What can prolonged use of certain polishing pastes lead to?

Prolonged use of certain polishing pastes can indeed lead to hypersensitivity due to enamel wear or irritation of the gingiva. This occurs because abrasive polishing pastes can remove layers of enamel over time, which can lead to dentin exposure. When the dentin is exposed, it can become more susceptible to stimuli, resulting in increased sensitivity to hot, cold, and sweet substances. Additionally, if the polishing paste irritates the gingiva, it may lead to inflammation or discomfort.

In contrast, improved enamel strength would typically not result from the use of polishing pastes; rather, excessive polishing might contribute to enamel wear. Stain accumulation is also not a characteristic effect of polishing pastes; instead, they are designed to reduce stain. Lastly, the reduction of gum swelling does not directly relate to the effects of polishing pastes, as their primary function is not therapeutic for gingival health in that sense. Therefore, the potential negative impacts of prolonged paste use lean more towards causing enamel damage and gum irritation, aligning with the correct answer.