2018 Volume 31 Issue 1 Pages 40-48
Zirconia used in dental materials has an elastic modulus of 200 to 250 Gpa, which is about twice that of titanium. Therefore, if zirconia is used as an implant body material, the concentration of stress on peripheral tissue is expected to be greater than with titanium implants.
In this study, we mounted superstructures on zirconia implants in beagles, subjected the implants to mechanical loads such as chewing, and then performed a morpho-histological evaluation of peri-implant bone tissue.
We fabricated φ3.0×15.5 mm (threads 9.5 mm, collar 2.0 mm, abutment 4 mm) one-piece zirconia implants for the experi ment. Experimental implants with a machined surface and a laser-treated surface were prepared. Two adult female beagles were used as the experimental animals. Mandibular bilateral molars were extracted, and after 6 months, 3 machined surface implants and 3 laser-treated surface implants were placed in the right sides and the left sides, respectively. Immediately after implantation, a metal protector was attached on adjacent teeth over the implants to prevent loading on the implants for 3 months.
Three months after implantation, the protector was removed. Samples were collected from one beagle as a no loading mod el. Metal superstructures were placed on the zirconia implants and a metal table was attached to the opposing maxillary pre molar area to make occlusal contact in the other beagle. Samples were collected 12 months after the start of occlusal loading. The bone-implant contact ratio (BIC) and bone area (BA) were measured on both the cortical and cancellous sides of the bone tissue samples. Marginal bone levels (MBL) were observed with X-rays before and after the occlusal load.
The direct contact between bone tissue and implant surface was confirmed with all specimens. No marginal bone losses were observed in all histological specimens and X-rays. No differences between the BIC ratio and BA were found between the machined and laser-treated surface types. In both surface types, the BIC ratio and BA after a 12-month occlusal load were higher than before starting the occlusal load.
Zirconia has a higher elastic modulus than titanium, and is predicted to be disadvantageous in terms of stress dispersion when used as an implant body material. However, no abnormal resorption of bone tissue peripheral to the zirconia implants under 12 months of occlusal loading was found in beagles, and these findings suggest that zirconia will be useful as an implant body material.
