Assunção WG, Barão VA, Tabata LF, de Sousa EA,
Gomes EA, Delben JA. Comparison between
complete denture and implant-retained
overdenture: effect of different mucosa thickness
and resiliency on stress distribution. Gerodontology
2009;26:273–81.