Editing Tooth enamel (section)

=== Acid-etching techniques ===

Invented in 1955, acid-etching employs dental etchants and is used frequently when bonding dental restoration to teeth.<ref>Summitt ''et al.'', p. 191.</ref> This is important for long-term use of some materials, such as [[dental composite|composites]] and [[dental sealant|sealants]].<ref name="ross443" /> By dissolving minerals in enamel, etchants remove the outer 10&nbsp;micrometers on the enamel surface and make a porous layer 5–50 micrometers deep.<ref name="summitt193">Summitt ''et al.'', p. 193</ref> This roughens the enamel microscopically and results in a greater surface area on which to bond.

The effects of acid-etching on enamel can vary. Important variables are the amount of time the etchant is applied, the type of etchant used, and the current condition of the enamel.<ref name="summitt193" />

There are three types of patterns formed by acid-etching.<ref name="summitt193" /> Type 1 is a pattern where predominantly the enamel rods are dissolved; type 2 is a pattern where predominantly the area around the enamel rods are dissolved; and type 3 is a pattern where there is no evidence left of any enamel rods. Besides concluding that type 1 is the most favorable pattern and type 3 the least, the explanation for these different patterns is not known for certain but is most commonly attributed to different crystallite orientation in the enamel.<ref name=":4" />