The Effect of Different Placement Strategies of Bulk Fill Composite on Marginal Leakage of Classii Restoration (Comparative in Vitro Study)
Author(s): Sura Y Alani and Abdulla MW Al-Shamma*
Introduction: In spite of huge revolution in composite materials and techniques, some drawback still exist which may hindered the success of composite especially in class II restorations such as volumetric shrinkage, micro-leakage and secondary caries.
Aims: The purpose of this in vitro study was to evaluate the effects of different placement strategies of bulk fill composites on the gingival micro leakage of class II restorations.
Material and methods: forty human extracted premolars teeth had received 2 proximal box preparation with the following criteria (Mesiodistal width: 2 mm, buccolingual width: 3 mm and the gingival margin located 1 mm above CEJ on mesial cavity while for the distal cavity located 1 mm below CEJ. All prepared cavities had received etch and rinse adhesive strategy and had been divided randomly to four groups. Group 1: Restored with bulk fill composite alone. Group 2: Restored with 1 mm flow able composite followed by bulk fill composite cured separately. Group 3: (Snow plow technique) which restored by application of 1 mm flow able and bulk fill composite and curing them simultaneously. Group 4: (Injection molding technique) Teeth were restored with adhedive+1 mm flowable+bulk fill composite and co-curing the three layers concurrently.
After one week storage in water, all specimens were thermo cycled for 500 cycle between 5°C and 55°C for dwell time of 30 sec. Using model wax, the root apices of the teeth were sealed. All specimens had received double coats of nail varnish except 1 mm around the restoration, and then all specimens had been immersed with 2% methylene blue dye for 24 hrs. After rinsing thoroughly with water, all specimens were embedded in self-curing epoxy resin and allowed to set for 24 h before sectioning.
Then one section had been made from mesial to distal margins and then examined under digital microscope 40X and the depth of dye penetration had been analysed according to 0-3 scoring system. All data were subjected to kruskal Wallis followed by Mann Whitney tests at p>0.05.
Results: Statistical significant differences between the tested groups was observed in enamel margin (mesial) with lower micro leakage were revealed in snow plow and injection molding techniques, while no significant difference was noticed in dentin (distal) margin. For intragroup comparison, all tested groups showed higher micro leakage score in dentin than enamel margin.
Conclusion: According to the results the present study, co-curing the flow able with overlaying bulk fill composite reduce gingival micro leakage. For dentinal margin, higher micro leakage score were presented compared to enamel
Keywords: Bulk fills, Snow plow and Injection molding technique