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Shear Bond Strength of Hydroxyapatite Liner to Composite Resin: Effect of Dentin Bonding Agents
Shiva Mishaeel1 and Amir H Namazi2
1Department of Operative Dentistry, Islamic Azad University of Medical Sciences, Iran
2Department of Restorative, UCLA School of Dentistry, USA
Submission: February 13, 2017; Published: May 31, 2018
*Corresponding author: Amir H Namazi, Department of Restorative, UCLA School of Dentistry, Los Angeles, USA, Tel: 3106004004; Email: firstname.lastname@example.org
How to cite this article: Shiva M,Amir H N. Shear Bond Strength of Hydroxyapatite Liner to Composite Resin: Effect of Dentin Bonding Agents. Adv Dent & Oral
Health. 2018; 9(2): 555760. DOI: 10.19080/ADOH.2018.09.555760
Introduction:Liners and bases which are applied beneath the composite restorations should have acceptable bond strength with composite resin to reduce the microleakage.
Objective:The aim of this study was to determine the effect of two current dentin bonding agents on shear bond strength of Lime-Lite to light cure composite resin.
Material and Methods:In this experimental study, 30 cylindrical specimens of hydroxyapatite containing liner with 4mm diameter and 8mm height and 30 cylindrical specimens of composite resin with 5mm diameter and 5mm height were prepared according to ISO-11405. The specimens were divided in three groups of 10 and one of the three adhesives (Den TASTIC, Single bond, bond) were applied for bonding between composite resin and liner according to their manufacture’s instruction. Specimens were kept in 100% humidity for 24 hours. Shear bond strength test was done at a crosshead speed of 1mm/min by a universal testing machine. Data were analyzed by ANOVA and POST HOC TUKEY HSD.
Results:Mean shear bond strength in Mpa were as follows: Den TASTIC: 9.94±3.63, Single bond: 12.79±2.92 and bond: 15.28±4.11. Statistical results showed that the shear bond strength of group three was significantly higher than group one. (P<0.05) There were no significant differences between group one & two and group two & three. (p>0.05)
Conclusions:Type of adhesive systems had effect on shear bond strength of hydroxyapatite containing liner to composite resin.
The Integrity of a restoration is very important in its long term durability. In a deep cavity which has lost significant amount of dentin and is decided to restore with composite resin there are some concerns about polymerization shrinkage, bonding of composite resin and prevention of further microleakage [1,2]. In these situations there is need to place a suitable liner or base to overcome the mentioned problems.
There are different kinds of bases with various chemical compositions and mechanical properties which can be applied on cavity floor prior to composite resin placement. Shear bond strength of liners and bases to composite resin will have some benefits.
Nowadays the most common materials that are used as liner and base under the composite restorations are glass ionomer cements . Glass ionomer is delivered in the form of powder and liquid, its preparation is hard and it might contact the walls of
the cavity during its insertion and consequently contaminate the bond surface which is going to bond with composite resin [3,4]. Therefore, if it could be replaced by a material with acceptable shear bond strength, easier application and less technique sensitivity it will be promising.
In recent years some materials have been introduced to the market with some advantages like easy application and special chemical composition. Lime-Lite is a new resin-based material that could be applied as a liner and base, according to the manufacturer. The material contains Hydroxy Apatite (HA) and releases hydroxyl, fluoride, and calcium. It is radiopaque as glass ionomer which helps to distinguish it from dental caries . Unfortunately, there is little evidence regarding the properties of this new material. There is a research about the compressive strength of this material with and without application of adhesives  but researches on glass ionomer is good guidance to do the study on this new material [7-10].
The aim of this experimental study was to evaluate the shear
bond strength of lime lite to composite resin with different
Composite resin samples: Thirty samples of composite resin
(Filtek Z250, color A2, 3MESPE, USA) were prepared in plastic
mold with 5mm diameter and 5mm height. Composite resin was
inserted in the mold in 2mm layers and each layer was cured
with coltolux2.5 (Coltene, Switzerland) with a beam of 400 mw/
cm2 , for 40 seconds and then for 60 seconds after removing the
samples from the mold . Polishing of composite samples were
done by polishing disks (Esthetix, Dentsply, USA) from coarse to
fine particle sizes. Each disk was used 10 seconds on each sample
. After polishing, the samples were rinsed and dried carefully
by air spray.
Liner samples: To prepare thirty samples of Lime-Lite
(Pulpdent, USA) a two-piece stainless steel cylindrical mold with a
4mm diameter and 8mm height was used. Lime-Lite was injected
by syringe into the mold in 0.5 mm layers; each layer was cured for
30 seconds according to the manufacture’s instruction under the
mention conditions . After removing the samples, curing was
performed from different sides for 30 seconds.
All the samples of two groups were maintained in humid
condition before application of adhesive. Samples of Lime-Lite
were divided into three groups of ten randomly for application of
adhesive systems as follows:
a) Group I: The surface of Lime-Lite was etched with
Phosphoric acid 38% (Etch-Rite, pulpdent, USA) for 15
seconds according to the manufacture’s instruction. After
rinsing for 20 seconds drying was done with a cotton pellet
. Two drops of Dent TASTIC (Pulpdent, USA) was well mixed
and applied with a brush on the surface of Lime-Lite according
to the manufacture’s instruction , then the sample was
placed on the surface of composite resin sample surface and
was cured from different sides for ten seconds, total of 60
b) Group II: The etching step was performed as in the first
group, then the adhesive, Singlebond (3MESPE, USA), a totaletch
two steps single bottle adhesive was applied on prepared
surface of Lime-Lite samples according to manufacturer’s
instruction and cured same as group1.
c) Group III: The self-etch adhesive, (Kuraray, Japan) a
self-etch one-step adhesive system, was used; Adhesive was
applied according to the manufacturer’s instruction with the
brush on Lime-Lite surface, then it was dried by air pressure
for 5 seconds and after being placed on the composite surface,
the curing was done like before .
The samples were kept in the 37°C with 100% humidity
conditions for 24 hours. Shear bond strength of the samples
were examined in a universal testing machine (Zwick Roell20,
Germany) and the force was applied to the interface of Lime-Lite
and composite resin with 1m/min speed until the failure happened
and bond strength was calculated by Force/Area formula in Mpa
. Finally the samples were evaluated for the failure type
(adhesive, cohesive, mixed) with 30 magnifications.
In this experimental research, the effects of three adhesive
systems, Den TASTIC (Pulpdent, USA), Single bond (3MESPE, USA)
and clearfils3 (Kuraray, Japan) were assessed on the shear bond
strength of the Lime-Lite to composite resin.
Table 1 shows the mean of shear bond strength of the three
groups. The Dent TASTIC group had the lowest and clearfils3 bond
had the highest shear bond strength. Figure 1 shows the mean
and the standard deviation of three groups with 95% confidence
The ANOVA showed that the adhesives under surveillance
have significant effects on the rate of the shear bond strength.
(P<0/05). The testing results of Post Hoc Tukey HSD showed
that the application of clearfils3 bond adhesive is significantly
increases the shear bond strength of composite and Lime-Lite
compared with the recommended Den TASTIC adhesive of the
Lime-Lite manufacturer. (P<0/05) But, there is no significant
difference for increment of the shear bond strength between the
application of Single bond and Den TASTIC; and Single bond and
clearfils3 bond, too. (P>0/05) (Table 2).
The Table 3 shows types of the fractured samples of the used
adhesives in segregation. The fractures were much of the type of
the mixed type, namely, adhesive and cohesive and no fracture
revealed as cohesive in Lime-Lite and composite.
The results extracted out of this research for examining the
effects of application of the three types of adhesives Den TASTIC,
Single bond, and clearfils3 bond on shear bond strength of Lime-
Lite to Z250 composite showed the application of clearfils3 bond
adhesive was more significant than Den TASTIC recommended
by the Lime-Lite Manufacturer however, there is no significant
difference revealed with Single bond. Unfortunately, the related
field articles and researches under this subject and in particular
to Lime-Lite were not much available. Furthermore, there are very
few researches in the field of its characteristics; therefore, many
semi-related articles reviewed for designing this research and for
interpreting the results thereof. In addition, all the due process
had investigated in accordance with the ISO 11405 .
In the restoration of all-wide cavities with the composite resin,
if the gap with the dental pulp is low, it is necessary to use suitable
liner and base [1,2]. Nowadays, the more common material used
as the liner and base beneath the composite restoration is the light
cure glass ionomer that is delivered in the form of powder and
liquid, however, the preparation of the mixture with appropriate
consistency is counting a difficult work and needs skill and
expertness. In the other hand while transferring to cavity, it may
contact the walls of the cavities and consequently contaminate the
bond surface. In the other hand, due to the powerful bond between
Glass ionomer and composite, while etching, the more powerful
bond is developing and it is probable that the Glass ionomer
may crack [3,4]. Approximately two years ago, the USA Pulpdent
factory presented a materiel as light cure Liner and Base having
the property of Calcium hydroxide along with higher physical and
mechanical characteristics. As the manufacturer claimed, Lime-
Lite without adhesive application attached to any composite resin
. This matter certainly calls for further future studies, too. It
also suggests that, for the improvement of the solidification of
the shear bond strength of Lime-Lite to composite, Den TASTIC
adhesive, the same product of the above-mentioned company
The results of this research rejected the claim of the
manufacturing co. In other words, it means that the suggested
adhesive application, it does not carry the shear bond strength, so
much, as it claims. The results of the research showed that there was
no significant difference statistically between the application of
two systems of Single bond and Den TASTIC adhesives. It is perhaps
that because both adhesives are having etching stages and so it
is probable with the efficacy of solvable and other characteristics
of Lime-Lite is the cause of reducing the bond strength between
composite and Lime-Lite which is prone to further research. In
this research, the clearfils3 bond caused the most bond strength
between composite and Lime-Lite. This adhesive is a seventh
generation self etch that presented in the form of single bottle.
This bonding produces in Japan Kuraray Factory Adhesives Group,
which has recently been in access. Regarding with the previous
research results, the Cearfil Adhesives groups develop the most
bond strength with composite, dentin and enamel. Furthermore,
Clearfil liner2v was selected as the best self etch adhesive last year.
Thus, the older generation of this material is having a lot of proven
advantages and properties [15-18]. It seems that being self etch
does not have any negative efficacy on the bond strength of Lime-
Lite to composite but other factors are effective. The survey of
Banava and her colleagues have investigated the effect of several
adhesive on the compressive strength of Lime-Lite and Calcium
hydroxide is the donator of the positive effect of self etch adhesive
comparing with Total etch adhesive . In clearfils3 bond adhesive,
the existing monomer is MDP (10 Meta Keriloloxydil dehydrogen
phosphate) which has more than 20 years of successful experience
among the existing adhesive monomers. The specified molecular
structure of this monomer causes adhesive to decalcify the tooth
tissue simultaneously, permeates in it, and develops chemical
bond with the calcium ions and Hydroxyapatite.
It seems that the same characteristic causes the bond strength
of the composite and Lime-Lite in this research compared to
other adhesives upper because this adhesive has had the ability of
attaching to the existing Hydroxyapatite in Lime-Lite, In the other
hand the chemical bond resulting from existing MDP, resistant
against hydrolyze. Therefore, clearfils3 bond adhesive is less under
the influence of hydrolyzes resulting from the saliva in enamel and
pulp liquid in dentin . On the other hand, the modern technology
the molecular diffusion “Molecular Dispersion Technology” in
preparation this adhesive has caused that this materiel without
needing to shake the bottle and mixing it concerning other self
etch adhesives available is necessary; the bonding abilities and
can act as multipurpose systems and surely with easier quicker
application and less technical sensitivity . The lack of the
significant difference between application of this mentioned
adhesive and Z250 Composite which both of them are from the
same factory or it is possible that due to the similar available
compositions in both single bond and clearfils3 bond. The fracture
type in the Lime-Lite groups are only 10% of the cases in the form
of adhesive and in 90% of cases are as the combined (adhesive,
codhesive) which is the indicator of the material interference and
the used adhesives. Regarding the obtained results of the present
research both researchers’ assumptions are rejected; namely the
adhesive application an effect on the shear bond strength of Lime-
Lite to composite and most fractures are of the cohesive type.
Hereby we would like to appreciate a lot and much to thank Dr.
Alizadeh the professor of Tehran Amirkabir University-Mechanic
Engineering Faculty for assisting us in the biomechanics portions
of the project.
We thank also Eng. Mr. bass Ostadzadeh due to his helpful
collaboration in guiding us to perform this Project. In addition,
special thanks to Dr. KharaziFard who counseled us on the
statistical points of the project.