Previous studies have suggested that probiotic supplements in dairy products may affect the oral microbial ecology. However, the possible effect of Lactobacillus paracasei SD1 on the oral microflora and the effect in orthodontic cleft patients have not previously been reported. The aim of the present study was to investigate the effect of short-term consumption of powdered milk containing Lactobacillus paracasei SD1 on the levels of salivary mutans streptococci and assessment of salivary pH after powdered milk consumption in the orthodontic cleft patients with fixed appliances.