TITLE:
Effect of Temperatures on Polymerization Stress and Microleakage of Class V Composite Restorations
AUTHORS:
Pavinee Padipatvuthikul Didron, Wojciech Chrzanowski, Ayman Ellakwa
KEYWORDS:
Preheating; Dental Composite; Polymerization Shrinkage; Contraction Stress; Microleakage
JOURNAL NAME:
Open Journal of Composite Materials,
Vol.3 No.4,
September
12,
2013
ABSTRACT: The loss of interfacial integrity was
identified as one of the major causes for replacement of resin composite
restorations. Preheating procedure has been proven to enhance flowability and adaptation
of resin composites and increase their degree of conversion. The purpose of this study was to
investigate polymerization contraction stress produced in resin composites
after preheating to 37℃ and 60℃, and measure microleakage of Class V
restorations restored with preheated composites. Three resin composites (GC Kalore,
Gradia Direct X, Filtek Supreme XT) at room
temperature, 37℃, and
60℃ were investigated. Maximum
contraction stress of the composites (n = 5) was evaluated in a modified low-compliance device. Samples were
light-cured for 40 seconds and the maximum force was recorded during 15 minutes.
Calculations were done to adjust for the system’s compliance and obtain linear shrinkage values of
composites. Data were analyzed by Multivariated Analysis of Variance (MANOVA)
and Tukey’s test for
multiple comparisons (α = 0.05).
Seventy-two Class V cavities were prepared on the buccal surfaces of extracted
premolars and divided into 9 groups. The teeth were restored with composites at
3 temperatures and were thermo-cycled between 5℃ and 55℃ with a one-minute dwell-time for 1000 cycles. The teeth were sealed with wax and nail vanish
before placed in 0.5% toluidine blue dye for 24 hours. The teeth were embedded
in self-curing resin and sectioned bucco-lingually with a slow-speed diamond
saw, providing 3 sections per restoration. Microleakage was rated by two
evaluators using a 0 - 4 ordinal scale at the occlusal and
cervical margins under light microscope. Microleakage data were analyzed with
Kruskal-Wallis ANOVA and Mann-Whitney U test (α = 0.05). Results indicate that
preheating composites to 37℃ and 60℃ significantly increased
polymerization contraction stress of composites (p 0.05). A significantly greater amount
of leakage was found at the cervical margins (p 0.05). For all tested materials,
preheating composites to 60℃ resulted in significantly less microleakage at the cervical margin.