The kinetics of ion release by glass-ionomer cements
Awosanya, Ibikunle (2008) The kinetics of ion release by glass-ionomer cements. PhD thesis, University of Greenwich.Full text not available from this repository.
Ten brands of GIC were used in this study: four commercial conventional GICs, one in-house conventional GIC made from G338 glass powder, one commercial glass-ionomer bone cement and four in-house novel aluminium free Fe2O3 based GICs. Cylindrical specimens of GICs were prepared in stainless steel moulds to form 6 mm height x 4 mm diameter cylinders which were then placed in a 37°C oven for one hour to cure and harden. These were then immersed in 5 ml aliquots of de-ionised water and 20mM lactic acid for storage periods of 14, 28 and 84 days, 8 weeks and 21 months. The leachate was collected daily, weekly and monthly respectively to determine the concentration of ions eluted using an optimised and validated method employing ICP-OES.
The kinetic study showed that ion release in GICs generally follows a two or three phase process. Initially, there is a short-term rapid burst of ion release, non-linear with respect to time (t). Thereafter under neutral conditions, release is a diffusion process as given by [F]c = a + bt1/2 + ct or [F]c = [F]l.t / (t1/2 + t) + ßt1/2. The latter equation best described the ion release profile of GICs when immersed in water. Under acid conditions, by contrast, long term release was found to be proportional to t, indicating that dissolution is the controlling force, as given by [F]c = [F]l.t / (t1/2 + t) + at.
HPLC was used to study ion release under dynamic conditions using crushed cement as the column packing material. This showed that these GICs are depleted of traceable amounts of Na, Ca, Al, Is and P within 2 days under these conditions. A speciation study by ion chromatography showed conclusively that phosphorus released from GICs into de-ionised water was present as simple monomeric phosphate. Unfortunately, results from 31PNMR were not as conclusive. However, the speciation result is consistent with previous studies, which have shown by MAS-NMR that phosphorus is also present within the set cement in simple monomeric form.
|Item Type:||Thesis (PhD)|
|Uncontrolled Keywords:||glass-ionomer cements, GIC, chemical kinetics,|
|Subjects:||R Medicine > RS Pharmacy and materia medica|
|School / Department / Research Groups:||School of Science|
School of Science > Department of Pharmaceutical, Chemical & Environmental Sciences
|Last Modified:||19 Apr 2012 15:57|
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