Objectives: This study was conducted to evaluate the effect of different surface coating materials on flexural strength and surface roughness of two different glass ionomer restorative materials.

Methods: 80 rectangular bars (12×2×2 mm) of glass ionomer materials; 40 highly viscous glass ionomer (HVGI) and 40 resin modified glass ionomer (RMGI) were prepared for flexure strength (FS) testing and divided into 4 groups (n=20) according to the applied surface coat; Group 0: no coat, Group 1: nano-filled resin coat, Group 3: total etch adhesive and Group 4: petroleum jelly. Another 80 cylindrical disks (6×2 mm) of the same materials were prepared for surface roughness (SR) testing and allocated to the same 4 groups as for FS testing (n=20). Samples were subjected to mechanical tooth brushing and then stored in distilled water at room temperature for either 24 hr or 7 d. For FS testing; a 3-point loading test was performed using a universal testing machine running at a crosshead speed of 0.5 mm/min up to failure. For SR testing; mechanical profilometer was used with a cut-off value of 0.25mm. Statistical analysis was performed using One-Way ANOVA/ Turkey's HSD post hoc test.

Results: The results showed that the nano-filled resin coat exhibited the highest Statistically significant FS values and the lowest statistically significant SR values among all tested groups.

Conclusions: Immediate surface coating enhances the flexure and roughness properties of HVGI and RMGI. The light cured nano-filled resin positively influences the FS and the SR of glass ionomers