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Today’s modern day dental implants 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.
Today, well over 95% of the dental implants placed are titanium alloys. There are literally hundreds of implant companies and systems worldwide and when scientific and surgical protocols are followed, the success of these implants are all well over 98% even after 10 years.
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.
The material is very strong and hard and has also been used for making crowns and bridges. 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.
Titanium and Zirconia—Pros and Cons
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.
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.
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.
In some cases, I have placed implants to find the bone is less than ideal. 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. I have had patients come in with fractured zirconia crowns or bridges but fortunately I have not had to remove a fractured zirconia implant (yet). Therefore anyone with heavy function (clenching or grinding) probably would not be an ideal candidate for zirconia.
Advantages of Zirconia Dental Implants
Advocates of zirconia state several advantages of the material:
- 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
According to CeraRoot, a manufacturer of zirconia implants: “The gradual degradation of materials by electrochemical attack is a concern particularly when a metallic implant is placed in the hostile electrolytic environment provided by the human body.” On the other hand, while zirconia has its perks, much less is known about the role played by surface modifications on the osseointegration of zirconia dental implants, according to a study by the Faculty of Dentistry at the University of Toronto. So who is right?
How To Make Sense Of All This
In general, I am a little cynical about many things and am a bit of a contrarian. I take a holistic and conservative approach to my patients, my practice philosophy and my life. Hence, I do not use mercury fillings, I have concerns regarding root canals, cavitations etc. and try to provide alternative treatments that have a scientific basis behind them.
On the other hand, I still mostly place titanium implants. Some sources will quote those same negative qualities of titanium as I listed above because you will have all these issues. But in reality, we just do not see it. Gray colour show-through is very rare and easily overcome by other methods. Corrosion and piezo-electric currents occur when two very dissimilar metals are placed in close proximity and are bathed in an electrolytic solution. Saliva can act as a electrolyte, but even in patients with old mercury fillings, I have not seen evidence of piezo currents or corrosion. Thermal conductivity whereby a person can feel it just does not occur.
I have two titanium implants in my mouth and will need a third one within a couple of months. I personally became very ill 17 years ago with extremely high levels of mercury, cadmium and lead in my body and had to go through a long process of chelation (treatment used in conventional medicine for removing heavy metals) to remove it. If I had concerns about the metal, I definitely would not even consider using it, let alone placing one in my body.
I become cynical when I see the only ones that are promoting a product are the ones that benefit from it. I see the same things with other products beyond dentistry whereby they only show the studies illustrating their product in a positive light, and/or the studies are biased in their favour. I also question the excerpt I quoted above about the degradation by electrochemical attack—what studies and what results are they basing those opinions on? Do those studies truly reflect the conditions and materials within the mouth? At this point, the comment is just an opinion, or at most, a limited observation but it is stated as if it were an irrefutable fact leading to health risks.
Nevertheless, I do have patients that either have multiple sensitivities or just do not want to take any risks or chances with metals and want to have zirconium implants only. I do not try to change people’s minds other than to explain any limitations or alterations they may need to their treatment plan. I will place zirconium implants for them once they understand these limitations.
Forgive me if I seem too critical of zirconia-advocates (like CeraRoot). I believe they are a good company with a good product that works reasonably well, but there is nothing quite like our natural teeth and we need to truly understand and accept the limitations of any material we use. I am just against exaggeration or fear-mongering for the sake of selling a product or idea.
About Dr. Balogh:
Dr. Balogh (DDS) is a dentist for Vancouver Centre for Cosmetic Implant Dentistry. He specializes in Dental Implantology and Cosmetic Dentistry. He has been providing dental implant services in the Greater Vancouver area since 1992. You can follow him on Google+.