The incremental growth lines observed in enamel are referred to as the Striae of Retzius.

- Enamel forms incrementally during tooth development, and these periodic growth lines represent the rhythmic deposition of enamel matrix.
- The Striae of Retzius appear as fine, incremental lines that run obliquely across the enamel rods and are best seen in cross-sections of the enamel.
- These lines represent the long-term growth pattern of enamel and are analogous to the growth rings in trees, indicating different stages of enamel mineralization.
- In contrast, the Lines of von Ebner are daily incremental lines seen within the enamel rods themselves.
- Imbrication lines are surface features in the enamel, contributing to the enamel’s outer texture.
- Hunter-Schreger bands are optical phenomena caused by the change in orientation of enamel rods, visible under reflected light.

Thus, among the options given, Striae of Retzius correctly refers to the incremental growth lines observed in enamel.

Reference: Ten Cate's Oral Histology, 9th Edition, Chapter 5: Enamel – Structure and Development / Page 80-85