Titanium dental implants demonstrate excellent biocompatibility and offer numerous treatment possibilities to improve patients’ quality of life. Nevertheless, questions regarding sensitivity to titanium have been arising in recent years. It has been claimed that some patients could develop clinical signs of hypersensitivity to titanium, and the inadequacy of conventional epicutaneous patch tests in detecting such allergies has been established. The MELISA® test is perhaps the most accurate available and the prevalence of titanium allergy has been estimated at 0.6% using this method. As a result the notion of an alternative to titanium implants has been growing for almost 40 years.
Zirconium dioxide (zirconia) ceramics with improved properties have been introduced as an alternative material to aluminum oxide. They were first used for the fabrication of crowns and implant abutments. The white opaque color of zirconia, along with early reports of good biocompatibility and low affinity to bacterial plaque, make it a material of interest in biomedical sciences. Zirconia also exhibits several promising physical and mechanical properties, including low thermal conductivity, high flexural strength, as well as wear and corrosion resistance. However, one of zirconia's negative properties is its low-temperature degradation or aging. In the presence of water or water vapor, progressive deterioration of the material is seen.
At present, only a few ceramic systems offer two-piece implants. Currently, the majority of zirconia implants produced are one-piece implants. However, such systems have several limitations. The surgical placement of the implant may not always meet the prosthodontic requirements, and angled abutments to correct misalignment are unavailable. Secondary corrections of the shape by grinding much be avoided as this severely affects the fracture strength of zirconia. Cementation is the only option for connection prosthodontic elements to one-piece implants. An increased risk for inadvertently leaving excess luting cement in the submucosal area may induce local infection, which occasionally instigates substantial tissue damage.
The major technical complication appears to be fracture of the implant. Osseointegration (or bone-implant integration) is a major factor in the success of modern dental implants. Titanium remains the material of choice for obtaining and maintaining this phenomenon.
From a biological point of view, zirconia presents with interesting assets. It has demonstrated a low affinity to bacterial plaque, small amounts of inflammatory infiltrate, and has good soft-tissue integration. These properties might lower the risk for peri-implant diseases.
Early failure rates of zirconia implant systems developed and tested so far were generally higher compared with titanium implants. Solid data on long-term outcomes is scarce. Technical failure as a result of fracture of the material is a sensitive issue and a critical factor for usability and acceptance in daily practice.
There is room for further technical progress of currently available zirconia implant systems. More clinical investigations need to be carried out to identify all relevant technical and biological factors with impact on success and patient satisfaction. At present, the evidence for a final verdict is still incomplete and the field is still changing in many ways.
As there is more awareness of the availability of zirconia implants on the market, we are available to discuss this option with you and see if it's a suitable option for your situation.