Fluoride in dentistry is a very important measure in both adult and children. Fluoride applications in the office (generally following a prophylaxis [some call it a 'cleaning'] are suggested to strengthen and protect dental enamel and thus helps in preventing dental caries (decay). Many times 'white spots' may be indications of what is called decalcification which can be incipient (beginning) decay -- with the use of fluorides (whether by rinse, gel or 'varnish') these 'white spots' can be strengthened and made more resistant to decay.
Many adults have some gingival recession (receeding gum lines) that exposes the root or dentin of the tooth. These exposed areas of the tooth/teeth are not covered by enamel and are more prone to decay as well as being more sensitive to sweets and cold. Topical fluorides assist in these cases as well in lessening the sensitivity and decay (cavity) development.
One of the newest members of the topical fluoride family are the fluoride 'varnishes' which are applied with a brush to the teeth once the prophylaxis has been completed. The fluoride varnish has a longer residual effect and uptake which in turn will provide greater effect and protection. Greater sensitivity protection is provided as well as a lower percentage of decay (cavity) formation - when used on a regular preventive basis.