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 degrees 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 microg/g to 324-697 microg/g and to decrease from 49 x 10(3) - 54 x 10(3) to 43 x 10(3) - 45 x 10(3) during 18-40 months, respectively. The content and total release of BPA in vitro after 34 months were 472 and 37.4 microg/g for bracket, 130 and 2.2 microg/g for denture plate, and 50 and 2.8 microg/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.