Kopi menyebabkan diskolorasi gigi. Asam oksalat daun bayam dan kalsium susu membentuk kristal kalsium oksalat. Untuk menganalisis pengaruh larutan ekstrak daun bayam dan susu terhadap tingkat diskolorasi gigi akibat kopi, spesimen yang terdiri atas kontrol serta kelompok yang direndam larutan ekstrak daun bayam 10%, 20%, dan 30% yang dicampur susu, kemudian dipapar kopi. Perubahan warna gigi diuji. ΔL berbeda bermakna pada Uji Kruskal-Wallis. T-Test dan uji Wilcoxon memperlihatkan perbedaan bermakna perubahan warna kelompok uji dan kontrol. Uji korelasi Pearson tidak menunjukkan korelasi bermakna konsentrasi dan perubahan warna. Larutan ekstrak daun bayam dan susu dapat mengurangi tingkat diskolorasi gigi akibat kopi.

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Coffee causes teeth discoloration. Spinach leaves oxalic acid and milk calcium form calcium oxalate crystal. To analyze level of tooth discoloration due to coffee, specimens consisted of control and groups immersed in 10%, 20%, and 30% spinach leaves extract plus milk were immersed in coffee. Teeth color change were measured. Kruskal-Wallis test showed significant difference of ΔL*. T-Test and Wilcoxon Test showed significant teeth color change between immersion group and control. Pearson Corelation Test showed no significant corelation between extract concentration and tooth color change. Spinach leaves extract solution and milk can decrease level of tooth discoloration due to coffee.