A 24 year old male presents to OPD with sensitivity to cold water. On intraoral examination, 46 is carious and dentist decides to restore the teeth with amalgam restorative material with zinc phosphate base. Which of the following is NOT a modification of this cement?
Copper cements are basically modified zinc phosphate cements. Silver salts or copper oxide are sometimes added to the powders of the zinc phosphate cements to increase their ‘antibacterial’ properties. Copper cements gradually fell out of favor because of their poor biological properties. It was highly acidic and the copper was considered toxic to the cell. 
This may have been due to the extremely high copper content (97%) in certain cements (Ames). There has been a renewed interest in copper cements recently. New formulations have come out with lower copper content (2%). It is claimed that these new generation copper cements are safe and is especially recommended for indirect pulp capping and where there is active caries. 
COMPOSITION

 Copper oxide (if cuprous oxide is used—cement is red, if cupric oxide is used, the cement is black)
 Zinc oxide
 Liquid used is clear phosphoric acid

Key Concept   
Copper phosphate and silver phosphate cements were developed to impart antibacterial properties and fluorophosphate cements to impart anticariogenic properties to the zinc phosphate cements. However, these materials are not in use now as they possess many disadvantages compared to conventional zinc phosphate cements.
Reference: Mannapallil p; 98
Copper phosphate cement
Silver phosphate cement
Resin modified cements
Fluorophosphate cement