Aim: This paper reviews the literature on the pathogenic genotypes of S. mutans that may be more virulent colonizers and the phenotypic variability of its main virulence factors. Methods: A thorough literature search on S. mutans was performed and the relevant datas supporting its association to dental caries were extracted. Results: Dental caries is a microbial disease caused by frequent intake of dietary sugars. Fermentation of sugars by biofilm microbiota produces acids that disrupt microbial homeostasis and cause dissolution of tooth minerals. Identifying S. mutans as the most important cariogenic microorganism has led to the design of target specific preventive measures that intend to reduce its presence in oral cavity. Conclusion: Due to environmental changes and selective pressure in the oral cavity, Streptococcus mutans endure extensive genotypic diversity thereby exhibiting new physiological and metabolic properties. However, the role of the variants are poorly understood.