[Penelitian ini dilakukan untuk mengamati perubahan kekerasan email gigi sapisetelah direndam dalam larutan ekstrak kelopak bunga rosela. Sepuluh buahspesimen gigi sapi direndam selama 15, dilanjutkan sampai menit ke 30, 45 danakhirnya 60. Pada permukaan email dilakukan uji kekerasan dan pengamatansecara mikroskopis. Kekerasan email gigi sapi sebelum perendaman adalah 328KHN dan setelah perendaman 15 sampai 60 menit menurun berturut-turutmenjadi 57,4 KHNdan 11 KHN. Disimpulkan, terjadi penurunan kekerasan emailyang signifikan (p<0,05). Gambar SEM memperlihatkan perubahan prisma emailsetelah perendaman sampai dengan 60 menit., Organic acid contained in roselle calyx are capable of causing acidic condition onoral cavity. The aim of the present study was to analyse the effect of immersion inroselle extract solution on hardness of bovine enamel. Ten specimen of bovinetooth were immersed in roselle extract solution up to 60 minutes. Bovine enamelsurface was characterized in hardness and in microscopy. Result showed hardnessvalue before immersion was 328 KHN while after immersion for 15 minutes up to60 minutes was 57,4 KHN and 11 KHN. In conclusion, hardness of bovineenamel was significantly decrease (p<0,05). SEM revealed changes of enamel rodafter immersion up to 60 minutes.]