Evaluation of Voids in Class-II Bulk-fill and Conventional Composite Restorations

Objectives: To analyze the presence of voids inside restorations made using incremental or bulk filling techniques by Optical Coherence Tomography (OCT)
Methods: Two Class-II cavities (4 length x 4 depth x 2 mm width) were made on 48 human molars, (n=24, 4 groups). Teeth were restored using: FOB - Filtek One Bulk Fill (3M Oral Care), bulk-filled using one increment; FXT - Filtek Z350 XT (3M Oral Care), incrementally-filled using 4 layers; FBF+FXT - Filtek Bulk Fill Flowable Restorative (3M Oral Care) bulk-filled and FF+FXT - Filtek Z350 XT Flow (3M Oral Care) incrementally-filled. Specimens were immersed into distilled water and stored at 37°C. After 48 hours, thermocycling was conducted (5000 cycles, 5°C to 55°C). OCT was used to detect the presence of voids, calculate the number and percentage of voids within each restoration, and characterize the materials directly from their syringes. Data was submitted to Chi-squared, Kruskall-Wallis and Dunn`s multiple comparison tests (α= 0.05).

Results: Voids were detected in all groups. FF+FXT presented voids in all the restorations and had significantly higher number of voids per restoration, when compared to the other groups (p < 0.05). FF+FXT restorations with presence of voids were significantly higher only when compared to FXT (p < 0.05). FBF+FXT presented significantly higher percentage of voids than FXT (p < 0.05). No significant differences referred to number or percentage of voids among restorations made using high viscosity composites with incremental or bulk filling techniques were detected (p ≥ 0.05). Only syringe samples of flowable composites showed defects in their structure.

Conclusions: The use of flowable composites can lead to an increased number and percentage of voids within restorations. The presence of voids within restorations appears to be more dependent of voids present inside the materials syringes than the incremental or bulk filling restorative techniques.