Comparison of corrosion resistance and surface characteristics of orthodontic bracket with same metal between one piece injection molding and soldering types

• Main Authors: Chien-Hsiu Chen, 陳芊秀
• Other Authors: 王蔚南
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/77915960267474763388

碩士 === 臺北醫學大學 === 牙醫學系碩博士班 === 96 === The ordinary orthodontic treatment would process for one year or longer. The metallic brackets would expose to a warm and humid oral environment for a long time and may suffer from corrosion. Corrosion may diminish the mechanical properties of the brackets and increase the wear rate, resulting in a poor orthodontic prognosis. Furthermore, corrosive ions release may cause adverse effects in the mouth, such as heavy metal toxicity, enamel discoloration or nickel hypersensitivity. The purpose of this study was to compare the changes of the surface morphology, ion release, and surface roughness of the 316L stainless steel brackets which were one piece injection molding type (group A), soldering type (group B) and soldering type without solder (group C) for various long time immersions in the artificial saliva under 37℃ at pH 7.0. These changes were observed by optic microscope (OM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and detected by atomic force microscope (AFM) respectively. The ion concentrations of the artificial saliva were measured by inductively coupled plasma-mass spectrometry (ICP-MS). The results were analyzed statistically. The results demonstrated that after immersion in the 37℃ pH7.0 artificial saliva, the corrosion phenomenons were first detected in the 3rd month under OM observation. These phenomenons could be found over the edge of the wing, slot and base in both A and B group. However, the locations easily attacked by corrosion in group A were different from those in group B while group A were at the reflection corner and group B were at the border near the brazing joint and the base. Besides, corrosion attacks were more severe in group B than in group A. The three groups of brackets were mainly composed of Fe, Cr and Ni and group B had large proportion of gold over the brazing joint by EDS detection. As for the ions release, Fe, Ni and Mo release increased with time in the C group while Ni and Mo release increased with time in the B group. Ion release in the group A was relatively constant as the time went by. During the same period of time, Fe, Cr and Mo release revealed the most in the C group while Ni release revealed the most in the B group. There were no statistically significant changes of the surface roughness among the three types of brackets for the five months immersion. The group B brackets had higher surface roughness at the first and fourth month immersion groups, however, it revealed no statistic significance. The conclusion was that after immersion for five months in the 37℃ pH7.0 artificial saliva, the corrosion phenomenons were first detected in the 3rd month under OM observation. These phenomenons could be found over the edge of the wing, slot and base in both A and B group. However, the easily corrosive locations were different while group A were at the reflection corner and group B were at the border near the brazing joint and the base. Besides, corrosion attacks in group B were more severe than group A. Gold was the main element of the soldering alloy of the two pieces bracket. Comparing the ion release, Fe, Ni, Mo increased as the time went by. Among the three types of brackets, group C appeared to have more Fe, Cr and Mo release while group B appeared to have more Ni release. There were no obvious differences of the surface roughness during five months immersion test among the three groups of brackets.