Alomari, Nusair, Ali tions.2 On the other hand, another study demon- strated no effect of soft-start polymerization on postoperative sensitivity.34 It has been claimed that the predominant rea- son for reduced shrinkage stress, attained with soft-start polymerization, is the decrease in the final conversion of the resin composite, which can affect its mechanical properties.13 On the con- trary, other studies have found that the degrees of conversion and microhardness of resin com- posite were not affected using various modes of LED curing lights.35-37 Previous research showed that soft-start curing to be effective in reducing microleakage.8,38 Our results showed that the fast-curing mode resulted in increased microle- akage at the dentin/cementum margins of class V cavities for box-shaped cavities, i.e., when the C-factor was high. For V-shaped cavities, i.e., for low C-factor cavities, there was no statistical dif- ference between soft-start curing and fast-curing mode of the same curing light. Traditionally, qualitative scoring systems were used to assess microleakage. Recently, with new advancements in image analysis software, quanti- tative microleakage measurements have become more popular.27,39 In this study, we compared the quantitative and qualitative scoring methods for microleakage to explore whether they produce dif- ferent results. In the quantitative measurements we measured the actual degree of microleakage in micrometers, using special software to capture standardized images of the sections. While for the qualitative measurements we measured the degree of microleakage on a 0-4 scale using the same images. Qualitative measurements could be done directly on the microscope without the need for special equipments. Both the quantitative measurements and the qualitative criteria gave the same results. ocnLusIons Under the conditions of this in vitro study, it can be concluded that: • Using fast curing mode in class V cavities with high C-factor resulted in more microleakage at the dentin/cementum margins. • In all the groups, microleakage was evident at both enamel and dentinal/cementum margins. And there was no statistical difference between the two margins except for group III (high C-factor October 2011 - Vol.5 cavities and cured with the fast curing mode). • Quantitative and qualitative methods for measuring microleakage gave the same results and can be used interchangeably. AcKnoWLEdGEMEnt This research is supported by Kuwait Univer- sity Grant No. DR 01/07. rEFErEncEs 1. Yap AU, Wang HB, Siow KS, Gan LM. Polymerization shrinkage of visible light-cured composites. Oper Dent 2000;25:98-103. 2. Briso AL, Mestrener SR, Delicio G, Sundfeld RH, Bedran- Russo AK, de Alexandre RS, Ambrosano GM. Clinical as- sessment of postoperative sensitivity in posterior compos- ite restorations Oper Dent 2007;32:421-426. 3. Alomari QD, Omar R, Akpata SE. Effect of LED curing modes on postoperative sensitivity after class II resin com- posite restorations. J Adhes Dent 2007;9:477-481. 4. Sakaguchi RL, Wiltbank BD, Murchison CF. Cure induced stresses and damage in particulate reinforced polymer matrix composites: a review of the scientific literature. Dent Mater 2005;21:43-46. 5. Ferracane JL. Developing a more complete understanding of stresses produced in dental composites during polym- erization. Dent Mater 2005;21:36-42. 6. Hofmann N, Hunecke A. Influence of curing methods and matrix type on the marginal seal of class II resin-based composite restorations in vitro. Oper Dent 2006;31:97-105. 7. Ilie N, Felten K, Trixner K, Hickel R, Kunzelmann KH. Shrinkage behavior of a resin-based composite irradiated with modern curing units. Dent Mater 2005;21:483-489. 8. Kubo S, Yokota H, Yokota H, Hayashi Y. The effect of light- curing modes on the microleakage of cervical resin com- posite restorations. J Dent 2004;32:247-254. 9. Leonard DL, Charlton DG, Roberts HW, Cohen ME. Polym- erization efficiency of LED curing lights. J Esthet Restor Dent 2002;14:286-295. 10. Lim BS, Ferracane JL, Sakaguchi RL, Condon JR. Reduction of polymerization contraction stress for dental composites by two-step light-activation. Dent Mater 2002;18:436-444. 11. Dewaele M, Asmussen E, Peutzfeldt A, Munksgaard EC, Benetti AR, Finné G, Leloup G, Devaux J. Influence of cur- ing protocol on selected properties of light-curing poly- mers: degree of conversion, volume contraction, elastic modulus, and glass transition temperature. Dent Mater 2009;25:1576-1584. 407 European Journal of Dentistry