Systematic reviews reveal the continued evolution of dental materials
One systematic review appraised the current clinical evidence regarding the use of high-viscosity GIC for long-term Class I, II and V tooth restorations placed in permanent teeth . This systematic review included 14 clinical studies, providing a total of 27 separate study results and concluded as follows:
· Most of the 27 results show no significant statistical difference between the success rate of high-viscosity GIC restoration and amalgam for treatment of the same clinical indications
· One of the 27 results show that high-viscosity GIC restorations in posterior class V cavities of permanent teeth had a 28% higher chance to be successful than amalgam after 6.3 years
· Two of the 27 results indicate that high-viscosity GIC restorations in posterior class I cavities of permanent teeth have a 6% higher chance after 2.3 years and a 9% higher chance after 4.3 years of being more successful than amalgam
· One of the 27 results show that high-viscosity GIC restorations in posterior class II cavities of permanent teeth have a 61% higher chance of being rated more successful than amalgam
· None of the 27 results indicate high-viscosity GICs being inferior to amalgam in clinic.
These results show that high-viscosity GIC is not inferior in comparison to traditional amalgam restorations under similar clinical conditions. In addition, two further systematic reviews revealed the following evidence:
· Tooth margins of single-surface GIC restorations in permanent teeth had significantly less carious lesions after 6 years than on amalgam restorations 
· A significantly higher fluoride release (p<0.05) of GIC than from compomers 
Further advances have revealed that a resin coating over a GIC restoration may increase its fracture toughness  and reduce microleakage . This resin layer may also not completely hinder the fluoride release activated by the GIC and thus its external anti-cariogenic effects within the oral cavity .