Arch width changes from 6 weeks to 45 years of age 10/9/09

Resident: Murphy
Date: 10/9/09
Article title: Arch width changes from 6 weeks to 45 years of age
Author(s): Bishara, Samir, Jane Jakobsen, et al.
Journal: American Journal of Orthodontics and Dentofacial Orthopedics
Vol.: 111, No. 4, pages 401-409

Major topic: Evaluation of maxillary and mandibular changes in arch widthType of Article: Clinical ReviewMethods: The purpose of this study was to study the changes in intercanine and intermolar widths over a 45 year span. In this study, 2 pools of patients were selected. In the first pool, 28 female and 33 male, healthy full term babies that would be accessible for frequent recall visits over the next 8 years(or so). These children were evaluated at 6 weeks, 1 year, and upon completion of the deciduous dentition. The second pool of was selected from the Iowa Growth Study. Originally 89 boys and 86 girls were selected to have models taken semiannually during childhood, annually during adolescence, and once in adulthood. Of the 175 children originally selected, 16 female and 15 males completed all the follow ups. On all of the casts, 5 maxillary and 7 mandibular landmarks were set from which the measurements were taken(see article for listing of landmarks). Variability between clinicians measurements was determined to be

Findings: There was a significant increase in max. interk9 width and intermolar arch width from 6 weeks to 2 years old in both boys and girls. The largest increase was between 6 weeks to 1 year. There was also a large increase in interk9 width from 3-8 years of age. Width decreased from age 13-45, however this was only statistically significant in the female subjects. In the mandible, interk9 and intermolar width increases up to 8 in boys and 13 in girls. After 13, there was a decrease in width in both sexes (correlating with the complete eruption of the permanent dentition). Furthermore, mandibular interk9 width is essentially set by 8 years of age, or after the complete eruption of the 4 incisors. (maybe it’s me, but the previous sentence stated that the width increases up to 13. Maybe this is just for the intermolar width, because the study ALSO says the interk9 width is set at 8. Am I missing something or is the study contradicting itself?)

Conclusions: Arch widths will change from birth to adulthood. The direction and magnitude of these changes do not provide a basis for expanding the arches in the average patient beyond its established dimension when canines and molars are completely erupted. Essentially, in terms of arch width, it is what it is, and we have to make due with what we’ve got.

Assessment of article: I think it’s a good article. Absolutely relevant to our ortho practice. As I stated previously, I found it a bit contradicting in places…or maybe it just didn’t clarify things well. Or maybe it’s me and I’m just slowly losing my mind.