Objective: Evaluation of the influence of newly introduced Zirconia reinforced glass ionomer when used as a base or as a restorative material on fracture resistance and fracture pattern of
class II restorations.
Methodology: Forty extracted, intact mandibular third molars with standardized MO cavities were randomly assigned into four groups according to the type restorative material: The control group was restored using nano hybrid resin composite (RC), Zirconia reinforced restorative glass ionomer group was used for restoring Zr group, resin modified glass ionomer cement as a base material below the resin composite restorations in RC/RMGI group and Zirconia reinforced restorative glass ionomer as a base material below the resin composite restorations in group RC/Zr group. After thermal cycling fracture resistance of the specimens was tested by the application of load in a universal testing machine. Fracture pattern of each specimen was also evaluated. Mean fracture resistance values for each group were calculated and compared using one way ANOVA
(P = 0.05).
Results: The highest mean load necessary to fracture the specimens was found in RC/RMGI followed by RC/Zr and RC groups respectively. While the lowest mean value was found in Zr group. The highest frequency of specimens' reparability was found in Zr group followed by RC/Zr and RC groups respectively. While the least frequency of reparability was found in RC/RMGI group.
Conclusions: Within the limitations of the current study, it could be concluded that despite higher fracture strength values of RMGIC as a base material below the resin composite restorations, clinicians might prefer using of Zirconomer Improved® as either a restoration or a base material as its fracture patterns are repairable.