Fracture load of implant-supported all-ceramic crowns luted with various cements

Objectives:

All-ceramic restorations should be bonded to tooth structure with adhesive resin cements for adequate stability and fracture resistance of the restorations. On the other hand, provisional luting agents are recommended for the cementation of implant-supported restorations for retrievability. This study evaluated the fracture load of implant-supported zirconia all-ceramic crowns cemented with various luting agents.

Methods:

Twenty-four cemented abutments were attached, using titanium screws to 24 fixture lab analogs. The abutment-analog complexes were tightened to 35 N㎝. The ceramic frameworks were fabricated with zirconium dioxide block (Everest® ZS-Blanks; Kavo, Germany) using CAD/CAM technology. All copings were then veneered with feldspathic porcelain. Temp-bond(group TB), Implant cement(group IC), Rely-X Unicem(group RX) were used for cementation (n=8). All specimens were subjected to cyclic mechanical loading (100,000 cycles, cyclic frequency 1.3 ㎐, invariable load 50 N) and thermal cycling (5℃-55℃, dwell time 10 seconds, 1,500 cycles). All specimens were loaded in a universal testing machine with a compressive load (N) at a constant crosshead speed of 0.1 ㎜/min until fracture. Statistical analysis of data was performed by one-way ANOVA test and Turkey's multiple comparison test.

Results:

All specimens survived the exposure to the dynamic loading and thermal cycling. The mean fracture load values were 741.21 ± 41.95 N, 1116.2 ± 77.32 N, 1560.78 ± 39.43 N for Group TB, Group IC and Group RX, respectively. Group RX showed the highest mean fracture load value and the Group IC and TB followed in descending order. All between-group comparisons were significant (P<0.05). In fracture pattern, all specimens of the ZOE cemented group exhibited fracture in the cement luting interface, but the resin cemented group hardly showed the fracture in the cement luting interface.

Conclusions:

These results suggest that resin or implant cement could be selected for implant-supported all-ceramic crowns according to clinical situation.