Abstract
To study long-term degradation of polycarbonate
(PC) and the formation and the release of bisphenol
A (BPA) in vivo and in vitro, PC brackets placed in
the oral cavity for 18-40 months as well as bracket,
denture plate, and temporary crown placed in
water at 37°C for 34 months were examined for the
changes of BPA content and molecular weight in
PC using high performance liquid chromatography
and size exclusion chromatography. BPA release in
vitro was also monitored. The BPA content and
molecular weight for the brackets in vivo showed a
tendency to increase from 38-60 μg/g to 324-
697 μg/g and to decrease from 49 x 103-54 x 103 to
43 x 103-45 x 103 during 18-40 months, respectively.
The content and total release of BPA in vitro after
34 months were 472 and 37.4 μg/g for bracket, 130
and 2.2 μg/g for denture plate, and 50 and 2.8 μg/g
for temporary crown, respectively. BPA appeared to
be released more in saliva than that expected
from the in vitro data. Additives contained in the PC
materials were suggested to influence the formation
of BPA.
