Comparison of Shear Bond Strength and Interfacial Failure Patterns of Glass Hybrid Ionomer, Resin-Modified Glass Ionomer, and Nanofilled Composite to Dentin: An In Vitro Study

This in vitro study evaluated and compared the shear bond strength (SBS) of three restorative materials bonded to dentin: a glass hybrid ionomer (EQUIA Forte HT), a resin-modified glass ionomer (RIVA Light Cure), and a nanofilled composite resin (Filtek Z350 XT). Additionally, their modes of failure were assessed. Thirty extracted human teeth were prepared and randomly assigned to three groups (n = 10) by restorative material: Group 1: Filtek Z350 XT; Group 2: EQUIA Forte HT; Group 3: RIVA Light Cure. All materials were applied following manufacturer instructions. SBS testing used a universal testing machine, applying a load at the tooth–restoration interface at 1 mm/min until failure. SBS values were recorded in megapascals (MPa). Failure modes were examined under a stereomicroscope at 40× magnification. A one-way ANOVA compared mean SBS among groups, with post hoc tests for pairwise group comparisons. Results: Filtek Z350 XT had the highest mean SBS (21 MPa), followed by RIVA Light Cure (7.5 MPa) and EQUIA Forte HT (7.2 MPa). One-way ANOVA indicated a statistically significant difference in SBS (p < 0.05). Post hoc analysis showed Filtek Z350 XT had significantly higher SBS than the glass ionomer-based materials, while EQUIA Forte HT and RIVA Light Cure did not differ significantly. Conclusions: Filtek Z350 XT demonstrated significantly higher shear bond strength to dentin than the glass ionomer-based materials. No significant SBS difference was found between the resin-modified and hybrid glass ionomers.