AUTHOR=Ferlias Nikolaos , Dalstra Michel , Cornelis Marie A. , Cattaneo Paolo M. 

TITLE=In Vitro Comparison of Different Invisalign® and 3Shape® Attachment Shapes to Control Premolar Rotation

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2022.840622

DOI=10.3389/fbioe.2022.840622

ISSN=2296-4185

ABSTRACT=Aim: To evaluate in-vitro the differences of various Invisalign® attachments in their effectiveness during derotation of an upper second premolar in terms of forces and moments created and compare them to the 3Shape® box attachment as well as to no attachment at all.
Materials & Methods: A Force System Identification (FSI) machine, comprising of two load sensors, was used in this study. Sensor 1 was connected to the test tooth (i.e. upper second premolar) carrying a different attachment design and the fixed sensor 2 was connected to the base model. Once the corresponding aligner was passively seated on the teeth, twelve different setups (i.e. eleven different attachments and one setup with no attachment at all) were tested by rotating the test tooth 4.5° mesially and 4.5° distally, in increments of 0.45°. 
Results: The vertical rectangular attachments were able to generate the highest derotational moment on both mesial and distal rotations, but also received the most side effects (intrusive force, torque and tipping). The no-attachment setup performed the least favourably in terms of derotational ability but exhibited the least side effects. In the Y-axis, all attachments received a buccal root torque with a lingual force during disto-rotation and a lingual root torque with a buccal force during mesio-rotation.
Conclusion: Attachments are necessary for derotating an upper second premolar. An aligner incremental change of more than 1° derotation can generate high moments. The vertical rectangular attachments perform best in derotations; however they exhibit the most side effects. Finally, despite presenting the least side effects, derotation of a premolar with no attachment is not as efficient.