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The validity of maxillary expansion indices
Y Nimkarn1, P G Miles, M T O'Reilly
1Dept. of Orthodontics, University of Pittsburgh, School of Dental Medicine, USA.
The Angle Orthodontist
|January 1, 1995
Summary
Common orthodontic indices like Pont's, Schwarz's, and McNamara's may overestimate the maxillary arch expansion needed for dental crowding. This study found these methods potentially overestimate required arch width, suggesting caution in their clinical application.
Area of Science:
- Dentistry
- Orthodontics
- Dental Anthropology
Background:
- Accurate assessment of maxillary arch width is crucial for treating dental crowding.
- Several indices, including Pont's index, Schwarz's analysis, and McNamara's rule of thumb, are used to estimate required arch expansion.
- The clinical validity of these indices in relation to actual crowding severity requires further investigation.
Purpose of the Study:
- To evaluate the accuracy of Pont's index, Schwarz's analysis, and McNamara's rule of thumb in predicting necessary maxillary expansion.
- To compare the correlation between these indices and objective measures of dental crowding.
Main Methods:
- Retrospective analysis of 40 patient records (20 males, 20 females).
- Correlation of discrepancies between actual and index-predicted arch widths (intermolar and interpremolar) with crowding severity.
- Computation of linear regressions to assess the relationship between indices and crowding.
Main Results:
- Males showed stronger correlations between arch width and crowding than females.
- Intermolar width measurements were more strongly correlated with crowding than intermolar widths.
- Pont's index and McNamara's rule overestimated required arch width (2.5-4.7 mm and 2.7-3.7 mm, respectively).
- Schwarz's analysis overestimated interpremolar width (2.5-4.3 mm) but was accurate for intermolar width in males.
Conclusions:
- Pont's index, Schwarz's analysis, and McNamara's rule of thumb may overestimate the maxillary arch expansion needed to correct dental crowding.
- Clinical application of these indices should consider their potential for overestimation, particularly in females and for interpremolar width assessment.