Quantitative comparison of internal adaptation between bulk-fill and traditional multi-increment-fill resin-based composite materials

Abstract

BACKGROUND: Currently, incremental placement is the standard technique used to overcome limitations related to resin-based composite (RBC) material. However, it has some drawbacks that affect its efficiency. Recently, many resin-based composite materials have been introduced to the market allowing for use of the bulk-fill technique with many advantages over the incremental placement technique. OBJECTIVES: To quantitatively evaluate the internal adaptation among different light-activated bulk-fill RBC materials and a traditional RBC placed incrementally by measuring the gap area between the restorative material and the tooth structure and to evaluate aging effect on the internal adaptation. METHODS: A Class I cavity with specific dimensions was prepared using 70 extracted human molar teeth. They were randomly distributed into five groups; four groups were restored with different resin-based composite systems using a bulk-fill technique (TEC, SF, QX, XF); the fifth group (the control) was restored with multi-increment-fill technique (FSU). Each group was divided equally and randomly into two groups; the first group was the control and the other was the aged group that was thermocycled. Then, each tooth was sectioned occluso-gingivally and three 2-mm thick slices were obtained. Digital images from all specimens were recorded and analyzed and the presence and dimension of gaps were measured. Data were analyzed using ANOVA with a 5-percent significance level. RESULTS: FSU had the smallest gap measurement values compared with the bulk-fill materials tested except QX and TEC (p ≤ 0.008). FSU had the smallest sum of all gap category values compared with the bulk-fill materials tested, except QX (p ≤ 0.021). QX was significantly smaller than SF (p = 0.0257). The CA gap location category had the highest incidence and gap size values. All aged groups had greater gap values in regard to the gap measurement and the sum of all gap categories compared with non-aged groups. CONCLUSION: The incrementally placed material FSU had the highest internal adaptation to the cavity surface while the other four materials using the bulk-fill technique showed various behaviors and results. The thermocycling aging technique influenced the existing gap quantities. The findings suggest that the increment-fill technique has advantages in terms of internal adaptation over the bulk-fill technique.