GSTM1 and periodontitis: Conversely, Concolino et al. [4] showed a significant association between both aggressive (N = 14) and chronic (N = 69) forms of periodontitis and the GSTM1-null variant in Italians (OR = 3.59, 95%CI = 1.66–7.84) regardless of smoking, patients’ age, sex, and hygienic habits.