Original article
Maxillary arch width and buccal corridor changes with orthodontic treatment. Part 1: Differences between premolar extraction and nonextraction treatment outcomes

https://doi.org/10.1016/j.ajodo.2013.10.017Get rights and content

Introduction

In this retrospective study, we examined and compared the pretreatment and posttreatment arch widths and buccal corridor changes in subjects who had received orthodontic treatment either with or without premolar extractions.

Methods

Pretreatment and posttreatment casts, frontal smiling photographs, and lateral cephalograms of 30 extraction and 27 nonextraction patients were analyzed to determine any significant differences in arch widths, buccopalatal inclinations of the teeth, and buccal corridor widths and areas, both within and between the 2 groups. Relationships between buccal corridor measurements and corresponding arch widths and buccopalatal inclinations of the teeth were also examined.

Results

There was a significant increase in the posttreatment maxillary intercanine width in the extraction group but not in the nonextraction group. Both the pretreatment and posttreatment arch widths between the maxillary first molars and at the level of the posterior rugae were greater in the nonextraction group than in the extraction group. There were no significant differences in any buccal corridor widths or areas measured between the extraction and nonextraction subjects.

Conclusions

Because they reflect different morphologies, there are likely to be significant differences in average maxillary anterior and posterior posttreatment arch widths in those treated with or without extractions. However, these arch width differences are not likely to be discernible in extraction and nonextraction patients as differences in the buccal corridor widths and areas.

Section snippets

Material and methods

Approval was obtained for this study from the Melbourne Dental School Human Ethics Advisory Group and Dental Health Services Victoria in Australia. A preliminary sample of pretreatment and posttreatment photographs of 137 patients (82 premolar extraction, 55 nonextraction) was assessed. The extraction patients had 4 premolars extracted (1 in each quadrant), with no discrimination toward which premolars were extracted. All subjects had been treated with maxillary and mandibular contemporary

Results

For the within-treatment group outcomes (Table IV), the mean intercanine pretreatment and posttreatment widths were not significantly different in the nonextraction group. In the extraction group, there was a significant mean treatment increase in this measurement of 1.54 mm. In both groups, there were significant treatment increases in the mean widths across the premolars (extraction, 3.85 mm; nonextraction, 1.65 mm) and at the level of the posterior rugae (extraction, 1.66 mm; nonextraction,

Discussion

Currently, a nonextraction approach is increasingly advocated to be the aim of orthodontic treatment when possible. The reasons for this are partly patient driven because of social media influences36 and partly because of the belief by some that extracting premolars leads to poor esthetic results through creating larger buccal corridors from constriction of the dental arches.25, 26

Conventionally, arch widths have been measured between the cusp tips of the canines, premolars, and molars.16, 27,

Conclusions

Taking into account the limitations of this study and the wide individual variations of the results, the following conclusions can be drawn.

  • 1.

    There are likely to be significant differences in average posttreatment maxillary anterior and posterior arch widths in patients treated with or without premolar extractions, largely reflecting their presenting morphology.

  • 2.

    Posttreatment anterior arch width widening is likely to be seen in both extraction and nonextraction patients.

  • 3.

    Both anterior and posterior

Acknowledgments

We thank Steve Vander Hoorn of the Statistical Consulting Centre at the University of Melbourne for his guidance with the statistical analysis of the study data, Geoffrey West for providing his Westcef analysis program, and Ari Sciacca for the loan of his inclination measuring gauge.

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      The details of the method used to measure the photographs to obtain the various buccal corridor widths and areas have been reported previously.22 The posttreatment measurements of the buccal corridor widths and areas from part 1 of this study that relate to the photographs shown to the panel members are documented in Table III and Figures 3 to 5.22 Abbreviations used for the buccal corridor measurements are listed in Table IV.

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    All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported.

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