Micro-CT Assessment of Internal and External Void Formation in Class II Restorations of Primary Molars Using Bulk-Fill Composites.

This study aimed to assess the formation of internal and external voids in class II restorations of primary molars using bulk-fill composites with different viscosities through micro-CT analysis. Standardized class II cavities were prepared on 50 extracted intact primary molars. The teeth were restored with bulk-fill materials of varying viscosity: SDR, Tetric EvoCeram bulk-fill, Viscalor bulk, Cention forte, and a control group (Dyract XP). They were then scanned using a computed microtomograph. The volumes of the internal and external voids were quantified and expressed as percentages (%) of the total restoration volume. The data were analyzed using one-way ANOVA, followed by Tukey's test (α = 0.05). The detected external and internal voids ranged from 0.19% to 0.62%. The data indicated no significant difference in the formation of external voids among the various bulk-fill materials or the control group ( > 0.05). Significantly fewer internal voids were observed with more flowable materials and when heat was applied ( < 0.05). The highest percentage of internal and external voids was observed when the layering restorative technique was used. It was concluded that in class II bulk-fill composite restorations in primary dentition, the percentages of both external and internal voids were relatively small compared with the entire volume of the restoration and decreased when more flowable materials were used.