You will see my post from several years ago about teeth and white spots. Some white spots are due to acid damage and a period of reduced brushing effectiveness or higher sugar diet. This can be common after braces because it is harder to clean around the wires.
Other white spots are more natural occurring as a hypomineralised layer of the tooth surface that appears frosty. Some of these are very superficial and and be removed in less than 5 minutes with a mild acid that we use for tooth bonding, followed by a fine mineral particle that helps clog the porosity and allow the tooth to regain it’s transluceny. Here is another case we did last week.