Comparative Evaluation of the Depth of Cure and Degree of Conversion of Two Bulk Fill Flowable Composites

Since the development of resin based composites, several improvements have been made to improve their physical and chemical properties. In an attempt to fasten and simplify the restoration process, a new class of resin based composite materials, called the bulk fill resin based composites have been introduced, which has been claimed to achieve a depth of cure of 4 mm without affecting the properties of the material.

To comparatively evaluate the depth of cure of two different bulk fill flowable composite resins by ISO 4049 method and to evaluate the degree of conversion of the same composite resins with Fourier Transform Infrared (FTIR) spectroscopy method.

Composite resin specimens (n=10) per group were prepared with bulk fill flowable composites, Surefil SDR flow (Dentsply Caulk, Milford, DE, USA) designated as Group A and Filtek bulk fill (3M ESPE, St.Paul, MN, USA) designated as Group B. Depth of cure was determined according to "ISO 4049; Depth of Cure" method, and FTIR spectroscopy method was used to estimate the degree of conversion of both the bulk fill flowable composites. The degree of conversion of monomer to polymer was estimated individually in coronal half (Group A1 and B1) and pulpal half (Group A2 and Group B2) by dividing each specimens into two halves. The data were analysed using Student's unpaired t-test at 5% level of significance.

The mean depth of cure of Group A was 3.89 mm (±0.103) and for Group B was 3.54 mm (±0.129). The degree of conversion percentage for Group A1=78.51 (±47.8), Group A2= 31.9 (±22.4), Group B1=39.8 (±5.2), Group B2=37.4 (±6.4). Statistical analysis revealed significant difference in the depth of cure between the two bulk fill flowable composites with Group A higher than Group B. The degree of conversion of the coronal half of Group A1 was significantly higher when compared to Group B1.

Surefil SDR bulk fill resin has better depth of cure and degree of conversion compared to Filtek bulk fill composites.