A LONGITUDINAL STUDY OF DENTAL ARCH WIDTH AT THE DECIDUOUS SECOND MOLARS ON CHILDREN 4 TO 8 YEARS OF AGE

¹ Department of Orthodontics and Iowa Child Welfare Research Station, Iowa City, Iowa

Major sections of this report treat: reliability of arch width measurements taken between the buccal aspects of the deciduous second molars; age and sex differences in width of the dental arches; growth of individuals from 4 to 8 years of age in maxillary and mandibular arch width; and relationships between arch size, arch change, and face size.

The subjects were 77 North American white children. Each had, throughout the 4-year period studied, 8 erupted deciduous first and second molars free from restorative dental work and orthodontic treatment.

Selected findings are:

1. Maximum transverse diameter of the dental arches at the deciduous second molars can be determined with high dependability. Reliability coefficients approximate r = 0.995, and differences between independent records rarely exceed 0.2 mm.

2. Interbuccal width at the deciduous second molars differs with arch, sex, and age. On the whole, the maxillary arch is 3.1 mm. wider than the mandibular arch, the male arches are 1.9 mm. wider than the female arches, and the dental arches at age 4 years are 1.7 mm. narrower than at age 8 years.

3. The maxillary dental arch is slightly more variable than the mandibular dental arch. Typifying standard deviations are 2.3 mm. for the maxillary arch and 1.9 mm. for the mandibular arch.

4. Changes in arch width between 4 and 8 years of age differ widely from child to child. Some arches are no wider at 8 years than at 4 years, while others increase as much as 3.5 mm. in this 4-year interval.

5. The two dental arches are positively related with regard to both size at a given age, and change in size with advance in age. The association between width of the two arches at age 4 is represented by r = 0.8, that between width change in the two arches from 4 to 8 years by r = 0.7.

6. There is a moderately high relationship between width of a given arch at 4 years and width of the same arch at 8 years, but there is no relationship between width of a given arch at 4 years and change in width between 4 and 8 years. The r values approximate 0.9 and zero, respectively.

7. Correlations between dental arch widths and widths of the face are positive but fairly low. The r's lie close to 0.4 for both maxillary arch width with bizygomatic diameter and mandibular arch width with bigonial diameter.