Monday, 30 July 2012

Comparison of Untreated and Treated Subjects, Occlusal Changes.

Post-Treatment and Physiologic Occlusal Changes Comparison. TheAngleOrthodontist, early online access.

The article compares the occlusal changes during retention of (PAR and Little indexes):

  1. 97 cases 4 premolar extraction cases and 
  2. 58 non extraction cases, versus 
  3. 114 untreated subjects.

What was found is that:

  • The treated groups showed more changes according to PAR and Little maxillary indexes than the untreated group in the observation period.
  • The post-treatment change of the mandibular anterior crowding of the treated extraction group was greater than the mandibular crowding caused by physiologic changes in the untreated group.

An article is published at the European Journal of Orthodontics, from a Finish group, "Dental arch width, overbite, and overjet in a Finnish population with normal occlusion between the ages of 7 and 32 years"

In this article there is a series of dental casts of Class I, Untreated Subjects, been analyzed:
  1. 18 women and 15 men
  2. at age 7, 10, 12, 15 and 32 years old
What was found is that:
  • Both arches at canine and molar region increase from 7-15 and decrease from 15-32 years of age.
  • Overjet and overbite changes are also noted from 15-32 years, as well as attrition and tooth wear that plays a role to the above mentioned occlusal changes.


Physiological changes in the occlusion is a major subject, that even though there are some very important studies been published in the past, we still do not know that much about.

It should be mentioned strongly to our patients that your dentition and your soft tissue for that matter WILL deteriorate with age, and whenever it is possible the orthodontist should be in doubt of what he/she sees and how it is explained to the patient. 

An example could be of course secondary mandibular crowding and the role of wisdom teeth eruption which is so effortlessly blamed by the orthodontist to be the cause of this crowding development. When we know or should know that canine width DOES decrease with age, especially in the lower jaw and that the contact points become surfaces (are worn out) and teeth tend to slowly migrate mesial with age...

Suggested previous literature:
  1. Sinclair PM, Little RM. Maturation of untreated normal occlusions. Am J Orthod. 1983;83:114–         123.
  2. Thilander B. Orthodontic relapse versus natural develop- ment. Am J Orthod Dentofacial Orthop. 2000;117:562–563.
  3. Al Yami EA, Kuijpers-Jagtman AM, van’t Hof MA. Stability of orthodontic treatment outcome: follow-up until 10 years postretention. Am J Orthod Dentofacial Orthop. 1999;115: 300–304.
  4. Bishara S E, Jakobsen J R, Treder J, Nowak A 1997 Arch width changes from 6 weeks to 45 years of age. American Journal of Orthodontics and and Dentofacial Orthopedics 111: 401–409
  5. Henrikson J, Persson M, Thilander B 2001 Long-term stability of dental arch form in Norman occlusion from 13 to 31 years of age. European Journal of Orthodontics 23: 51–61
  6. Thilander B 2009 Dentoalveolar development in subjects with normal occlusion. A longitudinal study between the ages of 5 and 31 years. European Journal of orthodontics 31: 109–120

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