TYPES OF DENTAL IMPLANT MATERIALS — TITANIUM VS ZIRCONIA
Today’s modern dental implants were developed through an accidental discovery in medical research back in 1952. A Swedish doctor by the name of Branemark found that when titanium was placed into contact with bone and left undisturbed, the bone grew right against the surface making the titanium objects unremovable without cutting out the bone around the titanium. This then developed into today’s implants.
HISTORY OF DENTAL IMPLANT MATERIALS
Prior to this and even since then, other materials have been tested and tried. Vitreous carbon was one material which worked very well in fusing to bone, but being brittle and having other issues made it impractical for use as a dental implant. Titanium seemed like an ideal material—its properties made it useful, practical and predictable. The initial implants were pure titanium, but they were a bit too soft so an alloy was developed to overcome the negative properties.
Since titanium dental implants have been in use, there has not been one report of an allergy or reaction to the metal itself. Nevertheless, there are some people who have either an allergy or sensitivity to other metals (e.g. prevalence of nickel allergy is about 5%) and/or simply have concerns about any metals within the body.
ZIRCONIUM – THE METAL-FREE OPTION?
In order to allay these concerns and have an implant option for these people, several companies have conducted further research and development into “metal-free” implants. This has led to the use of another metal called zirconium, which is just one row below titanium in the chemical periodic table. Zirconium first became popular in its crystalline cubic zirconia form due to its resemblance to a flawless diamond. For dental use, it is used in the form of zirconium oxide ZrO2. It is not pure ZrO2—there are trace amounts of another metal called hafnium (Hf) and the oxide is combined with yttrium (another metal) to improve its properties. The result is a white opaque-looking product and in this form, labeled as a ceramic, although there are metal atoms within the material.
With the search for alternative implant materials, it was discovered that zirconia also fused to bone (osseointegrated) much like titanium. It first became approved for use in Europe in 2008 and in Canada in 2013.
Both materials can integrate with bone with equal success provided certain protocols are followed. We do, however, have a much longer history with titanium. Some of my patients have titanium that is still functioning after 20-35 years. We may find the same success with zirconia, but until the material has been tested for the same amount of time as titanium, we simply will not know.
ZIRCONIA VS. TITANIUM – ADVANTAGES AND DISADVANTAGES
Advantages of Zirconia Dental Implants
No dark colour of the metal showing through the gums
No corrosion of the zirconia as with titanium
No piezo-electric currents between dissimilar metal in the mouth
It is thermally non-conductive
Disadvantages of Zirconia Dental Implants
Zirconium implants (the implant body and the post or abutment) on the other hand, are made as one piece. Therefore, the only option for the prosthetics is to cement the teeth into place. Secondly, there is very little room for error—one has to be very careful not to place an implant at an improper location or angle. Therefore surgical placement and volume of bone is absolutely critical.
With titanium implants, I am often able to place the implant, leave it buried under the gums and graft the area simultaneously. If it had been a zirconium implant which sticks above the gums, the ability to graft would be reduced or risky, and may need to do a separate procedure first to ensure the bone is 100%.
Both types of implants require several months for the bone to fuse or grow against the implant before we can place the final teeth. With one-piece zirconia implants, this healing phase can be a little more tricky as we cannot bury the implant under the gum tissue. if there is pressure or movement of the implant, it will not osseointegrate.
Another concern is the long-term strength. We no longer see fracture of titanium implants since the alloys were introduced, but zirconia implants have been known to fracture. If this occurs, usually the only option is to remove them and that can create a large defect in the bone. The smaller diameter implants (3.25 mm) are at the greatest risk. Therefore anyone with heavy function (clenching or grinding) probably would not be an ideal candidate for zirconia.
Advantages of Titanium Dental Implants
Titanium implants are much more versatile than zirconia because they can be made as one piece or two-piece systems. In two-piece systems, the implant replaces the root and is generally placed at the level of the underlying bone. Attached to this is a post or abutment—the part that sticks through the gums and is used to support or attach the teeth.
Two piece systems are a lot more versatile and offer many more options prosthetically. They can be used for overdentures (removable teeth) that snap into place as well as permanent teeth that are cemented or screwed onto the implants. Additionally, the implant can even be placed slightly off-angle and an angled or customized post can be fitted to correct it. Zirconium implants can also be modified if they are slightly off but are not as prosthetically ideal as what can be done with a separate post.
In some cases, placing an implant slightly off-angle is not a surgical error, but rather a necessity due to the volume and location of bone in the implant site. I could go on for pages, but basically titanium implants offer much more versatility with the final teeth and flexibility with their surgical placement.
Disadvantages of Titanium Dental Implants
The only downside of Titanium implant is that the metal implant is visible under light, it also causes concern for a minority of people with a history of allergy to metals.