The effect of Staphylococci on the dissolution of synthetic calcium phosphate biomaterials
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- Tez No: 400599
- Danışmanlar: DR. RACHEL SAMMONS
- Tez Türü: Yüksek Lisans
- Konular: Diş Hekimliği, Mühendislik Bilimleri, Bilim ve Teknoloji, Dentistry, Engineering Sciences, Science and Technology
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2001
- Dil: İngilizce
- Üniversite: The Unıversıty Of Bırmıngham
- Enstitü: Yurtdışı Enstitü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
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Özet (Çeviri)
Synthetic hydroxyapatite is widely used in coatings for dental and orthopaedic implants. Staphylococci are the main pathogens associated with infections involving biomaterials and dissolution of hydroxyapatite by staphylococci in vitro was previously reported. This study investigated the effect of staphylococci and streptococci on dissolution of commercially available hydroxyapatite (HA) or tricalcium phosphate (TCP) materials used in the production of plasma-sprayed coatings. Three calcium phosphate materials were subjected to investigation: Biotal HA (Plasma Biotal, UK.), Bioland HA and TCP (Bioland, France), These materials were selected because they are used to make plasma sprayed coatings commercially and because they had previously been shown to have no significant effect on the pH of cell culture medium, which is an important fector in dissolution of materials. Biotal HA was used in fired disc or powder form, while Bioland HA and TCF were used only in powder form due to inability to produce discs from these materials, S. epidermidis strains 11 and 257 were incubated in broth medium in the presence of Biotal HA discs for periods up to 96 h. HA discs surfaces were then investigated by a Scanning Electron Microscopy (SEM) at magnifications up to 15,000x. No visible signs of dissolution such as formation of holes on the surface were detected. Calcium concentrations in the medium in which discs were incubated were measured using a. colorimelric method. No increase in the concentration of calcium in the culture medium was detected. Bacteria were shown to adliere to HA discs. Powder forms of Biotal HA and Bioland HA and TCP were incubated in the presence of S, epidermidis, Bioland HA and TCP showed more dissolution, indicated by calcium release to the medium, when they were exposed to tire bacteria than when there were no bacteria present in the medium. Biotal HA powder did not dissolve in the presence of bacteria and even in a further experiment performed with an impure Biotal. HA powder supplied by the manufacturer with 15% TCP impurity no increase in calcium concentration in the medium after 24 h was shown. Similar results were obtained with S, aureus, S. sanguis and & mutam. The presence of HA powder in culture medium was found to have no effect on viability of bacteria. Further tests were carried out to determine the effect of bacteria and calcium phosphate powders on the pH of the medium. It was found tliat the pH of the medium was dropped from 7. 11 to 6,45 when HA or TCP were incubated with S. epidermidis for 24 h. The effect of this pH fall on dissolution of calcium phosphate materials was tested by incubation of these materials in a sterile medium, in the absence of bacteria, with artificially reduced pFI (pH 6.45). Bioland HA and TCP were shown to dissolve more at pH 6.45 than at pH 7.11. However BiotaJ HA, regardless of being pure or impure, did not dissolve at this lower pH. Fourier Infrared Transform Analysis (FUR) examinations of Bioland HA and Biotal .HA. showed that their spectra are characteristic to HA. Comparison of the Bioland HA spectrum with the spectra of this material after incubation in medium for 24 h in the presence or absence of S. epidermidis revealed loss of carbonate impurity after exposure to bacteria. .Investigation of these materials by X-Ray Diffraction Analysis (XRO) showed that no change in the crystal structure of the materials took place after incubation with bacteria, The effect of phosphatase activity of strains of & epidermidis on dissolution of HA or TCP were tested. Phosphatase activity of S. epidermidis were delected by two methods: Plate method and liquid quantitative method. Biotal HA discs and Biotal HA, Bioland HA and TCP powders were then incubated with strains of S. epidermidis with known phosphatase activity. No effect of phosphatase activity on dissolution of these materials, indicated by release of calcium, were found. The results indicate that staphylococci and streptococci can promote dissolution of synthetic calcium phosphates irndsr conditions of inflammation and Infection, when tissue pH falls- However some materials have been shown to resistant to dissolution whilst other more susceptible. The factors determining the dissolution behaviour of the materials in the presence of bacteria are yet to be investigated.
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