Effect of Temperatures on Polymerization Stress and Microleakage of Class V Composite Restorations
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was not confirmed by the results o f the present inv estiga-
tion. The results shows that preheating composite to high
temperatures lead to an increase in polymerization con-
traction stress but less microleakage at the cervical mar-
gin. This is in contrast with several studies that have
shown a direct relationship between contraction stress
and marginal leakage in resin composite restorations
[13-15]. This was also expected because resin compos-
ites exhibit a six to eight ti mes greater thermal expansion
than the surrounding tooth structures [9,16], polymeriza-
tion shrinkage along with thermal contraction might cre-
ate high interfacial stresses in preheated composites upon
thermal equilibrium, with detrimental effects on marginal
adaptation, integrity and seal [13]. Further investigation
is therefore needed regarding advantages and disadvan-
tages of dental composite preheating before we can make
a conclusion if this method is appropriate in dental prac-
tice.
5. Conclusion
The present finding suggests that in the challenging
situation of the cervical restoration which extends onto
the root surface, preheating composites to 60˚C signifi-
cantly reduced microleakage at the tooth-restoration in-
terfaces. Preheating however results in non-desirable
increase of polymerization contraction stress. More in-
vestigation should be done regarding the consequence of
the increased stress at the tooth restoration interfaces to
the strength of the restored tooth.
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