Survival rate, fracture strength and failure mode of ceramic implant abutments after chewing simulation

The aim of this study was to compare titanium-reinforced ZrO2 and pure Al2O3 abutments regarding their outcome after chewing simulation and static loading. Forty-eight standard diameter implants with an external hexagon were divided into three groups of 16 implants each and restored with three different types of abutments (group A: ZrO2 abutments with titanium inserts; group B: Al2O3 abutments; group C: titanium abutments). All abutments were fixated on the implants with gold-alloy screws at 32 Ncm torque, and metal crowns were adhesively cemented onto the abutments. The specimens were exposed to 1.2 million cycles in a chewing simulator. Surviving specimens were subsequently loaded until fracture in a static testing device. Fracture loads (N) and fracture modes were recorded. A Wilcoxon Rank test to compare fracture loads among the three groups and a Fisher exact test to detect group differences in fracture modes were used for statistical evaluation (P < 0.05). All specimens but one of group B survived chewing simulation. No screw loosening occurred. The median fracture loads (+/- s.d.) were as follows: group A, 294 N (+/- 53); group B, 239 N (+/- 83), and group C, 324 N (+/- 85). The smaller fracture loads in group B were statistically significant. The use of pure Al2O3 abutments resulted in significantly more abutment fractures. It is proposed that titanium-reinforced ZrO2 abutments perform similar to metal abutments, and can therefore be recommended as an aesthetic alternative for the restoration of single implants in the anterior region. All-ceramic abutments made of Al2O3 possess less favourable properties.