In-vivo evaluation of microleakage of nano-filled resin composite using two different restorative techniques

Abstract

The study was carried out to evaluate and compare dentine margin microleakage of nano-filled
resin composite restorations placed with a RMGIC using the co-cure technique and those placed with
an ‘all-in-one’ self-etch DBA. In premolar teeth, that had to be extracted for orthodontic reasons, two
proximal boxes with gingival margins placed in dentine were prepared. Restorations were inserted
using co-cure method with RMGIC plus a nano-filled resin composite in one proximal box, and self-etch
DBA plus nano-filled resin composite in other proximal box. After two weeks, teeth were extracted and
after sealing their root apices, were placed in 2% aqueous methylene blue dye for 48 hours. Each tooth
was sectioned mesio-distally. The dye leakage length was measured using a stereomicroscope.The mean
value of microleakage for co-cure technique was found to be lesser than that for all-in-one dentine
bonding agent. Co-cure technique was found significantly superior to all-in-one DBA in its sealing
ability at gingival margin.
Key words: Co-Cure, RMGIC, nano-composite, class II composite

Full text

311Pakistan Oral & Dental Journal Vol 32, No. 2 (August 2012)
In-vivo evaluation of microleakage of nano-filled resin composite
ORIGINAL A RTICLE
1Correspondence: Dr Fariha Naz, Assistant Professor, Department of Operative Dentistry, Lahore Medical
& Dental College, Lahore. 120-C, Park view Housing Society, DHA phase VIII, Lahore, Pakistan. Email:
farihashakeel@hotmail.com, Contact number: Cell:0321-4454855
² Professor of Conservative Dentistry, Salman Bin Abdul Aziz University, Alkharj, Saudi Arabia
³ Senior Registrar, Department of Operative Dentistry, CMH Institute of Dental Sciences, Lahore
INTRODUCTION
Dental composite is a valuable restorative material
because of its excellent esthetic properties. Continu-
ous research resulted in formulating the dental com-
posites with improved wear resistance and better
strength for its use as a posterior restorative material.1
D Composites being acrylic in nature, have the inher-
ent property of polymerization shrinkage.2 This poly-
merization shrinkage results in microleakage.3
Microleakage is thought to be responsible for dentinal
sensitivity, recurrent caries, and pulpal inflamma-
tion.4-7 The composite materials with nanotechnology
results in decrease polymerization shrinkage, better
esthetics and good handling characteristics.8
In clinical practice, a major problem is encountered
when using composites in class II cavities having
gingival margin entirely within dentine.9 Studies show
that the bond on gingival margins is not as effective
as on axial and occlusal margins in Class II restora-
tions.10, 11 Dentine bonding is more difficult as compared
to enamel as the heterogeneous nature of tissue re-
quires the bonding system to accommodate simulta-
neously the properties of hydroxyl-apatite, collagen,
smear layer, dentinal tubules and fluids.12Different
techniques are adopted to increase the seal between
composite restoration and gingival margin in class II
restorations.13Though, it is not possible to totally avoid
polymerization shrinkage, but a careful insertion and
curing technique can minimize the stresses resulting
from this phenomenon.14,15
Flowable composites or RMGI liner under a com-
posite restoration in root surface area may reduce
potential microleakage.16, 17, 18 Moreover, RMGI can be
used as a base material in co-cure technique where it
is cured together with first increment of composite
placed upon it. This may result in some chemical
bonding between two materials that enhances the seal
with micro-mechanical bonding.19 The evolution of ad-
hesive systems led to the development adhesives need-
ing single step of application by one-bottle system of
sixth generation dentine bonding agent.20, 21
IN-VIVO EVALUATION OF MICROLEAKAGE OF NANO-FILLED RESIN
COMPOSITE USING TWO DIFFERENT RESTORATIVE TECHNIQUES
¹FARIHA NAZ, BDS, FCPS
²SHAHID MAHMOOD, MDS
³BENA NAQI, BDS
ABSTRACT
The study was carried out to evaluate and compare dentine margin microleakage of nano-filled
resin composite restorations placed with a RMGIC using the co-cure technique and those placed with
an ‘all-in-one’ self-etch DBA. In premolar teeth, that had to be extracted for orthodontic reasons, two
proximal boxes with gingival margins placed in dentine were prepared. Restorations were inserted
using co-cure method with RMGIC plus a nano-filled resin composite in one proximal box, and self-etch
DBA plus nano-filled resin composite in other proximal box. After two weeks, teeth were extracted and
after sealing their root apices, were placed in 2% aqueous methylene blue dye for 48 hours. Each tooth
was sectioned mesio-distally. The dye leakage length was measured using a stereomicroscope.The mean
value of microleakage for co-cure technique was found to be lesser than that for all-in-one dentine
bonding agent. Co-cure technique was found significantly superior to all-in-one DBA in its sealing
ability at gingival margin.
Key words: Co-Cure, RMGIC, nano-composite, class II composite

312
Pakistan Oral & Dental Journal Vol 32, No. 2 (August 2012)
In-vivo evaluation of microleakage of nano-filled resin composite
Because of increased use of posterior composite
resins on dentin, methods are needed to minimize
leakage for more successful restoration. Literature
shows measurement of microleakage in vitro. 22 How-
ever, it is justified to assume that in-vitro studies do not
necessarily replicate the in-vivo situation.23 So a need
arises to conduct a study where the selected restor-
ative materials undergo natural intra-oral thermal
changes and occlusal loads before the degree of
microleakage is measured. Therefore this study was
planned to examine whether the Co-cure technique is
better than the use of self-etch DBA in vivo when
restoring proximal lesions in terms of microleakage at
restoration-cavity interface.
METHODOLOGY
Thirty patients (15-30 years age) requiring extrac-
tions of premolar teeth for orthodontic reasons were
selected for restorations after taking an informed
consent.
In selected premolar teeth, two proximal boxes
with gingival margins placed in dentine were prepared.
Slot style cavity was prepared having buccal and lin-
gual walls parallel to each other and at right angle to
axial wall and gingival floor in each tooth with flat
cylindrical straight fissure bur. No bevels were used in
cavity preparations and metallic matrix band with
retainer was placed along wooden wedge insertion.
In one proximal box, self-etch dentine bonding
agent (Adper Prompt L Pop; 3M ESPE,St. Paul, MN,
USA) was applied for 15 seconds and after gently air
drying the cavity, light curing with LED light was done
for 20 seconds. Two coats of the adhesive were applied.
Nano-filled composite (Filtek Supreme, 3M-ESPE, St.
Paul, MN, USA) was placed by incremental technique
and each increment was cured for 40 seconds.
In other proximal box, co-cure technique was used
and cavity was etched with 40% phosphoric acid. After
rinsing and air-dried, resin modified glass ionomer
cement (FujiBOND LC; GC Int., Tokyo, Japan) was
mixed and placed over gingival floor. First increment of
nano-filled composite was placed and was light cured
together with RMGIC for 40 seconds. The fifth genera-
tion dentine bonding agent (BC Plus TM; Vericom Co.
Ltd.) with primer and adhesive in one bottle was
applied over cavity walls and cavo- surface margins and
then cured for 20 seconds. The remaining restoration
was done by nano-filled composite using incremental
technique. Confounding variables were controlled
through matching. Patients were recalled after 2 weeks,
and careful extractions of restored teeth were done.
The extracted teeth were stored in 0.12% thymol
solution for two months.
Each tooth from the solution was gently rinsed in
water and air dried. The root apices were sealed with
sticky wax and root surfaces were coated with two
layers of nail varnish within 1.0 mm of the restoration
margins. All teeth were then placed in 2% aqueous
methylene blue dye (buffered to pH 7.0) for 48 hours at
room temperature.
Following washing in water, each tooth was
mounted on a mould and sectioned mesio-distally
through the centre in to two equal halves with a water-
cooled slow-speed diamond saw (Isomet; Beuhler Ltd,
Lake Bluff, IL, USA).
The length of dye leakage at the restoration /
preparation interface was measured in micrometers by
using a stereomicroscope (Olympus; 2x10 magnifica-
tions). The degree of microleakage was evaluated for
both mesial and distal groups.
The mean and standard deviation were calculated
and mean gingival margin microleakage measurement
for each mesial and distal proximal surface of each
tooth was compared between the two groups using
independent Student’s t-test (SPSS V12).The probabil-
ity level was set at p<0.05 for statistical significance.
RESULTS
Microleakage was found in all the samples. The
mean value of microleakage for co-cure technique was
found 305.833um + 82.7 and for all-in-one dentine
bonding agent was 364.17um + 94.4.
The restorations placed with co-cure technique
showed lesser degree of microleakage as compared to
those with all-in-one dentine bonding agent. After
applying the paired samples t-test, difference of mean
values between the two groups was found statistically
significant (p<0.05).
TABLE 1: DESCRIPTIVE STATISTICS FOR DATA ON MICROLEAKAGE
Restorative technique N Minimum Maximum Mean Std. Deviation
Co-cure 30 75 425 305.83 82.7031
All-in-one DBA 30 100 500 364.17 94.386

313Pakistan Oral & Dental Journal Vol 32, No. 2 (August 2012)
In-vivo evaluation of microleakage of nano-filled resin composite
DISCUSSION
The microleakage in present study was assessed by
using the dye penetration method but other methods
are, use of radioactive isotopes, neutron activation
analysis, scanning electron microscopy, chemical trac-
ers, open restoration method and air pressure method.24,
25 However, the dye penetration method is used more
frequently because it is easiest and most feasible one.
Nano-composite used in this study was found effica-
cious for clinical use in stress-bearing posterior cavi-
ties by Ernst et al.26
In this study restorations were placed in-vivo. Most
of the microleakage studies are in-vitro studies. How-
ever, the proper testing of any restorative material is
not complete without undertaking the in-vivo studies
or checking the clinical performance of the matieral.27
In all specimens, the dye penetrated to a considerable
depth between restoration and tooth structure in the
area of dentin but no dye was found in interface in area
of enamel. These high dye penetration values may be
attributed to the location of restorations. Stockton in
his study of microleakage in deep proximal cavities
demonstrated that despite more favorable conditions,
moderate to considerable amounts of leakage occurred
with all methods of composite restoration.25 His study
was an in-vitro where moisture control and cavity
access were easier to achieve as compared to working
intra-orally but none of the methods could give abso-
lute seal.
The higher microleakage values seen with Prompt
L-Pop were in accordance with other studies done on
this material. Oztas and Olmez found that composite
restorations with Prompt-L-Pop presented larger and
more frequent interfacial gaps than control restora-
tions bonded with conventional adhesive system.28
Similarly, Li et al and Yacizi et al found more
microleakage with Prompt L-Pop compared to fifth
generation adhesive systems. This might be due to lack
of separate primer that reduce infiltration depth or
wettability of dentin adhesives thereby reducing adhe-
sion and sealing capacity of Prompt L-Pop. However,
though number of studies showed quite high values of
microleakage with all-in-one DBA but in the present
study falling of most of the samples in the highest
values showed the failure of this technique in proximal
composite fillings. This may be due the study being in-
vivo as compared to the other studies which are in-
vitro. Co-cure technique resulted in lesser values of
microleakage but couldn’t succeed in its complete
arrest. Knight et al in their vitro study on co-cure
technique found very high bond strengths at tooth and
restoration interface.19 They modified technique by
placing auto-cure GIC and painted the very liquid
consistency of RMGIC over it. The restoration efficacy
is justified by the extent of microleakage in real life and
those values may not be coincident with bond
strengths.31
In in-vitro studies isolation and access to cavity are
not difficult. In clinical situations the access to the site
is not easy. This is especially difficult when the cavities
were made for the study purposes in which the dimen-
sions of the cavities had to be controlled for standard-
ization. Also in proximal restorations adhesives are
also not easy to be used. The contributory factors are
the difficult accessibility of the corners of the deep
proximal box; the adherence of materials to metal
matrix bands, which creates a potentially higher C
factor; and air drying, which may produce air voids
within the hybrid layer during the process of solvent
removal.32
Also in the gingival areas the direction of the
tubules is almost horizontal and mechanical bonding
through resin penetration into dentinal tubules is
negligible. Other factors that affect the marginal seal
TABLE 2: PAIRED SAMPLES TEST
Paired differences t Sig. (2-tailed)
Mean Std. Deviation
All-in-one DBA & co-cure 58.3333 110.7057 2.886 .007
TABLE 3: COMPARISON OF RANGES OF MICROLEAKAGE VALUES OF TWO TECHNIQUES
Microleakage in um Co-cure All-in-one DBA
No. of samples Percentage No. of samples percentage
< 125 3 10 2 6.67
125-325 15 50 6 20
> 325 12 40 22 73.33

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Pakistan Oral & Dental Journal Vol 32, No. 2 (August 2012)
In-vivo evaluation of microleakage of nano-filled resin composite
are contraction of the composite material, stresses at
tooth-restoration interface, stiffness and other me-
chanical properties of composite.33Usually bond be-
tween enamel and composite survive these stresses
while failures are observed at composite-dentin or
composite-cementum interfaces.33
In spite of all problems encountered in this study,
co-cure technique showed better performance in seal-
ing ability as compared to all-in-one dentine bonding
agent. However, none of methods could eliminate
microleakage in dentine region shows that microleakage
along dentinal margins remains an important issue.
CONCLUSION
Co-cure technique seems to be better option for
class II composite restorations that may produce a good
chemical adhesion between two materials.
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