It was interesting to read that the American Board of Orthodontists does not have special requirements for the facio-lingual inclination of roots (and my spell check won’t let me even type it without a hyphen). On the other hand “general root parallelism is required, and points are deducted…” (Am J Orthd Dentofacial Orthop 2012;142:139). This same article was discussing the use of cone beam technology to access the root positions of the teeth.
A few journal issues ago a different author revealed that the need to have roots parallel for stability was a myth. In the real world it is nice to simply be able to keep the roots within the bone and gums, and have the part that is covered with enamel stick out without attracting attention. When a layperson (your patient) doesn’t like something it doesn’t matter how many points you get from the rule books.
Being the person that quietly questions the commandments of the dental niches, I always felt there was something odd about the center of rotation theory. Rather than believing the ‘2/3 down the root’ idea, I proposed an alternative concept where a lateral force applied to the tooth would cause the tooth to effectively fulcrum off the alveolar crest. Proof for this theory which I called the ‘alternative center of rotation theory’ or ‘Z spot’ for obvious reasons.
Proof or support for my idea came in another article which tested the various energy within a periodontal ligament with applied force. The researchers found a higher force in the ‘Z spot’ although they did not seem to make the connection. Pleasured by this data I emailed one of my orthodontic gurus who responded that it could have some merit.
Rather than discuss the possible abuse potential of extended treatment times needed due to the difficultly in moving roots, and the radiation exposure that could kill off some of our clients, I am going to relax and have a cigarette and leave that to the reader to ponder.