How does systemic fluoride strengthen the enamel of a developing tooth?

Systemic fluoride strengthens the enamel of a developing tooth primarily by making it more resistant to acid. When fluoride is ingested, it becomes incorporated into the structure of the enamel during the mineralization process. This incorporation occurs primarily in the form of fluorapatite, which is less soluble in acid than the original enamel mineral hydroxyapatite. As a result, teeth that have been exposed to systemic fluoride are better equipped to withstand acid attacks from dietary sugars and bacteria, which helps to prevent cavities and enamel demineralization. This enhanced acid resistance is a key factor in fluoride's role in preventing dental caries.

The other options do not accurately describe the effects of systemic fluoride. While fluoride does not influence the actual size of teeth, enhance coloration, or affect saliva production directly, its main benefit lies in its ability to fortify enamel against acid erosion.