THE EFFECT OF ADDITION OF NaHF2 ON PHYSICO physicolcHEMICAL AND MECHANICAL PROPERTIES OF APATITE CEMENtS

The effect ofaddition ofnahf] on the cement setting and the set mass has been studiedas an initial step to determine how jluoride influences the characteristics of a calcium phosphatecement, consisting of tetracalcium phosphate [ttcp:ca4(p04hoj and dicalcium phosphatedihydrate [dcpd:cahp04.2h]oj.nahf] [0-10% }i't% ofpowder phasej has been dissolved in double distilled water and used as theliquid phase of the apatite cement (ac). powder x-ray diffraction analysis and ftirmeasurements revealed that fluoride was necessary in promoting the formation of the apatitephase. the setting time 11'qs decreased significantly by the addition ofnahf2from 0% to 6%, butincreased resulted in the ac(8-10%) . the set ac(2%) has the highest compressive strength andthe lowest porosity.the dissolution rate of set ac in weak acid. ph 5.5, was decreased with the amount of addednahf] from 0% to 6% but increased in the set ac 8-1o%.the formation of jluoroapatite in ac(6%) was provided the low solubility and good acidresistance which is necessary for dental application.sem observation showed needle-like apatite crystal growth over particulate matrix surface,however the amount of non-reactive ttcp or dcpd particles decreased by the addition ofnahf2. the calp ratio, which was determined by edax, increased significantly with the additionofnahf].