To evaluate the effect of three different resin cement on fracture strength of cemented machinable IPS e.max CAD specimens and provide guides for clinical luting procedure.

Sixty human molars were collected, and occlusal enamel were removed; IPS e. max CAD blocks were processed into plate-shape and etched with 9.5% hydrofluoric acid. All specimens were randomly divided into three groups (n = 20) and received there different luting treatments, (group A: Multilink^® N+ Monobonds-S, group B: RelyX^TM Ultimate+ Scotchbond^TM adhesive, group C: RelyX^TM Unicem 2). Then each group were divided into two sub-groups (group 1: the control group, group 2 received thermal cycling). Fracture load was measured with a universal testing machine. The results were analyzed by two-way ANOVA and LSD test.

Fracture load of each group were A1(1763 ± 128)N、A2(1563 ± 115)N、B1(1861 ±135)N、B2(1676 ± 137)N、C1(1446 ± 153)N、C2(1038 ± 95)N. Significant differences of fracture load were observed among all groups (F = 52.279, P＜0.001). Resin cement (F = 94.104, P＜0.001) and thermal cycling (F = 63.818, P＜0.001) affected the fracture load significantly. LSD test showed that significant differences of fracture load were observed among group A, B and C (P＜0.05). Group B illustrated the highest fracture load where as group C demonstrated the lowest one.

Resin cement that treats the ceramic and dentin surface simultaneously will strengthen the fracture load of the glass ceramic. Thermal cycling will reduce the fracture strength of cemented glass ceramic.