Glass Ionomers

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Compomers:introduction Compomers are composites modified with polyacid groups and are used for restorations in low stress baring areas, however a recent product (Dyract,AP) is recommended by the manufacturer for use in class 1 and 2 restorations in adults. Shortly after the introduction of resin modified glass ionomer cements(RMGICs) compomers were introduced to the market. They were marketed as a new class of dental materials that would provide combined benefits of composites (hence the”comp”in their name)and glass ionomers (omer).These materials have two main constituents : dimethacrylate monomer(s) with two carboxylic groups present in their structure and a filler that is similar to the ion-leachable glass present in glass ionomers (fluoride …show more content…

Factors as bulimia, gastric acid reflux,acidic medicines and frequent acidic diet exposure represent significant factors in the development of dental erosion(Machado C&Lacefield W,2008). The global increase in the ingestion of acidic beverages such as soft drinks and fruit juices is one of the main causes of high prevalence of dental erosion (Khmverdiz &Mohammed V,2013). Tooth colored direct restorations are often used in erosive lesions for dentin and enamel rehabilitation .physical and chemical properties of dental filling materials are indicators that predict their performance in a clinical setting .The roughening of the surface caused by wear and chemical degradation may affect gloss and consequently increase plaque retention, thus decreasing the longevity of the restoration (Lepri CP&Palma-Dibb RG,2013). Therefore failure or success of aesthetic restorations depends on their behavior under still persisting erosive conditions. The critical oral environment conditions, i.e. PH changes and humidity may increase dental materials biodegradation over time (Valinoti AC& Neves BG,2008). This is a complex process that may lead a composite, glass ionomer or compomer poly matrix to collapse, causing several problems such as a filler-polymer matrix debonding , release of residual monomers(Ruyter IE,1996). …show more content…

Resin- modified glass ionomers and copomers have a local and adverse systemic effects. These effects can be caused by substances that are released from resinous materials after polymerization(E.S Tunc&S Sari,2009) . Studies on degradation of on dental materials have confirmed the release of substances such as 2-hydroyethyl methacrylate ( HEMA) and triethylene glycol dimethacrylate (TEGDMA)from resin- based dental materials(S.A Mazzaoui&M.FBurrow,2002). HEMA and TEGDMA are a likely cause of cellular stress via formation of reactive oxygen species (ROS) . Demirci et al found a possible link between ROS production and cytotoxic activity. Moreover the induction of genotoxic effects of HEMA and TEGDMA have been demonstrated in vitro as well, indicating the compounds’ DNA reactivity(H.Schweikl . In addition , resin materials have been shown to cause cytoxicity and elevated numbers of micronuclei . Geurtsen et al .showed that elution of TEGDMA was one of the causes of the cytotoxic reactions evoked by light –cured glass ionomer cements and compomers they investigated. Thus this comonomer’s escape /liberation from resin restorations should be minimized or prevented. For many years ,halogen light-curing units (LCUs) were preferred as the most practical method for polymerizing light-cured resin. Composition of the

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