Download The effect of tempreture on microleakage of composite resin

The Effect Of Refrigerated Composite Resin
Restoration On The Sealing Ability Of Class V Cavities
By Dr. Wedad Y. Awliya BDS, MSc
Associate professor, Department of Restorative Dental
Science, College of Dentistry, King Saud University
Riyadh, Saudi Arabia
P.O. box 5967 Riyadh 114
E-mail [email protected]
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Abstract
Purpose: To investigate the effect of refrigerated and room temperature
composite resin restorations on the sealing ability of class V cavities placed at
intraoral temperature.
Materials and Methods: Class V cavities were prepared in the buccal and
lingual surfaces of twenty extracted human molar/premolar teeth. The prepared
teeth were then divided into four groups, each group contains five teeth. Two
groups were restored with refrigerated Composan and Renew composite resin
(Stored at 5 oC). The other two groups were restored with Composan and
Renew composite resin stored at room temperature (25 oC). Restorations of all
teeth were done in a chamber adjusted at intraoral temperature (32 oC). The
teeth were then prepared for the microleakage test. Specimens were immersed
in 2% methylene blue dye for 24 hours, then sectioned bucco-lingually and
viewed with a stereomicroscope.
Results: Refrigerated Composan composite resin showed significantly less
microleakage than Composan at room temperature. However, no significant
difference in microleakage was found between refrigerated and room
temperature Renew composite resin.
Conclusion: No adverse effect on marginal seal of class V cavities was found
using composite resin restorative materials directly from fridge.
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INTRODUCTION
Advances in adhesive dental technology have radically changed restorative
dentistry. However, polymerization shrinkage of composite resin is still unsolved
problem. The contraction stress-build up that occurs during polymerization,
adversely affects the bond interface between composite resins and the hard
dental tissues, leading to clinical failure of the restorations.1
Opening of the
restoration margins, which may result in microleakage of fluid, discoloration near
restoration margins, secondary caries, postoperative sensitivity are the most
frequent consequences of the polymerization shrinkage.2,3
Although some manufacturers recommend storage of restorative and adhesive
materials at room temperature, others recommend refrigerated storage to
extend shelf life. In clinical situations, Materials may be taken from a refrigerator
and used immediately without allowing time for equilibrium to room temperature,
and this reduced temperature could have possible detrimental consequences on
the efficacy of the bonding agent. Lowered temperature might increase the
viscosity of the polymeric materials, which might affect penetration of the
refrigerated adhesive material into dentin surface, with a resultant decrease in
bond strength.4 Additionally, the degree of polymerization of the bonding resin
decreases with lowered temperature,5 and this may adversely affect the physical
properties of the adhesive materials.6 However, Hagge et al found that a group
of refrigerated Scotchbond Muli-Purpose bonding system (at 3 oC) showed
significantly higher bond strength to dentin than the group used at room
temperature. 7
Therefore, the purpose of this study was to investigate the effect of using
refrigerated composite resin (5 oC) and composite resin stored at room
temperature (25 oC) on the sealing ability of class V cavities placed at intraoral
temperature (32 oC).
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MATERIALS AND METHODS:
Twenty extracted, non-carious, human molar/premolar were used within one
month after their extraction. The teeth were stored in saline until preparation.
Standardized buccal and lingual class V cavities (5 mm long, 3 mm wide, and 2
mm deep) were prepared in all teeth with # 330 carbide bur (MidWest Dental
Product Corp., Des Plaines IL, USA) using a high speed hand piece and air-water
spray. A new bur was used for every 10 preparations. The occlusal enamel
margins were beveled and the gingival walls were extended 1 mm below the
cemento-enamel junction. The prepared teeth were then randomly assigned into
four-experimental groups (each group contains 5 teeth, with two-cavity
preparations in each tooth). The prepared teeth were stored in saline in an
incubator, adjusted to simulate intraoral temperature (32 oC), 24 hours before
restoration.
Two types of composite resin restorative materials are used for this study (shade
A3.5) following manufacture’s instructions. Renew, light cured universal hybrid
composite resin (Bisco, 1100W. Irving Park Rd. Schaumburg, IL 60193, USA),
and
Composane
light
cured
microhybrid
composite
resin,
(Promdica,
Domagkstr. 31, 24537 Neumunster, Germany). To prevent temperature variation
in the refrigerated groups at the restoration time, 50% of the restorative
materials were subdivided into equal small increments and placed at small well
sealed, light blocked containers. Then these containers were stored in a
refrigerator at 5 oC for 24 hours before restorations placement in the cavities.
The other 50% of each material was stored at room temperature (25 oC).
In the first experimental group enamel surfaces were etched with 32%
phosphoric acid (Unietch, Bisco) for 30 sec, rinsed thoroughly, and excess water
was removed with brief burst of air. After etching, 2 consecutive coats of Onestep light cured universal dental adhesive (Bisco, Schaumburg, IL, 60193, USA)
were applied to prepared enamel and dentin structure. The adhesive was dried
for 10 sec. with an air syringe, then light cured for 10 sec. Renew composite
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resin material stored at room temperature was placed in one increment into the
cavity preparations, light cured for 40 sec. with light spectrum 800 (Dentsplay,
Detrey, Konstanz, Germany). In the second group, similar restorative procedures
as in first group were followed using refrigerated adhesive and Renew restorative
material.
Cica etching gel (Promdica, Domagkstr, 31, 24537 Neumunster, Germany) was
used as an etching gel for the third group for 30 sec., rinsed, then air-dried.
Compobond LCM system (Promdica) was applied. Primer was rubbed into dentin
for 30 sec., and then the excess primer was removed by a brush followed by
careful drying of the cavities with oil–free air. The adhesive was applied evenly
on all prepared dentin and enamel surfaces by using a new disposable brush,
dried with faint air stream and light-cured for 20 sec. Then Composan LC
restorative material which was stored at room temperature, applied to the
cavities in one increment.
The previous procedures, in the third group, were followed in the fourth group
using refrigerated Composan LC restorative system.
All the restorations were finished and polished using Soflex discs (3M Co.). All
procedures were conducted by the same operator in a chamber its temperature
was adjusted to simulate the intraoral temperature (32 oC).
In order to prepare the restored teeth for the microleakage test, the teeth apices
were sealed with a light–activated composite resin. Two coats of nail varnish
were applied to the teeth except for 1 mm around the restoration margins. The
restored teeth then were immersed in 2% methylene blue dye (Fisher Scientific,
Fair Lawn. NJ, USA) for 24 hours, then they were washed by distilled water to
remove the superficial dye. Each specimen was invested in separate clear resin
block and coded before its sectioning longitudinally in a bucco-lingual direction
with a low speed water-cooled diamond saw (Silverstone-Taylor Hard Tissue
Microtome, Scientific Fabrication, Littleton, CO., USA). Each section was then
inspected under a stereomicroscope (Wild Photomakroskop M400, Heerbrugg,
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Switzerland) at 32x magnifications. The staining along the tooth restoration
interface was recorded according to the following criteria:
0: no dye penetration
1: penetration of the dye to less than half of the cervical/occlussal wall
2: penetration of the dye further than half of the cervical/occlusal wall
3: penetration along the axial wall
Data were statistically analyzed using SPSS system. Wilcoxon signed rank test,
at 0.05 significance level was used to identify any difference between the
different restorative techniques. Combined occlusal and cervical scores within
each restoration were also compared.
RESULTS
Table 1 presents the microleakage data for the occlusal and gingival walls of
both materials in this study. Wilcoxon signed rank test indicated that refrigerated
Composan composite resin showed significantly less microleakage than
Composan at room temperature (P=0.014). However, no significant difference in
microleakage was found between refrigerated and room temperature Renew
composite resin (P=0.489). All enamel walls of both materials (refrigerated and
at room temperature) showed significantly better marginal seal than gingival
walls (P< 0.05). Comparing microleakage of both Composan and Renew
composite resin at room temperature no significant difference was found
(P=0.511). On the other hand, refrigerated Composan composite resin showed
significantly less leakage than refrigerated Renew composite resin at both
margins (P=0.002).
DISCUSSION
The dimensional rearrangement of monomers into polymer chains during resin
polymerization inevitably leads to volume shrinkage.8 In clinical situation, the
curing contraction is restrained by the developing bond of the restorative
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material to the cavity walls.9 This restriction induces polymerization contraction
stress, which counteracts the developing resin-tooth bond by pulling the setting
resin composite material away from the cavity walls.10,11 If the weakest link is
the bonding interface with the tooth, the resin-enamel bond may survive the
shrinkage, but the weaker resin-dentin interface may not.12 Although Enamel
adhesion is predictable and established entity in contemporary restorative
dentistry, an adequate bond to dentin is more difficult to achieve.13 This
explains the better sealing ability of all composite restorations in this study at
enamel walls.
Using composite resin directly from the refrigerator did not adversely affect the
sealing ability of the two composite resins in this study. In fact the results
showed that the sealing ability of Composan composite resin was significantly
improved by refrigeration. This obtained result might be due to the influence of
the factors that affect polymerization shrinkage. First, thermal expansion of
refrigerated composite should occur when the material reach intra oral
temperature. This expansion can compensate the high contraction stresses that
occur in the early stage of the setting reaction.14 Second, the curing rate and
the degree of cure decrease when setting reaction occur at lower temperature.14
Thus, in case of cooled resin composite the pre-gel period could be longer and
the setting stresses could be relived more easily by flow.12 Moreover, the
restorative material can reach temperature higher than intra oral temperature by
the thermal effect of the curing light.15 Consequently, a thermal contraction of
the restorative material should be induced when it drops to intra oral
temperature. This effect is reduced when cooled material are used because the
overall temperature of the restoration should be lower during light curing.
Therefore, the sealing ability of cooled material might be improved.
The marginal seal of both composite resins used in this study at room
temperature showed no significant difference. However, after refrigeration
Composan significantly showed better seal. This may be attributed to effect of
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temperature on the restorative resin as one component and the adhesive
systems as another component. Composan composite resin has BisGMA and
UDMA as difunctional monomers and both are extremely viscous. Although these
monomers were diluted by another difunctional monomer (TEDMA), Composan
viscosity seems to be higher than that of Renew, which contains Only BisGMA
diluted by TEGDMA. Shrinkage stress development in the restoration can be low
when shrinkage is accompanied by predominant (pre-gel) viscous flow property
of the material as early mentioned.16 Temperature also, might increase the
viscosity of the adhesive system. Stiffness or rigidity of a resin is quantified by
Young’s modulus of elasticity, which represents the resistance of the material to
elastic deformation.17 The lower Young’s modulus, the more the elastic capacity
will reduce contraction stress.18 Viscous adhesive resins produce thick resin
bonding layer between the stiff dentinal cavity wall and the shrinking restorative
resin composite. Stretching of this intermediate layer (with a low Young’s
modulus) may provide sufficient elasticity to relieve polymerization contraction
stresses of the restorative resin composite.19,20,21 Composan bonding system
is two-bottle adhesive (Primer and adhesive). On the other hand, the bonding
system used in this study with Renew composite resin, is one-bottle adhesive.
Two-bottle adhesive system may provide a thicker adhesive layer.22 However,
further investigation is needed to study the effect of increased viscosity of
adhesive system, because of refrigeration, on their wetting characteristics and
subsequently the bond strength to tooth structure.
Conclusions

The results of this study indicate that marginal leakage around dentin
margins is still an unsolved problem because bonding to dentin has not
reached the ideal performance as bonding to enamel has.

No Adverse effects on marginal seal, of class V cavities, were noted using
composite resins directly from refrigerator without allowing equilibrium to
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room temperature. In fact, Refrigeration significantly enhances the marginal
seal of class V cavities restored with Composan composite resin.

Since refrigeration improves significantly the sealing ability of Composan but
not Renew composite resin, Further research is needed to study the effect
of temperature on different adhesive systems, and on their bond strength
to tooth structure.
Acknowledgement
The author would like to express her thanks and appreciation to Dr. Hanan
Mahjoub for her help during the lab work of this study and to Dr. Nazeer Khan
for his assistance in the statistic of this study.
References
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Lutz F, krejci I, Barbakow F. Quality and durability of marginal adaptation in
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2.
Swift EJ, Perdigao J, Hey Mann HO. Bonding to enamel and dentin: A brief
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3.
Walshaw PR, McComb D. clinical considerations for optimal dentinal
bonding. Quintessence Int 27:619-625, 1996.
4.
Burrow MF, Taniguchi Y, Nikaido M, et al. Influence of temperature and
relative humidity on early bond strengths to dentin. J Dent 23:41-45, 1995.
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Bausch JR, de Lange C, Davidson CL. The influence of temperature on some
physical properties of dental composite. J Oral Rehabil 8:431-439, 1981.
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Greener EH, Greener CS, Moser JB. The hardness of composites as a
function of temperature. J Oral Rehabil 11:335-340, 1984.
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Hagge MS, Lindemuth JS, Broome JC et al. Effect of refrigeration on shear
bond strength of three dentine bonding systems. Am J Dent 12:131-133,
1999.
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8.
Feilzer AJ, de Gee AJ, Davidson CL. Curing contraction of composites and
glass ionomer cements. J Prosthet Dent 59:297-300,1988.
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Davidson CL. Resisting the curing contraction with adhesive composite. J
Prosthet Dent 55:446-447,1986.
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systems and interfacial initiator of polymerization in adhesive bonding of
resin to dentin. J Dent Res 70:1088-1091,1991.
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stresses at the margin of posterior composite resin restorations: a new
restorative technique. Quintessence Int 17:659-664,1986.
12. Davidson CL, de Gee AJ. Relaxation of polymerization contraction stress by
flow in dental composites. J Dent Res 63:146-148,1984.
13. Lopes GC, Andrada MC, Dental adhesion: present state of the art and future
perspectives. Quintessence Int 33:213-224, 2002.
14. Bandyopadhyay S. A study of volumetric setting shrinkage of some dental
materials. J Biomedical material Res 16(2):135-144, 1982.
15. Loney Rw, Price RB. Temperature transmission of high out put light-curing
units through dentin. Operative Dent 26(5):516-520, 2001.
16. Davidson CL, de Gee AJ. Relaxation of polymerization stresses by flow in
dental composite. J Dent Res 63:146-148, 1984.
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during the setting of dental composite resins J Dent Res 66;1713-1716,
1987.
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gaps in class v composite resin restorations. J Dent Res 67:841-845,1988.
19. Meerbeek V. Adhesion to mineralized tissues. Operative Dent 5:101-124,
1992.
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20. Kemp-Scholte CM, Davidson CL. Complete marginal seal of class V resin
composite restoration affected by increased flexibility. J Dent Res 69:12401243, 1990.
21. Kemp-Scholte CM, Davidson CL. Marginal integrity related to bond strength
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46:658-664, 1990.
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publisher, Vol I Chap 2: page 34
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Table 1. Microleakage Scores Of The Two Composite Resin Materials
(Refrigerated And At Room Temperature) At The Occlusal And Gingival Margins
Material
Microleakage scores at Microleakage scores at
the occlusal margins
the gingival margins
No
Score
0
Composan
(Room temperature)
Composan
(Refrigerated)
Renew
(Room temperature)
Renew
(Refrigerated)
No
Score
1
2
3
0
1
2
3
20 14
4
1
1
20 2
4
10
4
20 17
2
0
1
20 0
18
1
1
20 10
8
2
0
20 0
5
13
2
20 6
9
4
1
20 0
9
9
2
12