Method: Root halves of one-rooted lower premolars were used. Forty root halves were individually embedded in acrylic block and randomly divided into four equal groups (n=10) according to the materials bonded to root dentin surfaces. Group I: Nano-composite (Grandio Flow NR, Voco, Germany) was bonded to root dentin surface, group II: bonded with Microhybrid composite (Esthet X Flow, Dentsply, Maillefer, Switzerland), group III: bonded with light cured Nano-ionomer (Ketac™n100 restorative material, 3M ESPE) and group IV: bonded with conventional glass ionomer (Ionofil Molar, Voco, Germany). Each acrylic block with the embedded root slice and reinforcing material was loaded in a testing machine. A shearing load with tensile mode force was applied via materials testing machine at a crosshead speed of 0.5 mm/min. Mode of failure was observed under stereomicroscope. One-way ANOVA and Tukey’s test were used at 5% significant level for statistical analysis.
Result: Nano-composite group recorded the highest µ-shear bond strength mean value (23.52±3.997 MPa) followed by µ-Hybrid composite group (16.88±3.356 MPa) then nano glass-ionomer group (8.77±1.341 MPa) while conventional glass-ionomer group showed the lowest µ-shear bond strength mean value (4.062±0.9623 MPa). The difference was statistically significant in µ-shear bond mean values between all groups (P<0.05). Failure modes indicated that high bond strength showed cohesive or mixed modes, while low bond strength groups tended to exhibit adhesive, cohesive or mixed modes.
Conclusion: It is more favorable to use nano-composite resin rather than glass ionomer for reinforcement of weakened root dentin.