Objectives: The aim of this study was to evaluate in vitro the influence of fibre-reinforcement on the cantilever beam strength and rotational fatigue resistance of resin-based composites.
Methods: One hundred rectangular bar-shaped specimens (2 x 2 x 25 mm) made of resin-based composite were prepared in a stainless steel split-mould: (i) thirty specimens of particulate filler composite (PFC) (Filtek Z100, 3M ESPE, St Paul, MN, USA), (ii) thirty specimens of fibre reinforced composite (FRC) (Everstick C&B, Sticktech Ltd, Turku, Finland) and (iii) forty specimens of PFC and FRC combined in two longitudinal layers of equal thickness. Each specimen was trimmed into a cylindrical hourglass shape. The fracture resistance (cantilever beam test, n = 10) and the rotational fatigue resistance (rotating cantilever beam test; staircase method: 104 cycles, 1.2 Hz, n = 20) were determined. The cantilever beam strength, the elastic modulus, and the work-of-fracture were calculated. The fracture surface of failed specimens were analysed with SEM.
Results: The results and the statistical analysis are summarized in the table. ANOVA revealed that fibre-reinforcement had significant effect (P<0.001) on cantilever beam strength, rotational fatigue resistance, and work-of-fracture. Student t-test showed significant differences (P<0.001) in rotational fatigue resistance compared to cantilever beam strength.
Group | Cantilever beam strength (MPa) | Rotational fatigue resistance (MPa) | Elastic Modulus (GPa) | Work of Fracture (kJm-2) |
PFC | 164.9a (29.7) | 51.5e (32.3) | 24.6g (3.1) | 0.55h (0.19) |
PFC-FRC tension tested | 711.2b (46.4) | 104.4d (9.2) | 28.1g (5.3) | 14.20i (2.21) |
PFC-FRC compression tested | 109.2ad (33.1) | 24.8g (5.1) | 0.21h(0.13) | |
FRC | 936.1c (218.5) | 231.9f (2.9) | 27.9g (2.9) | 27.90j (14.17) |
Conclusion: Within the limitations of this study, the following conclusions can be drawn (i) the rotational fatigue resistance of resin-based composites is lower than their cantilever beam strength and (ii) FRC are more fatigue resistant than PFC or combinations of FRC and PFC.