THE GLASS IONOMER CEMENT POWDER

The glass ionomer cement powder

The glass ionomer cement powder

2. The glass ionomer cement powder

Glass ionomer cements are formed throughout an acid-base neutralization answer of an acidic polymer (typically a liquid) and a solid? rudimentary glass. A Glass Ionomer Cement (GIC) is a dental restorative material used in dentistry for filling teeth and luting cements. These materials are based on the reaction of silicate glass powder and polyalkenoic acid. These tooth-coloured materials were introduced in 1972 for use as restorative materials for anterior teeth (particularly for eroded areas? Class III and V cavities). As they bond chemically to dental hard tissues and release fluoride for a relatively long period modern day applications of GICs have expanded. The desirable properties of glass ionomer cements make them useful materials in the restoration of carious lesions in low-stress areas such as smooth-surface and small anterior proximal cavities in primary teeth. Results from clinical studies? do not support the use of conventional or metal-reinforced glass ionomer restorations in primary molars.

2.1 Formation of the powder

It is arranged by dissolving the constituents in pre-determined percentages in silismanite crucibles at temperatures between 1050 °C and 1350 °C for 45 - 120 min. The dissolve is then quenched and ground to a fine powder. The degree of fineness of the dust is controlled by the time of milling [14].

2.1.1 Content of the mixture

2.1.2 Influence of fusion temperature

Barry et al? 1979? investigated the personal properties? structure and last composition of the crystal arranged at differing fusion temperatures and discovered that well-homogenized G200 glass? arranged at overhead 1200 °C? yielded cements with poor manipulative properties (the paste quickly obtaining an elastomeric cob-webbing quality) and that arranged at 1150 °C yielded more workable pastes due to their higher fluoride content.

He resolved that the higher the warmth? the larger the last aluminum content? and the smaller the last fluoride content.

He attributed the compositional alterations to three mechanisms: i) decrease of fluorine and silicon at high temperatures by volatilization of silicon fluorine? ii) decrease of fluorine over a broad warmth variety by pyrohydrolysis of the fluorides by water present in the bathing tub or air? and iii) an boost in the alumina and silica content of the dissolve especially at high temperatures due to chemical answer with the sillimanite crucible [15].    

2.2 Physical properties of the powder

The dust is glass created of fluorine-containing aluminosilicate. Crisp and Wilson? 1973 described that its refractive catalogue was 1.486 and its density was 2.77 mg/m3 at 20 °C[16].

Wilson et al? 1977 claimed that the particles of dust utilised for restorative cements had greatest kernel dimensions of 45 µm? while that utilised for luting cements had finer powders with greatest kernel dimensions between 13 and 19 µm[17] .

The median element dimensions of a financial glass dust (G 200) was 10 nm in diameter and roughly 60 % w/w of the particles were bigger than this size[18] (Kent et al? 1979).

2.3 Microstructure of the powder

Most of the study on the microstructure of the dust has ...