Alomari, Nusair, Ali dIscuIon effect of the placement technique, the restorative According to the results of this study, the null- material was placed as one increment because hypothesis that combining the effect of fast cur- the depth of the cavities in all of the groups was ing mode and high C-factor cavity do not affect the only 2 mm. degree of microleakage was rejected. When the To simulate thermal stresses on the tooth-res- restoration of a class V cavity with a high C-factor toration interface, microleakage studies usually was cured with the fast-curing mode, this resulted employ thermocycling of different regimens.22-26 in more microleakage at the gingival margins. One microleakage study showed that microleak- Microleakage evaluation is the most common age of resin composite restorations will not be method of assessing the sealing efficiency of a re- affected by thermocycling, when the restorations storative system.27 Class V cavities located at the are cured with soft-start polymerization of LED CEJ of the vestibular surfaces of maxillary premo- curing light.23 On the other hand, the same study lars were used in this study. All the cavities were showed a difference in microleakage between prepared and restored by one investigator fol- thermocycled and non-thermocycled specimens lowing strict protocol. The adhesive system used when standard and high intensity curing modes (Excite) is a filled, light-curing, single component were used. For standardization, in our study, we and alcohol based type of bonding agent. In a pre- used one protocol of thermocycling for all the vious study, this adhesive system showed micro- groups. tensile bond strength values of over 30 MPa under both dry and moist conditions.28 After removal of To change the C-factor for the cavities, two dif- all etchant gen with a vigorous water spray for 10 ferent shapes of cavities were prepared, namely seconds, excess water was removed and dentin the V and box shapes. The sizes and surfaces surfaces were left moist. Using one adhesive sys- available for bonding were the same for the two tem and one resin composite restorative material shapes of the cavities (16 mm3 and ~32 mm2 re- reduced the confounding variables in the study. spectively). Previous studies showed contradic- Previous studies showed no effect of the inser- tory results regarding the effect of C-factor on tion technique on microleakage of class V cavi- composite resin restorations. Laboratory studies ties.15,16 On the contrary, another study found that showed that high C-factor increases the rate and the incremental placement technique reduces mi- amount of stresses resulting from polymeriza- croleakage when compared with the bulk place- tion shrinkage of resin composite restorations.19,29 ment technique in deep cavities.27 Furthermore, it Santini et al30 found no difference in the amount has been found that C-factor and placement tech- of microleakage between box-shaped cavities nique can affect the microtensile bond strength of and V-shaped cavities at both enamel and gingi- the adhesive system.20 In our study, to rule out the val margins. Using bovine incisors, a difference October 2011 - Vol.5 European Journal of Dentistry Table 4. Frequency (percentages) of enamel microleakage scores for the four groups. Kruskal-Wallis test value=0.735. Group 0 1 2 I 16 (80) 1 (5) 1 (5) II 15 (75) 1 (5) 0 (0) III 14 (70) 0 (0) 0 (0) IV 14 (70) 1 (5) 0 (0) Total 59 (74) 3 (4) 1 (1) 3 2 (10) 1 (5) 3 (15) 1 (5) 7 (9) Table 5. Frequency (percentages) of dentine/cementum microleakage scores for the four groups. Kruskal-Wallis test value=0.002. Group I II III IV Total 0 13 (65) 11 (55) 2 (10) 9 (45) 35 (44) 1 3 (15) 1 (5) 0 (0) 2 (10) 6 (7) 2 1 (5) 1 (5) 1 (5) 2 (10) 5 (6) 405 3 0 (0) 3 (15) 10 (50) 3 (15) 16 (20) 4 0 (0) 3 (15) 3 (15) 4 (20) 10 (12) 4 3 (15) 4 (20) 7 (35) 4 (20) 18 (23)