Objectives: Multidirectional short fiber-reinforced composite has been introduced as base material in large cavities after endodontic treatment. Adequate depth of cure would enable the use of a base material even in deep cavities of endodontically treated teeth avoiding root canal post preparation, thus preserving tooth structure. Surface microhardness is known to correlate to the degree of monomer conversion of resin based materials. The aim of this study was to evaluate the depth of cure by measuring the surface microhardness of a base material (Cavity FRC, StickTech Ltd), a flowable composite (Surefil® SDR Flow, Dentsply) and as reference material a particulate filler composite (3M Espe Filtek Z250).
Methods: Specimen cylinders (height= 5.0 mm, Ø 3.6 mm) were prepared at different depths with two light-curing times (20 s, 40 s). Cylinders were filled with testing materials of same shade and light-polymerized through Mylar strips and glass-plates. After light-polymerization the specimen were cut longitudinally and polished using SiC-paper (1200 grit, finalized with 4000 grit). Surface microhardness was determined with a Vickers microhardness tester (Stuers Duramin-2). Curing depth profiling was made every 0.5 mm up to 5 mm (n=6/group).
Results:
Measuring depth (mm) (20 s)
Group | 0.5 | 1.0 | 1.5 | 2.0 | 2.5 | 3.0 | 3.5 | 4.0 | 4.5 | 5.0 |
Surefil SDR Flow | 51 | 52 | 51 | 47 | 47 | 46 | 45 | 46 | 43 | 43 |
Cavity FRC | 80 | 79 | 75 | 67 | 63 | 63 | 61 | 62 | 60 | 60 |
Filtek Z250 | 125 | 131 | 121 | 120 | 120 | 118 | 119 | 117 | 112 | 108 |
ANOVA revealed that both factors (material and measuring depth) influenced the microhardness significantly (P< 0.05). With all materials, by increasing the curing depth, the surface microhardness was lowered. Highest surface microhardness was found with Filtek Z250 and lowest with Surefil SDR Flow.
Conclusion: This study suggests that Cavity FRC material has a similar curing behavior as Surefil SDR Flow and Filtek Z250 in terms of depth of cure.