Effect of different configuration factors on marginal gap formation of two composite resin systems

Aim: To evaluate the effect of different configuration factors “C-factors” on the marginal gap formation of two types of contemporary composite resin systems before and after thermal loading. Materials and methods: One hundred and twenty eight human sound molars were used. The occlusal surface of each tooth was wetground until flat dentin surfaces were obtained. Teeth were divided into four main groups in which cylindrical cavities were prepared representing different C-factors. Samples in each group were subdivided into 2 subgroups according to the type of composite resin system. The cavities in subgroup Awere restored with Clearfil SE bond and Clearfil Majesty Esthetic while those in subgroup B were restored with Futurabond DC and Grandio SO. Eight samples in each subgroup were thermo-cycled. All samples were processed for SEM evaluation to examine the restoration margins at (25Χ and 500Χ) magnification. The marginal gap was measured for all the samples using AutoCAD software. Results: The median values (IQR) of the marginal gap were 0 (0) in all the samples restored with Clearfil Majesty Esthetic. The same was found in samples restored with Grandio SO which were not subjected to thermo-cycling, while those subjected to thermocycling, a direct relation was found between C-factor and gap length. Thermo-cycling had a significant effect on marginal gap particularly in samples restored with Grandio SO with high C-factor preparations. The two tested composite resin systems had a significant effect on the marginal gap particularly in high C-factor preparations. The C-factor had no significant effect on the marginal gap except in samples restored with Grandio SO. Conclusion: The different C-factors had no effect on the marginal gap formation in the samples of both subgroups which were not subjected to thermo-cycling but could influence the marginal gap formation in the samples restored with Grandio SO subjected to thermo-cycling.