Jean Hong

Date of Award

Spring 2009

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)



First Advisor

Berzins, David W.

Second Advisor

Bradley, Gerald T.

Third Advisor

Liu, Dawei


Ceramic brackets are an alternative to stainless steel brackets for patients who desire a more esthetic approach to orthodontic treatment. However, ceramic brackets have many limitations, including tie-wing fractures, enamel wear, and slower tooth movement with extended treatment time. The properties of ceramic brackets are greatly affected by their composition and fabrication. The purpose of this study was to analyze monocrystalline (Radiance and Ice) and polycrystalline (20/40, Mystique, and Signature III) ceramic brackets using scanning electron microscopy (SEM), micro-focus X-ray computed tomography (microcn, x-ray diffraction (XRD) techniques, and optical microscopy to examine porosities and microscopic defects. Additionally, the microhardness of the various brackets was determined. Under SEM, all brackets were found_to be somewhat rough and porous. Comparing monocrystalline brackets, Radiance appeared to be less flawed and smoother than Ice. Within the family of polycrystalline brackets, 20/40 showed many pores, Mystique was rough throughout, and Signature Ill was found to have several flaws, including a flaw in the tie wing complex of one bracket. For the most part, MicroCT results confirmed the findings of SEM testing. Signature Ill had tie wing flaws including a crack, 20/40 showed many roughened areas, and Mystique had many pores throughout the slot. In terms of percent porosity, Ice had significantly greater porosity (p<0.05) than the other brands, all of which were statistically similar. Percent porosity ranged from 0.5 to 2.0%. XRD tests showed characteristic scans of a typical crystalline material composed of alumina for 3 of the 5 brackets. Due to its monocrystalline nature, the XRD of Radiance and Ice were less straightforward. Signature Ill, a polycrystalline bracket, showed that the wing was found to be less crystalline than the base, indicating that the structure is non-homogeneous. Hardness testing revealed that the ceramic brackets had very high hardness values. All brackets were found to have similar Knoop hardness values. However, with the Vickers indenter, Mystique was found to be significantly much harder (p<0.05) than Ice, Radiance, and Signature III. Optical microscopy, as with the SEM analysis, showed flaws in the brackets and the polycrystalline nature of the 20/40, Signature III, and Mystique brackets. Radiance had a relatively smooth and uniform structure, somewhat contrasting that of Ice.



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