Which method represents a type of permanent wave technology?

Ammonia-free perms represent a type of permanent wave technology because they use alternative chemicals that soften the hair’s natural bonds, allowing it to be reshaped into curls or waves. The key to a permanent wave is its ability to alter the hair structure for a lasting effect, which is achieved through a chemical process. In this case, the ammonia-free formulation is a gentler option that reduces the potential for damage while still allowing for a long-lasting wave.

Hot rollers and curling wands, while effective for creating curls and waves, do not alter the hair's structure permanently; they merely provide temporary texture through heat styling. Hair straightening also temporarily alters the appearance of hair but does not create waves or curls and generally focuses on removing curls or waves entirely. Thus, the distinction lies in the fact that ammonia-free perms are specifically designed for permanent wave technology, changing the hair's inner structure for a lasting result.