Evolution of Aligner Materials

Clear Aligners is an orthodontic technique that uses a series of computer-generated custom plastic aligners to guide the teeth into proper alignment. The use of clear aligner is a growing part of the orthodontic market and as a result many new products have become available.¹ The development of clear aligner technology in orthodontics has been characterized by several noteworthy breakthroughs.  The adventure started in 1945 when H.D. Kesling developed the idea of tooth positioners, the first tools for small tooth movements.  Nahoum invented thermoformed plastic appliances in 1960, providing a more comfortable and versatile dental repair option.  By creating the invisible retainer in 1971, Pontiz improved upon these developments even further and offered a covert way to keep teeth in alignment.² The 1980s witnessed another pivotal shift as silicon replaced plastic in retainer design, an improvement led by McNamara to enhance the durability and effectiveness of these devices. In 1993, Hilard and Sheridan introduced a progressive alignment approach using clear Essix appliances, laying the groundwork for modern clear aligner systems. The most transformative breakthrough came in 1997 when Zia Chishti and Kelsey Wirth invented the world’s first comprehensive clear aligner system, revolutionizing orthodontic treatment by making it more efficient, customizable, and aesthetically pleasing.¹ This innovation marked the beginning of a new era in orthodontics, making clear aligners a popular and accessible choice for patients worldwide also known as Invisalign, it involved a series of removable clear plastic aligners aimed at seeking discrete orthodontic treatment These are transparent, removable and moldable braces.² Instead of one pair of braces being constantly adjusted, a series of braces are worn in succession, each created by a computer they are worn for at least 22 hours a day for 3 weeks before changing to the next one.³ The length of treatment depends upon the severity of each case that is 3 weeks to 6 months. Clear aligners have become a popular choice for orthodontic treatment, particularly in cases of mild to moderate crowding or spacing. They are effective for the intrusion and extrusion of incisors, posterior dental expansion, deep bite correction, and management of unilateral open bites. Additionally, aligners can tip molars distally and assist in rotating incisors and canines with the help of bonded attachments. More complex movements, such as premolar extraction space closure, molar relationship correction, and comprehensive bite corrections, often require the use of attachments and specially designed aligners.³ The advantages of clear aligners are numerous. They are nearly invisible, thin, and do not interfere with speech. Being removable, they allow for easier oral hygiene. Clear aligners are particularly appealing to adults seeking a discreet and comfortable alternative to traditional braces, with faster results and a customized digital treatment plan. However, challenges include initial speech difficulties, discomfort with aligner changes, impression inaccuracies, the risk of losing aligners, and the need for strong patient compliance. Costs can also be relatively high

Different Generations of Aligners⁴

• First Generation

Based solely on aligner; no auxiliary elements

• Second Generation

Use of attachments like composite buttons and intermaxillary elastics

• Third Generation

Attachments placed via software to improve tooth movement control⁴ Analog CAT involves a physical model that is modified either by resetting the teeth or creating divots and voids in the model prior to vacuum-forming Digital CAT starts with a 3-D scan of the dental arches, an impression, or a plaster model.⁵

THERMOPLASTIC MATERIALS

• Poly Methyl Methacrylate
• Polycarbonate
• Polyethylene –Copolyester
• polyethylene terephthalate
• polyethylene terephthalate glycol modified
• Polypropylene
• Ethylene vinyl acetate
• Polyurethane

There has been a rapid evolution in the clear aligner therapy and their materials starting from kesling’s retainer to Invisalign. There are a number of thermoplastic materials used for aligner fabrication based on their evolution and also the various companies. Thermoplastic material is a plastic polymer that becomes pliable or moldable at a certain elevated temperature and solidifies on cooling.