Effect of the aging of titanium and zirconia abutment surfaces on the viability, adhesion, and proliferation of cells and the adhesion of microorganisms.

Statement of Problem: The longevity of dental implants depends on the maintenance of peri-implant tissue and absence of inflammation. How the physical-chemical properties intrinsic to each material over time can affect adhesion, given constant cell turnover and biofilm development, remains unclear.
Purpose: The purpose of this in vitro study was to evaluate the influence of aging on the viability, adhesion, and proliferation of normal oral keratinocytes (Nok-si) and on the multispecies biofilm formation of Fusobacterium nucleatum (F. nucleatum), Porphyromonas gingivalis (P. gingivalis), and Streptococcus sanguinis (S. sanguinis).
Material and Methods: Zirconia (ZrO ₂ ) and titanium (Ti) disks were analyzed by surface roughness, water contact angle, and X-ray diffraction before and after aging in an autoclave. The Nok-si cell viability was evaluated by using a 3-(4.5-dimethylthiazole-2-yl)2.5-diphenyl tetrazolium bromide assay (MTT), morphology by scanning electron microscopy (SEM), and proliferation and adhesion by using a confocal microscope. Multispecies biofilms were analyzed quantitatively by colony-forming units per milliliter (CFU/mL) and qualitatively by SEM.
Results: For Ti, the aging process affected the roughness and wettability. However, for ZrO ₂ , the aging did not affect roughness but did affect wettability and the ratio of the tetragonal to monoclinic phase (P<.05). A significant difference was found in the bacterial growth for Ti (nonaged and aged) in relation to the control, and no differences were found in Ti before and after aging; however, ZrO ₂ had increased growth of microorganisms after aging. For ZrO ₂ , a statistically significant difference was found between aged ZrO ₂ and the control (P<.001).
Conclusions: The results indicate that, after the aging, Ti showed better cell adhesion and proliferation and lower biofilm adhesion than zirconia.
(Copyright © 2019 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)