Korean J Orthod.  1985 Sep;15(2):261-270.

A study on tensile strength and physical alteration of thermally recycled metal brackets

• Park CG

Abstract

The purpose of this study was to measure and compare tensile strength for 3 types of new direct-bond brackets and the same brackets agter recycling and to evaluate recycled brackets to determine the extent of physical alteration after recycling. Three types of new direct-bond brackets were bonded to recently extracted human premolar teeth and the tensile strength was measured by Universal Testion Machine. The brackets were recycled by thermal process and the tensile test was repeated. To determine the extent of physical alteration after recycling, the slot width and the hardness of metal brackets were measured and to analyze the microstructure of the brackets, photographs of the bracket microstructure were taken. Following results were obtained 1. The tensile strength of recycled brackets was lower than that of new brackets, but was no statistically significant difference. (p>0.05) 2. In the new and recycled brackets, the tensile strength of mini-mesh base bracket was statistically higher than that of conturlok base bracket, (p< or =0.05) but there was no statistically significant difference between production of other ocmpanies. (p>0.05) 3. The slot width of metal bracket was enlarged from 0.459mm to 0.469mm as a result of the recycling process. (p>0.005) 4. As temperature was increased in thermal treatment, the grains of bracket metal grasually became coarser and the hardness was decreased.

MeSH Terms

Bicuspid
Edible Grain
Hardness
Humans
Recycling
Tensile Strength*
Tooth