The reduced prosthetic flexibility of one-piece zirconia implants may pose a problem if:
- the patient’s prosthetic requirements mean that the implant needs to be re-used in a different type of reconstruction in future
- the abutment has to be reshaped and ground without damaging the chances of osseointegration. The speakers mentioned that they do grind zirconia abutments for minor adjustments and do not encounter any problems
- the restoration has to be cemented in a highly scalloped area because it could be hard to remove the cement completely
The wider uptake of zirconia implants may be hindered because of its reduced portfolio. There are no narrow zirconia implants available or solutions for tilted implants or zygomatic implants etc. Further, zirconia implants are classed as a premium product because of the high cost associated with them.
“The wider uptake of zirconia implants may be hindered because of its reduced portfolio”
When it comes to two-piece zirconia implants, the restoration cannot be completely metal-free. For mechanical reasons, titanium is used in the abutment base and the screw. It is unclear whether the interface between these two materials will pose a problem, as medium-term clinical data on this matter is still lacking. Further technical progress will allow us to overcome the current limitations of the material.
There is also currently no clinical data on the prevalence of peri-implantitis in zirconia implants. It seems that this would be related more to surface topography and implant design than material, but data to corroborate this theory is lacking.
“There is also currently no clinical data on the prevalence of peri-implantitis in zirconia implants”
Zirconia implants are mainly used as single-tooth or short-term fixed partial dentures (FPDs). These types of cases represent around 80% of cases treated in the average private European office, but there are some clinicians trying to ‘push the envelope’ who perform completely metal-free full-arch reconstructions.
The risk of fractures is a concern for zirconia implants because of the innate brittleness of ceramics. A clinical study on 170 one-piece zirconia implants (Gahlert et al. 2012) reported a fracture-rate of 10% in 3.25mm diameter implants at a mean follow-up of around three years. It is recommended that zirconia implants have a diameter of no less than 4mm in order to reduce the risk of fracture by overloading. Other related issues which clinicians should be mindful of while using zirconia implants are:
- avoid over-torqueing during implant insertion
- be careful in patients with bruxism
- avoid cantilevers, because zirconia is not as flexible as titanium
“The risk of fractures is a concern for zirconia implants because of the innate brittleness of ceramics”
The aging of zirconia because of low-temperature degradation does not represent a clinically relevant problem. More time is needed, however, to answer this question definitively.
- no difference in osseointegration: evidence type IV (pre-clinical studies)
- no difference in soft tissue integration: evidence type IV (pre-clinical studies)
- no differences in clinical performance (survival rates and marginal bone stability): evidence type I-II (RCTs), provided that the implant diameters were at least 4 mm