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Arch width changes following first premolar extractions: a comparison between invisalign and fixed appliances.
Hengyu Hu1, Zhaowei Cen1, Shuai Huang1
1Nanjing Stomatological Hospital, Affiliated Hospital of Medical School, Institute of Stomatology, Nanjing University, Nanjing, China.
Clinical Oral Investigations
|July 13, 2026
Summary
Clear aligners (CAs) resulted in wider arch width and greater incisor retroclination compared to fixed appliances (FAs) in extraction cases. Careful case selection is advised for CA treatments involving extractions.
Area of Science:
- Orthodontics
- Dental Materials
Background:
- Arch width (AW) is crucial for space availability and anchorage control in orthodontic extractions.
- Clear aligners (CAs) and conventional fixed appliances (FAs) offer different biomechanical approaches to tooth movement.
Purpose of the Study:
- To compare arch width changes between patients treated with CAs and FAs after four first premolar extractions.
- To evaluate incisor inclination differences between the two treatment modalities.
Main Methods:
- Retrospective study of 60 Class I patients (30 CAs, 30 FAs) post-extraction.
- Digital dental casts and cephalometric radiographs analyzed pre- and post-treatment.
- Measurements included maxillary and mandibular intercanine, interpremolar, and intermolar widths.
Main Results:
- Clear aligner patients showed significantly greater maxillary and mandibular canine arch width post-treatment.
- Both groups experienced interpremolar width reduction, more pronounced with FAs.
- Intermolar arch width remained stable with CAs but reduced significantly with FAs.
Conclusions:
- Clear aligner treatment in extraction cases leads to a wider arch width and increased incisor retroclination compared to fixed appliances.
- Wider arch width and incisor retroclination with CAs may necessitate careful case selection due to potential mechanical demands on aligners.
