Metal ion release and surface analysis of recycled brackets by sandblasting
Nonglak P. Sombuntham, Chairat Wiwatwarrapan
Srinakharinwirot University, and ChulalongkornUniversity, Bangkok, Thailand
This research is supported by Srinakharinwirot University Research Grant No. 065/2545
Status: Published in Journal of Dental Association of Thailand 2005;55(1-2):24-34.
Abstract
Sandblasting was recently introduced to recycle used orthodontic metal brackets. The study investigated Nickel and Chromium ion released from recycled brackets by sandblasting, and elemental analysis of bracket bases. The controls included 42 new brackets as Group1. Samples of 42 new brackets debonded in laboratory were Group 2. The bracket base was cleaned by a sandblaster using 50 mm Aluminium Oxide. Group 3 comprised of 41 bonded-failure brackets collected from dental clinics and recycled by sandblasting. 36 brackets of each group were immersed in plastic bottles containing 15 ml. distilled water and made into six replicates. The samples were kept in an incubator at 37°C over a period of 180 days. 8 ml. solution was drawn from each bottle to evaluate for Nickel and Chromium ion released at the time 0 hr., 24 hrs., 30, 90 and 180 days. Nickel and Chromium ion release were analyzed by Inductively Coupled Plasma Atomic Emission Spectrometer. Elemental analysis at base of brackets was carried out by Scanning Electron Microscope with an Energy Dispersive X-ray spectrometer. Kruskal Wallis test indicated highly significant difference of Nickel ion released among the three groups over the period of 180 days (p<0.001). Nickel ion released from group 2 was greater than the others while from group 3 was the least. The release of Chromium ion was less than the minimum value that could be detected. From elemental analysis, there was no significant difference in metal composition of the new and recycled brackets except Chromium (p<0.05). The cumulative amounts of Nickel ion release averaged over the period of 180 days did not exceed the normal daily intake.
