Marginal microleakage evaluation of class II bulk-fill composite restorations in primary molars – in vitro study

Introduction
Dental restorative treatments are the most prevalent procedure in dental clinics. Multiple clinical steps are entailed in these treatments especially when using risen composites, which require a properly long chair-time. Bulk-fill composites may be reliable restorative materials for saving time and cooperative behavior with pediatric patients.

Objectives
The aim of this research was to assess a laboratory comparison of the marginal microleakage of bulk- fill and conventional composites in primary molars’ class II cavities.

Material and methods
Forty-eight standardized class II cavities were prepared in primary molars and divided into three groups (n = 16). Group 1 was restored by conventional composite (Arabesk-Voco) applied via one bulk technique. Group 2 was restored by bulk-fill composite (X-tra fil-Voco) applied also through one bulk technique. Group 3 was incrementally restored by conventional composite (Arabesk-Voco). Phosphoric acid with 37% concentration and bonding agent (Solo bond M-Voco) were used in all specimens. Teeth were sectioned mesiodistally, after having been subjected to 1,500 water cycles and immersed into 0.5% methylene blue to evaluate dye penetration by a four-degree scale. Data was collected and analyzed by SPSS V24.

Results
The three groups did not show complete prevention of dye penetration on the gingival or occlusal margins. No significant difference was observed in terms of dye penetration between the three groups on the gingival margins (p = 0.534). Greater occlusal microleakage in the conventional incremental composite group than X-tra fil bulk-fill group was observed. The comparison between the gingival and occlusal margins in each group showed higher leakage on the gingival margins in the bulk filling groups 1 and 2.

Conclusions
There was no significant difference among the groups in terms of gingival microleakage in small class-II cavities in the primary molars. In fact, the application of composite restoration in thin layers on the occlusal section increased the microleakage.