Original article
Comparison of arch forms between Korean and North American white populations

https://doi.org/10.1016/j.ajodo.2003.10.038Get rights and content

The purpose of this study was to evaluate morphologic differences in the mandibular arches of Korean and North American white subjects. The subjects were grouped according to arch form (tapered, ovoid, and square) to compare the frequency distribution of the 3 arch forms between the ethnic groups in each Angle classification. The sample included 160 white (60 Class I, 50 Class II, and 50 Class III) and 368 Korean (114 Class I, 119 Class II, and 135 Class III) subjects. The most facial portion of 13 proximal contact areas was digitized from photocopied images of the mandibular dental arches. Clinical bracket points were calculated for each tooth according to mandibular tooth thickness data, and then 4 linear and 2 proportional measurements were taken. Arch width was statistically significantly smaller in the white group than in the Korean group, but arch depth did not differ. In the Korean group, the most frequent arch form was square, whereas in the white group the tapered arch form predominated. When the subjects were regrouped by arch form, the Korean arches had a tendency to be larger and deeper than the white arches within each of the 3 arch form types.

Section snippets

Material and methods

The database for this study consisted of 2 sample groups, white and Korean. The white group consisted of the pretreatment mandibular dental models of 60 Class I, 50 Class II, and 50 Class III patients from the University of Southern California, Department of Orthodontics, and a private practice in San Diego, Calif. The Korean group consisted of models from 114 Class I, 119 Class II, and 135 Class III patients obtained from Wonkwang University, Department of Orthodontics, Korea (Table I). All

Results

Table II depicts the arch dimension measurements and results of analysis of covariance for the white and Korean Class I, II, and III samples. The white group showed significantly smaller intercanine and intermolar widths for all 3 Angle classifications. In addition, the white group showed significantly smaller canine and molar W/D ratios for Class I and Class II malocclusions than the Korean group. All the Class I, II, and III samples demonstrated statistically significant differences in widths

Discussion

With the widespread use of superelastic wires, it might be more clinically appropriate and accurate to select the most suitable arch form according to each patient's pretreatment arch form, ethnicity, and type of malocclusion to achieve a stable, functional, and esthetic goal. Clinical bracket points corresponding to a bracket slot were used in this study, according to a method described in a recent report.13 From the standpoint of clinical orthodontics, this method seems to offer greater value

Conclusions

This study demonstrates that when treating Korean patients, one should expect to use square arch forms in a significant percentage of patients. The current preformed superelastic wires are too narrow for many patients in Asian populations and should be modified when these patients are being treated.

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