Ultraviolet light treatment for the restoration of age-related degradation of titanium bioactivity.
OBJECTIVE
To examine the bioactivity of differently aged titanium (Ti) disks and to determine whether ultraviolet (UV) light treatment reverses the possible adverse effects of Ti aging.


METHODS
Ti disks with three different surface topographies were prepared: machined, acid-etched, and sandblasted. The disks were divided into three groups: disks tested for biologic capacity immediately after processing (fresh surfaces), disks stored under dark ambient conditions for 4 weeks, and disks stored for 4 weeks and treated with UV light. The protein adsorption capacity of Ti was examined using albumin and fibronectin. Cell attraction to Ti was evaluated by examining migration, attachment, and spreading behaviors of human osteoblasts on Ti disks. Osteoblast differentiation was evaluated by examining alkaline phosphatase activity, the expression of bone-related genes, and mineralized nodule area in the culture.


RESULTS
Four-week-old Ti disks showed = or < 50% protein adsorption after 6 hours of incubation compared with fresh disks, regardless of surface topography. Total protein adsorption for 4-week-old surfaces did not reach the level of fresh surfaces, even after 24 hours of incubation. Fifty percent fewer human osteoblasts migrated and attached to 4-week-old surfaces compared with fresh surfaces. Alkaline phosphatase activity, gene expression, and mineralized nodule area were substantially reduced on the 4-week-old surfaces. The reduction of these biologic parameters was associated with the conversion of Ti disks from superhydrophilicity to hydrophobicity during storage for 4 weeks. UV-treated 4-week-old disks showed even higher protein adsorption, osteoblast migration, attachment, differentiation, and mineralization than fresh surfaces, and were associated with regenerated superhydrophilicity.


CONCLUSIONS
Time-related degradation of Ti bioactivity is substantial and impairs the recruitment and function of human osteoblasts as compared to freshly prepared Ti surfaces, suggesting a "biologic aging"-like change of Ti. UV treatment of aged Ti, however, restores and even enhances bioactivity, exceeding its innate levels.
Hori
Norio
N
The Jane and Jerry Weintraub Center for Reconstructive Biotechnology, UCLA School of Dentistry, Los Angeles, CA, USA.
Ueno
Takeshi
T
Suzuki
Takeo
T
Yamada
Masahiro
M
Att
Wael
W
Okada
Shunsaku
S
Ohno
Akinori
A
Aita
Hideki
H
Kimoto
Katsuhiko
K
Ogawa
Takahiro
T
D000327:Adsorption / Q000528:radiation effects; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry / Q000528:radiation effects; D002417:Cattle; D002448:Cell Adhesion; D002465:Cell Movement; D002478:Cells, Cultured; D005353:Fibronectins / Q000737:chemistry; D006801:Humans; D016348:Osseointegration; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism / Q000502:physiology; D015675:Osteocalcin / Q000096:biosynthesis; D053495:Osteopontin / Q000096:biosynthesis; D012709:Serum Albumin / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry* / Q000528:radiation effects*; D014466:Ultraviolet Rays; D017155:Wettability
D001672:Biocompatible Materials; D005353:Fibronectins; D012709:Serum Albumin; D015675:Osteocalcin; D053495:Osteopontin; D014025:Titanium