Probiotics may also prove useful in addressing problems arising from the excessive use of antibiotics, specifically the appearance of bacterial resistance. To date, however, the potential beneficial effects of probiotics for oral pathology have had limited study. The aim of the present study was undertaken to investigate whether short-term consumption of powdered milk containing Lactobacillus paracasei SD1 would affect the levels of salivary mutans streptococci and assessment of salivary pH after powdered milk consumption in orthodontic cleft patients with fixed appliances. The strategy approach used in the present study included subjects with increased caries risk. The intervention started 3 months after the insertion of the appliances to avoid the confounding effect of an immediate decrease in bacterial counts that may take place at appliance insertion [4]. Powdered milk containing Lactobacillus paracasei SD1 was chosen as the vehicle for the probiotic supplement because of its convenience to storage and use, long shelf life, health benefits and low cariogenic potential. In addition Lactobacillus paracasei SD1 is a normal flora that isolated form caries-free children, Thus, this strain may be useful for a potentially probiotic microbial strain for oral cavity.