Abstract
This study aimed to evaluate the survival rates of several external hexagon implants directly connected to zirconia crowns after thermomechanical fatigue. The deformation of the hexagons and the integrity of zirconia crowns were also evaluated. A monolithic zirconia crown (Y-TZP) and four different external hexagon dental implants (n = 10, N = 40) were mounted together and embedded in polyurethane. The specimens were subjected to thermomechanical cycling for 2.5 × 106 cycles, at 3.0 Hz frequency, at 200 N loading. The interface of the implant/zirconia crown system, zirconia crowns integrity before and after cycling, and the implant hexagon surface were evaluated under stereomicroscopy and SEM. A nanohardness analysis was performed to verify the hardness of zirconia and implants. Statistical analysis was performed using the Kaplan-Meier test, Multi-Sample Survival Tests, Logrank Test, (p = 0.05). The data did not show significant differences in the survival rates of different implant groups. However, some crowns presented fractures (16.67%) and the external hexagon region of the implants presented plastic deformations (100%). During chewing simulation, the interface between titanium implant and zirconia abutment can promote plastic deformation in the metal and surface defects in the ceramic. In addition, the types of interface defects can be affected by the external hexagon design.
Highlights
The success of dental implants can be evaluated by the aesthetic and mechanical conditions
To fulfill aesthetic requirements, aesthetic abutments were developed with high strength polycrystalline ceramics, such as alumina and zirconia [4,5,6,7]
As observed in the present study and others that used the same test setup [17,18] one-piece zirconia abutments have a tendency for lower stability and fracture during fatigue cycling
Summary
The success of dental implants can be evaluated by the aesthetic and mechanical conditions. For excellent osseointegration (macro and microstructurally), shape and implant type, abutment-implant connection, gaps, thread design and surface characteristics are factors that play an important role [1,2]. The wide variety of products and the choice for restorative materials can make this list even more complex to dentists. Another important factor is the rehabilitation with implant-supported restorations. Several types of abutments can be used providing different characteristics for the peri-implant tissue and mechanical response. Metallic abutments made of titanium alloy have been proven to be a durable treatment option and are considered the “gold standard” [3]. To fulfill aesthetic requirements, aesthetic abutments were developed with high strength polycrystalline ceramics, such as alumina and zirconia [4,5,6,7]
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