A method and system for increasing beneficial bacteria populations in a subject's oral cavity and decreasing pathogenic bacteria to address a variety of diseases and conditions, thereby enhancing a person's oral and overall health, including through the use of oral strips that adhere to surfaces in the oral cavity and that include at least one of xylitol, Lachnospira, Veillonella, Faecalibacterium and/or Rothia bacteria, including bacteria transformed via a CRISPR system. Certain embodiments employ light to modify oral cavity bacterial populations, including the use of bioluminescent oral strips that promote the growth of beneficial bacteria and decrease pathogenic bacteria populations.