Dynamic wear characteristics and fracture strength of high-translucent monolithic zirconia crowns

The dental ceramic restorations inevitably undergo a wear damage. The dynamic wear behavior and fracture strength after wear fatigue of the high-translucent zirconia crowns have rarely been studied. In the present study, the zirconia crowns were fabricated using a high-translucent zirconia material and subsequently cemented to the PMMA abutments with a resin cement. The specimens were fixed in a chewing simulator and dynamically loaded for 3.6 million fatigue cycles (a maximal load of 350 N, 1.7 Hz). The wear volume and wear rate at the designated checkpoints between 0–36 × 105 cycles with an interval of 3 × 105 cycles were measured. The fracture strength of the zirconia specimens before wear fatigue as well as after 9, 24 and 36 × 105 cycles was analyzed. The morphology of the wear surface was observed by SEM. The results showed that the wear volume increased with the wear cycles. In the initial stage (0–9 × 105 cycles), the wear rate remained at a significantly high level (about 0.289–0.349 mm3/105 cycles). Subsequently, it decreased rapidly and stabilized at a relatively low level (about 0.052–0.081 mm3/105 cycles). As the number of fatigue cycles was increased, the fractured strength decreased significantly, except after 9 × 105cycles. The worn surface after wear were flattened, and only a small number of scattered cracks and small punctate defects were observed. The high-translucent zirconia crowns exhibited dynamic wear characteristics, and the fracture strength decreased significantly.