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Int Chin J Dent 2006; 6: 39-44.

The influence of silicone remover on the tensile bond strength ofresilient denture liner to an acrylic denture base resin
Guang Hong, DDS, PhD, Hiroshi Murata, DDS, PhD, Ying-Ai Li, DDS, Shinsuke
Sadamori, DDS, PhD, Takeshi Maeda, DDS, and Taizo Hamada, DDS, PhD
Department of Prosthetic Dentistry, Graduate School of Biomedical Sciences, Hiroshima University,
Hiroshima, Japan
Purpose: The purpose of this study was to determine the influence of silicone remover on tensile bond strengthof eight silicone-resilient denture liners to a denture base resin. Durability of bond strength of resilient denture
liner to denture base resin was also examined by thermal cycling test.
Materials and Methods: Eight commercial silicone resilient denture liners were used. The specimens were
exposed to thermal cycles. Approximately 2 mL of silicone remover was applied with the brush between theresilient denture liner and the denture base resin at 0 cycle. The test specimens were placed under tension, until
failure, in a materials testing machine.
Results: A significant difference was found between different silicone resilient denture liners for tensile bondstrength in the application, and no application of silicone remover, at 0 cycle (p<0.05). When silicone remover
was applied, the tensile bond strength of all silicone resilient denture liners to the denture base resin decreased
significantly (p<0.05). The bond strength of all resilient denture liners tested exhibited at higher than 0.46 MPa.
Conclusion: The following conclusions were drawn: 1) Significant differences were found among the tensile
bond strengths between various resilient denture liners and denture base resin. 2) The influence of thermal
cycles exerted on bond strength between resilient denture liners and denture base resin varied according to theresilient denture liner used. 3) Silicone removal material was found to be effective in the removal of silicone
resilient denture liners from the denture base resin. (Int Chin J Dent 2006; 6: 39-44.)
Key Words: resilient denture liner, silicone remover, tensile bond strength, thermal cycling.

Introduction
Resilient denture liner is used for a patient who has excessive absorption of the alveolar bone, and lesion of
the alveolar mucousa due to long-term use of complete denture.1 Most resilient denture liners were made withsilicone, acrylic resin, isoprene or polyolefin.2,3 Silicone resilient denture liners have the advantage of being
inherently soft over a long period.4,5 However, some silicone resilient denture liners have inadequate bonding to
the denture base resin.3,6,7 One of the serious problems is the failure of adhesion between the resilient denture
liner and the denture base resin. The loss of bonding of the resilient denture liner to the denture base resin resultin lining failure.8-10 Khan et al.9 reported that 10 pounds per inch (0.45 MPa) would be satisfactory for clinicaluse of resilient denture liner materials.
Sometimes, dentists fail to take an accurate denture lining because of air bubbles. And some problems
associated with long-term use of resilient denture liners include staining, porosity, and loss of elasticity. In thesecases, it is necessary to remove the failed resilient denture liners quickly and completely. Recently, silicone
removing agent has been developed. Several tests have been used to assess the bond strength of resilient denture
liners. Wright11 estimated the bond strength of nine resilient denture liners using a peeling test. Kulak-Ozkan etal.7 assessed the bond strength of six silicone based resilient denture liners using a tensile test. Al-Athel and
Jagger12 measured the bonding properties of silicone resilient denture liner using tensile, shear and peeling tests.
Although the bonding of different types of resilient denture liner has been investigated,6,9,10,13-17 conclusive
evidence about the influence of silicone remover on the bond strength of silicone resilient denture liners to adenture base resin can not be found.
The purpose of this study was to determine the influence of silicone remover on tensile bond strength of eight39

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Int Chin J Dent 2006; 6: 39-44.

silicone resilient denture liners to a denture base resin, and to confirm whether or not these was adequate bondstrength of these resilient denture liners to the denture base resin. Furthermore, the durability of the bonding
strength of resilient denture liner to denture base resin was examined by thermal cycling test.

Materials and Methods
Table 1 gives details of the eight commercial silicone resilient denture liners used in the present study. Sevenroom-temperature vulcanized materials and one high-temperature vulcanized material were used. Denture baseacrylic resin specimens (Acron, powder 0212241, liquid 310842, GC Corp., Tokyo, Japan) were polymerizedaccording to the manufacturer’s recommended procedures to the rectangular blocks (35×10×10 mm). The
section surfaces of tensile test specimens were abraded with 400 grit waterproof abrasive paper, and were rinsed
with tap water for 15 s, and were allowed to air dry for at least 5 minutes. The adhesive agents of each material
were applied to tensile test section surfaces of resin blocks.
Table 1.

Materials used in this study.

Material

Abbreviation

Type

Manufacturer

Lot number

Molloplast-B
Ufi Gel C
Sofreliner Tough
Sofreliner Super SoftGC Reline Ultra Soft
Mollosil Plus
Permafix
Evathouch Soft

MB
UGC
SRT
SRS
GRU
MP
PF
ETS

HTV
RTV
RTV
RTV
RTV
RTV
RTV
RTV

Detax GmbH & Co., Ettlingen, Germany
Voco, Cuxhaven, Germany
Tokuyama Dental Corp., Tokyo, Japan
Tokuyama Dental Corp., Tokyo, JapanGC Corp., Tokyo, Japan
Detax GmbH & Co., Ettlingen, Germany
Kohler., Neuhausen, Germany
Neo Dental Chemical Products Co., Tokyo, Japan

991265
97065
VSD11210
104
0303251
000101000502
LG01

HTV, High temperature vulcanized silicone; RTV, Room temperature vulcanized silicone.

Two denture base resin blocks were placed back into the metal mold with a 2 mm-thick spacer, and theresilient denture liners were then packed into the space (Fig. 1), and vulcanized according to the manufacturer’s
recommended procedures. Five specimens were prepared for each material and experiment. After curing, thespecimens were exposed to thermal cycles between 4°C and 60°C water for 1 minute (0, 1,250, 2,500, 5,000 and
10,000 cycles). Ten specimens were prepared for 0 cycle. And it was divided into two groups of application
silicone removing agent group (five specimens) and without silicone removing agent group (five specimens).
Approximately 2 mL of silicone removing agent (Siliconeremover, 006, Tokuyama Dental Co., Tokyo, Japan)
was applied with the brush between the resilient denture liner and the denture base resin at 0 cycle. The
specimens were placed under tension, until failure, in a mechanical testing machine (Model 5565, Instron Corp.,
Canton, USA) using a crosshead speed of 20 mm/minute. The load (N) at which failure occurred was recorded
together with the type of failure. The tensile bond strengths were calculated as follows: Tensile bond strength(MPa) = Load (N)/Cross-sectional area (mm2).

Means and standard deviations of five specimens were

determined for all materials. The type of failure was assessed visually, and was recorded as being cohesive,adhesive, or mixed, depending on whether the fracture surface was in the resilient denture liner only, at thedenture base resin-resilient denture liner interface only, or in both.
Results were compared using one-way analysis of variance testing (ANOVA) and two-way ANOVA. The
difference in these values among the materials of bond strength were tested with Student-Newman-Keuls
multiple comparison tests and t-test. All data were analyzed at a 0.05 level of significance.

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Fig. 1.

Test specimen.

Results
The mean and standard deviation values of tensile bond strength without silicone remover at 0 cycle areshown in Fig. 2. A significant difference (p<0.05, one-way ANOVA) was found between different silicone
resilient denture liners for tensile bond strengths at 0 cycle.

Results of Student-Newman-Keuls multiple

comparison tests showed no significant difference among the SRT, MB, and UGC, or among the GRU, PF andMP, or between SRS and ETS specimens of tensile bond strength at 0 cycle (p>0.05). The SRT (2.1 MPa), MB(2.0 MPa), and UGC (2.0 MPa) specimens exhibited higher values of tensile bond strength than other materials.
The SRS and ETS specimens exhibited lower values of tensile bond strength between resilient denture liners anddenture base acrylic resin than other materials.
3

Tensile Bond Strength (MPa)

A

A
A

2

B
B
B

1

C
C

Tensile Bond Strength (MPa)

3

2
A

1

B, C

B

B, C

B

C, D

D
D

0

0
SRT

MB

UGC

GRU

PF

MP

SRS

ETS

SRT

MB

UGC

GRU

PF

MP

SRS

ETS

Fig. 2.
Fig. 3.
Tensile bond strength at 0 thermal cycle. Fig. 2 (left) shows the results without application of the silicone remover, whereas Fig.
3 (right) shows the results after application of the silicone remover. Identical letters indicate no significant difference.

The mean and standard deviation values of tensile bond strength in the application silicone remover at 0 cycle
are shown in Fig. 3. A significant difference (p<0.05, one-way ANOVA) was found between different silicone
resilient denture liners for tensile bond strength at 0 cycle. Student-Newman-Keuls multiple comparison tests
showed that the MB specimen (1.3 MPa) exhibited higher values of tensile bond strength than other materials.
The SRS and ETS specimens exhibited lower values of tensile bond strength between resilient denture liners anddenture base acrylic resin than other materials. When the silicone remover was applied between the denture baseresin and resilient denture liner, the tensile bond strength of all silicone resilient denture liners to the denturebase resin decreased significantly (p<0.005, ANOVA and t-test).
The influence of thermal cycling on tensile bond strength is shown in Fig. 4. Significant differences were
found as the tensile bond strength between the resilient denture liners at 1,250, 2,500, 5,000, and 10,000 cycles(p<0.05, ANOVA), except for SRT and MB. The change of tensile bond strength values from 0 cycle to 10,000
cycles are; from 2.1 to 2.4 MPa for SRT (p=0.744), from 2.0 to 1.7 MPa for MB (p=0.115), from 1.95 to 0.85
MPa for UGC (p<0.05), from 1.5 to 1.2 MPa for GRU (p<0.05), from 1.2 to 1.7 MPa for PF (p<0.05), from 1.2

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to 1.4 MPa for MP (p<0.05), from 0.6 to 1.1 MPa for SRS (p<0.05), and from 0.5 to 0.6 MPa for ETS (p<0.05).
At the UGC, PF, and SRS, all specimens showed adhesive failures; the SRT, MB, GRU, and MP specimens
showed most adhesive failures at 0 cycle. Most of the specimens showed adhesive failures except ETS with anincrease in thermal cycling. The failure mode of all resilient denture liners was adhesive, when the silicone
remover was applied at 0 cycle.
SRT
SRS
GRU
PF

Tensile Bond Strength (MPa)

3

UGC
MB
MP
ETS

2

1

Fig. 4.
The influence of thermal
cycling on tensile bondstrength.
0
0

2500

5000

7500

10000

Thermal Cycling (cycles)

Discussion
Resilient denture liners have been a valuable asset for prosthesis clinically, because of their viscoelastic
properties. They have been used when the oral mucosa exhibits a reduced tolerance to loads applied bydentures.1 Sufficient bond strength between the resilient denture liner and the acrylic denture base resin isrequired to avoid interfacial separation of the prosthesis. This study measured the tensile bond strength between
eight commercial silicone resilient denture liners to a denture base resin, and the influence of silicone removeron tensile bond strength. In addition, the influence that thermal cycling exerted on bond strength between
resilient denture liners and denture base resin was examined.
The peel test6,11,18 shear test12,13 and tensile test7,9,10,19 have been used to measure the bond strength between
resilient denture liner and denture base resin. Although the peel test closely simulates the force applied at theinterface between the resilient denture liner and the denture base, direct gripping of the resilient denture liner inthe peel test may damage the sample integrity at the gripped region. The force may not be applied at theinterface between both materials directly, because the applied force may depend on the properties of the resilient
denture liner.
The tensile test did not simulate the clinical forces that may induce separation between the resilient denture
liner and the denture base resin; however, the force was applied to the bonding area of both materials. This test
was effective in ranking the materials, and in evaluating the failure mode. Then, the tensile bond test was usedin this study. The highest tensile bond strength between resilient denture liners and denture base acrylic resin
was seen with SRT, MB, and UGC specimens in the no application silicone remover at 0 cycle. Because MB isa high temperature vulcanized material, this may be the reason that high temperatures promoted the vulcanizedreaction, and established good bonding eventually. SRT and UGC materials may be the reason for improvementof the adhesive agent, and to be the cause for high bond strength. The SRS and ETS specimens exhibited lower
values of tensile bond strength between resilient denture liners and denture base acrylic resin. ETS showed an

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Int Chin J Dent 2006; 6: 39-44.

even more significantly lower value of bond strength, because the ETS polymerizes with condensation reaction.
However, it polymerizes with other silicone resilient denture liners with the addition reaction. Therefore, thetear strength of ETS samples is small. This may be reflected in the bond strength of the material.
The results of this study indicate that the force for failure is higher than 0.46 MPa for all resilient denture
liners tested. It has been reported that 10 pounds per inch (0.45 MPa) would be satisfactory for clinical use ofresilient denture liner materials.9,20,21 Considering this criterion, all resilient denture liners tested had satisfactorybond strength to denture base resin.
When the silicone remover was applied, the tensile bond strength of all silicone resilient denture liners to thedenture base resin decreased significantly (p<0.05, ANOVA). The failure mode of all resilient denture liners
was adhesive, when the silicone remover was applied. The component of adhesive agent for silicone resilient
denture liners is silicone polymer in solvent or γ-methacryloxypropyl trimethoxysilane.22 Tensile bond strengthof silicone resilient denture liners to a denture base resin decreased significantly by using silicone remover. Thismay be the cause for why the silicone remover dissolves the component of the adhesive agent.
The tensile bond strength of resilient denture liners to the denture base resin increased significantly with anincrease in thermal cycles (p<0.05, ANOVA), except for UGC, MB, and SRT specimens. This may account for
the finding that at high temperatures, thermal cycles promoted the vulcanized reaction, and bond strength
between resilient denture liner and denture base resin increased eventually. The tensile bond strength of UGC
and MB specimens to the denture base resin decreased significantly with increasing thermal cycles. This may
explain the distinct difference in behaviour for water sorption and desorption between denture base resin andresilient denture liners to cause the interfacial stress concentration.23 The tensile bond strength of SRT samples
to the denture base resin was shown to be a stable value with increase thermal cycling. The difference of water
sorption and desorption between resin and liners may be little. And, improvement of the adhesive agent may
have an influence on bond strength.
For the UGC, PF, and SRS, all specimens showed adhesive failures. The SRT, MB, GRU, and MP specimens
showed adhesive failures at 0 cycle, which implies that the tear strength of the resilient denture liners was greaterthan bond strength to the denture base resin. At 0 cycle, the ETS specimen showed cohesive failures. This
indicates that the tear strength of the resilient denture liners is weaker than the bond strength to denture baseresin. Most specimens showed adhesive failures except ETS specimen with an increase in thermal cycling. The
high temperatures of thermal cycles may have promoted the vulcanized reaction, and bond strength to denturebase resin grew greater than tear strength of the resilient denture liners.

CONCLUSION
Within the limitations of the present study, the following conclusions were drawn:
1.

The use of different materials showed significant differences in tensile bond strength between the denturebase resin and resilient denture liners.

2.

The influence of thermal cycles on bond strength between resilient denture liners and denture base resin
varied according to the resilient denture liners used.

3.

Silicone removal material was found to be effective in removal silicone resilient denture liners from thedenture base resin.

4.

The bond strength of all resilient denture liners tested exhibited at higher than 0.46 MPa.

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Acknowledgment
This research was supported in part by a Grant-in-Aid for Scientific Research (15390593) from the Ministry of Education,
Culture, Sports, Science and Technology, Japan.

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Correspondence to:
Dr. Guang Hong
Department of Prosthetic Dentistry, Graduate School of Biomedical Sciences, Hiroshima University
1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan
FAX: +81-82-257-5684 E-mail: hong@hiroshima-u.ac.jp
Received December 2, 2005. Revised January 13, 2005. Accepted January 17, 2006.
Copyright ©2006 by the International Chinese Journal of Dentistry.

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