Objective: The aim of this study was to evaluate the morphology of the resin-dentin interface formed in vivo with two posterior resin composite placement techniques (incremental and bulk). Method and materials: After approval from the patients, 12 Class II cavities with margins in enamel (2.5 × 2.5 × 4.5 mm) were prepared in caries-free premolars scheduled to be extracted for orthodontic reasons (n = 6). The cavities were restored with Single Bond + Filtek P60 as a bulk condensable technique or Single Bond + Filtek Z250 as an oblique incremental technique. After 1 week, the teeth were extracted with minimal trauma to the restored area. After the teeth were sectioned, a polyvinyl siloxane impression was taken from the resin-dentin interface to control for artifacts created during preparation for scanning electron microscopy. The specimens were subsequently processed for and observed under a scanning electron microscope to assess gap formation. Results: The mean percentage of gap formation was 6.1% for teeth restored with the incremental placement technique and 18.7% for teeth restored with the bulk placement technique. The difference was statistically significant. Conclusion: The incremental placement of posterior resin composites may still provide better seal than the new bulk condensable technique.