Which section of the teeth has the poorest prognosis when stained with tetracycline?

Staining of teeth with tetracycline leads to a yellow-gray discoloration that is most pronounced in the gingival third of the teeth. This region has the poorest prognosis primarily because tetracycline can become incorporated into the dental structure during tooth development, particularly affecting the areas where enamel is thin or where the dentin is more accessible. The gingival third is often more susceptible to these discolorations since it is located closer to the gingival margin where dentin exposure can occur due to recession, resulting in less favorable treatment outcomes.

When considering the other sections of the teeth, the incisal and middle thirds tend to have better prognoses since they are often less affected by tetracycline incorporation, as enamel thickness is more pronounced in these areas and the staining isn't as heavily concentrated. Therefore, while discoloration can occur across various sections of the teeth, the gingival third specifically demonstrates a more significant challenge in terms of aesthetic treatment and restoration.