Comparative Evaluation of the Marginal Integrity and Microleakage of a Nanofill, Nanohybrid and Microfill Composite in Prepared Class II Cavities: An In Vitro study

BACKGROUND: Polymerization shrinkage is the major drawback of resin based composites Because of polymerization shrinkage, undesirable space or gaps are frequently detected in the proximal gingival margins of class II restorations. The filler content and the resin matrix composition of compositeresin dictate the amount of volumetric shrinkage.So this in-vitro study was undertaken to evaluate themicroleakage and marginal adapatation of amicrofill, nanofill and nanohybrid composites in prepared class II cavities. MATERIALS AND METHODS: Standardized Class II Mesio-Occluso- Distal cavities were prepared in 90 intact human mandibular premolars with the gingival floor ending lmm coronal to the CEJ in the mesial side and 1 mm apical to CEJ in the distal side.Restored teeth were then divided into two main groups. Group 1 for microleakage evaluation (n=45). Group 2 for marginal adaptation evaluation (n=45).Groupl was then further subdivided into Group 1 a(Filtek Z350 nanofill composite), Group lb (Herculite précis nanohybrid composite) and Group lc (Heliomolar microfill composite).Similar grouping was done in Group 2 (Marginal adaptation). For microleakage evaluation, therestored teeth were stored in a incubator at 37°C for 24 hours followed by thermocycling. Nail varnish application was done, except for an area approximately 1 mm around the margins of the restoration. Then the specimens were stored in 0.2 % methylene blue aqueous solution for 24 hours. After which the samples were sectioned mesiodistally by using a fine grit diamond disk.Microleakage for the sectioned specimens was evaluated by using a stereomicroscope. For theevaluation of marginal adaptation, scanning electron microscopic analysis was performed, prior and after performing the loading cycles. STATISTICAL ANALYSIS: For microleakage evaluation, the data was statisticaly analyzed by using the Kruskal-Wallis test at 0.05 level of significance. For marginal adaptation, the data was statisticaly analyzed byusing ANOVA and Post-Hoc analysis by using Bonferroni Test at 0.05 level of significance. RESULTS: The Results of this study indicated that lower mean microleakage scores and higher continuous margin percentages was found for Filtek Z350 Nanofill composite group followed by the Herculite précis nanohybrid composite and finally for Heliomolarmicrofill composite. For marginal adaptation, statisticaly significant values were found between all the involved groups. The results were not statistically significant for the microleakage group