Glass-ionomer Cements - Performance

The performance of polyelectrolyte materials is determined by several factors, including the extent to which the dental material adheres to the tooth, cario-static properties of the restoration, pulpal and tissue sensitivity in the vidnity of the restorative material, long-term stability of the dental material, and perhaps most importantly, the aesthetic appeal of the restorative material. Poor adhesion leads to the formation of gaps, which become sites for infection. Biodegradation of the cement can cause increased pulpal and oral-tissue sensitivity, as well as systemic responses. Several recent reviews on the performance of GICs [121,173,230-232] are available, so the subject is only briefly discussed here. 

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The physical properties of glass-ionomer cements are influenced by several factors, including powder liquid ratio, concentration of polyacid, particle size of the glass powder and age of the specimens. In addition, for hand-mixed cements, the experience of the operator has an influence, though the reasons for this are not completely clear [86], Care is needed therefore in making generalizations about properties and part of the success of glass-ionomers may arise because they perform satisfactorily even when not properly mixed, or allowed to mature under optimum conditions. 

Since this time, there have been numerous studies to compare the clinical effectiveness of glass-ionomer cements with that of composite resin sealants. These have typically determined the relative retention rates, and they have usually found that glass-ionomer sealants show inferior performance [149]. However, when caries rate in teeth are compared it turns out that glass-ionomers are at least as effective as composite resins [150,151]. It has been suggested that this is due to retention of glass-ionomer cement deep within the fissure and also because of the fluoride release into the enamel prior to the loss of the bulk cement [1]. 

The relevant International Standard for resin-modified glass-ionomer cements uses flexural strength as the criterion of acceptable mechanical performance [26], and further specifies a minimum flexural strength of 20 MPa for these materials. No distinction is made between values required for liner/base materials and full restoratives, or indeed for materials intended for any other application, such as luting, but most brands of resin-modified glass-ionomer cement comfortable exceed this minimum value [27]. 

Resin-modified glass-ionomer cements have been used for both Class II and Class III restorations in primary teeth [97,98]. Their lower brittleness compared with conventional glass-ionomers make them appropriate for these applications, though composite resin again appears preferred for these types of cavity in permanent teeth [94], Various clinical studies have shown resin-modified glass-ionomers to perform well in these restorations [99,100], and in addition they have been shown to have useful caries inhibition properties as a result of their fluoride release [101]. 

T.P. Croll, Y. Bar-Zion, A. Segura, K.J. Donly, Clinical performance of resin-modified glass ionomer cement restorations in primary teeth a retrospective evaluation, J. Am. Dent. Assoc. 132 (2001) 1110-1116. 

J. Rutar, L. MacAllan, M.J. Tyas, Three-year clinical performance of glass ionomer cement in primary molars, Int. J. Paediatr. Dent. 12 (2002) 146-147. 

Enhanced performance resin-modified glass-ionomer cement... 

Clinical studies have shown that ART is an effective treatment in a variety of countries of the world (Frencken et al. 2004). Modern conventional glass-ionomer cements for use with this technique have been formulated with optimized particle size and size-distribution glass powders, and they are found to perform very well in patients. Long survival times are being recorded, with almost no problems of debonding in clinical service. 

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