Plaque index ( PI ) , gingival bleeding index ( GBI ) , salivary flow rate , saliva buffer capacity , salivary pH , and Streptococcus mutans and Lactobacillus counts in saliva were determined at three time points : before orthodontic appliance placement ( T0 ) , 4 weeks after bonding ( T1 ) , and 8 weeks after bonding ( T2 ) .