Is it advisable to have a bone graft after extraction when there was an infection?

Tooth 18 and 19 need to be extracted due to deterioration and infection. The infection has been ongoing since November 2013 and has not cleared up. If I need a bone graft should it be done after infection is cured or can it be done immediately after extraction? If I need to wait, how long should I wait before a bone graft can be done?