Corrosion of orthodontic bracket bases

Area of Science:

• Dental Materials Science
• Corrosion Engineering
• Oral Hygiene

Background:

• Directly bonded stainless steel brackets are commonly used in orthodontics.
• Black and green stains have been observed in association with these brackets.
• The etiology of these stains requires further investigation.

Purpose of the Study:

• To investigate the cause of black and green stains on directly bonded stainless steel orthodontic brackets.
• To analyze the composition of the stains and the bracket-stainless steel interface.

Main Methods:

• Intraoral photography of 12 clinical cases with stains.
• Removal and scanning electron microscope examination of brackets.
• Preliminary chemical analysis of stain composition.

Main Results:

• Multiple voids were found at the resin-bracket interface, particularly at the periphery.
• Deterioration of the alloy base and mesh structure was evident in void areas.
• Preliminary analysis indicated the presence of chromium compounds in the stains.

Conclusions:

• Voids at the resin-bracket interface, combined with poor oral hygiene, likely cause crevice corrosion of Type 304 stainless steel.
• Corrosion byproducts form colored compounds, leading to enamel stains.
• Utilizing stainless steels with enhanced corrosion resistance is recommended to prevent staining.