Aim of the study: Aim of this study is to assess the changes in salivary flow rate, salivary pH, plaque index, Streptococcus mutans, Lactobacillus, and Candida albicans in patients undergoing fixed orthodontic treatment, before and after placement of fixed orthodontic appliances. Materials and Method: In present study salivary samples from 60 patients (30 Males and 30 Females) with age group of 14-25 years would be undergoing fixed orthodontic treatment at the department of orthodontics. Salivary flow rate, pH, plaque index and microbial colony count were measured. Streptococcus mutans, Lactobacillus and Candida albicans colony counts were measured using mitis salivarius agar, rogosa agar and sabouraud dextrose agar respectively. Saliva collected for 5 mins and measured in ml/min. salivary pH measured with digital pH meter. Salivary samples obtained from the same patients at intervals of 8 weeks and 16 weeks after commencement of orthodontic treatment and evaluated for the same. Result: This study showed fixed orthodontic appliances increases salivary flow rate (p=0.0001), decreases salivary pH (p=0.03), increases plaque index (p=0.0001), also increases Streptococcus mutans, Lactobacillus and Candida albicans colony count (p=0.0003, p=0.0001and p=0.019 respectively). Independent t test reported salivary flow rate significantly increases more in male patients at 16 weeks interval (p=0.03). Conclusion: The results of this study confirmed that after placement of fixed orthodontic appliances plaque retention increases, which sequentially decrease the salivary pH and decreased salivary pH promote the growth of microbiota.