Glass ionomer cement is a kind of dental cement that was developed in and began to be used in restorative dentistry in Made of a silicate glass. Whereas traditional glass ionomer cements were opaque, newer resin-modified glass ionomers have attained a much better esthetic match to dentin and. Glass Ionomer Cement. Glass ionomer cements (GIC) are the only direct restorative material to bond chemically to hard dental tissues owing to the formation of.
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Glass ionomer cements are tooth-coloured materials that bond chemically to dental hard tissues and release fluoride for a relatively long period. They have therefore been suggested as the materials of choice for the restoration of carious primary teeth. However, the clinical performance of conventional and metal-reinforced glass ionomer restorations in primary molars is disappointing.
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And although the inoomer and physical properties of the resin-modified materials are better than their predecessors, more clinical studies lgass required to confirm their efficacy in the restoration of primary molars. Restoring carious teeth is one of the major treatment needs of young children. A restoration in the primary dentition is different from a restoration in the permanent dentition due to the limited lifespan of the teeth and the lower biting forces of children.
Basic Chemistry In general, glass ionomer cements are classified into three main categories: When the powder and liquid are mixed together, an acid-base reaction occurs. As the metallic polyalkenoate salt begins to precipitate, gelation begins and proceeds until the cement sets hard.
Recently, several faster setting, high-viscosity conventional glass ionomer cements have become available. Called viscous or condensable glass ionomer cements ionnomer some ionnomer, 9 these restorative materials were originally developed in the early s for use with the atraumatic restorative treatment in some developing countries.
Metal-reinforced glass ionomer cements were first introduced in The addition of silver-amalgam alloy powder to conventional materials increased the physical adlaah of the cement and provided radiopacity. Inresin-modified glass ionomer cements were developed that could be light cured. In these materials, the fundamental acid-base reaction is supplemented by a second resin polymerization usually initiated by a light-curing process.
More complex materials have been developed by modifying the polyalkenoic acid with side chains that could polymerize by light-curing mechanisms ceemnt the presence of photo initiators, but they remain glass ionomer cements by their ability to set by means of the acid-base reaction. Advantages Glass ionomer cements exhibit a number of advantages over other restorative materials.
Glass ionomer cement – Wikipedia
Adhesion By bonding a restorative material to tooth structure, the cavity is theoretically sealed, protecting the pulp, eliminating secondary caries and preventing leakage at the margins.
This also allows cavity forms to be more conservative and, to some extent, reinforces the remaining tooth by integrating restorative material with the tooth structures. Calcium ions are displaced equally with the phosphate ions so as to maintain adalab equilibrium. The shear bond strength of conventional glass ionomer cements to conditioned enamel and dentin is relatively low, varying from 3 to 7 MPa.
In addition, when the enamel surface is etched with phosphoric acid, the bond strength of the resin-modified materials is close to that of composite-resin bonded to etched enamel.
Margin Adaptation and Leakage The coefficient of thermal expansion of conventional glass ionomer cements is close to that of dental hard tissues and has been cited as a significant reason for the good margin adaptation of glass ionomer restorations. An in vitro study has shown that conventional glass ionomer cements were less reliable in sealing enamel margins than composite-resin. Fluoride Release Fluoride is released from the glass powder at the time of mixing and lies free within the matrix.
It can therefore be released without affecting the physical properties of the cement. Despite the constant fluoride release of glass ionomer restorations, results from clinical studies are not so promising. Kaurich and others 30 compared glass ionomer and composite-resin restorations over one year and concluded that there was little clinical advantage in using glass ionomer cement.
Tyas 31 examined cervical composite-resin and glass ionomer restorations five years after placement and found no significant difference in recurrent caries rates.
More clinical studies would therefore be needed to confirm the cariostatic effect of glass ionomer cements. Esthetics Conventional glass ionomer cements are tooth-coloured and available in different shades. Although the addition of resin in the modified materials has further improved their translucency, they are still rather opaque and not as esthetic as composite-resins.
In addition, surface finish is usually not as good. The colour of resin-modified materials has been reported to vary with the finishing and polishing techniques used. Biocompatibility The biocompatibility of glass ionomer cements is very important because they need to be in direct contact with enamel and dentin if any chemical adhesion is to occur.
In an in vitro study, freshly mixed conventional glass ionomer cement was found to be cytotoxic, but the set cement had no effect on cell cultures. More recently, Snugs and others 36 have even demonstrated dentin bridging in monkey teeth where mechanical exposures in otherwise healthy pulps were capped with a glass ionomer liner. Therefore, lining is normally not necessary under conventional glass ionomer restorations when there is no pulpal exposure.
Concern has been raised regarding the biocompatibility of resin-modified materials since they contain unsaturated groups. A cell culture study revealed poor biocompatibility of a resin-modified liner. As a result of this uncertainty, use of resin-modified materials in deep unlined cavities is probably not advisable.
Disadvantages The use of glass ionomer cements can have limitations in very specific circumstances. Physical Strengths The main limitation of the glass ionomer cements is their relative lack of strength and low resistance to abrasion and wear. Conventional glass ionomer cements have low flexural strength but high modulus of elasticity, and are therefore very brittle and prone to bulk fracture. Water Sensitivity Conventional glass ionomer restorations are difficult to manipulate as they are sensitive to moisture imbibition during the early setting reaction and to desiccation as the materials begin to harden.
Although it was believed that the occurrence of the resin polymerization in the modified materials reduces the early sensitivity to moisture, 23 studies have shown that the properties of the materials changed markedly with exposure to moisture. Clinical Success in Primary Molars Clinical trials investigating the longevity of glass ionomer restorations in primary molars are mostly short-term studies of less than three years. The longest survival rates for glass ionomer restorations are in low stress areas such as Class III and Class V restorations.
The longest clinical study has been conducted by Walls and others 43 who compared conventional glass ionomer restorations with amalgam restorations in primary molars. Although they reported no significant difference in overall failure rates after two years, follow-up of the restorations up to five years showed that glass ionomer glads had iohomer inferior survival time to amalgam.
Other short-term trials also show poor success rates of conventional glass ionomer restorations in primary molars. Fuks and others 46 compared the clinical performance of a glass ionomer cement with amalgam in Class II restorations in primary molars. Papathanasiou and others 47 investigated the mean survival time of different types of restorations in primary molars and found that the mean survival time for glass ionomer restorations was only 12 months compared to more than five axalah for stainless steel crowns and amalgam restorations.
In a recent study, the median survival time for Class II glass ionomer restorations acalah primary molars was also reported to be significantly shorter than for amalgam restorations. Short-term clinical studies have shown that the performance of Class II glass cermet restorations in primary molars is significantly worse than conventional materials.
Only limited data are available for resin-modified glass ionomer restorations in primary molars and they are mostly in the form of clinical experience 50 or glazs. Until then, the choice of resin-modified qdalah ionomer restorations in primary molars remains a relatively empirical one and should therefore be restricted to aalah well supported by surrounding tooth structures, such as small Class I and Class II restorations.
In cases where high occlusal load is expected, other alternatives such as amalgam or stainless steel crowns should be considered.
Conclusion 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, however, do not support the use of conventional or metal-reinforced glass ionomer restorations in primary molars. More clinical studies are required to confirm the efficacy of resin-modified glass ionomer restorations in primary molars.
The authors have no declared financial interest in any company manufacturing the types of products mentioned in this article. The use of a reinforced glass-ionomer cermet for the restoration of primary molars: Br Dent J ; Hickel R, Voss A. A comparison of glass cermet cement and amalgam restorations in primary molars. The clinical development of glass ionomer cement. Aust Dent J ; Glass ionomer cement, Chicago: Making the most of glass ionomer cements. Dent Update ; Resin-modified glass ionomer materials.
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A Review of Glass Ionomer Restorations in the Primary Dentition
Bonding to tooth structure: Mechanism of adhesion of polyelectrolyte cements to hydroxyapatite. J Dent Res ; Bond strength of resin-reinforced glass ionomer cements after enamel etching.
Am J Dent ; 6: The influence of glass ionomer cement. Microleakage pattern of a resin-veneered glass-ionomer cavity liner. J Prosthet Dent ; Morabito A, Defabianis P. The marginal seal of various restorative materials in primary molars. J Clin Pediatr Dent ; Effect of a surface sealant on microleakage of Class Lgass restorations. Am J Dent ; 9: Microleakage of resin-modified glass ionomer cement restorations: Dent Mater ; 9: Clinical placement of modern glass ionomer cements.
Short- and long-term fluoride release from glass ionomers and other fluoride-containing filling materials in vitro. Scand J Dent Res ;