An ultrafiltration filter has a pore size around 0.01 micron. A microfiltration filter has a pore size around 0.1 micron, so when water undergoes microfiltration, many microorganisms are removed, but viruses remain in the water. Ultrafiltration would remove these larger particles, and may remove some viruses.
Fluoridation of water is supported by many national and international organizations. The World Health Organizations, Centers for Disease Control and Prevention, Health Canada, and multiple dental associations, including the American, Canadian and provincial associations believe water fluoridation helps with dental problems. Health Canada has even declared water fluoridation a public health issue.