Assessment of Internal porosities for different placement techniques of bulk-fill resin-based composites: A Micro-computed tomography study

Abstract

Abstract Purpose: The aim was to compare the porosity of different bulk-fill resin-based composites (RBCs) placement techniques to the conventional incremental technique using microcomputed tomography (μ-CT). Methods: Occlusal cavities were prepared on extracted human molars that were allocated into five placement technique groups (n=10): Monoblock-two-step technique: SureFil SDR flow+Ceram.X; Monoblock with sonic activation technique: SonicFill2; Monoblock-one-step technique: Tetric EvoCeram Bulk-Fill; Monoblock-two-step technique: Tetric EvoFlow Bulk-Fill+Tetric EvoCeram Bulk-Fill, and incremental technique: Filtek Z250. The number, volume of closed pores, and the total porosity was evaluated (μ-CT). Data were analyzed with analysis of variance on ranks (Student-Newman-Keuls method and Mann-Whitney rank-sum test) to verify the RBC viscosity and the socination placement technique significance. Porosity characteristics correlation was performed (Spearman correlation) (α= 0.05). Results: The SonicFill2 group presented a higher number of closed pores than the other groups (p<0.05). The volume and total porosity characteristics were similar among all groups (p>0.05). The overall porosity within the restoration bulk seemed greater in the following order: Filtek Z250>SonicFill2>Tetric EvoFlow Bulk-Fill+Tetric EvoCeram Bulk-Fill>Tetric EvoCeram Bulk-Fill>SureFil SDR Flow+Ceram.X. Sonication tended to increase the number (p=0.005) and volume (p=0.036) of closed pores. Increased viscosity of the materials tended to increase the closed pores volume (p=0.036). There was a strong correlation between the number and volume of closed pores (R2=0.549, p<001). Conclusions: The different placement techniques resulted in significantly less internal porosity than the monoblock with sonic activation technique (SonicFill2). Sonication during application contributed to the higher number and volume of closed pores than the passive bulk-fill RBCs application.