Electronic Thesis and Dissertation Repository


Master of Clinical Science




Siqueira, Walter


The aim of this study was to investigate the effect of different orthodontic materials on the formation of the protein pellicle on the bracket surface.

Materials and Methods: We used X-ray Photoelectron Spectroscopy (XPS) to analyze the atomic composition of orthodontic metallic and ceramic brackets. Following XPS, the brackets were immersed in human whole saliva supernatant for 2-hour incubation at 37°C. Hydroxyapatite (HA) discs were used as control. Acquired pellicle was harvested with sonication for each group, and liquid chromatography electrospray ionisation mass spectrometry was used for protein identification.

Results: Differences reported by XPS and mass spectrometry were noted among the tested groups. Most of the proteins present on the acquired pellicle were identified specifically to each group, indicating little overlap in the acquired pellicle proteins; 84% of proteins present on the HA discs were unique to this group, 74% were unique to ceramic brackets and 79% were unique to metallic brackets. Despite the fact that most proteins were unique to each bracket material, proteins related to antimicrobial, lubrication and remineralization biological functions were present in all groups. However, proteins associated with inflammatory processes and biofilm formation were found only on ceramic brackets.

Conclusions: The results demonstrate that the protein pellicle formed on the bracket surface is dependent on the molecular composition of the bracket. Therefore, our findings suggest that modulation of the bracket pellicle via alteration of bracket surface is a possibility.

Thesis November 13 .docx (1005 kB)
thesis after corrections from thesis committee