Bonding is greatly improved when etch is used on the surface of dentin to remove:

The use of etch on the surface of dentin for bonding is particularly effective because it removes organic material. Dentin is composed of both mineral content and organic constituents, including collagen fibers. When etching is performed, it effectively demineralizes the surface, exposing the underlying collagen matrix and allowing for better penetration of bonding agents.

By removing the organic material that can interfere with the bonding process, the bonding agent can form a more intimate connection with the collagen fibers, creating a stronger bond when the adhesive is applied. This is crucial for the longevity and success of dental restorations as it enhances the retention and stability of the bonded interface.

In contrast, while it is important to consider moisture levels and stains, the primary focus of etching in improving bonding is the removal of organic material. Excess moisture can be a concern but is typically managed after the etching process. Stains, although they may affect aesthetics, do not directly impact the bonding strength the same way that the removal of organic components does. Moreover, the removal of mineral content through etching is indeed part of the process, but it is specifically the exposure of the organic collagen that significantly enhances bonding effectiveness.