Micro computed tomography evaluation of Invisalign aligner thickness homogeneity

Area of Science:

• Orthodontics
• Biomaterials Science
• Dental Technology

Background:

• Invisalign clear aligners are widely used in orthodontic treatment.
• Understanding aligner material properties, such as thickness homogeneity, is crucial for treatment predictability.

Purpose of the Study:

• To evaluate the thickness homogeneity of Invisalign clear aligners using micro-computed tomography (micro-CT).
• To identify any significant variations in aligner thickness across different regions and sites.

Main Methods:

• 20 Invisalign aligners were scanned using micro-CT.
• Multiplanar reconstructions were analyzed by a blinded orthodontist.
• Thickness was measured in incisor, canine, and molar regions at various sites (gingival-buccal, buccal, occlusal, lingual, gingival-lingual).
• Statistical analysis, including linear regression and Student's t-tests, was performed.

Main Results:

• Mean aligner thickness varied slightly across regions: incisor (0.582-0.639 mm), canine (0.569-0.644 mm), and molar (0.566-0.634 mm).
• No significant thickness differences were found across regions when stratified by site.
• A significant difference in thickness homogeneity was observed in the molar region (P = .024), with the gingival-lingual edge being thinner than the occlusal aspect.

Conclusions:

• Invisalign aligner thickness exhibits minimal variations.
• A significant thickness difference exists in the molar region, specifically at the gingival-lingual edge.
• This localized thinning in the molar region may contribute to reduced predictability in certain orthodontic tooth movements.