Effect of Esterase on the Physicomechanical Properties of Glass Ionomers

Objectives:
Dental biomaterials are susceptible to degradation by host and bacteria enzymes. The aim of this study was to assess the effects of esterase enzyme on the physicomechanical properties and fluoride release of conventional (GIC) and resin-modified glass ionomer cements (RM-GIC).
Methods: Rectangular (2×2×10mm, n=6) specimens were prepared for 3-point flexural strength analysis (FS). Disk-shaped specimens (15mm × 1.5mm thickness, n=5) were prepared for water sorption, solubility (SS) and fluoride release (FR). Two RM-GICs (Fuji Automix LC – FA, Ketac Nano - KN,) and one GIC (Fuji IX GP Extra - FE) were investigated and compared to two resin composites - RC (G-aenial Sculpt – GE, Filtek Supreme Ultra - FSU). All specimens were immersed in 0.1M phosphate buffered saline (PBS) for 3 days, followed by incubation in either porcine liver esterase or buffer (0.2M PBS) for 8 days at 37°C. Statistical analysis was performed using two-way ANOVA and dedicated post-hoc tests (α=0.05).
Results:
FS (mean ± SD, in MPa) of specimens stored in PBS were: FSU = 76.5 ± 2.5, GE = 71.1 ± 10.9, KN = 51.9 ± 13.9, FA = 56.9 ± 2.1 and FE = 35.0 ± 16.6. The FS of RC groups were significantly higher (p<0.001), followed by RM-GIC (p=0.008). Incubation in esterase significantly reduced the FS of FSU (p=0.041), no effects on FS were observed for the other materials (p>0.05). Esterase incubation only affected the water SS of FE (p<0.05). Among groups, KN showed a significantly higher water sorption, while FSU and GE showed the lowest (p<0.05). After 3 days, the highest amounts of fluoride were released by KN. Esterase incubation increased fluoride release of FA (p=0.005).
Conclusions:
The physical properties of RM-GICs and GIC were affected differently by esterase, while not affecting the flexural strength. Surfaces of RM-GICs and GIC are susceptible to esterase degradation.