Inclusion Criteria  Influence of smoking habit on apical periodontitis healing after non-surgical endodontic treatment  Smoker group- everyday cigarette smoking habit, older than 18 years Control group-healthy non-smoker patients, older than 18 years, paired with smoker group according to age and sex  Influence of diabetes mellitus on apical periodontitis healing after non-surgical endodontic treatment  Diabetic group-patients having type 2 diabetes mellitus, older than 18 years, non-smokers Control group-healthy patients, non-smokers, older than 18 years, paired with diabetic group according to age and sex  Exclusion Criteria:  Influence of smoking habit on apical periodontitis healing after non-surgical endodontic treatment  Smoker group-systemic disease, pregnancy, taking medications that interfere with bone metabolism and immunologic response, former and occasional smokers Control group-former, occasional and present smokers,systemic disease, pregnancy, taking medications that interfere with bone metabolism and immunologic response Influence of diabetes mellitus on apical periodontitis healing after non-surgical endodontic treatment Diabetic group-pregnancy, taking medications that interfere with bone metabolism and immunologic response, smokers Control group-patients having diabetes mellitus, pregnancy, taking medications that interfere with bone metabolism and immunologic response, smokers