Design can influence the performance of zirconia dental implants
Zirconia dental implants can offer an alternative to traditional titanium implants. New research from Malmö University shows how differences in their design influence stress distribution and fracture resistance, while highlighting the need for more long-term clinical evidence.
“Zirconia implants should not be viewed as a uniform category. Different designs can behave differently under load, so their performance needs to be evaluated individually,” says Abdulaziz Gul, who recently defended his doctoral thesis at the Faculty of Odontology.
Interest in dental implants made of zirconium dioxide, often called zirconia, has grown in recent years. Zirconia is a biocompatible ceramic with a tooth-like colour that is particularly valued in aesthetically demanding areas, especially at the front of the mouth. This can be advantageous when thin gum tissue or gum recession might otherwise allow the grey colour of a titanium implant to become visible.
However, knowledge about how different zirconia implant designs perform under loading remains limited.
Zirconia implants are available in several designs. One-piece implants combine the implant body and abutment—the part supporting the artificial tooth—in a single unit. Two-piece implants have a separate implant body and abutment.
Two-piece implants also come in different types. In bone-level designs, the connection between the implant and abutment is near the bone. Tissue-level designs position this connection higher, at the level of the gum. The connection itself can also vary. In screw-retained systems, an abutment screw secures the abutment to the implant, and this screw may be made of titanium or ceramic.
“Zirconia is strong, but it is more brittle than titanium. This makes careful implant design and selection important,” says Gul.
His dissertation comprises three studies investigating clinical outcomes, stress distribution and fracture resistance.
The first study systematically reviewed previous clinical research. The review found promising five-year survival results for one-piece zirconia implants. Acid-etched surfaces were associated with more favourable outcomes. No clear survival differences were detected between the implant lengths and diameters examined, although the evidence was limited.
Gul also used finite element analysis—a computer simulation—to investigate where stresses developed when different implant designs were subjected to load.
Compared with one-piece implants, the two-piece designs showed lower stresses within the implant body but higher stresses in the surrounding structure in the computer model. Tissue-level two-piece designs generally showed more favourable stress patterns than bone-level designs under the simulated conditions.
The final study involved repeated loading in a moist environment, followed by laboratory testing until fracture. All the evaluated designs demonstrated fracture resistance sufficient to support further clinical investigation. Among the examined designs, tissue-level two-piece implants had the highest fracture resistance, followed by one-piece implants and then bone-level two-piece implants.
These mechanical findings apply to the particular implant designs and experimental conditions studied.
“Clinical evidence is better established for one-piece zirconia implants, while evidence for two-piece designs remains more limited. More long-term clinical studies are needed to determine whether the differences observed in laboratory testing translate into meaningful differences for patients,” says Gul.
