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A peptide coating preventing the attachment of Porphyromonas gingivalis on the surfaces of dental implants
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- Author / Creator
- Fang, Dongdong
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Background:
Most late implant failures are related to peri-implantitis, which is an inflammatory condition involving both soft and hard tissues surrounding the implant. Various factors contributing to peri-implantitis have been identified, such as poor oral hygiene, a history of periodontitis, smoking, and diabetes. However, its primary cause is the microbial biofilm. Most common microorganisms associated with peri-implantitis are gram negative anaerobes, such as Porphyromonas gingivalis, Tannerella forsythia, and Prevotella intermedia. Moreover, current treatments, including nonsurgical and surgical interventions, are usually unsatisfactory. Therefore, prevention of biofilm formation has been intensively investigated in implant dentistry.
Recently, two peptides that prevent bacterial attachment to surfaces were designed and preliminary tested. They were shown to inhibit the attachment of Escherichia coli on the titanium surface and promote proliferation of mammalian cells. However, Escherichia coli are not common pathogens associated with peri-implantitis.
Objective:
The objective of this study was to investigate whether these two hexapeptide coatings could prevent the adhesion of Porphyromonas gingivalis, one of the key human pathogens associated with peri-implantitis, on the surfaces of dental implants.
Materials and Methods:
Part I preliminary studies: 1) Porphyromonas gingivalis were seeded on titanium discs at different densities: 103/ml, 104/ml, 105/ml, and 106/ml. After incubation under anaerobic conditions overnight, the concentration of bacteria was quantified by spectrophotometer readings. 2) Discs with or without hexapeptide coatings were placed on agar seeded with Porphyromonas gingivalis. Plates with filter-paper discs soaked in penicillin and streptomycin and plates without Porphyromonas gingivalis were included as positive and negative controls, respectively. After incubation under anaerobic conditions for 48 hours, the zone of inhibition was measured. The agar in contact with the surfaces of the discs was harvested and cultured under anaerobic conditions for 24 hours and the number of Porphyromonas gingivalis were quantified. Agar which had only bacteria growing was used as negative control. 3) Titanium discs were coated with two novel peptides (hexapeptide 1 and 2). Porphyromonas gingivalis were seeded on the discs. After incubation under anaerobic conditions overnight, bacteria were detected with red fluorescent dye and semi-quantified by fluorescence intensity.
Part II: A salivary pellicle was created on the surfaces of hexapeptide 1-coated bare discs and verified with anti-human immunoglobulin G, A and M, and anti-fibrinogen. Early colonizers, Veillonella parvula and Streptococcus sobrinus, and the later colonizer, Porphyromonas gingivalis, were labeled with green and red fluorescent dyes, respectively, and seeded on the discs. Bacterial attachment was semi-quantified by fluorescence intensity.
Results:
In part I preliminary studies: 1) Wells with 105/ml of Porphyromonas gingivalis had a significant higher bacterial load after overnight incubation when compared with the ones with 103/ml and 104/ml of Porphyromonas gingivalis. However, there was comparable bacterial load when seeding at 106/ml. Therefore, 105/ml was considered the optimal seeding density and was used for subsequent experiments.
2) No zone of inhibition was observed around the titanium discs with/without hexapeptide coatings. After culturing the agar contacting the discs, as expected, no bacteria grew out from the antibiotic control disc. The titanium discs with/without hexapeptide coatings had comparable bacterial growth to the control well which had only bacteria growing, indicating that the hexapeptide coatings do not have antimicrobial effects.
3) Hexapeptide 1 coating significantly reduced the attachment of bacteria, while hexapeptide 2 coating resulted in comparable bacterial attachment as control group. We concluded that coating with hexapeptide 1, but not hexapeptide 2, significantly reduced the attachment of Porphyromonas gingivalis. Therefore, part II of the thesis was focused on hexapeptide 1.
In part II, we found that the salivary pellicle was evenly distributed on the discs, with or without the peptide coating, with an average thickness of 3.84 µm. These results show that the hexapeptide-1 coating does not disturb the normal formation of the salivary pellicle. A multi-species dental biofilm was created on the salivary pellicle. The peptide-coating resulted in an approximate 25% reduction in the attachment of Veillonella parvula and Streptococcus sobrinus, and a 50% reduction in Porphyromonas gingivalis, when compared to control, uncoated implant discs.
Conclusion:
The novel hexapeptide coating does not kill bacteria, but can inhibit the attachment of Porphyromonas gingivalis and prevent the formation of the dental biofilm. It may have the potential to impede the development of peri-implantitis. -
- Subjects / Keywords
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- Graduation date
- Fall 2020
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.