Schneider H G, Graehn G, Mayrock B, Schirmer I
Stomatol DDR. 1979 Jun;29(6):469-74.
The ratio of subjects without periodontal diseases to those with periodontal diseases is 40:60 for individuals having gained a primary school-leaving certificate, and 53:47 for individuals with higher educational level.
对于获得小学毕业证书的个体,无牙周疾病者与有牙周疾病者的比例为40:60;对于受教育程度较高的个体,该比例为53:47。