Efek Probiotik Lactobacillus casei terhadap Jumlah Koloni Candida albicans pada Rongga Mulut Anak Penderita Leukemia Limfositik Akut yang sedang Menjalani Kemoterapi = Effects of Probiotic Lactobacillus Casei on Candida albicans Colony Count in Oral Cavity of Children with Acute Lymphocytic Leukemia during Chemotherapy