Oral diseases represent a major public health problem, especially for economically marginalized communities with limited access to health services. In addition, the constant increase in bacterial resistance to many of the antibiotics contributes to worsen the problem. In this context, great importance had been given to natural compounds for the discovery of new drugs that contribute to the prevention and control of oral affection. The present study proposed a systematic review of articles that used the techniques of agar diffusion and broth dilution to measure the efficiency of plant samples against Streptococcus mutans, one of the main agents involved in the development of dental cavities. Families and plant species most used in the study, the concentration and polarity measurements of the samples used in the tests, the disk and well variants in the agar diffusion technique, as well as the most outstanding results presented by the articles are reported. The review highlights the bacteriostatic effect of natural products against S. mutans and strengthened parameters that could validate the best strategy for the identification of natural products with antimicrobial action, having as object the S. mutans. The agar diffusion test should not be neglected as screening test but scientific measurements should be taken into consideration to obtain plant extracts which are likely to undergo clinical usage against S. mutans.