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Ahmed N Elsherbini, Wilhelm Niedermeier
352
WJD
Comparison of Different Methods of Abutment Splinting
and Attachments on Teeth Kinetics (Part I)
1Ahmed N Elsherbini, 2Wilhelm Niedermeier
ABSTRACT
Aim: The aim of this study was to measure the effect of
different attachments: telescopic crown, double Akers’ (DA)
clasp, distal clasp (DC)-retained removable partial dentures
(RPDs), and cantilever bridge on the intrusive movement of the
abutment teeth.
Materials and methods: A model imitating mandibular ridge of
Kennedy Class I was fabricated with rst and second premolar
as abutments. A telescopic crown, DA, DC-retained RPDs, and
cantilever bridge were fabricated. Each partial denture was
placed at a time on the model; 50 N force was applied on each
partial denture using ZWICK universal testing machine. The
intrusion of the abutments was recorded using SOLARTON
device. Data were collected and tabulated.
Results: The mean values of the intrusive movement in tele-
scopic separated (TS) RPD, telescopic joined (TJ) RPD, DA
RPD, DC RPD, and cantilever bridge in tooth 35 were 147, 75,
57, 334, and 307 µm respectively, and in tooth 45 were 136,
81, 65, 435, and 335 µm respectively.
Conclusion: It can be concluded from the retrieved data that
DA clasp-retained RPD caused less intrusion of the abutments
than telescopic crown-retained RPD, followed by the DC than
cantilever bridge.
Clinical signicance: The DA clasp is most favorable in the
utilization in mandibular Kennedy Class I situation followed by
telescopic crowns.
Keywords: Abutment intrusion, Cantilever bridge, Double
Akers, Telescopic crown.
How to cite this article: Elsherbini AN, Niedermeier W. Com-
parison of Dif ferent Methods of Abutment Splinting and Attach-
ments on Teeth Kinetics (Part I). World J Dent 2017;8(5):352-357.
Source of support: Nil
Conict of interest: None
INTRODUCTION
Removable partial dentures are necessary to provide
restoration of the mandible and the maxilla in cases
of a shortened dental arch. There are several classes
of remaining dentitions, whereby the posterior distal
ORIGINAL ARTICLE
1Department of Prosthodontics, Modern Sciences and Arts
University, Cairo, Egypt
2Department of Prosthodontics, University of Cologne, Cologne
Germany
Corresponding Author: Ahmed N Elsherbini, Department
of Prosthodontics, Modern Sciences and Arts University, Cairo
Egypt, e-mail: ahmed-elsherbini@live.com
10.5005/jp-journals-10015-1464
extension is the most frequent as a result of the early
loss of molars. In this class with remaining anterior teeth
(Kennedy Class I), commonly a bilateral distal extension
RPD is applied to reconstruct the lost teeth.1,2
The denture is teeth supported anteriorly, while it is
tissue supported posteriorly. This difference in support
between the anterior and posterior ends of these bases
results in undesirable movements that cause damage to
the supporting tissues (both abutment teeth and residual
ridges) due to the difference of tissue resiliency.
Many treatment modalities have been suggested to
overcome related problems of this class of edentulous
ridges.
Cantilever bridges deliver good masticatory functions
and improved the supporting structures by providing
good occlusal and neuromuscular stability.3 However, it
was also proved that cantilever bridges induced tilting
and rotational movements on the abutments rather than
along vertical long axis of the abutment. Telescopic
crowns were also introduced as a treatment option,
where it equalized forces on the supporting structures
and decreased the tilting of the abutments.4
Another suggestion was the DA clasp (Bonwill), with
placement of the support away from the distal extension
and engaging distobuccal undercut instead of the mesio-
buccal undercut. It remarkably reduced the transmitted
forces to the terminal abutments and improved the rate
of residual bone resorption.5,6
The location of loading points influenced both the
magnitude and direction of the abutment tooth and
denture base movement.7
There was a need to carry out a research that high-
lights the best treatment options for such situation, so
the aim of this study is to compare the cantilever bridge,
telescopic crowns, DA clasp, and DC on the intrusion of
the abutments in Kennedy Class II situation.
Hypothesis
There is no effect on the intrusion of abutments when
using different attachments.
MATERIALS AND METHODS
Due to many variables in the biomechanics of different
treatment options, and the ethical problems of in vivo
research, our study was limited to a pseudorealistic in
Comparison of Different Methods of Abutment Splinting and Attachments on Teeth Kinetics
World Journal of Dentistry, September-October 2017;8(5):352-357
353
WJD
vitro model, which bears a resemblance to the natural
tooth abutment. A model with bilateral distal extension
was fabricated. The first and second premolars were
chosen as abutments, and dowel pins were extended from
the abutments for measuring procedure (Fig. 1).
Fabrication of Treatment Options
Cantilever Bridge
A replica mold of the model was made and poured with
high-strength HERAEUS® dental stone. Wax pattern
was made on the prepared abutments using inlay wax
S-U-ÄSTHETIKWACHS-O®; the extension pontic was
made with inlay wax. The wax pattern was tried-in first
on the original model, and then invested with BEGO®
investment material, casted with BEGO WIROBOND®
chromium cobalt alloy, finished, and polished.
Telescopic Crown
Replica mold was poured with high-strength HERAEUS®
dental stone. Wax patterns of the primary crowns were
milled using DEGUSSA® milling machine, using cylindri-
cal burs to produce a parallel pattern. The primary crowns
were joined as one unit. Wax pattern was invested using
BEGO® investment material. The casted primary crowns
were finished using DEGUSSA® milling machine, to
produce parallel walled primary crowns. Wax patterns
for the secondary crowns were made. Wax pattern was
invested with BEGO® investment material, then finished
and polished. A replica mold of the model with the primary
and secondary crowns was made. Wax pattern of the metal
framework was done, invested, finished, and polished. The
metal framework and the secondary crowns were welded
together by laser by Dental Technik HARTWICH. Acrylic
teeth made from PALAVIT® acrylic and acrylic for the free-
end saddle made from PALAPRESS® was used.
Conventional Clasp (DA Clasp and DC)
Replica mold of the model was poured with high-strength
HERAEUS® dental stone. Wax pattern was made on
the prepared abutments using blue inlay wax; occlusal
rests were prepared on the distal and mesial thirds of
the first and second premolars respectively, and on the
occlusodistal third in the second premolar. Investment
using BEGO® investment materials, casted with BEGO-
WIROBOND® chromium cobalt alloy, was finished and
polished. The crowns were cemented to the cast using
temporary cement Temp Bond® (Kerr Company) and
a replica mold was made using additional silicon and
poured with investment material. Wax pattern of the
partial denture was made with ready-made wax, then
invested, casted, and finished. Metal framework was
tried-in on the model with the crowns retained in place
with temporary cement. The acrylic teeth were added
to the framework, and acrylic resin PALAPRESS® was
used. Two designs of RPD were constructed; the DA clasp
(Bonwill) and the DC.
Measuring Procedure
The model was fixed with a screw to a holding rod, which
in turn was fixed with a screw to the ZWICK machine,
and then the load applicator of the ZWICK machine was
centralized on the model. The SOLARTON sensor was
lined up parallel and on the same line with abutment to
contact the end of the dowel pin of each abutment, and
the sensor was held in place using special arm device
fixed to the holding rod. A metallic rod was placed on
the model with the different prostheses, and the load
applicator of the ZWICK machine applied the force at
the center of this metallic rod. A special plastic ring was
made, attached on the prostheses at the indicated posi-
tions, and numbered (Fig. 2).
Steps of Measuring
The prostheses were placed in position on the testing
model.
For the TJ, TS, DA clasp and DC RPD, three positions
were tested:
1. Position one: front of the saddle,
Fig. 1: Fabricated model with bilateral distal extension: (A) Abutment teeth FRASACO®; (B) silicon
SILASOFT N® around abutments; (C) silicon SILASOFT N® on saddle; (D) acrylic PALAPRESS®
VARIO; and (E) dowel pin
Ahmed N Elsherbini, Wilhelm Niedermeier
354
2. Position two: middle of the saddle,
3. Position three: end of the saddle.
For the cantilever bridge, there was only one position
on the pontic.
For the TJ, TS, DA, and cantilever bridge, the teeth 34,
35, 44, and 45 will be tested. For the DC only the teeth 35
and 45 were tested.
When the load with the ZWICK machine reached 50
N, the sensor was started to take 20 readings at an interval
of 1 second. Then, every 15 seconds a reading was taken
until full recovery of the silicon, indicated by reaching
the 0.000 mark.
RESULTS
Force applied onto the Tooth-supported Region
of the Saddle (Position 1)
The mean values of the intrusive movement in TS RPD,
TJ RPD, DA RPD, DC RPD, and cantilever bridge in tooth
35 were 147, 75, 57, 334, and 307 µm respectively, and in
tooth 45 were 136, 81, 65, 435, and 335 µm respectively.
Table 1 shows mean values of intrusion. The results of
analysis of variance (ANOVA) revealed a statistically
significant difference between the groups (p < 0.001).
Bar chart shows mean values of intrusive movement for
teeth 35 and 45 (µm) for the different treatment options
in an increasing order: TJ RPD; TS RPD; DA RPD; DC-
retained RPD; and (CA) cantilever bridge. Different
capital letters denote a significant difference according
to Tukey’s pairwise comparison test for tooth 35, while
different small letters denote a significant difference
according to Tukey’s pairwise comparison test for tooth
45. The mean values of the intrusive movement in TS
RPD, TJ RPD, DA RPD, and cantilever bridge in tooth
34 were 139, 55, 58, and 35 µm respectively, and in tooth
44 were 135, 46, 61, and 44.1 µm respectively. The results
of ANOVA revealed a statistically significant difference
between the groups (p < 0.001). Bar chart shows mean
values of intrusive movement for teeth 34 and 44 (µm) for
the different treatment options in an increasing order:
TJ RPD, TS RPD, DA RPD, and (CA) cantilever bridge.
Different capital letters denote a significant difference
according to Tukey’s pairwise comparison test for tooth
34, while different small letters denote a significant
difference according to Tukey’s pairwise comparison
test for tooth 44 (Graph 1). In position 1, the abutment
teeth were more active in supporting the RPDs, so the
intrusion was higher. The intrusion of the abutment
teeth decreased gradually with changing the positions,
and moving toward the end of the distal extension base.
This is because the residual ridge became more active
in supporting the RPD, and larger portion of the acting
load was carried out by the ridge, so lower loads were
transmitted to the abutment teeth, resulting in lower
intrusion in position 2 followed by position 3.
Force applied onto the Middle of the
Saddle (Position 2)
The mean values of the intrusive movement in TS RPD,
TJ RPD, DA RPD, and DC RPD in tooth 35 were 89, 27.4,
35.3, and 118 µm respectively, and in tooth 45 were 78.3,
37.2, 43, and 131.5 µm respectively. The results of ANOVA
revealed a statistically significant difference between
the groups (p < 0.001). Bar chart shows mean values of
intrusive movement for teeth 35 and 45 (µm) for the dif-
ferent treatment options in an increasing order: TJ RPD,
TS RPD, DA RPD, and DC-retained RPD. Different capital
letters denote a significant difference according to Tukey’s
pairwise comparison for the significant ANOVA for tooth
35, while different small letters denote a significant dif-
ference according to Tukey’s pairwise comparison test for
tooth 45. The mean values of the intrusive movement in
TS RPD, TJ RPD, and DA RPD in tooth 34 were 83.3, 16.4,
and 19.8 µm respectively, and in tooth 34 were 72.1, 11.7,
and 32.3 µm respectively. The results of ANOVA revealed
a statistically significant difference between the groups
(p < 0.001). Bar chart shows mean values of intrusive move-
ment for teeth 34 and 44 (µm) for the different treatment
Fig. 2: Model was xed with a screw to a holding rod. (a) Loading
applicator, (b) metallic rod, (c) testing model, (d) Solarton sensor,
(e) holding arm, (f) holding rod
Table 1: Mean values of intrusive movement of tooth 35 (µm)
for the different treatment options
RPD type Mean ± SD CV (%) Minimum Maximum Range
TS RPD 147 ± 2.87 1.76 142 150 8
TJ RPD 75 ± 5.82 8.38 69 89 20
DA RPD 57 ± 2.6 4.46 52 62 10
DC retained 334 ± 19.1 5.65 314 372 58
Cantilever
RPD
307 ± 12.3 3.95 297 333 36
SD: Standard deviation, CV: Coefcient of variation
Comparison of Different Methods of Abutment Splinting and Attachments on Teeth Kinetics
World Journal of Dentistry, September-October 2017;8(5):352-357
355
WJD
options in an increasing order: TJ RPD; TS RPD; and DA
RPD. Different capital letters denote a significant differ-
ence according to Tukey’s pairwise comparison test for
tooth 34, while different small letters denote a significant
difference according to Tukey’s pairwise comparison test
for tooth 44 (Graph 2).
Force applied onto the Tissue-supported
Region of the Saddle (Position 3)
The mean values of the intrusive movement in TS RPD,
TJ RPD, DA RPD, and DC RPD in tooth 35 were 7.3, 8.1,
4.8, and 9.9 µm respectively, and in tooth 45 were 7.5,
8, 5, and 10.7 µm respectively. The results of ANOVA
revealed a statistically significant difference between
the groups (p < 0.001). Bar chart shows mean values of
intrusive movement for teeth 35 and 45 (µm) for the
different treatment options in an increasing order: TJ
RPD, TS RPD, DA RPD, and DC-retained RPD. Different
capital letters denote a significant difference according
to Tukey’s pairwise comparison test for tooth 35, while
different small letters denote a significant difference
according to Tukey’s pairwise test for tooth 45. The mean
Graphs 1A and B: (A) Mean values of intrusive movement for teeth 35 and 45 (µm) for the different treatment options are shown
in an increasing order: TJ RPD; TS RPD; DA RPD; DC retained RPD; and (CA) cantilever bridge. Different capital letters denote
a signicant difference according to Tukey’s pairwise comparison test for tooth 35, while different small letters denote a signicant
difference according to Tukey’s pairwise comparison test for tooth 45; and (B) Mean values of intrusive movement for teeth 34 and
44 (µm) for the different treatment options in an increasing order: TJ RPD, TS RPD, DA RPD, and (CA) cantilever bridge. Different
capital letters denote a signicant difference according to Tukey’s pairwise comparison test for tooth 34, while different small letters
denote a signicant difference according to Tukey’s pairwise comparison test for tooth 44
Graphs 2A and B: (A) Mean values of intrusive movement for teeth 35 and 45 (µm) for the different treatment options in an increasing
order: TJ RPD, TS RPD, DA RPD, and DC retained RPD. Different capital letters denote a signicant difference according to Tukey’s
pairwise comparison for the signicant ANOVA for tooth 35, while different small letters denote a signicant difference according to
Tukey’s pairwise comparison test for tooth 45; and (B) Mean values of intrusive movement for teeth 34 and 44 (µm) for the different
treatment options in an increasing order: TJ RPD; TS RPD; and DA RPD. Different capital letters denote a signicant difference
according to Tukey’s pairwise comparison test for tooth 34, while different small letters denote a signicant difference according to
Tukey’s pairwise comparison test for tooth 44
A B
BA
Ahmed N Elsherbini, Wilhelm Niedermeier
356
values of the intrusive movement in TS RPD, TJ RPD,
and DA RPD in tooth 34 were 6.9, 1.3, and 2.2 µm respec-
tively, and in tooth 44 were 6.4, 1.3, and 3.4 µm respec-
tively. The results of ANOVA revealed a statistically
significant difference between the groups (p < 0.001).
Bar chart shows mean values of intrusive movement for
teeth 34 and 44 (µm) for the different treatment options
in an increasing order: TJ RPD, TS RPD, and DA RPD.
Different capital letters denote a significant difference
according to Tukey’s pairwise comparison test for tooth
34, while different small letters denote a significant dif-
ference according to Tukey’s pairwise comparison test
for tooth 44 (Graph 3).
When loading on positions 2 and 3, the bending
moment arm is longer than position 1 loading case. Thus,
larger moment and, consequently, larger deflection8 is
expected in positions 2 and 3 and less intrusion.
The cantilever bridge is tooth supported with no
support from the residual ridge, so the abutment teeth
are baring total load applied on the pontic. This is shown
with the high intrusive movement on the second premolar
(35, 45). Due to the leverage action of the cantilever bridge,
the first premolars (34, 44) responded with extremely low
intrusive movement.
The abutment nearest the pontic receives more than
half the load placed against the pontic.9
Cantilevered pontic caused tilting and rotational
movements without mentioning anything about the
intrusive movements.10
The telescopic retained RPD, the intrusion of the
(35, 45) abutments were low, and the values decreased
gradually, with moving among positions 1, 2, and 3.
The intrusion of the (34, 44) abutments was lower than
(35, 45) as they are located away from the distal extension
base, so lesser load transmitted, leading to less intrusive
movement. The intrusion of the abutment teeth in TJ
crowns was almost half of that of the TS crowns. The
lower values of intrusion of abutments in TJ-retained
RPD are due to the large surface area onto which load
is applied.
Since stress is inversely proportional to area, as the
area increases and the force applied is constant; the stress
produced decreases.11
When the telescopic crowns were joined, this i ncreased
the surface area of the abutment teeth, leading to less
stress, resulting in less intrusion of the abutment.12,13
In the DA (Bonwill)-retained RPD, the intrusion of the
abutment teeth was low, and decreased gradually with
moving from positions 1, 2, and 3. This is due to distrib-
uting the stresses on both abutments of same side at the
same time with the joined occlusal rests, and relative
flexibility of the clasp. In addition, placing the occlusal
rest on the occlusomesial surface of the second premolar
decreases the fulcrum line and lever arm, leading to less
movement of abutment teeth. In addition, disengage-
ment of the clasps during loading decreases the stresses
transmitted to the abutment teeth, so the residual ridge
is bearing much of the load.14 ,15
In the DC-retained RPD, the intrusion of the abutment
teeth was high and decreased gradually with moving
from position 1, 2, and 3, as the residual ridge became
more active in supporting and bearing the loads. Also
by moving posteriorly, the forces transmitted became
with a deflection effect rather than intrusive. In addition,
Graphs 3A and B: (A) Mean values of intrusive movement for teeth 35 and 45 (µm) for the different treatment options in an
increasing order: TJ RPD, TS RPD, DA RPD, and DC-retained RPD. Different capital letters denote a signicant difference according
to Tukey’s pairwise comparison test for tooth 35, while different small letters denote a signicant difference according to Tukey’s
pairwise test for tooth 45; and (B) Mean values of intrusive movement for teeth 34 and 44 (µm) for the different treatment options
in an increasing order: TJ RPD, TS RPD, and DA RPD. Different capital letters denote a signicant difference according to Tukey’s
pairwise comparison test for tooth 34, while different small letters denote a signicant difference according to Tukey’s pairwise
comparison test for tooth 44
A B
Comparison of Different Methods of Abutment Splinting and Attachments on Teeth Kinetics
World Journal of Dentistry, September-October 2017;8(5):352-357
357
WJD
the second premolars (35, 45) were the only used abut-
ments, so they are the only abutments bearing the load,
so more stress was transmitted to them, leading to more
intrusion. Placing clasp on the occlusodistal surface of
the abutment acts as a Class I lever leading to more intru-
sion of the abutment teeth.14 As already described, “this
could be considered a cantilever design, and detrimental
first-class lever force may be imparted to the abutment if
tissue support under the extension base allows excessive
vertical movement toward the residual ridge.”
The DA clasp transmitted the least stresses causing
movement of the abutment teeth in clasp-retained
RPDs.6
The telescopic crowns caused less movement of the
supporting teeth than cantilever bridge.13
The cantilever bridge and the DC-retained RPD
caused the highest intrusive movement of the second
premolars (35, 45) due to concentration of stresses on
the second premolar. The separated telescope-retained
partial denture followed them. Then, joined telescope
and DA clasp-retained RPD caused the lowest intrusive
movement of the abutment teeth.
The cantilever had the lowest intrusive movement on
the first premolars (34, 44) due to the leverage action of the
cantilever bridge. In the DC-retained RPD they were not
utilized, so no forces of intrusive nature were transmitted
to them. Then, the joined telescopic retained RPD and the
DA clasp retained RPD. The separated telescopic-retained
RPD caused the highest intrusive movement.
CONCLUSION
It can be concluded from this study that DA clasp with
the joined telescopic crown-retained RPD produced
the least intrusion of the abutment teeth; the DA clasp-
retained RPD has the advantage of being cheaper than
the telescopic-retained RPD. In addition, DA (Bonwill
clasp) provides no need for crowning as in the joined
telescopic-retained RPD.
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