Clear Aligners generations and orthodontic tooth movement

Orthodontic tooth movement is an intricate system that requires the coordinated reaction of biochemical reactions, cell signalling that allows cellular differentiation and bone remodelling. The process of bone modelling involves the synchronized removal of mineralized bone by osteoclasts, followed by the formation of the bone matrix through osteoblasts, which ultimately become mineralized.

For smooth orthodontic tooth movement to occur, clear aligners are expected to fulfil elaborate criteria and given the massive growth and development of aligner technology, this is much better executed today than it would be a few decades earlier. The past 15 years have witnessed the most progress in clear aligner technology in terms of its versatility to correct an array of dental anomalies as well as to accomplish a wider range of tooth movements.

That being said, very little is known about the potential of clear aligners and if they can actually achieve the results they claim to. This article describes the different generations of clear aligners that have been available from the onset and how their uses have been highlighted in orthodontics.

This study was conducted by authors Hennessy, J and Al-Awadhi EA from Dublin, Ireland. It was published in the Journal of Orthodontics.

Clear aligners generations and orthodontic tooth movement.

Hennessy J(1), Al-Awadhi EA(2).

J Orthod. 2016 Mar;43(1):68-76. doi: 10.1179/1465313315Y.0000000004.

Author information:

• Dublin Dental University Hospital, Specialist Registrar in Orthodontics, Child Dental Health and Orthodontics, Lincoln Place, Dublin, Ireland.
• Dublin Dental University Hospital, Consultant, Child Dental Health and Orthodontics, Lincoln Place, Dublin, Ireland.

Clear aligner generations

In 1999, Align technology was the first to launch a clear aligner system using CAD/CAM technology, popularly known today as Invisalign®. While it was first adopted to benefit orthodontics, today, it has expanded to general practitioners as well. The Invisalign® system consists of a series of thermoplastic clear aligners that are switched every 1 to 2 weeks until the desired positioning of the teeth is achieved. Each aligner is staged to achieve anywhere from 0.25 to 0.30 mm of orthodontic tooth movement per tray.

Each generation of clear aligners has adapted new enhancements to achieve varied results.

• First generation: The first generation of clear aligners worked based on a displacement-driven system, meaning that they relied solely on the shape of the aligners to achieve results. No auxiliary elements were incorporated and limited research was available to support the efficacy of these aligners.
• Second generation: In this generation, the use of auxiliary elements began gaining momentum. These auxiliaries were used to enhance the efficacy of orthodontic tooth movement and included the use of attachments, the incorporation of composite buttons, and intermaxillary elastics.
• Third generation: By far the latest generation of clear aligners, the third generation further enhanced the concept of using auxiliaries and introduced optimized attachments that can be placed automatically by the manufacturer’s software. These aligners are intended to improve control of tooth movements by adapting their shape with consideration to the individual tooth morphology. These are typically placed when complex tooth movements like derotations, extrusions and root movements are required. The most commonly used types of attachments are ellipsoid, bevelled, and rectangular attachments.

Various studies have been done on the three generations of aligners. Refer table below:

The study was finally able to conclude that while clear aligners could potentially achieve good results with milder cases of malocclusion, they were not as helpful in achieving more complex orthodontic movements. Until more clinical research becomes available, aligners cannot be routinely prescribed as an effective alternative to fixed labial appliances.