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Comparative Evaluation of Microleakage in Three Core Materials with Conventional and Unconventional Placement of Crown Margins-An In-vitro Study

Aims: To compare microleakage in three core materials (Multicore Flow, Fuji IX and Ketac Silver) with conventional and unconventional placement of crown margins. Methods and Material: Sixty extracted human premolars were selected for the study. The teeth were divided into three main groups of 20 each for three materials tested. A large class II cavity extending up to the cemento-enamel junction were prepared on the teeth and then restored with the core materials respectively. Then each tooth was prepared to receive a PFM crown of which 10 samples in each group were prepared with conventional placement of crown margins and in the other 10 samples the margins were placed on the core material. Later the crowns were cemented with Rely X U 200 luting cement. The cemented samples were subjected to mechanical loading and thermocycling followed by the immersion of the samples in 0.5% aqueous Basic Fuschin solution for 8 hours for three days. Later the samples were sectioned mesio-distally using a diamond disc and then the samples were assessed for microleakage under the stereomicroscope. The extent of dye penetration was recorded using an ordinal scale. Statistical analysis used: ChiSquare and Mann Whitney U tests. Results: The results showed that there was no significant difference in the microleakage among the two different materials being used and when compared, it was found that Multicore Flow had the least amount of microleakage among the three materials making it the material of choice among the three. Conclusions: Microleakage were comparable among the samples with gingival margins placed on the tooth and on the core structure Hence it was concluded that margin placement can be done even on the core material and there by preserve the remaining tooth structure to improve the retention and resistance form of the final tooth preparation.