Evaluation of maxillary dimensional changes in the mixed dentition: clear aligners vs acrylic expanders

Area of Science:

• Orthodontics
• Pediatric Dentistry
• Dental Materials

Background:

• Orthodontic treatment in the mixed dentition aims to correct developing discrepancies.
• Maxillary expansion is a common procedure to address transverse discrepancies.
• Digital (Invisalign First) and conventional (removable acrylic expander) appliances are used for this purpose.

Purpose of the Study:

• To compare the effectiveness of Invisalign First (IF) and removable acrylic expanders (RE) in modifying upper arch dimensions and molar inclination during mixed dentition.
• To evaluate the predictability of expansion with IF treatment.

Main Methods:

• A retrospective study comparing 17 patients treated with IF to an age-matched group treated with RE.
• Measurements included intercanine width, intermolar width, arch depth, molar inclination, and palatal surface area/volume.
• Statistical analysis included ANOVA and Kruskal-Wallis tests.

Main Results:

• Both IF and RE significantly increased intercanine width, with no significant difference between groups.
• RE showed significantly greater increases in palatal surface area and volume compared to IF.
• IF treatment resulted in mesiobuccal rotation of first molars, while RE did not.
• Expansion predictability for IF was higher for canines (70.28%) than for first molars (34.12%).

Conclusions:

• Both appliances are effective for intercanine expansion in growing patients.
• Removable acrylic expanders may be preferred for expansion targeting the molar region due to better predictability and volume increase.
• Invisalign First shows lower predictability for molar expansion and can lead to unwanted molar rotation.