Microleakage at Occlusal Margins Versus Cervical Margins of Thermocycled Preheated Class V Resin Composite Restorations

Aim: to quantify the effect of presence of enamel wall and thermocycling on marginal microleakage of class V cavities restored with preheated bulk-fill or preheated nano-filled composite. Methods: Class V cavities were prepared on the buccal surface of forty-eight extracted maxillary first premolars. The teeth were divided into two groups according to the type of preheated composite used (either bulk-fill or Nano-filled) and further subdivided according to thermocycling or no thermocycling. The teeth were immersed in 0.5% methylene blue dye solution for 24 hours at room temperature and then sectioned buccolingually to examine the extent of microleakage by dye penetration. Microleakage was assessed by a stereomicroscope at 40x magnification and measured in micrometers depending on the extent of dye penetration for both occlusal and gingival walls separately. Statistical analysis was done by Kruskal-Wallis test for comparison between groups and Mann-Whitney test for comparing occlusal and gingival dye penetration in each group. Results: preheated Nano-filled composite subjected to thermocycling showed more significantly microleakage than other groups (P < 0.05). Microleakage was significantly more (P < 0.05) in gingival (cervical) walls of teeth compared to occlusal walls in all groups except preheated Nano-filled composite directed to thermocycling which showed no significant difference between gingival and occlusal walls (P > 0.05). Conclusions: thermocycling of preheated Nano-filled composite produced more microleakage than thermocycling of preheated bulk-filled composite. More microleakage was recorded in cervical areas than occlusal areas of class V cavities.