Dr Halazonetis’s recent letter to editor (Am J Orthod Dentofacial Orthop 2008;133:484-5) entitled “Friction and anchorage loading” certainly made frictional forces seem simple; he referred to “classical mechanics” twice, and I must admit that term is confusing. When I was in engineering school, we studied statics, dynamics, thermodynamics, and so on, but never classical mechanics. I think that part of the difference of opinion in
this controversy is that no one has defined friction in real terms and its relationship to resistance to sliding. Dr Halazonetis did not distinguish between the passive and active states of tooth movement.

Download and read the rest of the article HERE.