Which type of restoration is associated with pulpal irritation when using Zinc Phosphate?

The correct choice highlights that deep caries restorations are particularly associated with pulpal irritation when Zinc Phosphate is used. This occurs because deep caries often means that the decay is close to the pulp chamber. When restorative materials like Zinc Phosphate are placed on a tooth with deep caries, they can cause thermal sensitivity and will not insulate as effectively as other materials might. This can lead to irritation of the pulp, especially since Zinc Phosphate is acidic during the initial setting phase, which can further compromise the vitality of the pulp in cases of deep decay.

In contrast, shallow caries typically do not put the pulp at such a high risk of irritation, and Class V restorations are usually placed in areas where they are less impacted by thermal changes or closeness to the pulp. Thus, while the other types of restoration may have their own considerations, the significant risk of pulpal irritation is predominantly associated with deep caries restorations due to their proximity to the vital structures within the tooth.